Clinical recommendation		Evidence rating	References	Comments
Colorectal cancer screening
All adults 50 years and older should be screened for colorectal cancer.		A	3–6, 12	Most colorectal cancers arise from adenomatous polyps.
Routine screening for colorectal cancer should continue until 75 years of age.		A	6	The U.S. Preventive Services Task Force recommends against continued routine screening in previously screened adults 75 to 85 years of age and against any screening in adults older then 85 years.
Options for colorectal cancer screening include:
	Annual FOBT	A	12, 13	Decreased mortality from colorectal cancer, but not all-cause mortality
	Flexible sigmoidoscopy every five years (with or without FOBT)	A	6, 12, 16–18, 20	Decreased mortality from colorectal cancer; effect on all-cause mortality unknown
				Mortality benefit less in black persons older than 60 years and in women
	Colonoscopy every 10 years	B	3, 7, 12, 24, 25	Mortality benefit not proven
				Greater single-test accuracy than FOBT or sigmoidoscopy, but higher risk of serious complications
Primary prevention of colorectal cancer
Fiber supplementation should not be recommended to decrease the risk of colorectal cancer.		A	49	Not recommended for chemoprevention; no evidence of benefit
Aspirin and nonsteroidal anti-inflammatory drugs should not be routinely used for chemoprevention of colorectal cancer.		A	50	Increased harms, such as gastrointestinal bleeding and renal impairment, limit routine use
Risks and benefits should be considered when recommending hormone therapy for women to decrease the risk of colorectal cancer.		B	54, 55	Good evidence of benefit to decrease the risk of colon cancer; inconsistent evidence for rectal cancer
				Increased risk of more advanced colon cancers with estrogen use; estrogen use associated with thromboembolic events and breast cancer
Antioxidants should not be recommended to decrease the risk of colorectal cancer.		A	57	Not recommended for chemoprevention; vitamin E associated with increased risk of adenomatous polyps