Cancer is the uncontrolled growth and spread of cells that may affect almost any tissue of the body. Lung cancer, colorectal cancer and stomach cancer are among the five most common cancers in the world for both men and women. Among men, lung and stomach cancer are the most common cancers worldwide. For women, the most common cancers are breast and cervical cancer. Cancer is a disease of cells. It is an abnormal growth of cells which tend to proliferate in an uncontrolled
way and, in some cases, to metastasize (spread). Cancer is also called malignancy. A cancerous growth or tumor is sometimes referred to as a malignant growth or tumor. A non-malignant growth or tumor is referred to as benign. Benign tumors are not cancer. Cancer is not one disease. It is a group of more than 100 different and distinctive diseases. Cancer is not contagious. Cancer can involve any tissue of the body and have many different forms in each body area. Most cancers are named for the type of cell or organ in which they start. If a cancer spreads (metastasizes), the new tumor bears the same name as the original (primary) tumor.
Cancer is a disease where cells grow out of control and invade, erode and destroy normal tissue. The driving forces behind the development of cancer are damaged genes. The gene damage is often caused by environmental factors like smoking. Cancer is used generically for more than 100 different diseases, including malignant tumours of different sites, such as breast, cervix, prostate, stomach, colon/rectum, lung and, mouth. Other examples of cancer are leukaemias, sarcomas, Hodgkin´s disease and non-Hodgkin´s lymphomas. The disease arises principally as a consequence of individual exposure to carcinogenic agents in what individuals inhale, eat and drink, or are exposed to in their personal or work environment. Personal habits, such as tobacco use, dietary and physical activity patterns - as well as occupational and environmental conditions - rather than genetic factors, play the major roles in the development of cancer. There are over 200 different types of cancer that can occur anywhere in the body. They all have different causes, different symptoms and require different types of treatment. Cancers develop because of a complicated interaction between our genes, our environment and chance. Have a look at our information on reducing your risk of developing cancer.
Cancers have many different causes and sources. One of these sources is a group of chemicals called carcinogens. These carcinogens have been found in industrial pollutants, pesticides, and food additives. People who are exposed to these carcinogens through their occupation or other activities have been known to be more susceptible to cancer. The development of cancer also has been closely linked to heredity. A genetic mutation (a change in the genetic code) could be passed to a child through the sperm or egg. A family history of cancer could be due to a dominant gene that makes cancer more likely to be passed down from generation to generation.
Cancer is a disease of genes gone awry. Genes that control the orderly replication of cells become damaged, allowing the cell to reproduce without restraint and eventually to spread into neighboring tissues and set up growths throughout the body. Cancer results from mutations of certain genes that allow the cells to begin their uncontrolled growth. These mutations are either inherited or acquired. Acquired mutations are caused by repeated insults from triggers (e.g., cigarette smoke or ultraviolet rays) referred to as carcinogens. There is usually a latency period of years or decades between exposure to a carcinogen and the appearance of cancer. This, combined with the individual nature of susceptibility to cancer, makes it very difficult to establish a cause for many cancers. All cancer is genetic, in that it is triggered by altered genes. However, just a small portion of cancer is inherited: a mutation carried in reproductive cells, passed on from one generation to the next, and present in cells throughout the body. Most cancers come from random mutations that develop in body cells during one's lifetime - either as a mistake when cells are going through cell division or in response to injuries from environmental agents such as radiation or chemicals.
Cancer usually arises in a single cell. The cell's progress from normal to malignant to metastatic appears to follow a series of distinct steps, each one controlled by a different gene or set of genes. Several types of genes have been implicated. Oncogenes normally encourage cell growth; when mutated or overexpressed, they can flood cells with signals to keep on dividing. Tumor-suppressor genes normally restrain cell growth; when missing or inactivated by a mutation, they allow cells to grow and divide uncontrollably. (The inherited genes that predispose for breast and ovarian cancer, Li-Fraumeni syndrome, retinoblastoma, Wilms' tumor, and familial adenomatous polyposis are malfunctioning tumor-suppressor genes.) DNA repair genes appear to trigger cancer - and perhaps other inherited disorders - not by spurring cell growth but by failing to correct mistakes that occur as DNA copies itself, letting mutations accumulate at thousands of sites. (Genes that have been linked to hereditary colon cancer are such "proofreader" genes.)
