Colorectal Cancer

Overview

Colorectal cancer is the second leading cause of cancer death in the United States. The disease strikes both men and women, and women account for roughly half of the 143,000 new cases diagnosed each year.

The colon and rectum are parts of the body’s digestive system and together form a long, muscular tube called the large intestine. The colon is the first 6 feet of the large intestine and the rectum is the last 8 to 10 inches.

Colorectal cancer begins in cells that line the colon or rectum. If detected early, cancer cells may only be found in the colon or rectum. If not detected early, the cancer may invade adjacent organs and spread through the lymph and blood systems throughout the body to the liver, lungs, and other organs.

Prevention and Screening

The chance of an individual developing cancer depends on both genetic and non-genetic factors. A genetic factor is an inherited, unchangeable trait, whereas a non-genetic factor is a variable in a person’s environment, which can often be changed. Non-genetic factors may include diet, exercise, or exposure to other substances present in our surroundings.

Hereditary or Genetic Factors

People with a personal or family history of adenomatous polyps or familial adenomatous polyposis (FAP) are at an increased risk for developing colorectal cancer. Adenomatous polyps are non-cancerous tumors that grow in the colon or rectum and can become cancerous, ultimately developing into colorectal cancer. Familial adenomatous polyposis (FAP) is a genetic disease that causes hundreds of adenomatous polyps to form in the colon or rectum. FAP most often affects adolescents and young adults, many of whom develop colorectal cancer at an early age.

Hereditary nonpolyposis colorectal cancer (HNPCC) is a genetic syndrome caused by mutation in one of several genes. HNPCC accounts for about 3 to 5 percent of all colorectal cancer. With HNPCC, people generally develop a single colorectal cancer rather than an unusual number of polyps, as in FAP. Individuals with the HNPCC gene mutations have an 80 percent lifetime risk of developing colorectal cancer.

Individuals with a family history of colorectal cancer or colorectal adenomas (polyps) also have an increased risk of developing colorectal cancer, as do those with a personal history of either of these conditions. In addition, people suffering from inflammatory bowel disease have a greater chance of developing colorectal cancer.

Environmental or Non-Genetic Factors

Diet: Studies have suggested that high intake of red meat or alcohol increases the risk of colorectal cancer.

Obesity: Obesity has consistently been linked with an increased risk of colon cancer in men. The extent to which obesity influences colon cancer risk in women is less clear, although larger waist circumference has been linked with increased colon cancer risk in both men and women.

Smoking: Studies of the link between tobacco and risk of colorectal cancer have been inconsistent. A pooled analysis of the Women’s Health Initiative studies found an increased risk of rectal cancer among smokers, but no increased risk of colon cancer. Some previous studies, however, have reported a link between smoking and colon cancer.

Prevention

Exercise: Numerous studies have demonstrated that regular physical activity reduces the risk of colorectal cancer. Talk with your doctor before starting an exercise program.

Healthy body weight: Achieving and maintaining a healthy body weight may reduce the risk of several types of cancer, including colorectal cancer.

Detection and Treatment of Precancerous Polyps: For cancers such as breast cancer, screening does not prevent the development of the cancer; instead, screening detects the cancer at an early stage when treatment is most likely to be successful. In the case of colorectal cancer, however, screening can sometimes prevent the development of cancer by identifying precancerous polyps. Removing these polyps can prevent the later development of cancer.

Colorectal cancer screening tests are described in more detail below.

Nonsteroidal Anti-inflammatory Drugs (NSAIDS): NSAIDS (drugs such as aspirin and ibuprofen) are used to reduce inflammation and pain. Studies have suggested that NSAIDS may reduce the risk of colorectal cancer. The potential benefits of regular use of these drugs, however, must be weighed against the potential risks. In 2007, the U.S. Preventive Services Task Force (USPSTF) recommended against routine use of aspirin or other NSAIDS for the prevention of colorectal cancer in individuals at average risk of the disease.

People at high risk for colorectal cancer as a result of personal or family history may wish to talk with their doctor about steps they can take to reduce their risk.

Calcium and vitamin D: Calcium and vitamin D may reduce the risk of colorectal polyps. Adequate intake of both nutrients is also recommended for optimal bone health.

Screening and Early Detection

For several types of cancer, progress in the area of cancer screening has led to earlier cancer detection and better outcomes. The term screening refers to the regular use of certain examinations or tests in persons who do not have any symptoms of a cancer but are at risk for that cancer.

Screening is crucial for the prevention and early detection of colorectal cancer. The American Cancer Society currently recommends that people at average risk of colorectal cancer begin being screened for colorectal cancer at the age of 50. Screening may need to begin at a much earlier age for people with a personal or family history of adenomatous polyps, FAP, HNPCC, colorectal cancer, or chronic inflammatory bowel disease.

