What is Prevention?
Carcinogenesis
Risk Factors
Interventions That are Known to Lower Cancer Risk
Interventions That Are Not Known to Lower Cancer Risk
Get More Information From NCI
Changes to This Summary (06/25/2009)
Questions or Comments About This Summary
About PDQ

What is Prevention?

Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.

Cancer is not a single disease but a group of related diseases. Many things in our genes, our lifestyle, and the environment around us may increase or decrease our risk of getting cancer.

Scientists are studying many different ways to help prevent cancer, including the following:

• Ways to avoid or control things known to cause cancer.
• Changes in diet and lifestyle.
• Finding precancerous conditions early. Precancerous conditions are conditions that may become cancer.
• Chemoprevention (medicines to treat a precancerous condition or to keep cancer from starting).

Carcinogenesis

Key Points for This Section

Carcinogenesis is the process in which normal cells turn into cancer cells. Changes (mutations) in genes occur during carcinogenesis.

Carcinogenesis is the process in which normal cells turn into cancer cells.

Carcinogenesis is the series of steps that take place as a normal cell becomes a cancer cell. Cells are the smallest units of the body and they make up the body’s tissues. Each cell contains genes that guide the way the body grows, develops, and repairs itself. There are many genes that control whether a cell lives or dies, divides (multiplies), or takes on special functions, such as becoming a nerve cell or a muscle cell.

Changes (mutations) in genes occur during carcinogenesis.

Changes (mutations) in genes can cause normal controls in cells to break down. When this happens, cells do not die when they should and new cells are produced when the body does not need them. The buildup of extra cells may cause a mass, or tumor, to form.

Tumors can be benign or malignant (cancerous). Malignant tumor cells, but not benign tumor cells, invade nearby tissues and spread to other parts of the body.

Risk Factors

Key Points for This Section

Factors That are Known to Increase the Risk of Cancer Cigarette Smoking and Tobacco Use Infections Radiation Factors That May Affect the Risk of Cancer Diet Alcohol Physical Activity Obesity

Scientists study risk factors and protective factors to find ways to prevent new cancers from starting. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.

Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Risk factors that a person can control are called modifiable risk factors.

This summary reviews only the major cancer risk factors and protective factors that can be controlled or changed to reduce the risk of cancer. Risk factors that are not described in the summary include certain sexual behaviors, the use of estrogen, and being exposed to certain substances at work or to certain chemicals.

Factors That are Known to Increase the Risk of Cancer

Cigarette Smoking and Tobacco Use

Tobacco use is strongly linked to an increased risk for many kinds of cancer. Smoking cigarettes is the leading cause of the following cancers:

• Acute myelogenous leukemia (AML).
• Bladder cancer.
• Cervical cancer.
• Esophageal cancer.
• Kidney cancer.
• Lung cancer.
• Oral cavity cancer.
• Pancreatic cancer.
• Stomach cancer.

Not smoking or quitting smoking lowers the risk of getting cancer and dying from cancer. Scientists believe that cigarette smoking causes about 30% of all cancer deaths in the United States.

See the following PDQ summaries for more information:

• Lung Cancer Prevention ¹
• Prevention and Cessation of Cigarette Smoking: Control of Tobacco Use ²

Infections

Certain viruses and bacteria are able to cause cancer. Viruses and other infection -causing agents cause more cases of cancer in the developing world (about 1 in 4 cases of cancer) than in developed nations (less than 1 in 10 cases of cancer). Examples of cancer-causing viruses and bacteria include:

• Human papillomavirus (HPV) increases the risk for cancers of the cervix, penis, vagina, anus, and oropharynx.
• Hepatitis B and hepatitis C viruses increase the risk for liver cancer.
• Epstein-Barr virus increases the risk for Burkitt lymphoma.
• Helicobacter pylori increases the risk for gastric cancer.

Two vaccines to prevent infection by cancer-causing agents have already been developed and approved by the U.S. Food and Drug Administration (FDA). One is a vaccine to prevent infection with hepatitis B virus. The other protects against infection with strains of human papillomavirus (HPV) that cause cervical cancer. Scientists continue to work on vaccines against infections that cause cancer.

