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Colorectal Cancer Health Center

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Colorectal Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Overview

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

Factors Associated With Increased Risk of Colorectal Cancer

Excessive alcohol use

Based on solid evidence from observational studies, excessive alcohol use is associated with an increased risk of colorectal cancer (CRC).[1,2,3]

Magnitude of Effect: A pooled analysis of eight cohort studies estimated an adjusted relative risk (RR) of 1.41 (95% confidence interval [CI], 1.16-1.72) for consumption exceeding 45 g/day.

Study Design: Cohort studies.
Internal Validity: Fair.
Consistency: Fair.
External Validity: Fair.

Cigarette smoking

Based on solid evidence, cigarette smoking is associated with increased incidence and mortality from CRC.

Magnitude of Effect: A pooled analysis of 106 observational studies estimated an adjusted RR (current smokers vs. never smokers) for developing CRC of 1.18 (95% CI, 1.11-1.25).

Study Design: One-hundred six observational studies.
Internal Validity: Fair.
Consistency: Good.
External Validity: Good.


Based on solid evidence, obesity is associated with increased incidence and mortality from CRC.

Magnitude of Effect: In one large cohort study, the adjusted RR for developing colon cancer for women with a body mass index of more than 29 was 1.45 (95% CI, 1.02-2.07). A similar increase in CRC mortality was found in another large cohort study.

Study Design: Large cohort studies.
Internal Validity: Fair.
Consistency: Good.
External Validity: Good.

Factors Associated With a Decreased Risk of Colorectal Cancer

Physical activity

Based on solid evidence, regular physical activity is associated with a decreased incidence of CRC.

Magnitude of Effect: A meta-analysis of 52 observational studies found a statistically significant 24% reduction in CRC incidence (RR = 0.76; 95% CI, 0.72-0.81).

Study Design: Cohort studies and meta-analysis.
Internal Validity: Fair.
Consistency: Good.
External Validity: Good.

Interventions Associated With Decreased Risk of Colorectal Cancer

Nonsteroidal anti-inflammatory drugs


There is inadequate evidence that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the risk of CRC. In people without genetic predisposition but with a prior history of a colonic adenoma that had been removed, three randomized controlled trials (RCT) found that celecoxib [9,10] and rofecoxib [11] decrease the incidence of recurrent adenoma, although follow-up was too short to determine whether the incidence of CRC would have been affected.

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