High Fat Diet
Fiber, Fruits, and Vegetables
Nonsteroidal Anti-Inflammatory Drugs
Cigarette Smoking
Postmenopausal Hormone Use
Colonoscopy

Note: Separate PDQ summaries on Screening for Colorectal Cancer; Colon Cancer Treatment; and Rectal Cancer Treatment are also available.

Epidemiologic, experimental (animal), and clinical investigations suggest that diets high in total fat, protein, calories, alcohol, and meat (both red and white) and low in calcium and folate, are associated with an increased incidence of colorectal cancer.

Levels of Evidence

3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group, that have a cancer incidence endpoint.

4aii: Ecologic (descriptive) studies that have a cancer incidence endpoint.

Cereal fiber supplementation and diets low in fat and high in fiber, fruits, and vegetables, however, do not reduce the rate of adenoma recurrence over a 3-year to 4-year period.

Level of Evidence

1b: Evidence obtained from at least one well-designed and conducted randomized controlled trial that has a generally accepted intermediate endpoint (adenomatous polyps) for studies of colorectal cancer prevention.

Nonsteroidal anti-inflammatory drugs including piroxicam, sulindac, and aspirin may prevent adenoma formation or cause adenomatous polyps to regress in individuals with prior colorectal cancer or adenomatous polyps and in the setting of familial adenomatous polyposis.

Levels of Evidence

1b: Evidence obtained from at least one well-designed and conducted randomized controlled trial that has a generally accepted intermediate endpoint (adenomatous polyps) for studies of colorectal cancer prevention.

3ai,3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group that have cancer mortality and cancer incidence endpoints.

Cigarette smoking is associated with an increased tendency to form adenomas and develop colorectal cancer.

Level of Evidence

3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group that have a cancer incidence endpoint.

Postmenopausal female hormone use is associated with a decreased risk of colon cancer but not rectal cancer.

Level of Evidence

3aii: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group with a cancer incidence endpoint.

Colonoscopy with removal of adenomatous polyps may reduce the risk of colorectal cancer.

Level of Evidence

3ai: Evidence obtained from well-designed and conducted cohort or case-control analytic studies, preferably from more than one center or research group that have a cancer mortality endpoint.

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