Loss of contact inhibition accounts for two other characteristics of cancer cells: invasiveness of surrounding tissues, and metastasis, or spreading via the lymph system or blood to other tissues and organs. Whereas normal cells have a limited lifespan controlled by the telomere gene, which signals the end of the cell line, cancer cells contain telomerase, an enzyme that alters the telomere gene and allows the cell to continue to divide. Cancer tissue, growing without limits, competes with normal tissue for nutrients, eventually killing normal cells by nutritional deprivation. Cancerous tissue can also cause secondary effects, in which the expanding malignant growth puts pressure on surrounding tissue or organs or the cancer cells metastasize and invade other organs.
The most significant avoidable carcinogens are the chemical components of tobacco smoke. Dietary components, like excessive consumption of alcohol or of foods high in fat and low in fiber rather than fruits and vegetables that contain antioxidants and necessary micronutrients, have also been linked with various cancers. Some cancers may be triggered by hormone imbalances. For example, some daughters of mothers who had been given DES (diethylstilbestrol) during pregnancy to prevent miscarriage developed vaginal adenocarcinomas as young women. Aflatoxins are natural mold byproducts that can cause cancer of the liver. Certain carcinogens present occupational hazards. For example, in the asbestos industry, workers have a high probability of developing lung and colon cancer or a particularly virulent cancer of the mesothelium (the lining of the chest and abdomen). Benzene and vinyl chloride are other known industrial carcinogens. X rays and radioactive elements are also carcinogenic; the high incidence of leukemia and other cancers in Japanese survivors of the atomic bombing of Hiroshima and Nagasaki and the increased incidence of thyroid cancer after the Chernobyl nuclear disaster give evidence of this. Exposure to the ultraviolet radiation of sunlight is the leading cause of skin cancer. Many other substances have been identified as carcinogenic to a greater or lesser extent, including chemicals in pesticides that leave residues on foods. The Delaney clause, an amendment (1958) to the U.S. Food, Drug, and Cosmetic Act that prohibits even minuscule amounts of carcinogens in the food supply, has provided the impetus for the investigation of many such chemicals but has also been a source of controversy between industry and environmentalists.
Cancer tissue has a distinctive appearance under the microscope. Among the distinguishing traits are a large number of dividing cells, variation in nuclear size and shape, variation in cell size and shape, loss of specialized cell features, loss of normal tissue organization, and a poorly defined tumor boundary. Instead of finding a benign or malignant tumor, microscopic examination of a biopsy specimen will sometimes detect a condition called "hyperplasia." Hyperplasia refers to tissue growth based on an excessive rate of cell division, leading to a larger than usual number of cells. Nonetheless, cell structure and the orderly arrangement of cells within the tissue remain normal, and the process of hyperplasia is potentially reversible. Hyperplasia can be a normal tissue response to an irritating stimulus. For example, a callus that may form on your hand when you first learn to swing a tennis racket or a golf club is produced by hyperplasia.
In addition to hyperplasia, microscopic examination of a biopsy specimen can detect another type of noncancerous condition called "dysplasia." Dysplasia is an abnormal type of excessive cell proliferation characterized by loss of normal tissue arrangement and cell structure. Often such cells revert back to normal behavior, but occasionally, they gradually become malignant. Because of their potential for becoming malignant, areas of dysplasia should be closely monitored by a health care professional. Sometimes they need treatment. The most severe cases of dysplasia are sometimes referred to as "carcinoma in situ." In Latin, the term "in situ" means "in place," so carcinoma in situ refers to an uncontrolled growth of cells that remains in the original location. However, carcinoma in situ may develop into an invasive, metastatic malignancy and, therefore, is usually removed surgically, if possible.