See the following PDQ summaries for more information:

• Cervical Cancer Prevention ³
• Liver (Hepatocellular) Cancer Prevention ⁴
• Stomach (Gastric) Cancer Prevention ⁵
• Oral Cancer Prevention ⁶

Radiation

Being exposed to radiation is a known cause of cancer. There are two main types of radiation linked with an increased risk for cancer:

• Ultraviolet radiation from sunlight: This is the main cause of nonmelanoma skin cancers.
• Ionizing radiation from medical x-rays and radon gas in our homes: Scientists believe that ionizing radiation causes leukemia, thyroid cancer, and breast cancer in women. Ionizing radiation may also be linked to myeloma and cancers of the lung, stomach, colon, esophagus, bladder, and ovary.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Skin Cancer Prevention ⁸

Factors That May Affect the Risk of Cancer

Diet

The foods that you eat on a regular basis make up your diet. Diet is being studied as a risk factor for cancer. It is hard to study the effects of diet on cancer because a person’s diet includes foods that may protect against cancer and foods that may increase the risk of cancer.

It is also hard for people who take part in the studies to keep track of what they eat over a long period of time. This may explain why studies have different results about how diet affects the risk of cancer.

Some studies show that fruits and nonstarchy vegetables may protect against cancers of the mouth, esophagus, and stomach. Fruits may also protect against lung cancer.

Some studies have shown that a diet high in fat, proteins, calories, and red meat increases the risk of colorectal cancer, but other studies have not shown this.

It is not known if a diet low in fat and high in fiber, fruits, and vegetables lowers the risk of colorectal cancer.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹

Alcohol

Studies have shown that drinking alcohol is linked to an increased risk of the following types of cancers:

• Mouth cancer.
• Esophageal cancer.
• Breast cancer.
• Colorectal cancer (in men).

Drinking alcohol may also increase the risk of liver cancer and female colorectal cancer.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹
• Esophageal Cancer Prevention ¹⁰
• Oral Cancer Prevention ⁶
• Liver (Hepatocellular) Cancer Prevention ⁴

Physical Activity

Studies show that people who are physically active have a lower risk of certain cancers than those who are not. It is not known if physical activity itself is the reason for this.

Studies show a strong link between physical activity and a lower risk of colorectal cancer. Some studies show that physical activity protects against postmenopausal breast cancer and endometrial cancer.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹
• Endometrial Cancer Prevention ¹¹

Obesity

Studies show obesity is linked to a higher risk of the following cancers:

• Postmenopausal breast cancer.
• Colorectal cancer.
• Endometrial cancer.
• Esophageal cancer.
• Kidney cancer.
• Pancreatic cancer.

Some studies show that obesity is also a risk factor for cancer of the gallbladder.

Studies do not show that losing weight lowers the risk of cancers that have been linked to obesity.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹
• Endometrial Cancer Prevention ¹¹
• Lung Cancer Prevention ¹

Interventions That are Known to Lower Cancer Risk

Key Points for This Section

Chemoprevention is being studied in patients who have a high risk of developing cancer. New ways to prevent cancer are being studied in clinical trials.

An intervention is a treatment or action taken to prevent or treat disease, or improve health in other ways. Many studies are being done to find ways to keep cancer from starting or recurring (coming back).

Chemoprevention is being studied in patients who have a high risk of developing cancer.

Chemoprevention is the use of substances to lower the risk of cancer, or keep it from recurring. The substances may be natural or made in the laboratory. Some chemopreventive agents are tested in people who are at high risk for a certain type of cancer. The risk may be because of a precancerous condition, family history, or lifestyle factors.

Some chemoprevention studies have shown good results. For example, selective estrogen receptor modulators (SERMS) such as tamoxifen or raloxifene have been shown to reduce the risk of breast cancer in women at high risk. Finasteride has been shown to reduce the risk of prostate cancer.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Prostate Cancer Prevention ¹²

New ways to prevent cancer are being studied in clinical trials.

Chemoprevention agents that are being studied in clinical trials include COX-2 inhibitors. They are being studied for the prevention of colorectal and breast cancer.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹

Clinical trials are taking place in many parts of the country. Check NCI's PDQ Cancer Clinical Trials Registry for cancer prevention trials ¹³ that are now accepting patients.

