Cancer is a group of diseases that involve abnormal cell growth with the potential to attack or spread to other parts of the body. Contrast this with benign tumors, which do not spread to other parts of the body. Possible signs and symptoms include bumps, abnormal bleeding, prolonged cough, unexplained weight loss and changes in bowel movement. While these symptoms may indicate cancer, they may have other causes. More than 100 types of cancer affect humans.
Tobacco use is responsible for about 22% of cancer deaths. The other 10% are caused by obesity, poor diet, lack of physical activity or excessive alcohol drinking. Other factors include certain infections, ionizing radiation exposure and environmental pollutants. In developing countries, 15% of cancers are caused by infections such as Helicobacter pylori, hepatitis B, hepatitis C, human papillomavirus infection, Epstein-Barr virus and human immunodeficiency virus (HIV). These factors act, at least in part, by altering the cell genes. Usually, many genetic changes are needed before cancer develops. About 5-10% of cancers are caused by an innate genetic disorder of a person's parent. Cancer can be detected with certain signs and symptoms or a screening test. It is usually investigated further by medical imaging and confirmed by biopsy.
Many cancers can be prevented by not smoking, maintaining a healthy weight, not drinking too much alcohol, eating lots of vegetables, fruits and grains, vaccinating against certain infectious diseases, not eating too much processed and red meat and avoiding too much sun exposure.. Early detection through screening is useful for cervical and colorectal cancer. The benefits of screening for breast cancer are still controversial. Cancer is often treated with some combination of radiation therapy, surgery, chemotherapy and targeted therapy. Pain and symptom management are an important part of treatment. Palliative care is very important in people with advanced disease. The chance of survival depends on the type of cancer and the extent of the disease at the beginning of treatment. In children under 15 at the time of diagnosis, the five-year survival rate in developed countries averages 80%. For cancer in the United States, the average five-year survival rate is 66%.
By 2015, about 90.5 million people have cancer. Approximately 14.1 million new cases occur one year (excluding skin cancer other than melanoma). This caused about 8.8 million deaths (15.7% of deaths). The most common types of cancer in men are lung cancer, prostate cancer, colorectal cancer, and stomach cancer. In women, the most common types are breast cancer, colorectal cancer, lung cancer and cervical cancer. If skin cancer other than melanoma is included in the total case of new cancer each year, it will cause about 40% of cases. In children, acute lymphoblastic leukemia and brain tumors are the most common, except in Africa where non-Hodgkin's lymphoma occurs more frequently. In 2012, about 165,000 children under 15 are diagnosed with cancer. The risk of cancer increases significantly with age, and many cancers occur more commonly in developed countries. Prices are rising as more people live to old age and lifestyle changes occur in developing countries. Cancer finance costs an estimated $ 1.16 trillion USD per year in 2010.
Video Cancer
Definition
Cancer is a large family of diseases that involve abnormal cell growth with the potential to attack or spread to other parts of the body. They form a subset of neoplasms. Neoplasm or tumor is a group of cells that have experienced unregulated growth and often form mass or lump, but can be diffused diffusely.
All tumor cells show six superiority of cancer. This characteristic is required to produce a malignant tumor. They include:
- Cell growth and division there is no exact signal
- Continuous growth and sharing even gives the opposite signal
- Avoid programmed cell death
- Unlimited cell division
- Promote vein construction
- Network invasion and metastasis formation
The development of normal cells to the cells that can form a detectable mass to cancer directly involves several steps known as malignant development.
Maps Cancer
Signs and symptoms
When cancer starts, it does not produce symptoms. Signs and symptoms appear as the mass grows or boils. The resulting findings depend on the type and location of the cancer. Some symptoms are specific. Many often occur in individuals who have other conditions. Cancer is a "master imitator". Thus, it is common for people diagnosed with cancer to have been treated for other illnesses, which are hypothesized to be the cause of their symptoms.
People can be anxious or depressed patients post-diagnosis. The risk of suicide in people with cancer is about twice that.
Local symptoms
Local symptoms may occur due to tumor mass or ulcers. For example, the mass effect of lung cancer can prevent the bronchus from causing coughing or pneumonia; esophageal cancer may cause narrowing of the esophagus, making it difficult or painful to swallow; and colorectal cancer can cause narrowing or blockage in the intestine, affecting bowel habits. Mass in the breast or testicles can produce an observable lump. Ulceration can cause bleeding which, if it occurs in the lungs, will cause coughing up the blood, in the intestine into anemia or rectal bleeding, in the bladder to the blood in the urine and in the uterus until vaginal bleeding. Although local pain can occur in advanced cancer, early swelling is usually painless. Some cancers can cause fluid accumulation in the chest or abdomen.
Systemic symptoms
Symptoms commonly occur due to effects unrelated to direct spread or metastasis. These may include: accidental weight loss, fever, excessive fatigue and changes in the skin. Hodgkin's disease, leukemia and liver or kidney cancer can cause persistent fever.
Some cancers can cause certain groups of systemic symptoms, called paraneoplastic syndrome. Examples include the emergence of myasthenia gravis in thymoma and clubbing in lung cancer.
Metastasis
Cancer can spread from the original site to local spread, spreading lymphatics to regional lymph nodes or through the spread of hematogens through blood to distant places, known as metastasis. When the cancer spreads through the hematogenous route, it usually spreads throughout the body. However, the 'seed' cancer grows on selected sites only ('soils') as hypothesized in soil hypotheses and seeds of metastatic cancer. The symptoms of metastatic cancer depend on the location of the tumor and may include enlarged lymph nodes (which can be felt or sometimes seen under the skin and usually hard), enlarged liver or enlarged spleen, which can be felt in the stomach, pain or fracture. affected bone and neurological symptoms.