Since cancer can arise from such a wide variety of sites and develop with many differing patterns of spread, there are no clear-cut symptoms. Cancer is unlike many more specific diseases such as heart disease or arthritic disease. The precise nature of symptoms of cancer depends not only on primary site but specifically where the tumor is located in an organ, rate of development and also secondary spread is present or not.
The relative importance of cancers as a cause of death is increasing. The incidence of lung cancer and cancers of the colon and rectum, breast and prostate, generally increases in parallel with economic development, as stomach cancer declines. Cancer is also strongly associated with social and economic status. Cancer risk factors are highest in groups with the least education. In addition, patients in the lower socioeconomic classes have consistently poorer survival rates than those in higher strata. Many of the chronic disease risks, and the diseases themselves, overlap. In developed countries, cancer is the second-biggest cause of death after cardiovascular disease (CVD), and epidemiological evidence points to this trend emerging in the less developed world. This particularly true in countries of "transition" or middle income countries, such as in South America and Asia. Already more than half of all cancer cases occur in developing countries. Dietary factors are estimated to account for approximately 30% of cancers in western countries, making diet second only to tobacco as a preventable cause of cancer. This proportion is thought to be about 20% in developing countries and is projected to grow. As developing countries become urbanised, patterns of cancer, particularly those most strongly associated with diet and physical activity, tend to shift towards the patterns of economically developed countries. Cancer rates also change as populations move between countries and adopt different dietary patterns. In recent years, substantial evidence has pointed to the link from overweight and obesity, to many types of cancer such as oesophagus, colorectum, breast, endometrium and kidney. The composition of the diet is also important since fruit and vegetables may have a protective effect by decreasing the risk for some cancer types such as oral, oesophageal, gastric and colorectal cancer.
There are approximately 20 million people living with cancer at the moment; by 2020 there will be an estimated 30 million. And the impact is far greater than the number of cases alone would suggest. Regardless of prognosis, the initial diagnosis is often perceived by patients as life-threatening, with over one-third of sufferers experiencing clinical anxiety and depression. Cancer can also be profoundly distressing as well as economically disruptive to patients’ families. The clinical care of cancer patients is a costly element in public health budgets.
Cancer often takes many years to develop. The process typically begins with some disruption to the DNA of a cell, the genetic code that directs the life of the cell. There can be many reasons for disruptions, such as diet, tobacco, sun exposure, reproductive history or certain chemicals. Some cells will enter a precancerous phase, known as dysplasia. Some cells will progress further to the state of carcinoma in situ, in which the cancer cells are restricted to a microscopic site, surrounded by a thick covering and do not pose a great threat.Eventually, unless the body's own immune system takes care of the wayward cells, a cancer will develop. It may take as long as 30 years for a tumor to go through the entire process and become large enough to produce symptoms. Many primary tumors cause local swelling or lump if they arise at a visible or accessible part of the body, such as a skin, breast, testicle or oral cavity. A typical swelling due to a cancer is initially painless, though ulceration (skin breakdown) can occur, which may then become painful.
There is no single test that can accurately diagnose cancer. The complete evaluation of a patient usually requires a thorough history and physical examination along with diagnostic testing. Many tests are needed to determine whether a person has cancer, or if another condition (such as an infection) is mimicking the symptoms of cancer. Effective diagnostic testing is used to confirm or eliminate the presence of disease, monitor the disease process, and to plan for and evaluate the effectiveness of treatment. In some cases, it is necessary to repeat testing when a person’s condition has changed, if a sample collected was not of good quality, or an abnormal test result needs to be confirmed. Diagnostic procedures for cancer may include imaging, laboratory tests (including tests for tumor markers), tumor biopsy, endoscopic examination, surgery, or genetic testing.