See the NCI Web site ¹⁴ for more information about cancer prevention.

Interventions That Are Not Known to Lower Cancer Risk

Key Points for This Section

Vitamin and dietary supplements have not been shown to prevent cancer. New ways to prevent cancer are being studied in clinical trials.

Vitamin and dietary supplements have not been shown to prevent cancer.

An intervention is a treatment or action taken to prevent or treat disease, or improve health in other ways.

There is not enough proof that taking multivitamin and mineral supplements or single vitamins or minerals can prevent cancer. The following vitamins and mineral supplements have been studied, but have not been shown to lower the risk of cancer:

• Vitamin B6.
• Vitamin B12.
• Vitamin E.
• Vitamin C.
• Beta carotene.
• Folic acid.
• Selenium.

The use of supplements to prevent cancer is still being studied.

See the following PDQ summaries for more information:

• Breast Cancer Prevention ⁷
• Colorectal Cancer Prevention ⁹
• Lung Cancer Prevention ¹
• Prostate Cancer Prevention ¹²

New ways to prevent cancer are being studied in clinical trials.

Clinical trials are taking place in many parts of the country. Check NCI's PDQ Cancer Clinical Trials Registry for cancer prevention trials ¹³ that are now accepting patients.

See the NCI Web site ¹⁴ for more information about cancer prevention.

Get More Information From NCI

Call 1-800-4-CANCER

For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 a.m. to 4:30 p.m. Deaf and hard-of-hearing callers with TTY equipment may call 1-800-332-8615. The call is free and a trained Cancer Information Specialist is available to answer your questions.

Chat online

The NCI's LiveHelp® ¹⁵ online chat service provides Internet users with the ability to chat online with an Information Specialist. The service is available from 9:00 a.m. to 11:00 p.m. Eastern time, Monday through Friday. Information Specialists can help Internet users find information on NCI Web sites and answer questions about cancer.

Write to us

For more information from the NCI, please write to this address:

NCI Public Inquiries Office

Suite 3036A

6116 Executive Boulevard, MSC8322

Bethesda, MD 20892-8322

Search the NCI Web site

The NCI Web site ¹⁶ provides online access to information on cancer, clinical trials, and other Web sites and organizations that offer support and resources for cancer patients and their families. For a quick search, use our “Best Bets” search box in the upper right hand corner of each Web page. The results that are most closely related to your search term will be listed as Best Bets at the top of the list of search results.

There are also many other places to get materials and information about cancer treatment and services. Hospitals in your area may have information about local and regional agencies that have information on finances, getting to and from treatment, receiving care at home, and dealing with problems related to cancer treatment.

Find Publications

The NCI has booklets and other materials for patients, health professionals, and the public. These publications discuss types of cancer, methods of cancer treatment, coping with cancer, and clinical trials. Some publications provide information on tests for cancer, cancer causes and prevention, cancer statistics, and NCI research activities. NCI materials on these and other topics may be ordered online or printed directly from the NCI Publications Locator ¹⁷. These materials can also be ordered by telephone from the Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237), TTY at 1-800-332-8615.

Changes to This Summary (06/25/2009)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

Questions or Comments About This Summary

If you have questions or comments about this summary, please send them to Cancer.gov through the Web site’s Contact Form ¹⁸. We can respond only to email messages written in English.

About PDQ

PDQ is a comprehensive cancer database available on NCI's Web site.

PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at NCI's Web site ¹⁶. PDQ is provided as a service of the NCI. The NCI is part of the National Institutes of Health, the federal government's focal point for biomedical research.

PDQ contains cancer information summaries.

The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries are available in two versions. The health professional versions provide detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions provide current and accurate cancer information.

The PDQ cancer information summaries are developed by cancer experts and reviewed regularly.

Editorial Boards made up of experts in oncology and related specialties are responsible for writing and maintaining the cancer information summaries. The summaries are reviewed regularly and changes are made as new information becomes available. The date on each summary ("Date Last Modified") indicates the time of the most recent change.

PDQ also contains information on clinical trials.

