A risk factor is anything that increases a person’s chance of developing a specific disease. Cancer is not a single disease but a group of more than 100 different diseases. With so many types of cancer affecting various parts of the body, the risk factors for developing cancer vary greatly depending on the specific type.
Risk factors for certain cancers can be related to environmental factors, genetic predispositions, compromised immune systems or viral infections. Other cancers have no known causes.
Most cancers have more than one risk factor. These can include things such as age, race, sex, family history, diet, lifestyle factors, exposure to chemicals, radiation and socioeconomic status. While some risk factors are within a person’s control, such as lifestyle habits, other factors, including family history and genetics, cannot be controlled.
Having one or more risk factors for a type of cancer means an individual is more likely to develop that disease. It does not mean the person will absolutely develop the disease. In some cases, people with known risk factors never have cancer in their lifetime. In other cases, cancer occurs in seemingly healthy people with no risk factors. The relationship of risk factors to disease is never completely certain because after a person develops cancer, there is no way to prove a risk factor was responsible for causing the disease.
About risk factors for cancer Cancer is a group of more than 100 different diseases, each with its own unique set of risk factors. Risk factors are elements that increase the possibility of developing a specific disease or condition. Over a lifetime, it is estimated that one in three people will develop cancer, according to the National Cancer Institute (NCI). Cancer develops as a result of an uncontrolled growth of cells. In normal cell function, cells divide and die in an organized fashion. As cells grow old, they die, allowing for new cells to take their place. When old cells do not die and the body continues to create new cells, they collect to form a tumor. A tumor can be either benign (noncancerous) or malignant (cancerous).
There is more than one risk factor for most cancers. Some risk factors can be controlled, such as lifestyle habits. These factors can include smoking, alcohol use, diet and exercise. Other risk factors cannot be controlled by an individual, such as age, race, sex and genetic factors. Although risk factors may be divided into controllable and uncontrollable categories, such distinctions may be counterproductive. In many cases, an environmental risk factor may combine with a genetic predisposition and create an opportunity for cancer to develop. Researchers believe that the development of cancer often involves environmental factors that directly or indirectly alter cells. These experts contend that nearly all cancers occur as a result of a combination of factors and it is nearly impossible to determine a single cause.
Controllable and uncontrollable factors can combine to a point where identifying one or the other as the exact cause is extremely difficult. The division of risk factors into categories may serve to provide better awareness for both patients and medical professionals. Awareness of controllable risk factors can help patients avoid them by quitting smoking, maintaining a healthy weight and protecting their skin from sun exposure.
Awareness of both controllable and uncontrollable risk factors in a patient’s medical history provides physicians with valuable information to schedule screening tests and make diagnoses. Many risk factors have been identified by scientists conducting epidemiological studies that analyze both environmental and genetic risk factors.
According to the American Cancer Society, about 75 to 80 percent of cancers can be attributed to environmental factors, including tobacco use, diet, infectious agents and occupational exposure. Much of this information has come from studying people who migrate from an area of high cancer risk to an area of low cancer risk (or vice versa). These migrant studies demonstrate that these people soon take on the cancer rates of their new area. Because genetic changes take several generations, it suggests that the cancer attack rates may be related to environmental causes.
Controllable risk factors for cancer Different cancers have different risk factors. Some of the major risk factors associated with various cancers that are considered controllable include:
Tobacco use.
A direct link between smoking and cancers of the lung, mouth, larynx, bladder, kidney, cervix, esophagus and pancreas has been established. Lung cancer is the leading cause of cancer deaths in the United States.Tobacco use includes cigarettes, cigars, pipe smoking, chewing tobacco and snuff. Smoking causes one-third of all cancer deaths and is the number one cause of preventable death in the United States, according to the National Cancer Institute (NCI). Like smoking, chewing tobacco is also considered a carcinogen (cancer-causing substance). It is strongly linked to oral, oropharyngeal and laryngeal cancers. Since snuff is placed directly against mouth tissues, it greatly increases the risk of oral cancers. In addition, nonsmokers who spend significant time around smokers are exposed to secondhand smoke, which increases their risk for lung cancer.
Obesity, diet and exercise.
The body’s immune system is significantly helped by the maintenance of an ideal weight through proper nutrition and regular exercise. Obesity is a known risk factor for several cancers, including cancer of the breast, colon, rectum, kidney, uterus and gallbladder. Some recent research also links obesity to an increased risk of ovarian cancer. It is estimated that nearly one-third of all cancer deaths are related to a combination of dietary factors and lack of physical activity in adulthood. For example, a high-fat diet may play a role in prostate cancer and colorectal cancer. The body’s immune system is bolstered through moderate exercise and proper nutrition. Colorectal cancer affects the colon and rectum and is a leading cause of cancer death in the U.S. A prostate needle biopsy is a surgical procedure to collect a tissue sample from the prostate gland.
Alcohol and drugs.