Clinical chemistry uses chemical processes to measure levels of chemical components in body fluids and tissues. The most common specimens used in clinical chemistry are blood and urine. Many different tests exist to detect and measure almost any type of chemical component in blood or urine. Components may include blood glucose, electrolytes, enzymes, hormones, lipids (fats), other metabolic substances, and proteins. Cancer screening is the widespread uses of tests to detect cancers in the population. It is often an inexpensive, noninvasive procedure. If signs of cancer are detected, more definitive and invasive followup tests are performed to confirm the diagnosis. Screening for cancer is controversial in cases when it is not yet known if this test actually saves lives. The controversy arises when it is not clear if the benefits of screening outweigh the risks of follow-up diagnostic tests and cancer treatments. For example when screening for prostate cancer, the PSA test may detect small cancers that would never become life threatening, but once detected will lead to treatment. This situation, called overdiagnosis, puts men at risk for complications from unnecessary treatment such as surgery or radiation. Followup procedures used to diagnose prostate cancer (prostate biopsy) may cause side effects, including bleeding and infection. Prostate cancer treatment may cause incontinence (inability to control urine flow) and erectile dysfunction (erections inadequate for intercourse). For these reasons, it is important that the benefits and risks of diagnostic procedures and treatment be taken into account when considering whether to undertake cancer screening.
Screening for cancer can lead to earlier diagnosis. Early diagnosis may lead to extended life. A number of different screening tests have been developed. Colon cancer can be detected through fecal occult blood testing and colonoscopy, which reduces both colon cancer incidence and mortality, presumably through the detection and removal of precancerous polyps. Similarly, cervical cytology testing (using the Pap smear) leads to the identification and excision of precancerous lesions. Over time, such testing has been followed by a dramatic reduction of cervical cancer incidence and mortality. Breast cancers can be detected by breast self-examination and regular screening mammograms. Testicular self-examination – is recommended for men from the age of 15 years to detect testicular cancer. Prostate cancer can be screened for by a digital rectal exam along with annual prostate specific antigen blood testing.
A biopsy leads to the definitive diagnosis of most malignancies. It requires the removal of cells and/or pieces of tissue for examination by a pathologist. The tissue diagnosis indicates the type of cell that is proliferating, its severity (degree of dysplasia), its extent and size, and - sometimes with help from cytogenetics and immunohistochemistry - prognostic and therapeutic determinants. Biopsy can be curative if the whole lesion is removed; in this case, the borders of the sample are examined closely to see if all malignant tissue has truly been excised. The nature of the biopsy depends on the organ that is sampled. Many biopsies (such as those of the skin, breast or liver) can happen on an outpatient basis. Biopsies of other organs are performed under anesthesia and require
Cancer is treatable through a number of options. Surgery, radiation therapy, and chemotherapy are some of the most common, however hormone and biological therapies also exist. The doctor may use one of these methods or a combination of methods for treatment. The aim of cancer treatment is to cure the patient and save life. The cases where complete cure is not possible, treatment aims to control the disease and to keep the patient normal and comfortable as long as possible. The treatment of each patient is designed to suit an individual and depends on the age of the patient, stage and type of disease. There may be only one treatment or combination of treatments. There are four main modalities of treatment : Surgery, Radiation therapy, Chemotherapy, hormonetherapy and Immunotherapy. Surgery and radiotherapy aim at eradicating the disease at the primary site (site of origin) of cancer whereas chemotherapy, hormonetherapy and immunotherapy deal with disease which may have spread outside the site of origin of cancer. Surgery is the most important part of the cancer treatment. Surgery attempts to remove cancer cells from the body by cutting away the tumor and any tissues surrounding it which may contain cancer cells. It is a simple, safe and effective method when cancer is small and confined to the site of origin. It is best suited for certain type of cancers such as, breast cancer, head and neck cancers, early cancers of the cervix and lung, many skin cancers, soft tissue cancers and gastrointestinal cancers. Radiotherapy has become the pre-eminent form of cancer treatment since beginning of this century and now it is used for fifty percent of patients. Improvements in radiotherapy equipment, technique and applications, have led to an increasing role both in local treatment and also in its use as a whole-body treatment , as part of bone marrow transplantation techniques for leukaemia and other malignant diseases.
