Doctors cannot always explain why one person gets cancer and another does not. However, scientists have studied general patterns of cancer in the population to learn what things around us and what things we do in our lives may increase our chance of developing cancer.
Anything that increases a person’s chance of developing a disease is called a risk factor; anything that decreases a person’s chance of developing a disease is called a protective factor. Some of the risk factors for cancer can be avoided, but many cannot. For example, although you can choose to quit smoking, you cannot choose which genes you have inherited from your parents. Both smoking and inheriting specific genes could be considered risk factors for certain kinds of cancer, but only smoking can be avoided. Prevention means avoiding the risk factors and increasing the protective factors that can be controlled so that the chance of developing cancer decreases.
Although many risk factors can be avoided, it is important to keep in mind that avoiding risk factors does not guarantee that you will not get cancer. Also, most people with a particular risk factor for cancer do not actually get the disease. Some people are more sensitive than others are to factors that can cause cancer. Talk to your doctor about methods of preventing cancer that might be effective for you.
The purposes of this summary on colorectal cancer prevention are to:
Give information on colorectal cancer and how often it occurs.
Describe colorectal cancer prevention methods.
Give current facts about which people or groups of people would most likely be helped by following colorectal cancer prevention methods.
You can talk to your doctor or health care professional about cancer prevention methods and whether they would be likely to help you.
Colorectal cancer is the second leading cause of cancer deaths in the United States. The number of new cases of colorectal cancer in the United States has been decreasing slightly, and the number of deaths due to colorectal cancer has been decreasing. The risk of colorectal cancer tends to increase after the age of 40.
Colorectal cancer can sometimes be associated with known risk factors for the disease. Many risk factors can be changed, but not all can be avoided.
Diet and Lifestyle: Diet and lifestyle may affect colorectal cancer risk. Many factors are under study.
Studies show colorectal cancer risk may be affected by the following factors:
Vitamin D: Studies show that taking 1,000 IU of vitamin D daily may cut the risk of colorectal cancer in half.
Physical activity: A lack of physical activity, especially combined with a diet high in fat, may increase colorectal cancer risk.
Smoking: Cigarette smoking has been linked to increased colorectal cancer risk.
Alcohol: Drinking alcohol may increase colorectal cancer risk.
It is not known if a diet low in fat and high in fiber, fruits, and vegetables decreases the risk of colorectal cancer.
Nonsteroidal Anti-Inflammatory Drugs: It is not known if the use of nonsteroidal anti-inflammatory drugs (NSAIDs) decreases the risk of colorectal cancer. Studies have shown that NSAIDs lower the risk of adenomas (noncancerous tumors), but it is not clear if this results in a lower risk of cancerous tumors. Use of NSAIDs, however, increases the risk of heart attack, heart failure, stroke, and bleeding in the stomach and intestines.
Polyp Removal: Studies have shown that removing polyps, which may develop into cancer, decreases the risk of colorectal cancer. Bleeding and infection sometimes occur after polyps are removed during colonoscopy or sigmoidoscopy. Rarely, the procedure tears the colon.
Female Hormone Use: Studies show that postmenopausal use of combined estrogen and progesterone lowers the risk of colorectal cancer, but use of estrogen alone does not. Combined estrogen and progesterone use, however, increases the risk of breast cancer, blood clots, and heart disease.
Statin Use: There is no evidence that statin use affects the risk of colorectal cancer.
Changes were made to this summary to match those made to the health professional version.
If you have questions or comments about this summary, please send them to Cancer.gov through the Web site’s Contact Form. We can respond only to email messages written in English.
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.
Web sites and Organizations
The NCI Web site 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. There are also many other places where people can get materials and information about cancer treatment and services. Local hospitals may have information on local and regional agencies that offer information about finances, getting to and from treatment, receiving care at home, and dealing with problems associated with cancer treatment.
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. 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.
The NCI's LiveHelp service, a program available on several of the Institute's Web sites, 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.
For more information from the NCI, please write to this address:
NCI Public Inquiries Office
6116 Executive Boulevard, MSC8322
Bethesda, MD 20892-8322
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. 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.
People who are at high risk for a certain type of cancer may want to take part in a clinical trial. 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 prevention methods, the risks involved, and how well they do or do not work. If a clinical trial shows that a new method is better than one currently being used, the new method may become "standard."
Listings of clinical trials are included in PDQ and are available online at NCI's Web site. 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.