A clinical trial is a study to answer a scientific question, such as whether a certain drug or nutrient can prevent cancer. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients and those who are at risk for cancer. During prevention clinical trials, information is collected about the effects of a new prevention method and how well it works. If a clinical trial shows that a new method is better than one currently being used, the new method may become "standard." People who are at high risk for a certain type of cancer may want to think about taking part in a clinical trial.

Listings of clinical trials are included in PDQ and are available online at NCI's Web site ¹⁹. Descriptions of the trials are available in health professional and patient versions. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237); TTY at 1-800-332-8615.

Glossary Terms

An aggressive (fast-growing) disease in which too many myeloblasts (immature white blood cells that are not lymphoblasts) are found in the bone marrow and blood. Also called acute myeloblastic leukemia, acute myeloid leukemia, acute nonlymphocytic leukemia, AML, and ANLL.

A chemical substance found in beer, wine, and liquor. Alcohol is also found in some medicines, mouthwashes, essential oils (scented liquid taken from plants), and household products.

The opening of the rectum to the outside of the body.

A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.

A growth that is not cancer. It does not invade nearby tissue or spread to other parts of the body.

A substance found in yellow and orange fruits and vegetables and in dark green, leafy vegetables. The body can make vitamin A from beta carotene. Beta carotene is being studied in the prevention of some types of cancer. It is a type of antioxidant.

The organ that stores urine.

Cancer that forms in tissues of the bladder (the organ that stores urine). Most bladder cancers are transitional cell carcinomas (cancer that begins in cells that normally make up the inner lining of the bladder). Other types include squamous cell carcinoma (cancer that begins in thin, flat cells) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). The cells that form squamous cell carcinoma and adenocarcinoma develop in the inner lining of the bladder as a result of chronic irritation and inflammation.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

An aggressive (fast-growing) type of B-cell non-Hodgkin lymphoma that occurs most often in children and young adults. The disease may affect the jaw, central nervous system, bowel, kidneys, ovaries, or other organs. There are three main types of Burkitt lymphoma (sporadic, endemic, and immunodeficiency related). Sporadic Burkitt lymphoma occurs throughout the world, and endemic Burkitt lymphoma occurs in Africa. Immunodeficiency-related Burkitt lymphoma is most often seen in AIDS patients.

A measurement of the energy content of food. The body needs calories as to perform its functions, such as breathing, circulating the blood, and physical activity. When a person is sick, their body may need extra calories to fight fever or other problems.

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.

The process by which normal cells are transformed into cancer cells.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

Cancer that forms in tissues of the cervix (the organ connecting the uterus and vagina). It is usually a slow-growing cancer that may not have symptoms but can be found with regular Pap tests (a procedure in which cells are scraped from the cervix and looked at under a microscope).

The lower, narrow end of the uterus that forms a canal between the uterus and vagina.

The use of drugs, vitamins, or other agents to try to reduce the risk of, or delay the development or recurrence of, cancer.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical study.

The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.

Cancer that develops in the colon (the longest part of the large intestine) and/or the rectum (the last several inches of the large intestine before the anus).

A nonsteroidal anti-inflammatory drug used to relieve pain and inflammation. COX-2 inhibitors are being studied in the prevention of colon polyps, and as anticancer drugs. Also called cyclo-oxygenase-2 inhibitor.

The things a person eats and drinks.

Cancer that forms in the tissue lining the uterus (the small, hollow, pear-shaped organ in a woman's pelvis in which a fetus develops). Most endometrial cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids).

A common virus that remains dormant in most people. It causes infectious mononucleosis and has been associated with certain cancers, including Burkitt lymphoma, immunoblastic lymphoma, and nasopharyngeal carcinoma. Also called EBV.

Cancer that forms in tissues lining the esophagus (the muscular tube through which food passes from the throat to the stomach). Two types of esophageal cancer are squamous cell carcinoma (cancer that begins in flat cells lining the esophagus) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids).

The muscular tube through which food passes from the throat to the stomach.

A type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones. Estrogens can also be made in the laboratory. They may be used as a type of birth control and to treat symptoms of menopause, menstrual disorders, osteoporosis, and other conditions.