Chemotherapy is the treatment of disease with drugs that interfere with cancer cells’ growth and reproduction. These drugs may affect the cancer cells in different ways and can be given in a combination of several drugs together or as a single drug. Chemotherapy can also be used during radiation therapy. Depending on the type of cancer and how advanced it is, the goal of chemotherapy can be to cure the cancer, to control its spread or to relieve symptoms of the cancer. Chemotherapy can be given in a variety of different ways, depending upon the drug that is prescribed by your doctor. Most commonly, chemotherapy is given intravenously (through a vein), orally (by mouth), by injection (a shot) or topically (applied to the skin). Because some drugs work better together than alone, often two or more drugs are given at the same time. This is called combination therapy. Chemotherapy is the treatment of cancer with drugs that can destroy cancer cells. These drugs often are called "anticancer" drugs. Normal cells grow and die in a controlled way. When cancer occurs, cells in the body that are not normal keep dividing and forming more cells without control. Anticancer drugs destroy cancer cells by stopping them from growing or multiplying. Healthy cells can also be harmed, especially those that divide quickly. Harm to healthy cells is what causes side effects. These cells usually repair themselves after chemotherapy. Because some drugs work better together than alone, two or more drugs are often given at the same time. This is called combination chemotherapy. Chemotherapy drugs interfere with the cancer cells' ability to grow or multiply. Different groups of drugs act on cells in different ways. Identification of the type of disease is important because certain chemotherapies work best for certain diseases. For example, a patient treated for acute myelogenous leukemia is treated with different agents than one treated with Hodgkin's disease. Even patients diagnosed with the same disease may be treated with different agents, depending on what is known to be most effective for the particular circumstances. Chemotherapy can damage normal cells as well as cancer cells. Those normal cells most effected are ones which divide rapidly. These include the hair follicles, cells in the gastrointestinal (GI) tract, and bone marrow. Consequently, side effects can occur including: hair loss, mouth sores, difficulty in swallowing, nausea, vomiting, constipation, diarrhea, infection, anemia, and increase risk of bleeding. These side effects will be discussed in greater detail later. The side-effects of the chemotherapy include nausea, vomiting, hair loss, fever etc. which are temporary and completely reversible. Hormone therapy has limited use in cancer treatment since only a small minority of tumors are hormone sensitive e.g. breast and prostate cancer. This therapy provides systemic means of treatment, i.e. to the whole body, but without the side effects of chemotherapy. In summary, it is misconception that all cancers are incurable. Current methods of treatment are effective for many cancers. A large number of cancer patients are cured and more patients could be cured if their cancers were detected early and treated promptly.
The goal of radiation therapy is to kill the cancer cells with as little risk as possible to normal cells. Doctors carefully limit the doses of radiation and spread the treatment out over time to protect normal cells. They also shield as much normal tissue as possible while they aim the radiation at the site of the cancer. Radiation is a special kind of energy carried by waves or a stream of particles originating from radioactive substances and delivered by special machines. These radioactive x-rays or gamma rays can penetrate the cell wall and damage the nucleus of the cell which prevents growth and division of cells. This also affects the normal cells but these cells recover more fully than cancer cells. Chemotherapy uses drugs which interfere with the growth and division of malignant cells. Once the drugs are administered, they circulate throughout the body. It is advantageous over surgery & radiation for treating cancer that is systemic (spread throughout the body). Chemotherapy is very useful in treating cancers like leukemia, lymphomas, testicular cancer. Chemotherapy can be given as the primary treatment, or following surgery or radiotherapy to prevent reappearance of cancer. Radiation therapy (also called radiotherapy, x-ray therapy, or irradiation) is the use of a certain type of energy (called ionizing radiation) to kill cancer cells and shrink tumors. Radiation therapy injures or destroys cells in the area being treated (the "target tissue") by damaging their genetic material, making it impossible for these cells to continue to grow and divide. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly. The goal of radiation therapy is to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue.