Several screening strategies are currently available. Individuals interested in colorectal cancer screening should discuss the options with their physician in order to determine the most appropriate procedure.

Fecal Occult-Blood Test (FOBT): The fecal occult-blood test checks for hidden blood in the stool. Blood may indicate the presence of polyps and the need for additional evaluation.

Fecal Immunochemical Test (FIT): Fecal immunochemical tests are a newer type of fecal occult-blood test. Unlike traditional FOBT, FIT does not require drug or dietary restrictions on the part of the patient.

Flexible sigmoidoscopy: During this procedure, a physician uses a lighted tube to look inside the rectum and the lower part of the colon (sigmoid colon) for polyps or areas suspicious for cancer. The physician may perform a biopsy in order to collect samples of suspicious tissues or cells for closer examination. This is an outpatient procedure that does not require sedative anesthesia or pain medication. There are no or few complications associated with this procedure.

Colonoscopy: During this procedure, a longer flexible tube that is attached to a camera is inserted through the rectum, allowing physicians to examine the internal lining of the colon for polyps or other abnormalities. The physician may perform a biopsy in order to collect samples of suspicious tissues or cells for closer examination. This is a more difficult procedure than sigmoidoscopy to perform, requiring anesthesia or heavy sedation, but it allows the entire colon to be viewed.

CT Colonography (virtual colonoscopy): CT colonography requires the same bowel preparation as colonoscopy, but uses a computed tomography (CT) scanner to visualize the large intestine. The procedure is less invasive than colonoscopy (which may make people more willing to be screened), but individuals who are found to have colorectal growths will still need to undergo a traditional colonoscopy in order to have those growths removed. There is also some debate about the accuracy of CT colonography.

Double-contrast barium enema: A chalky substance called barium is inserted through the rectum and into the colon and rectum. The patient then undergoes x-rays of the colon and rectum so that the physician can evaluate the area for polyps or other abnormalities. The barium helps open the colon so that the x-rays are more detailed and clear.

Predictive genetic testing: A predictive test for hereditary colorectal cancer is now available. This test detects disease-causing mutations in two genes, MLH1 and MSH2, which are responsible for the majority of hereditary non-polyposis colorectal cancer (HNPCC). This test may allow patients who are identified to be at a high risk for HNPCC to have earlier and more frequent exams and to have pre-cancerous polyps removed. Individuals interested in genetic testing should consult with their physicians about the risks and benefits of this procedure.

Learn More

Treatment approaches differ between cancers of the colon and rectum. In order to learn more about the most recent information available concerning the treatment of colon or rectal cancer, click on the one of the following:

Colon cancer
Rectal cancer

References:

American Cancer Society. Cancer Facts & Figures 2010. Available at: http://www.cancer.org/docroot/stt/stt_0.asp (Accessed June 3, 2010).

Chao A, Thun MJ, Connell CJ et al. Meat consumption and risk of colorectal cancer. JAMA. 2005; 293:172-182.

Cho E, Smith-Warner SA, Ritz J et al. Alcohol intake and colorectal cancer: a pooled analysis of cohort studies. Annals of Internal Medicine. 2004;140:603-13.

Thygesen LC, Gronbaek M, Johansen C et al. Prospective weight change and colon cancer risk in male US health professionals. International Journal of Cancer. 2008:123:1160-5.
Pischon T, Lahmann PH, Boeing H et al. Body size and risk of colon and rectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC). Journal of the National Cancer Institute. 2006;98:921-31.

Paskett ED, Reeves KW, Rohan TE et al. Association between cigarette smoking and colorectal cancer in the Women’s Health Initiative. Journal of the National Cancer Institute. 2007;99:1729-35.

Howard RA, Freedman DM, Park Y, Hollenbeck A, Schatzkin A, Leitzmann MF. Physical activity, sedentary behavior, and the risk of colon and rectal cancer in the NIH-AARP Diet and Health Study. Cancer Causes and Control. 2008;19:939-53.

Friedenreich C, Norat T, Steindorf K et al. Physical activity and risk of colon and rectal cancers: the European prospective investigation into cancer and nutrition. Cancer Epidemiology Biomarkers & Prevention. 2006;15:2398-407.

Jacobs E, Thun M, Bain E, et al. A large cohort study of long-term daily use of adult-strength aspirin and cancer incidence. Journal of the National Cancer Institute. 2007; 99: 608-615.
U.S Preventive Services Task Force. Routine Aspirin or Nonsteroidal Anti-inflammatory drugs for the primary prevention of colorectal cancer: U.S. preventive services task force recommendation statement. Annals of Internal Medicine. 2007;146:361-364.

Grau MV, Baron JA, Sandler RS, Haile RW, Beach ML, Church TR, Heber D. Vitamin D, calcium supplementation, and colorectal adenomas: results of a randomized trial. Journal of the National Cancer Institute. 2003; 95: 1765-1771.