Cause
The majority of cancers, about 90-95% of cases, are caused by genetic mutations of environmental factors. The remaining 5-10% is caused by inherited genetics. The Environment , as used by cancer researchers, means any genetically inherited cause, such as lifestyle, economic and behavioral factors and not just pollution. Common environmental factors that contribute to cancer deaths include tobacco (25-30%), diet and obesity (30-35%), infections (15-20%), radiation (both ionizing and non-ionizing, up to 10%), stress , lack of physical activity and pollution.
It is generally not possible to prove what causes certain cancers because the various causes do not have a specific fingerprint. For example, if a person using tobacco is suffering from lung cancer, it may be caused by tobacco use, but because everyone has less chance of developing lung cancer as a result of air pollution or radiation, the cancer may have developed for one that reason. Except for the rare transmissions that occur with pregnancy and organ donation occasionally, cancer is generally not a contagious disease.
Chemicals
The display of certain substances has been associated with certain types of cancer. These substances are called carcinogens .
Tobacco smoke, for example, causes 90% of lung cancers. It also causes cancer in the larynx, head, neck, abdomen, bladder, kidney, esophagus and pancreas. Tobacco smoke contains more than fifty known carcinogens, including nitrosamines and polycyclic aromatic hydrocarbons.
Tobacco is responsible for about one in five cancer deaths worldwide and about one in three deaths in developed countries. The mortality rate of lung cancer in the United States has reflected the smoking pattern, with the increase in smoking followed by a dramatic increase in lung cancer mortality rates and, more recently, a decrease in smoking rates since the 1950s followed by a decrease in lung cancer mortality rates men since 1990.
In Western Europe, 10% of cancers in males and 3% of cancers in women are associated with exposure to alcohol, especially liver and gastrointestinal cancers. Cancer from exposure to work-related substances can cause between 2 and 20% of cases, causing at least 200,000 deaths. Cancers such as lung cancer and mesothelioma can come from inhaling tobacco smoke or asbestos fibers, or leukemia from benzene exposure.
Diet and sports
Diet, physical activity and obesity are linked up to 30-35% of cancer deaths. In the United States overweight is associated with the development of many types of cancer and is a factor in 14-20% of cancer deaths. A study in the UK including data on more than 5 million people showed a higher body mass index associated with at least 10 types of cancer and is responsible for about 12,000 cases each year in the country. Physical inactivity is believed to contribute to cancer risk, not only through its effects on weight but also through negative effects on the immune system and endocrine system. More than half the effects of diet are due to excess nutrients (overeating), rather than eating too little vegetables or other healthy foods.
Some foods are linked to certain cancers. High salt diet associated with stomach cancer. Aflatoxin B1, a frequent food contaminant, causes liver cancer. Chewing betel fruit can cause oral cancer. The national differences in dietary practices can partly explain the differences in cancer incidence. For example, stomach cancer is more common in Japan due to a diet high in salt while colon cancer is more common in the United States. Immigrant cancer profiles develop a mirror of their new state, often in a generation.
Infection
Worldwide about 18% of cancer deaths are linked to infectious diseases. This proportion ranges from 25% in Africa to less than 10% in developed countries. Viruses are common agents of infection that cause cancer but cancer and parasitic bacteria can also play a role.
Oncoviruses include human papillomavirus, Epstein-Barr virus (B cell lymphoproliferative disease and nasopharyngeal carcinoma), Kaposi's sarcoma sarcoma (Kaposi's sarcoma and primary effusion lymphoma), hepatitis B and hepatitis C virus (carcinoma hepatocellular) and human T-cell T-cell leukemia (T-cell leukemia). Bacterial infections may also increase the risk of cancer, as seen in Helicobacter pylori - induced gastric carcinoma. Parasitic infections associated with cancer include Schistosoma haematobium (squamous cell carcinoma of the bladder) and hepatic worms, Opisthorchis viverrini and Clonorchis sinensis (cholangiocarcinoma).
Radiation
Up to 10% of invasive cancers are associated with radiation exposure, including ionizing radiation and non-ionizing ultraviolet radiation. In addition, the majority of non-invasive cancers are non-melanoma skin cancer caused by non-ionizing ultraviolet radiation, mostly from sunlight. Ionizing radiation sources include medical imaging and radon gas.
Ionizing radiation is not a very strong mutagen. Residential exposure to radon gas, for example, has the same cancer risk as passive smokers. Radiation is a potential source of cancer when combined with other cancer-causing agents, such as radon plus tobacco smoke. Radiation can cause cancer in most parts of the body, in all animals and at any age. Children and adolescents are twice as likely to develop leukemia from radiation as adults; radiation exposure before birth has ten times the effect.
The medical use of ionizing radiation is a source of cancer caused by small but growing radiation. Ionizing radiation can be used to treat other cancers, but this can, in some cases, lead to a second form of cancer. It is also used in some types of medical imaging.
Prolonged exposure to ultraviolet radiation from the sun can cause melanoma and other skin malignancies. Clear evidence establishes ultraviolet radiation, especially non-ionizing mid-wave UVB, as the cause of most non-melanoma skin cancers, which are the most common form of cancer in the world.
Non-ionizing radio frequency radiation from cell phones, power transmission and other similar sources has been described as a possible carcinogen by the International Agency for International Cancer Research of the World Health Organization. However, studies have not found a consistent relationship between cell phone radiation and cancer risk.
Heredity
Most cancers are non-hereditary (sporadic). Hereditary cancer is primarily caused by congenital genetic disorders. Less than 0.3% of the population is a genetic mutation carrier that has a major effect on cancer risk and this accounts for less than 3-10% of cancers. Some of these syndromes include: certain inherited mutations in the BRCA1 and BRCA2 gene with more than 75% risk of breast and ovarian cancer, or Lynch syndrome), which is present in about 3% of people with colorectal cancer, among others.
