Use of Nonsteroidal Anti-Inflammatory Drugs
        Benefits
        Harms
Postmenopausal Hormone Use
        Benefits
        Harms
Polyp Removal
        Benefits
        Harms
Diet Modification
        Benefits
        Harms

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

There is inadequate evidence that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) reduces the risk of colorectal cancer (CRC). Celecoxib decreases the adenoma burden and may be a useful adjunct in reducing CRC risk associated with adenomatous polyposis of the colon. However, celecoxib does not have a role in reducing the risk of sporadic CRC because its long-term efficacy in preventing CRC has not been shown due to attributed increased risk of cardiovascular events and because there are other effective ways, such as screening, to reduce CRC mortality.[1] Based on solid evidence, NSAIDs reduce the risk of adenomas, but the extent to which this translates into a reduction of CRC is uncertain.

Description of the Evidence

• Study Design: No adequate studies.
• Internal Validity: N/A.
• Consistency: N/A.
• Magnitude of Effects of Health Outcomes: N/A.
• External Validity: N/A.

Based on solid evidence, harms of NSAID use include upper gastrointestinal bleeding and serious cardiovascular events such as myocardial infarction, heart failure, and hemorrhagic stroke.[2].

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: The estimated average excess risk of upper gastrointestinal complications attributable to chronic low-dose aspirin is about five extra cases per 1,000 aspirin users per year. The excess risk varies with the underlying gastrointestinal risk, however, it might exceed ten extra cases per 1,000 person-years in more than 10% of aspirin users.[3]
• External Validity: Good.

Based on solid evidence, postmenopausal estrogen plus progesterone hormone use decreases the incidence of CRC, but this benefit is not applicable to estrogen alone use.[4]

Description of the Evidence

• Study Design: Evidence obtained from a randomized controlled trial and meta-analysis of 18 obeservational studies.
• Internal Validity: Good.
• Consistency: One randomized study and a meta-analysis.
• Magnitude of Effects on Health Outcomes: In the Women's Health Initiative (WHI), there was a 44% reduction in CRC incidence in the estrogen and progesterone group but not in the estrogen-only group. A meta-analysis of 18 observational studies showed a 20% reduction in colon cancer incidence among women who had ever used hormone replacement therapy (relative risk [RR] = 0.80; 95% confidence interval [CI], 0.74–0.86) compared with nonusers and a 34% reduction among current users (RR = 0.66; 95% CI, 0.59–0.74).[4,5]
• External Validity: Good.

Based on solid evidence, harms of postmenopausal combined estrogen plus progestin hormone use include increased risk of breast cancer, coronary heart disease, and thromboembolic events.

Description of the Evidence

• Study Design: Evidence from randomized controlled trials.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: The WHI showed a 26% increase in invasive breast cancer in the combined hormone group, a 29% increase in coronary heart disease events, a 41% increase in stroke rates, and a twofold higher rate of thromboembolic events.[6]
• External Validity: Fair.

Based on fair evidence, removal of adenomatous polyps reduces the risk of CRC.

Description of the Evidence

• Study Design: Evidence obtained from cohort studies.
• Internal Validity: Good.
• Consistency: N/A.
• Magnitude of Effects on Health Outcomes: Unknown.[7]
• External Validity: Good.

Based on solid evidence, harms of polyp removal include infrequent perforation of the colon during the procedure as well as bleeding and infection following the procedure.

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials and cohort studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: 35 events per 10,000 procedures.[8]
• External Validity: Good.

A Diet Low in Fat and High in Fiber, Fruits, and Vegetables

There is inadequate evidence to suggest that a diet low in fat and high in fiber, fruits, and vegetables decreases the risk of CRC. However, these studies were powered to detect differences in adenoma incidence and not cancer incidence.

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials.
• Internal Validity: Fair.
• Consistency: N/A.
• Magnitude of Effects on Health Outcomes: N/A.
• External Validity: N/A.

There are no known harms from dietary modification, including reduction of fatty acids and increase in the intake of fiber, fruits, and vegetables.

Description of the Evidence

• Study Design: Multiple types.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: None known.
• External Validity: Good.

References

1. Arber N, Eagle CJ, Spicak J, et al.: Celecoxib for the prevention of colorectal adenomatous polyps. N Engl J Med 355 (9): 885-95, 2006.  [PUBMED Abstract]
   
   
2. Solomon SD, Pfeffer MA, McMurray JJ, et al.: Effect of celecoxib on cardiovascular events and blood pressure in two trials for the prevention of colorectal adenomas. Circulation 114 (10): 1028-35, 2006.  [PUBMED Abstract]
   
   
3. Hernández-Díaz S, García Rodríguez LA: Cardioprotective aspirin users and their excess risk of upper gastrointestinal complications. BMC Med 4: 22, 2006.  [PUBMED Abstract]
   
   
4. Chlebowski RT, Wactawski-Wende J, Ritenbaugh C, et al.: Estrogen plus progestin and colorectal cancer in postmenopausal women. N Engl J Med 350 (10): 991-1004, 2004.  [PUBMED Abstract]
   
   
5. Nelson HD, Humphrey LL, Nygren P, et al.: Postmenopausal hormone replacement therapy: scientific review. JAMA 288 (7): 872-81, 2002.  [PUBMED Abstract]
   
   
6. Writing Group for the Women's Health Initiative Investigators.: Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women's Health Initiative randomized controlled trial. JAMA 288 (3): 321-33, 2002.  [PUBMED Abstract]
   
   
7. Robertson DJ, Greenberg ER, Beach M, et al.: Colorectal cancer in patients under close colonoscopic surveillance. Gastroenterology 129 (1): 34-41, 2005.  [PUBMED Abstract]
   
   
8. Nelson DB, McQuaid KR, Bond JH, et al.: Procedural success and complications of large-scale screening colonoscopy. Gastrointest Endosc 55 (3): 307-14, 2002.  [PUBMED Abstract]
   
   

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