A record of the relationships among family members along with their medical histories. This includes current and past illnesses. A family history may show a pattern of certain diseases in a family. Also called family medical history.

In food, fiber is the part of fruits, vegetables, legumes, and whole grains that cannot be digested. The fiber in food may help prevent cancer. In the body, fiber refers to tissue made of long threadlike cells, such as muscle fiber or nerve fiber.

A drug used to reduce the amount of male hormone (testosterone) produced by the body.

A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Folic acid helps to make red blood cells. It is found in whole-grain breads and cereals, liver, green vegetables, orange juice, lentils, beans, and yeast. Folic acid is water-soluble (can dissolve in water) and must be taken in every day. Not enough folic acid can cause anemia (a condition in which the number of red blood cells is below normal), diseases of the heart and blood vessels, and defects in the brain and spinal cord in a fetus. Folic acid is being studied with vitamin B12 in the prevention and treatment of cancer. Also called folate.

An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The Food and Drug Administration also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called FDA.

Cancer that forms in tissues of the gallbladder. The gallbladder is a pear-shaped organ below the liver that collects and stores bile (a fluid made by the liver to digest fat). Gallbladder cancer begins in the innermost layer of tissue and spreads through the outer layers as it grows.

Cancer that forms in tissues lining the stomach. Also called stomach cancer.

The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.

A type of bacterium that causes inflammation and ulcers in the stomach or small intestine. People with Helicobacter pylori infections may be more likely to develop cancer in the stomach, including MALT (mucosa-associated lymphoid tissue) lymphoma. Also called H. pylori.

A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact. Also, infants born to infected mothers may become infected with the virus.

A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through blood or sexual contact. Also, infants born to infected mothers may become infected with the virus.

A member of a family of viruses that can cause abnormal tissue growth (for example, genital warts) and other changes to cells. Infection with certain types of human papillomavirus increases the risk of developing cervical cancer. Also called HPV.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body and can spread throughout the body. The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on where the infection occurs. When the body’s natural defense system is strong, it can often fight the germs and prevent infection. Some cancer treatments can weaken the natural defense system.

In medicine, a treatment or action taken to prevent or treat disease, or improve health in other ways.

A type of radiation made (or given off ) by x-ray procedures, radioactive substances, rays that enter the Earth's atmosphere from outer space, and other sources. At high doses, ionizing radiation increases chemical activity inside cells and can lead to health risks, including cancer.

One of a pair of organs in the abdomen. Kidneys remove waste from the blood (as urine), produce erythropoietin (a substance that stimulates red blood cell production), and play a role in blood pressure regulation.

Cancer that forms in tissues of the kidneys. Kidney cancer includes renal cell carcinoma (cancer that forms in the lining of very small tubes in the kidney that filter the blood and remove waste products) and renal pelvis carcinoma (cancer that forms in the center of the kidney where urine collects). It also includes Wilms tumor, which is a type of kidney cancer that usually develops in children under the age of 5.

Cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of blood cells to be produced and enter the bloodstream.

Primary liver cancer is cancer that forms in the tissues of the liver. Secondary liver cancer is cancer that spreads to the liver from another part of the body.

One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.

Cancer that forms in tissues of the lung, usually in the cells lining air passages. The two main types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope.

Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.

In medicine, a lump in the body. It may be caused by the abnormal growth of cells, a cyst, hormonal changes, or an immune reaction. A mass may be benign (not cancer) or malignant (cancer).

Refers to the practices and procedures used for the prevention, treatment, or relief of symptoms of a diseases or abnormal conditions. This term may also refer to a legal drug used for the same purpose.

In medicine, a mineral is a nutrient that is needed in small amounts to keep the body healthy. Mineral nutrients include the elements calcium, magnesium, and iron.

Any change in the DNA of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited. Certain mutations may lead to cancer or other diseases.

Cancer that arises in plasma cells, a type of white blood cell.

NCI, part of the National Institutes of Health of the United States Department of Health and Human Services, is the Federal Government's principal agency for cancer research. It conducts, coordinates, and funds cancer research, training, health information dissemination, and other programs with respect to the cause, diagnosis, prevention, and treatment of cancer. Access the NCI Web site at http://www.cancer.gov. Also called National Cancer Institute.