Statistically for cancer that causes the majority of deaths, the relative risk of developing colorectal cancer when a first-degree relative (parent, sibling or child) has been diagnosed with it is about 2. Relative relative risk is 1.5 for lung cancer , and 1.9 for prostate cancer. For breast cancer, the relative risk is 1.8 with first-degree relatives developing it at age 50 or older, and 3.3 when the relatives develop when younger than 50 years.
Physical agent
Some substances cause cancer mainly through physical effects, not chemicals. A striking example is the prolonged exposure to asbestos, the natural mineral fiber that is the main cause of mesothelioma (serous membranous cancer) is usually the serous membrane that surrounds the lungs. Other substances in this category, including natural synthetic asbestos fibers, such as wollastonite, attapulgite, glass wool and rock wool, are believed to have a similar effect. Non-fibrous particulate materials that cause cancer include metal and nickel cobalt powder and crystalline silica (quartz, cristobalite and tridymite). Usually, physical carcinogens must enter the body (such as through inhalation) and require years of exposure to produce cancer.
Physical trauma that causes cancer is relatively rare. Claims that fractures result in bone cancer, for example, have not been proven. Similarly, physical trauma is not accepted as a cause of cervical cancer, breast cancer or brain cancer. One accepted source is the frequent long-term application of hot objects to the body. It is possible that repeated burns on the same part of the body, such as those produced by kanger and cairo heating, can produce skin cancer, especially if carcinogenic chemicals are present. Often consuming boiling hot tea can lead to esophageal cancer. Generally, it is believed that cancer appears, or pre-existing cancer is pushed, during the healing process, not directly by trauma. However, repeated injuries to the same tissue can increase excessive cell proliferation, which can then increase the likelihood of cancer mutations.
Chronic inflammation has been hypothesized to directly cause mutations. Inflammation can contribute to proliferation, survival, angiogenesis and migration of cancer cells by affecting the tumor microenvironment. Oncogens build an inflammatory pro-tumorigenic microenvironment.
Hormones
Some hormones play a role in the development of cancer by promoting cell proliferation. Growth factors such as insulin and its binding protein play a key role in the proliferation of cancer cells, differentiation and apoptosis, suggesting a possible involvement in carcinogenesis.
Hormones are important agents in sex-related cancers, such as breast cancer, endometrium, prostate, ovary and testis and also thyroid cancer and bone cancer. For example, female girls with breast cancer have significantly higher levels of estrogen and progesterone than girls without breast cancer. Higher levels of this hormone can explain the higher risk of breast cancer, even in the absence of breast cancer genes. Similarly, African men have higher testosterone levels than men of European descent and have higher rates of prostate cancer. Asian ancestral men, with the lowest levels of testosterone-activated androstanediol glucuronide, had the lowest rates of prostate cancer.
Other relevant factors: Obese people have a higher rate of some hormones associated with cancer and higher rates of cancer. Women who use hormone replacement therapy have a higher risk of cancer associated with the hormone. On the other hand, people who exercise much higher than average have lower hormone levels and lower cancer risk. Osteosarcoma can be promoted by growth hormone. Some treatments and preventive approaches take advantage of this cause by artificially reducing hormone levels and thereby shrinking hormone-sensitive cancers.
Autoimmune Disease
There is a link between celiac disease and an increased risk of all cancers. People with untreated celiac disease have a higher risk, but this risk declines with time after strict diagnosis and treatment, possibly because of the application of a gluten-free diet, which seems to have a protective role against the development of malignancy in people with celiac disease.. However, delays in the diagnosis and initiation of gluten-free diets seem to increase the risk of malignancy. Gastrointestinal cancer rates are elevated in people with Crohn's disease and ulcerative colitis, due to chronic inflammation. Also, immunomodulators and biological agents used to treat the disease can increase extra-intestinal malignancy.
Pathophysiology
Genetics
Cancer is basically a disease of tissue growth regulation. In order for normal cells to turn into cancer cells, genes that regulate cell growth and differentiation should be altered.
The affected gene is divided into two broad categories. Oncogenes are genes that promote cell growth and reproduction. Tumor suppressor genes are genes that inhibit cell division and survival. Malignant transformation can occur through the formation of new oncogens, over-expression of normal oncogenes that are not appropriate, or by poor expression or deactivation of tumor suppressor genes. Usually, changes in some genes are needed to convert normal cells into cancer cells.
Genetic changes can occur at different levels and by different mechanisms. The gain or loss of an entire chromosome can occur through mitotic error. More common are mutations, which are changes in the genomic DNA nucleotide sequence.
Large-scale mutations involve removal or partial acquisition of chromosomes. Genomic amplification occurs when cells obtain copies (often 20 or more) from small chromosome loci, usually containing one or more oncogenes and adjacent genetic material. Translocation occurs when two separate chromosomal regions become unusually abnormal, often in a typical location. A well-known example of this is the Philadelphia chromosome, or translocation of chromosomes 9 and 22, which occurs in chronic myelogenous leukemia and results in the production of the BCR-abl fusion protein, an oncogenic tyrosine kinase.
Small-scale mutations include point mutations, deletions, and insertions, which may occur in the region of the gene promoter and affect its expression, or may occur in the gene encoding sequence and alter the function or stability of the protein product. Single gene disorders may also occur due to the integration of genomic material from DNA viruses or retroviruses, leading to the expression of viral oncogenes in affected cells and offspring.
The replication of data contained in probabilistic living cell DNA will result in some error (mutation). Complex correction and error prevention are incorporated into the process and protect cells against cancer. If significant errors occur, damaged cells can self-destruct through programmed cell death, called apoptosis. If the error control process fails, then the mutation will survive and be forwarded to the child cell.
Some environments make mistakes more likely to appear and spread. Such an environment may include the presence of a disturbing substance called carcinogens, recurrent physical injury, heat, ionizing radiation or hypoxia.
Errors that cause cancer to strengthen themselves and compounding, for example:
- A mutation in a cell's error correction engine can cause cells and their children to collect errors faster.