The excessive use of alcohol and addictive drugs can weaken the body’s defense system. When the immune system is weakened, the body is less able to fight off disease, including cancer. For example, some studies have shown a connection between alcohol consumption and an increased risk of breast cancer. Alcohol is also a risk factor for cancers in other body areas, including the lungs, mouth, lips, colon, pancreas, liver, esophagus and the larynx.
Ultraviolet (UV) radiation.
Each year, more than 1 million skin cancers are diagnosed in the United States, according to the American Cancer Society (ACS). Non-melanoma skin cancer is the leading type of cancer diagnosed in the United States. Many of these cases could have been prevented through proper protection from the sun’s ultraviolet rays.
Occupational exposure.
According to the U.S. Centers for Disease Control and Prevention (CDC), each year an estimated 20,000 cancer deaths and 40,000 new cancer diagnoses are related to occupational exposure. Professions that are considered high-risk include uranium miners, and workers in asbestos factories, nuclear power plants and chemical plants. Certain chemicals, metals and pesticides can increase the risk of cancer. Some of the more commonly recognized carcinogens that workers can be exposed to include asbestos, nickel, formaldehyde, cadmium, uranium, vinyl chloride, benzidine and benzene. Occupational exposures to substances such as solvents, pesticides, oil products, rubber, vinyl chloride, or ionizing radiation may increase the risk of developing cancer. Working with tobacco products also appear to increase the risk of certain cancers. In most cases, the risk of developing cancer increases with the level and length of exposure.
Radon.
This radioactive gas is present in nearly all air as a result of being released from decaying uranium that is in rocks and soil. Radon levels vary, but can enter homes through tiny cracks in the walls, floors or foundations, as well as being released from building materials. This can be a significant problem for homes that are well-insulated or built over soil that has high levels of uranium. People who are exposed to radon over long periods of time can develop lung cancer. These lung cancer cases have occurred in both smokers and nonsmokers. Both the National Toxicology Program and the International Agency for Research on Cancer have classified radon as a known human carcinogen. Testing the indoor air quality is the only way to detect radon in the home.
Pollution.
The exhaust from vehicles and the air pollution from industrial power plants increase the risk of lung cancer in people exposed over a long period of time, according to the ACS.
Heterocyclic amines (HCAs).
Research from the NCI has shown that certain muscle meats (beef, pork, fowl and fish) cooked at high temperatures, particularly on a grill, create chemicals that increase cancer risk. Among these chemicals, heterocyclic amines (HCAs) may pose a human cancer risk.
Radiation exposure.
Diagnostic tests, including x-rays and computerized axial tomography (CAT) scan are being used more often among the general population due to increased availability. CAT scan is an imaging test used in cancer diagnosis, to guide treatment and to monitor for relapse.However, there is a link between radiation exposure and the development of cancer in a person’s lifetime. This is of particular concern for children because the NCI estimates that between 2 million and 3 million CAT scans are performed on children each year. The benefits of such tests may outweigh the risks and newer techniques and equipment have decreased the amount of radiation exposure. Radiation exposure during cancer treatment may also increase the risk of developing another cancer.
Reproductive and hormonal factors.
This category mainly pertains to women and has received considerable attention over the years. Many hormonal and reproductive factors have been associated with either risk or prevention of cancers. For example, if a woman has children before the age of 30 her risk of breast cancer decreases. The risk of cervical cancer increases in women who have a history of sexually transmitted diseases. Other related risk factors include: Not breastfeeding.
Breastfeeding seems to have a protective effect on both mother and child. For mothers who breastfed their children, a lower incidence of breast cancer has been reported, while those who did not breast feed had a higher rate of breast cancer.
Diethylstilbestrol (DES).
This synthetic form of estrogen was used by pregnant women between the early 1940s and 1971. Its use increased the risk of women developing breast cancer and cervical cancer. The daughters born from DES-exposed pregnancies have shown increased risks of some rare cervical and vaginal cancers, in addition to fertility problems and pregnancy complications.
Fertility drugs.
Research studies have reached conflicting results on whether or not fertility drugs increase a woman’s risk of developing ovarian cancer or uterine cancer.
Oral contraceptives.
Birth control pills have been linked to an increased risk of cancer, particularly breast cancer.
Hormone replacement therapy (HRT).
HRT or other extended exposure to estrogen or progesterone increases a woman’s risk of developing breast cancer. The risk varies based on a number of factors such as menopausal status and reproductive history. A considerable amount of research has been devoted to the benefits and risks of HRT in women. In addition to individual risk factors, certain lifestyle choices or behaviors can dramatically increase a person’s risk for cancer, particularly when they are combined. These factors which include tobacco use, alcohol use, diet, infectious diseases, as well as exposure to chemicals and radiation, cause an estimated 75 percent of all cancer cases in the United States. Tobacco use, unhealthy diet and physical inactivity are considered the most likely factors to affect personal cancer risk.
