Colon Cancer Screening and Prevention
Colorectal cancer is the second leading cause of cancer death in the United States. The disease strikes both men and women, with more than 140,000 cases diagnosed each year. Approximately 50,000 people die from colorectal cancer each year. The good news is that earlier detection of colorectal cancer through screening, coupled with improved treatment, has led to better colorectal cancer survival. Mortality rates have declined by almost three percent per year since 1998.1
The chance of an individual developing cancer depends on both inherited genetic factors as well as environmental or behavioral factors. By understanding what factors can increase the risk of colorectal cancer, you may be able to take steps to reduce your risk or to detect the cancer at an early stage.
People with a family history of colorectal cancer are at increased risk for the disease, but risk is particularly elevated to people with certain inherited genetic conditions. Familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC; also called Lynch Syndrome) each greatly increase the risk of colorectal cancer. FAP and HNPCC account for a relatively small percentage (5-10%) of all colorectal cancers, but people with these conditions have a high lifetime risk of colorectal cancer, and often develop cancer at a much younger age than other people.
HNPCC is the most common type of hereditary colorectal cancer, and results from inherited mutations in genes involved in DNA mismatch repair.2 In individuals with HNPCC, the average age at diagnosis of colorectal cancer is about 45 years. Other cancers that are more common in HNPCC families include cancers of the endometrium (the lining of the uterus), ovary, small intestine, ureter, and renal pelvis.
FAP results from inherited mutations in the adenomatous polyposis coli (APC) gene. People with FAP tend to develop numerous colorectal polyps, and polyps may occur as early as the preteen years.
All people with a family history of colorectal cancer should discuss their history with their physician in order to identify the optimal approach to surveillance and prevention. Screening may need to begin at a very early age for some people.
Inflammatory Bowel Disease (IBD): The two major types of inflammatory bowel disease—ulcerative colitis and Crohn’s disease—substantially increase the risk of colorectal cancer. An estimated 10-15% of deaths among people with IBD are due to colorectal cancer.3 Because of this increased risk, people with IBD often undergo earlier and more frequent colorectal cancer screening.
Diet: Many aspects of diet have been studied in relation to colorectal cancer, often with mixed results. Dietary factors that have been reported to increase the risk of colorectal cancer include red meat and alcohol.4 Research suggests that consideration of an individual’s overall dietary pattern may also be important. A study of more than 76,000 women, for example, found that a diet rich in fruits, vegetables, legumes, fish, poultry and whole grains was linked with a lower risk of colon cancer (but not a lower risk of rectal cancer) than a diet high in red and processed meats, sweets, and refined grains.5
Obesity: Obesity has consistently been linked with an increased risk of colon cancer in men.6 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 (but not rectal cancer risk) in both men and women.7
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.8 Some previous studies, however, have reported a link between smoking and colon cancer.
We may not be able to completely eliminate our risk of developing colorectal cancer, but there are steps that we can take to reduce our risk.
Diet: Eating a diet rich in fruits, vegetables, and whole grains may reduce the risk of colorectal cancer in addition to providing other health benefits. Since red meat and alcohol may increase the risk of colorectal cancer, these should be consumed in moderation (if at all). Finally, since obesity may increase the risk of colorectal cancer, it’s important to eat a diet that allows you to achieve or maintain a health body weight.
Exercise: Studies suggest that regular physical activity reduces the risk of colon cancer.9 10 11 Exercise may also reduce the risk of rectal cancer, but results for rectal cancer have been somewhat mixed.
Talk with your doctor before starting an exercise program. If your doctor decides that it’s appropriate for you, you may benefit from following exercise guidelines such as those provided by the American Cancer Society.12 Developed for the general population (and not specifically for cancer survivors), the guidelines recommend that adults engage in at least 30 minutes of moderate-to-vigorous physical activity on five or more days per week. A longer duration of exercise (45 to 60 minutes) may provide additional benefits.
Moderate-intensity activity includes brisk walking and cycling on level terrain. Vigorous activity includes cycling or walking up hills and jogging.
Detection and Treatment of Precancerous Polyps: For cancers such as breast cancer, screening does not prevent the development of the cancer; rather, 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 here.
Nonsteroidal Anti-inflammatory Drugs (NSAIDS): NSAIDS are used to reduce inflammation and pain; they include drugs such as aspirin and ibuprofen. Studies have suggested that NSAIDS reduce the risk of colorectal cancer.13 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 ataverage risk of colorectal cancer.14
The following points contributed to this decision:
The USPSTF notes, however “These recommendations do not apply to patients with a personal history of colorectal cancer or other conditions that put them at high risk for the disease.” It is also important to note that these recommendations do not alter previous recommendations about the use of low-dose aspirin in people at increased risk of cardiovascular disease.
Patients 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. A study of people with hereditary non-polyposis colorectal cancer (HNPCC) found that daily aspirin use cut the risk of colorectal cancer by roughly half.15
Calcium: Calcium may provide a modest colorectal cancer benefit. One study showed that patients taking 1200 mg of calcium daily demonstrated a 20% reduction in colorectal adenoma formation and a 45% reduction in advanced adenoma formation.16 Physicians surmise that a reduction in adenoma formation would lead to a reduction in cancer rates. Furthermore, calcium and Vitamin D may work synergistically to decrease adenoma formation.17
Vitamin D: Vitamin D is a fat-soluble vitamin that comes from dietary supplements, foods such as fortified milk and cereal, certain kinds of fish (including salmon, mackerel, and tuna), and exposure to sunlight. Vitamin D is hypothesized to play a role in the prevention of some types of cancer, including colon cancer. According to results from two large studies – the Health Professionals Follow-up Study and the Nurses’ Health Study – individuals with higher blood levels of vitamin D may have a reduced risk of developing colon cancer.18
Preventive surgery: Preventive surgery may be recommended for some people at very high risk of colorectal cancer, such as those with FAP. Surgery is performed to remove the colon (and sometimes the rectum and other organs as well) before cancer develops.
1 American Cancer Society. Cancer Facts & Figures 2011.
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11 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.
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14 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.
15 Burn J, Gerdes A-M, Macrae F et al. Long-term effect of aspirin on cancer risk in carriers of hereditary colorectal cancer: an analysis from the CAPP2 randomised controlled trial. Lancet. Early online publication October 28, 2011
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17 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.
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19 U.S. Preventive Services Task Force. Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement. Annals of Internal Medicine. 2008;149:627-637.
20 Zubarik R, Fleisher DE, Mastropietro C, et al. Prospective analysis of complications 30 days after outpatient colonoscopy. Gastrointestinal Colonoscopy. 1999;50:322-8.
21 Itzkowitz SH, Brand R, Jandorf L, et al. A simplified, noninvasive stool DNA test for colorectal cancer detection. American Journal of Gastroenterology. 2008; 103:2862-70.