Radiation therapy may be used to treat almost every type of solid tumor, including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, spine, stomach, uterus, or soft tissue sarcomas. Radiation can also be used to treat leukemia and lymphoma (cancers of the blood-forming cells and lymphatic system, respectively). Radiation dose to each site depends on a number of factors, including the type of cancer and whether there are tissues and organs nearby that may be damaged by radiation. Radiation therapy is the treatment of disease using penetrating beams of high-energy waves or streams of particles called ionizing radiation. The radiation used for cancer treatment comes from special machines or from radioactive substances. Radiation therapy equipment aims specific amounts of the radiation at tumors or areas of the body where there is disease. Radiation in high doses kills cells or keeps them from growing and dividing by damaging their genetic material. Because cancer cells grow and divide more rapidly than most of the normal cells around them, radiation therapy can successfully treat many kinds of cancer. Normal cells are also affected by radiation but, unlike cancer cells, most of them recover from the effects of radiation.
Surgery is the oldest form of treatment for cancer. Surgery has an important role in diagnosing and staging (finding the extent) of cancer. Advances in surgical techniques today allow surgeons to successfully operate on a growing number of patients. Approximately 60% of all cancer patients undergo some type of surgical procedure. Often more limited and less invasive operations are done to remove tumors and to try to preserve as much normal function as possible. Surgery offers the greatest chance for cure for many types of cancer, especially those that have not yet spread to other parts of the body. Surgery, in conjunction with other technologies, can be used as a minimally invasive procedure, to diagnose, biopsy and better stage different tumors, curatively remove or destroy tumors, and help relieve the discomfort and symptoms often associated with cancer, even in those settings when a cure may not be possible. In other situations, major surgery is required. In many cases, additional therapies such as radiation or chemotherapy closely follow cancer surgery. If the tumor is localized, surgery is often the preferred treatment. Example procedures include prostatectomy for prostate cancer and mastectomy for breast cancer. The goal of the surgery can be either the removal of only the tumor, or the entire organ. Since a single cancer cell can grow into a sizeable tumor, removing only the tumor leads to a greater chance of recurrence. Surgery is used in several ways to help cancer patients. According to the American Cancer Society (ACS), it is the oldest form of cancer treatment. It provides the best chance to stop many types of cancer, and it also plays a part in diagnosing, staging, and supporting cancer treatment. Having surgery for cancer is different for every patient, depending on the type of surgery, the type of cancer, and the patient's health. For some people, surgery is a major medical procedure with life-changing side effects. For others, surgery is quick and has few side effects.
Several types of surgery are helpful to people with cancer. Some surgeries are used in combination with other types of treatment. Curative surgery removes the cancerous tumor or growth from the body. Surgeons use curative surgery when the cancerous tumor is localized to a specific area of the body. This type of treatment is often considered the primary treatment. However, other types of cancer treatments, such as radiation, may be used before or after the surgery. Preventive surgery is used to remove tissue that does not contain cancerous cells, but may develop into a malignant tumor. For example, polyps in the colon may be considered precancerous tissue and preventative surgery may be performed to remove them. Diagnostic surgery helps to determine whether cells are cancerous. Diagnostic surgery is used to remove a tissue sample for testing and evaluation (in a laboratory by a pathologist). The tissue samples help to confirm a diagnosis, identify the type of cancer, or determine the stage of the cancer. Staging surgery works to uncover the extent of cancer, or the extent of the disease in the body. Laparoscopy (a viewing tube with a lens or camera is inserted through a small incision to examine the inside of the body and to remove tissue samples) is an example of a surgical staging procedure. Debulking surgery removes a portion, though not all, of a cancerous tumor. It is used in certain situations when removing an entire tumor may cause damage to an organ or the body. Other types of cancer treatment, such as chemotherapy and radiation, may be used after debulking surgery is performed.
Regular physical activity has also been seen to have a protective effect in reducing the risk of breast and colorectal cancer. High intake of preserved meat or red meat might be associated with increased risk of colorectal cancer. Another aspect of diet clearly related to cancer risk is the high consumption of alcoholic beverages, which convincingly increases the risk of the oral cavity, pharynx, larynx, oesophagus, liver and breast cancers. Many cases of cancer can be prevented by not using tobacco products, avoiding the harmful ultraviolet rays of the sun, and choosing foods with less fat and more fiber. In addition, regular checkups and self-examination often can reveal cancer at an early stage, when treatment is likely to be more effective.