- Further mutations in oncogens can cause cells to reproduce faster and more often than normal.
- Further mutations can lead to the loss of tumor suppressor genes, disrupt the pathways of apoptotic signaling and immortalize cells.
- Further mutations in the signaling machine can send the error-causing signal to surrounding cells.
The transformation of normal cells into cancer is similar to the chain reaction caused by initial error, which binds to more severe errors, each increasingly allowing the cell to escape more controls that limit normal tissue growth. Such a scenario of rebellion is an unwanted survival of the fittest, in which the driving force of evolution works against the body's design and enforcement of order. Once the cancer begins to develop, this ongoing process, called clonal evolution, promotes progress toward a more invasive stage. Clonal evolution leads to intra-tumor heterogeneity (cancerous cells with heterogeneous mutations) that make designing an effective treatment strategy difficult.
The characteristic capabilities developed by cancer are divided into categories, particularly apoptotic avoidance, independence in growth signals, insensitivity to anti-growth signals, continuous angiogenesis, infinite replicative potential, metastasis, reprogramming of energy metabolism and avoidance of immune destruction.
Epigenetics
The classical view of cancer is a set of diseases that are driven by progressive genetic disorders that include mutations in tumor suppressor genes and oncogenes and chromosomal abnormalities. The role of further epigenetic alteration is identified.
Epigenetic changes refer to functionally functionally relevant modifications to the genome that do not alter the order of the nucleotides. Examples of such modifications are changes in DNA methylation (hypermethylation and hypometilation), histone modifications and changes in chromosome architecture (caused by improper protein expression such as HMGA2 or HMGA1). Each of these changes regulates gene expression without altering the underlying DNA sequence. This change can remain through cell division, lasting for generations and can be regarded as epimutasi (equivalent to mutation).
Epigenetic changes are common in cancer. For example, one study listed gene protein coding that is often altered in their methylation in association with colon cancer. These include 147 hypermethylation genes and 27 hipometilasi. Of the hypermethylated genes, 10 are hypermethylated in 100% of colon and many other cancers that are hypermethylated in more than 50% of colon cancers.
While epigenetic changes are found in cancer, epigenetic changes in DNA repair genes, leading to reduced expression of DNA repair proteins, may be very important. This kind of change is thought to occur early in the development of cancer and is a likely cause of the characteristics of genetic instability of the cancer.
Reduced expression of DNA repair gene interferes with DNA repair. This is shown in the figure at the 4th level from the top. (In the picture, the red words indicate the central role of DNA damage and defects in DNA repair in progression to cancer.) When DNA repair lacks DNA damage remains in cells at a higher level than usual (level 5) and causes an increase in mutation frequency and/or epimutasi (level 6). The rate of mutation increases substantially in the damaged cells in repair of DNA mismatch or improvement of homologous recombination (HRR). Rearranging chromosomes and aneuploidy also increases the damaged cells of HRR.
Higher levels of DNA damage lead to increased mutations (right side of the picture) and increased epimutation. During repair of double strand DNA damage, or repair of other DNA damage, repair sites that are not repaired can cause silencing of epigenetic genes.
The protein deficient expression of DNA repair due to inherited mutations may increase the risk of cancer. Individuals with an inherited disorder in one of 34 DNA repair genes (see article repair-deficient in DNA disorders) have increased cancer risk, with some defects ensuring a lifelong chance of 100% cancer (eg p53 mutations). DNA mutations of germ line repair are recorded on the left side of the image. However, germline mutations (which cause very penetrant cancer syndrome) are the cause of only about 1 percent of cancer.
In sporadic cancers, deficiencies in DNA repair are sometimes caused by mutations in DNA repair genes but are more often caused by epigenetic changes that reduce or eliminate DNA repair gene expression. This is shown in the figure at the 3rd level. Many studies of heavy metal induced carcinogenesis suggest that such heavy metals lead to decreased expression of DNA repair enzymes, some via epigenetic mechanisms. Inhibition of DNA repair is proposed to be the dominant mechanism in heavy metal induced carcinogenicity. In addition, epigenetic changes often occur from the DNA sequence code for small RNAs called microRNAs (or miRNAs). Mirna does not encode proteins, but can "target" protein-coding genes and reduce their expression.
Cancer usually arises from a collection of mutations and epimutations that provide selective advantages leading to clonal expansion (see Damage of the field in progression to cancer). Mutations, however, may not be as frequent in cancer as epigenetic changes. The average cancer of the breast or colon can have about 60 to 70 mutations that alter the protein, in which about three or four may be a "driver" mutation and the rest may be a "passenger" mutation.
Metastasis
Metastasis is the spread of cancer to other locations in the body. The dispersed tumor is called a metastatic tumor, whereas the original tumor is called the primary tumor. Almost all cancas metastasize. Most deaths from cancer are due to cancer that has spread.
Metastasis often occurs in the late stages of cancer and can occur through the blood or lymphatic system or both. Typical steps in metastasis are local invasion, intravasation into blood or lymph, circulation through the body, extravasation into new tissues, proliferation and angiogenesis. Different types of cancer tend to metastasize to certain organs, but overall the most common place for metastasis to occur is the lungs, liver, brain and bone.
Diagnosis
Most cancers are initially well-known because of the appearance of signs or symptoms or through screening. None of this leads to a definitive diagnosis, which requires examination of tissue samples by pathologists. People with suspected cancer were investigated with medical tests. These usually include blood tests, X-rays, (contrast) CT scans and endoscopes.
The tissue diagnosis of the biopsies shows the types of cells that breed, their histologic levels, genetic disorders and other features. Together, this information is useful for evaluating the prognosis and choosing the best treatment.
Cytogenetics and immunohistochemistry are another type of tissue test. These tests provide information about molecular changes (such as mutations, fusion genes and numerical chromosome changes) and thus also can show the best prognosis and treatment.