A type of cell that receives and sends messages from the body to the brain and back to the body. The messages are sent by a weak electrical current. Also called neuron.

Skin cancer that forms in basal cells or squamous cells but not in melanocytes (pigment-producing cells of the skin).

A condition marked by an abnormally high, unhealthy amount of body fat.

Cancer that forms in tissues of the oral cavity (the mouth). The tissues of the oral cavity include the lips, the lining inside the cheeks and lips, the front two thirds of the tongue, the upper and lower gums, the floor of the mouth under the tongue, the bony roof of the mouth, and the small area behind the wisdom teeth.

The part of the throat at the back of the mouth behind the oral cavity. It includes the back third of the tongue, the soft palate, the side and back walls of the throat, and the tonsils.

One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are located in the pelvis, one on each side of the uterus.

Having to do with the pancreas.

A disease in which malignant (cancer) cells are found in the tissues of the pancreas. Also called exocrine cancer.

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

An external male reproductive organ. It contains a tube called the urethra, which carries semen and urine to the outside of the body.

Having to do with the time after menopause. Menopause (“change of life”) is the time in a woman's life when menstrual periods stop permanently.

A term used to describe a condition that may (or is likely to) become cancer. Also called premalignant.

In medicine, action taken to decrease the chance of getting a disease or condition. For example, cancer prevention includes avoiding risk factors (such as smoking, obesity, lack of exercise, and radiation exposure) and increasing protective factors (such as getting regular physical activity, staying at a healthy weight, and having a healthy diet).

Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men.

Something that may decrease the chance of getting a certain disease. Some examples of protective factors for cancer are getting regular physical activity, staying at a healthy weight, and having a healthy diet.

A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

Energy released in the form of particle or electromagnetic waves. Common sources of radiation include radon gas, cosmic rays from outer space, medical x-rays, and energy given off by a radioisotope (unstable form of a chemical element that releases radiation as it breaks down and becomes more stable).

A radioactive gas that is released by uranium, a substance found in soil and rock. Breathing in too much radon can damage lung cells and may lead to lung cancer.

The active ingredient in a drug used to reduce the risk of invasive breast cancer in postmenopausal women who are at high risk of the disease or who have osteoporosis. It is also used to prevent and treat osteoporosis in postmenopausal women. It is also being studied in the prevention of breast cancer in certain premenopausal women and in the prevention and treatment of other conditions. Raloxifene blocks the effects of the hormone estrogen in the breast and increases the amount of calcium in bone. It is a type of selective estrogen receptor modulator (SERM).

To come back or to return.

Something that may increase the chance of developing a disease. Some examples of risk factors for cancer include age, a family history of certain cancers, use of tobacco products, certain eating habits, obesity, lack of exercise, exposure to radiation or other cancer-causing agents, and certain genetic changes.

A person who has studied science, especially one who is active in a particular field of investigation.

A drug that acts like estrogen on some tissues but blocks the effect of estrogen on other tissues. Tamoxifen and raloxifene are selective estrogen receptor modulators. Also called SERM.

A mineral that is needed by the body to stay healthy. It is being studied in the prevention and treatment of some types of cancer. Selenium is a type of antioxidant.

A person's behaviors, desires, and attitudes related to sex and physical intimacy with others.

An organ that is part of the digestive system. The stomach helps digest food by mixing it with digestive juices and churning it into a thin liquid.

Cancer that forms in tissues lining the stomach. Also called gastric cancer.

Adding nutrients to the diet.

A drug used to treat certain types of breast cancer in women and men. It is also used to prevent breast cancer in women who have had ductal carcinoma in situ (abnormal cells in the ducts of the breast) and in women who are at a high risk of developing breast cancer. Tamoxifen is also being studied in the treatment of other types of cancer. It blocks the effects of the hormone estrogen in the breast. Tamoxifen is a type of antiestrogen. Also called tamoxifen citrate.

Cancer that forms in the thyroid gland (an organ at the base of the throat that makes hormones that help control heart rate, blood pressure, body temperature, and weight). Four main types of thyroid cancer are papillary, follicular, medullary, and anaplastic thyroid cancer. The four types are based on how the cancer cells look under a microscope.