Classification
Cancer is classified by a cell type that resembles a tumor cell and is therefore suspected to be the origin of the tumor. These types include:
- Carcinoma: Cancer derived from epithelial cells. This group includes many of the most common cancers and includes almost everything in the breast, prostate, lung, pancreas and colon.
- Sarcoma: Cancer arising from connective tissue (ie bone, cartilage, fat, nerves), each of which develops from cells originating from the mesenchymal cells outside the bone marrow.
- Lymphoma and leukemia: Both of these classes come from hematopoietic (blood-forming) cells that leave the marrow and tend to mature in lymph nodes and blood, respectively.
- Germ cell tumor: Cancer derived from pluripotent cells, most commonly present in the testes or ovaries (seminomas and dysgerminomas, respectively).
- Blastoma: Cancer derived from immature "precursor" cells or embryonic tissue.
Cancer is typically named using -carsinoma , -sarcoma or -blastoma as a suffix, with Latin or Greek for the organ or home network as root. For example, parenchymal liver cancer that arises from malignant epithelial cells is called hepatocarcinoma, while the malignancy arising from primitive liver cell precursors is called hepatoblastoma and cancer arising from fat cells is called liposarcoma . For some common cancers, the name of British organs is used. For example, the most common type of breast cancer is called breast ductal carcinoma . Here, the adjective ductal refers to the appearance of cancer under a microscope, indicating that it originates from the milk ducts.
Benign (non-cancerous) tumors are named using -oma as a suffix with the name of the organ as the root. For example, a benign tumor of a smooth muscle cell is called leiomyoma (the common name of a benign tumor that often occurs in the uterus is fibroid ). Confusingly, some cancers use -noma suffix, examples include melanoma and seminoma.
Some cancers are named for the size and shape of cells under a microscope, such as giant cell carcinoma, spindle cell carcinoma and small cell carcinoma.
Prevention
Cancer prevention is defined as an active action to reduce the risk of cancer. Most cases of cancer are caused by environmental risk factors. Many of these environmental factors are lifestyle choices that can be controlled. Thus, cancer can generally be prevented. Between 70% and 90% of common cancers are due to environmental factors and therefore potentially preventable.
More than 30% of cancer deaths can be prevented by avoiding risk factors including: tobacco, overweight/obesity, poor diet, physical activity, alcohol, sexually transmitted infections and air pollution. Not all environmental causes can be controlled, such as naturally occurring background radiation and cancer caused by hereditary genetic disorders and therefore can not be prevented through personal behavior.
Diet
While many dietary recommendations have been proposed to reduce cancer risk, evidence to support them is not definitive. The main dietary factors that increase the risk are obesity and alcohol consumption. Low diet fruits and vegetables and high red meat have been involved but the review and meta-analysis did not arrive at a consistent conclusion. Meta-analysis 2014 found no association between fruits and vegetables and cancer. Coffee is associated with a reduced risk of liver cancer. Studies have linked the excess consumption of red meat or processed meat to an increased risk of breast cancer, colon cancer and pancreatic cancer, a phenomenon that may be caused by the presence of carcinogens in meat cooked at high temperatures. In 2015, the IARC reports that eating processed meats (eg, bacon, ham, hot dogs, sausages) and, to a lesser extent, red meat is associated with several types of cancer.
Dietary recommendations for cancer prevention usually include emphasis on vegetables, fruits, grains and fish and avoid processed and red meats (beef, pork, lamb), animal fats, pickled foods and refined carbohydrates.
Medication
Drugs can be used to prevent cancer in some circumstances. In the general population, NSAIDs reduce the risk of colorectal cancer; However, due to cardiovascular and gastrointestinal side effects, they cause overall damage when used for prevention. Aspirin has been found to reduce the risk of dying from cancer by about 7%. COX-2 inhibitors may decrease the rate of polyp formation in people with familial adenomatous polyposis; However, this is related to the same side effects as NSAIDs. Daily use of tamoxifen or raloxifene reduces the risk of breast cancer in high-risk women. Benefits versus hazards to 5-alpha-reductase inhibitors such as finasteride are unclear.
Vitamin supplements do not seem to be effective in preventing cancer. While low levels of vitamin D in the blood are correlated with an increased risk of cancer, whether this association is causal and vitamin D supplements are unspecified protective. One review of 2014 found that supplements did not have a significant effect on cancer risk. Another 2014 review concluded that vitamin D 3 could reduce the risk of dying from cancer (one less death in 150 treated people over 5 years), but concerns about data quality were noted.
Better-carotene supplements increase lung cancer rates in those at high risk. Folic acid supplementation is not effective in preventing colon cancer and can improve colon polyps. It is not clear whether selenium supplementation has any effect.
Vaccinations
Vaccines have been developed that prevent infection by some carcinogenic viruses. Human papillomavirus vaccine (Gardasil and Cervarix) decreases the risk of cervical cancer. The hepatitis B vaccine prevents infection with hepatitis B virus and thus reduces the risk of liver cancer. Vaccination of human papillomavirus and hepatitis B is recommended when resources permit.
Screening
Unlike diagnostic efforts that are prompted by symptoms and medical signs, cancer screening involves attempting to detect cancer after it is formed, but before visible symptoms appear. This may involve a physical examination, blood or urine test or medical imaging.
Cancer screening is not available for many cancers. Even when tests are available, they may not be recommended for everyone. Universal filtering or bulk screening involves screening everyone. Selective investigation identifies people at higher risk, such as those with a family history. Several factors are considered to determine whether the benefits of filtering outweigh the risks and cost of screening. These factors include:
- Possible dangers of screening tests: for example, X-ray images involve exposure to potentially harmful ionizing radiation
- Possible tests correctly identify cancer
- Possible cancer: Screening is usually not useful for rare cancer.
- Possible danger of follow-up procedure
- Is the appropriate treatment available
- Whether early detection improves treatment results
- Whether cancer will require care
- Are the tests acceptable to people: If screening tests are too burdensome (eg, very painful), then people will refuse to participate.
- Cost
Recommendations
AS. Preventive Service Task Force
The US Preventive Services Task Force (USPSTF) provides recommendations for different types of cancer:
- Highly recommend screening cervical cancer in women who are sexually active and have cervices at least until the age of 65 years.
- Suggest that Americans be screened for colorectal cancer through occult blood tests, sigmoidoscopy, or colonoscopy from 50 to 75 years of age.
- Evidence is not enough to recommend or oppose screening for skin cancer, oral cancer, lung cancer, or prostate cancer in men under 75.
- Regular screening is not recommended for bladder cancer, testicular cancer, ovarian cancer, pancreatic cancer, or prostate cancer.
- Recommend mammography for breast cancer screening every two years from age 50-74, but does not recommend breast self-examination or clinical breast examination. Overview Cochrane 2013 concludes that breast cancer screening by mammography has no effect in reducing deaths due to overdiagnosis and overtreatment.
Japanese
The screen for stomach cancer uses photofluorography because of the high incidence there.
Genetic testing
Genetic testing for individuals at high risk for certain cancers is recommended by unofficial groups. These mutation carriers can then undergo better supervision, chemoprevention, or preventive surgery to reduce subsequent risks.
Management
Many treatment options for cancer. The main ones include surgery, chemotherapy, radiation therapy, hormonal therapy, targeted therapy and palliative care. Treatment used depends on the type, location and level of cancer as well as the health and preferences of the patient. Treatment intent may or may not be curative.
Chemotherapy
Chemotherapy is the treatment of cancer with one or more cytotoxic anti-neoplastic drugs (chemotherapeutic agents) as part of standard regimens. The term includes a variety of drugs, which are divided into broad categories such as alkylation agents and antimetabolites. Traditional chemotherapy agents act by killing the cells that divide rapidly, the critical nature of most cancer cells.
Targeted therapy is a form of chemotherapy that targets specific molecular differences between cancer and normal cells. The first targeted therapy blocks estrogen receptor molecules, inhibiting the growth of breast cancer. Another common example is the Bcr-Abl inhibitor class, which is used to treat chronic myelogenous leukemia (CML). Currently, targeted therapies exist for many of the most common types of cancer, including bladder cancer, breast cancer, colorectal cancer, kidney cancer, leukemia, liver cancer, lung cancer, lymphoma, pancreatic cancer, prostate cancer, skin cancer, and thyroid cancer. as well as other types of cancer.
The efficacy of chemotherapy depends on the type of cancer and its stage. In combination with surgery, chemotherapy has proven useful in types of cancer including breast cancer, colorectal cancer, pancreatic cancer, osteogenic sarcoma, testicular cancer, ovarian cancer and certain lung cancers. Chemotherapy is curative for some cancers, such as some leukemia, ineffective in some brain tumors, and unnecessary to others, such as non-melanoma skin cancer. The effectiveness of chemotherapy is often limited by its toxicity to other tissues in the body. Even when chemotherapy does not provide permanent cure, it may be useful to reduce symptoms such as pain or to reduce the size of the tumor that is inoperable in the hope that surgery will become possible in the future.
Radiation
Radiation therapy involves the use of ionizing radiation as an attempt to heal or improve symptoms. It works by damaging DNA from cancer tissue, killing it. To save normal tissues (such as skin or organs, which radiation should pass to treat the tumor), radiation-shaped rays are directed from multiple angles of exposure to intersect the tumor, giving a much larger dose than the surrounding, healthy tissue. Like chemotherapy, cancer varies in response to radiation therapy.
Radiation therapy is used in about half of cases. Radiation can be from an internal source (brachytherapy) or an external source. This radiation is most often a low energy ray to treat skin cancer, while higher energy rays are used for cancer in the body. Radiation is usually used in addition to surgery and or chemotherapy. For certain types of cancer, such as head and neck cancers, can be used alone. For painful bone metastases, it has been found to be effective in about 70% of patients.
Surgery
Surgery is the main method of treatment for most isolated isolated cancers and may play a role in palliative and prolong survival. This is usually an important part of a definitive diagnosis and staging of a tumor, since a biopsy is usually necessary. In localized cancers, surgery usually tries to lift the whole mass together, in certain cases, the lymph nodes in the area. For some types of cancer this is enough to remove cancer.
Palliative care
Palliative care refers to treatments that try to help patients feel better and can be combined with efforts to treat cancer. Palliative care includes measures to reduce physical, emotional, spiritual, and psycho-social disorders. Unlike treatments aimed at killing cancer cells directly, the primary goal of palliative care is to improve the quality of life.
People at all stages of cancer treatment usually receive some type of palliative care. In some cases, professional medical specialist organizations recommend that patients and doctors respond to cancer only with palliative care. This applies to patients who:
- displays low performance status, implying limited ability to take care of yourself
- did not receive benefits from previous evidence-based care
- are not eligible to participate in the appropriate clinical trials
- there is no strong evidence to suggest that care will be effective
Palliative care may be confusing with hospice and therefore only shown when people approach the end of life. Like hospital care, palliative care efforts to help patients address their immediate needs and to improve comfort. Unlike hospital care, palliative care does not require people to stop treatment aimed at cancer.
Some national medical guidelines recommend early palliative care for patients whose cancer has produced distressing symptoms or who need help to overcome their illness. In patients first diagnosed with metastatic disease, palliative care may be demonstrated immediately. Palliative care is indicated for patients with a prognosis of less than 12 months of life and even given aggressive treatment.
Immunotherapy
Various therapies using immunotherapy, stimulating or helping the immune system to fight cancer, have been in use since 1997. Approaches include antibodies, checkpoint therapies and cell transfer lift.