A group or layer of cells that work together to perform a specific function.

A plant with leaves that have high levels of the addictive chemical nicotine. The leaves may be smoked (in cigarettes, cigars, and pipes), applied to the gums (as dipping and chewing tobacco), or inhaled (as snuff). Tobacco leaves also contain many cancer-causing chemicals, and tobacco use and exposure to secondhand tobacco smoke have been linked to many types of cancer and other diseases. The scientific name is Nicotiana tabacum.

Invisible rays that are part of the energy that comes from the sun. Ultraviolet radiation also comes from sun lamps and tanning beds. It can damage the skin and cause melanoma and other types of skin cancer. Ultraviolet radiation that reaches the Earth's surface is made up of two types of rays, called UVA and UVB rays. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass deeper into the skin. Scientists have long thought that UVB radiation can cause melanoma and other types of skin cancer. They now think that UVA radiation also may add to skin damage that can lead to skin cancer and cause premature aging. For this reason, skin specialists recommend that people use sunscreens that reflect, absorb, or scatter both kinds of ultraviolet radiation. Also called UV radiation.

A substance or group of substances meant to cause the immune system to respond to a tumor or to microorganisms, such as bacteria or viruses. A vaccine can help the body recognize and destroy cancer cells or microorganisms.

The muscular canal extending from the uterus to the exterior of the body. Also called birth canal.

In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.

A nutrient that the body needs in small amounts to function and stay healthy. Sources of vitamins are plant and animal food products and dietary supplements. Some vitamins are made in the human body from food products. Vitamins are either fat-soluble (can dissolve in fats and oils) or water-soluble (can dissolve in water). Excess fat-soluble vitamins are stored in the body’s fatty tissue, but excess water-soluble vitamins are removed in the urine. Examples are vitamin A, vitamin C, and vitamin E.

A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Vitamin B12 helps make red blood cells, DNA, RNA, energy, and tissues, and keeps nerve cells healthy. It is found in liver, meat, eggs, poultry, shellfish, milk, and milk products. Vitamin B12 is water-soluble (can dissolve in water) and must be taken in every day. Not enough vitamin B12 can cause certain types of anemia (a condition in which the number of red blood cells is below normal) and neurologic disorders. It is being studied with folate in the prevention and treatment of some types of cancer. Also called cobalamin and cyanocobalamin.

A nutrient in the vitamin B complex that the body needs in small amounts to function and stay healthy. Vitamin B6 helps keep nerves and skin healthy, fight infections, keep blood sugar levels normal, produce red blood cells, and some enzymes work properly. Vitamin B6 is a group of related compounds (pyridoxine, pyridoxal, and pyridoxamine) found in cereals, beans, peas, nuts, meat, poultry, fish, eggs, and bananas. It is water-soluble (can dissolve in water). Not enough vitamin B6 can cause mouth and tongue sores and nervous disorders. Vitamin B6 is being studied in the prevention of hand-foot syndrome (a disorder caused by certain anticancer drugs and marked by pain, swelling, numbness, tingling, or redness of the hands or feet). Also called pyridoxine.

A nutrient that the body needs in small amounts to function and stay healthy. Vitamin C helps fight infections, heal wounds, and keep tissues healthy. It is an antioxidant that helps prevent cell damage caused by free radicals (highly reactive chemicals). Vitamin C is found in all fruits and vegetables, especially citrus fruits, strawberries, cantaloupe, green peppers, tomatoes, broccoli, leafy greens, and potatoes. It is water-soluble (can dissolve in water) and must be taken in every day. Vitamin C is being studied in the prevention and treatment of some types of cancer. Also called ascorbic acid.

A nutrient that the body needs in small amounts to function and stay healthy. Vitamin E helps prevent cell damage caused by free radicals (highly reactive chemicals). It is fat-soluble (can dissolve in fats and oils) and is found in seeds, nuts, leafy vegetables, and vegetable oils. Not enough vitamin E can result in infertility (the inability to produce children). It is being studied in the prevention and treatment of some types of cancer. Vitamin E is a type of antioxidant.

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.