Laser therapy
Laser therapy uses high-intensity light to treat cancer by shrinking or destroying tumors or precancerous growth. Lasers are most often used to treat superficial cancers that exist on the surface of the body or layers of internal organs. It is used to treat basal cell skin cancers and the earliest stages of others such as lung cancer of the cervical, penile, vaginal, vulva, and non-small cells. Often combined with other treatments, such as surgery, chemotherapy, or radiation therapy. Laser-induced interstitial thermotherapy (LITT), or interstitial laser photocoagulation, uses lasers to treat some cancers using hyperthermia, which use heat to shrink tumors by damaging or killing cancer cells. Lasers are more precise than surgery and cause less damage, pain, bleeding, swelling, and scarring. The disadvantage is that the surgeon should have special training. Probably more expensive than other treatments.
Alternative medicine
Complementary and alternative cancer treatments are a diverse group of therapies, practices and products that are not part of conventional medicine. "Complementary medicine" refers to the methods and substances used in conjunction with conventional medicine, while "alternative medicine" refers to a compound used as a substitute for conventional medicine. Most complementary and alternative medicine for cancer has not been studied or tested using conventional techniques such as clinical trials. Some alternative treatments have been investigated and proven to be ineffective but are still being marketed and promoted. Cancer researcher Andrew J. Vickers stated, "Label 'is not proven' inappropriate for such therapy, it's time to point out that many alternative cancer therapies have been 'unproven'."
Prognosis
The survival rate varies by type of cancer and at the stage in which it is diagnosed, ranging from majority survival to complete death five years after diagnosis. Once the cancer has spread, the prognosis usually becomes much worse. About half of patients receiving treatment for invasive cancer (excluding in situ carcinoma and non-melanoma skin cancer) die of cancer or treatment.
Survival is worse in developing countries, partly because the most common types of cancer are more difficult to treat than those associated with developed countries.
Cancer survivors develop a second primary cancer at about twice the rate of those who have never been diagnosed. The increased risk is believed to be a random possibility of developing any cancer, possibly surviving the first cancer, the same risk factors that produce the first cancer, undesirable side effects from treating the first cancer (especially radiation therapy), and for better adherence to screening.
Predicting short or long term survival depends on many factors. The most important is the type of cancer and the patient's age and overall health. Those who are weak with other health problems have a lower survival rate than healthy people. Centenarians are unlikely to survive for five years even if treatment is successful. People who report higher quality of life tend to last longer. People with a lower quality of life can be affected by depression and other complications and/or disease progression that disrupts the quality and quantity of life. In addition, patients with a poor prognosis may experience depression or report a worse quality of life because they feel that their condition may be fatal.
Cancer patients have an increased risk of blood clots in the blood vessels. The use of heparin appears to improve survival and reduce the risk of blood clotting.
Epidemiology
In 2008, approximately 12.7 million cancers were diagnosed (excluding non-melanoma skin cancer and other non-invasive cancers) and by 2010 nearly 7.98 million people died. Cancer is responsible for about 13% of deaths. The most common are lung cancer (1.4 million deaths), stomach cancer (740,000), liver cancer (700,000), colorectal cancer (610,000) and breast cancer (460,000). This makes invasive cancer the leading cause of death in the developed world and the second leading in the developing world. More than half of cases occur in developing countries.
Death from cancer of 5.8 million in 1990. Death has increased mainly due to longer life span and lifestyle changes in developing countries. The most significant risk factor for developing cancer is age. Although cancer may attack at any age, most patients with invasive cancer are over 65. According to cancer researcher Robert A. Weinberg, "If we live long enough, sooner or later we will all get cancer." Some associations between aging and cancer are associated with immunosenescence, errors accumulated in DNA over lifetime and age-related changes in the endocrine system. The effects of aging on cancer are complicated by factors such as DNA damage and inflammation promoting it and factors such as vascular aging and endocrine changes inhibit it.
Some slow-growing cancers are very common, but are often not fatal. Autopsy studies in Europe and Asia show that up to 36% of people have undiagnosed thyroid cancer and appear to be harmless at the time of their deaths and that 80% of men develop prostate cancer by age 80. Because these cancers do not cause patient death, identifying them will represent overdiagnosis rather than useful medical treatments.
The three most common childhood cancers are leukemia (34%), brain tumors (23%) and lymphoma (12%). In the United States cancer affects about 1 in 285 children. The rate of childhood cancer increased by 0.6% annually between 1975 and 2002 in the United States and by 1.1% per year between 1978 and 1997 in Europe. The deaths from cancer in childhood were reduced by half since 1975 in the United States.
History
Cancer has existed for all human history. The earliest written records of cancer date from about 1600 BC in Egypt's Edwin Smith Papyrus and describe breast cancer. Hippocrates (about 460 BC - about 370 BC) describes several types of cancer, referring to them with the Greek word ???????? karkinos (crab or crayfish). The name is derived from the surface appearance of a solid, malignant tumor piece, with "veins stretched across all sides as crab animals have legs, whence their names come from." Galen states that "breast cancer is so called because of the likeness of a crush given by the lateral extension of the tumor and the adjacent distended vein." Celsus (about 25 BC - 50 AD) translates karkinos into Latin cancer , also means crabs and recommended surgery for treatment. Galen (2nd century AD) disagrees with the use of surgery and is recommended as a laxative. This recommendation mostly stood for 1000 years.
In the 15th, 16th and 17th centuries, it became acceptable for doctors to dissect dead bodies to find the cause of death. German Professor Wilhelm Fabry believes that breast cancer is caused by a clump of milk in the mammary duct. Dutch Professor Francois de la Boe Sylvius, a follower of Descartes, believes that all diseases are the result of chemical processes and acidic lymph fluids are the cause of cancer. Contemporary Nicolaes Tulp believes that cancer is a toxin that is slowly spreading and concludes that it is contagious.
Doctor John Hill described tobacco tobacco as the cause of nasal cancer in 1761. This was followed by a report in 1775 by British surgeon Percivall Pott that the smokestack sweeps' carcinoma, scrotal cancer, is a common disease among sweep chimneys. With the widespread use of microscopes in the 18th century, it was discovered that 'cancer toxins' spread from the primary tumor through the lymph nodes to other sites ("metastasis"). This view of the disease was first formulated by British surgeon Campbell De Morgan between 1871 and 1874.
Society and culture
Although many diseases (such as heart failure) may have a worse prognosis than most cases of cancer, cancer is the subject of widespread fear and taboo. Euphemism "after a long illness" is still frequently used, reflecting a clear stigma. In Nigeria, a local name for cancer is translated into English as "an incurable disease". The deep belief that cancer is a difficult and usually lethal disease is reflected in the system chosen by the public to develop cancer statistics: the most common form of cancer - non-melanoma skin cancer, accounting for about a third of cancer cases worldwide. , but very few deaths - are excluded from cancer statistics specifically because they are easily treated and almost always heal, often in a single, short outpatient procedure.
The Western conception of patient rights for cancer sufferers includes the obligation to fully disclose the medical situation to the person, and the right to engage in joint decision making in a way that respects the person's own values. In other cultures, other rights and values ​​are preferred. For example, most African cultures value the whole family rather than individualism. In some parts of Africa, diagnosis is generally made so late that healing is impossible, and treatment, if available at all, will quickly bankrupt families. As a result of these factors, African healthcare providers tend to let family members decide whether, when and how to disclose the diagnosis, and they tend to do it slowly and circling, because the person shows interest and ability to deal with dreary news. People from Asian and South American countries also tend to prefer a slower and less open approach to disclosure than idealized in the United States and Western Europe, and they believe that sometimes it is better not to be informed about the diagnosis of cancer. In general, disclosure of diagnosis is more common than in the 20th century, but full disclosure of prognosis is not offered to many patients worldwide.
In the United States and some other cultures, cancer is considered a disease that must be "fought" to end "civil rebellion"; The War on Cancer is declared in the US. Military metaphors are very common in the description of the human effects of cancer, and they emphasize both the state of the patient's health and the need to immediately take decisive action on its own rather than delay, ignore or depend entirely on others. Military metaphors also help rationalize the destructive radical treatment.
In the 1970s, the relatively popular alternative cancer treatment in the US was a special form of speech therapy, based on the idea that cancer is caused by a bad attitude. People with "cancerous personalities" - depressed, repressed, self-hating and afraid to express their emotions - are believed to have manifested cancer through the will of the subconscious. Some psychotherapists say that treatment to change the patient's outlook will cure cancer. Among other effects, this belief allows people to blame the victim for causing cancer (by "wanting it") or has prevented its healing (by not being happy enough, unafraid and loving). It also increases the anxiety of the patient, because they mistakenly believe that the natural emotions of sadness, anger or fear shorten their lives. The idea was ridiculed by Susan Sontag, who published Illness as Metaphor while he was recovering from treatment for breast cancer in 1978. Although his original idea is now generally regarded as nonsense, the idea of ​​some survives in a reduced form with widespread, but incorrect, beliefs that deliberately inculcate positive thinking habits will improve survival. This idea is very strong in the culture of breast cancer.
One idea of ​​why people with cancer are blamed or stigmatized, so-called equitable hypotheses, is that blaming cancer on a patient's actions or attitude allows slanderers to regain control. It is based on the belief of the blam that the world is basically just and so are the dangerous diseases, such as cancer, should be a kind of punishment for a bad choice, because in a fair world, bad things will not happen to good people.
Economic effects
In 2007, the overall cost of cancer in the US - including indirect care and death costs (such as loss of workplace productivity) - was estimated at $ 226.8 billion. In 2009, 32% of Hispanics and 10% of children 17 years of age or younger did not have health insurance; "Uninsured patients and those from ethnic minorities are substantially more likely to be diagnosed with cancer at a later stage, when treatment can be wider and more expensive."
Research
Since cancer is a class of illness, it is unlikely there will be one "cure for cancer" more than there will be a single treatment for all infectious diseases. The angiogenesis inhibitor was mistakenly thought to have potential as a "silver bullet" treatment applicable to many types of cancer. Angiogenesis inhibitors and other cancer therapies are used in combination to reduce cancer morbidity and mortality.
Experimental cancer treatments were studied in clinical trials to compare proposed treatments with the best available treatment. Successful treatment in one type of cancer can be tested against another type. Diagnostic tests are under development to better target the right therapy for the right patient, based on their individual biology.
Cancer research focuses on the following issues:
- Agents (eg viruses) and events (eg mutations) that cause or facilitate genetic changes in cells destined to become cancerous.
- Proper properties of genetic damage and genes influenced by it.
- The consequences of genetic changes in cell biology, both in generating the defining properties of cancer cells and in facilitating additional genetic events leading to further development of cancer.
Increased understanding of molecular biology and cellular biology due to cancer research has led to new treatments for cancer since US President Richard Nixon declared a "Cancer War" in 1971. Since then, the country has spent more than $ 200 billion on cancer research, including resources from the public and private sectors. Cancer mortality rates (adjusting for size and age of population) decreased by 5 percent between 1950 and 2005.
Competition for financial resources appears to have suppressed the creativity, cooperation, risk-taking and original thinking necessary to make fundamental discoveries, too supportive of low-risk research into small, stepwise increases in more risky and more innovative research. Another consequence of competition seems to be a lot of research with dramatic claims whose results can not be replicated and deviant incentives push grant recipients to grow without making sufficient investment in their own faculties and facilities.
Virotherapy, which uses virus conversion, is being studied.
Pregnancy
Cancer affects about 1 in 1,000 pregnant women. The most common cancer is found
Source of the article : Wikipedia
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