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

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Magnitude of Effect: The estimated average excess risk of upper gastrointestinal complications in average-risk people attributable to NSAIDs is 4/1,000 to 5/1,000 people per year. The excess risk varies with the underlying gastrointestinal risk, however, it likely exceeds ten extra cases per 1,000 people per year in more than 10% of users. Serious cardiovascular events are increased by 50% to 60%.

Study Design: Evidence obtained from RCTs and high quality systematic reviews and meta-analyses.[13,14]
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Aspirin

Benefits

Based on solid evidence, daily aspirin (acetylsalicylic acid [ASA]) for at least 5 years reduces CRC incidence and mortality. This is based on two reports of extended follow-up of two RCTs [16,17] and meta-analysis of observational studies.[16] A third report that adds extended follow-up of an additional two RCTs (with a meta-analysis of all four RCTs) adds certainty to this conclusion.[18]

Magnitude of Effect: After 23 years of follow-up, incidence of CRC in the placebo group was 3.8% and in the ASA group 2.5% (hazard ratio [HR] = 0.63; 95% CI, 0.47–0.85). In the report from all four RCTs, the 20-year risk of death due to CRC in trials that allocated ASA for at least 5 years was reduced by about 40% (HR = 0.60; 95% CI, 0.45–0.81), absolute risk reduction was from about 3.1% to 1.9%. The primary effect was on mortality from proximal colon cancer.

Study Design: Extended follow-up of four RCTs.
Internal Validity: Fair, some data from registries and death certificates, some loss to follow-up; variation in ASA dose; adherence to ASA unknown after end of trials (5–9 years).
Consistency: Consistent.
External Validity: Fair, most data from British men; fewer data from women.

Harms

Based on solid evidence, harms of ASA use include excessive bleeding, including gastrointestinal bleeds and hemorrhagic stroke.

Magnitude of Effect: The estimated average excess risk of upper gastrointestinal complications is 10 to 30 per 1,000 people for a period of 10 years, on the higher end for men and on the lower end for women. Risk increases with age.

Study Design: Evidence obtained from large databases.[15,20]
Internal Validity: Good.
Consistency: Good.
External Validity: Good, data from national databases.

Postmenopausal hormones

Benefits

Based on solid evidence, postmenopausal estrogen plus progesterone hormone use, but not estrogen alone, decreases the incidence of CRC.[21]

Magnitude of Effect: 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. The absolute reduction in the incidence of CRC was 0.6 cancers per 1,000 women, from 1.6 cancers per 1,000 women to 1.0 cancer per 1,000 women. A meta-analysis of 18 observational studies showed a 20% reduction in colon cancer incidence among women who had ever used hormone therapy (RR = 0.80; 95% CI, 0.74–0.86) compared with nonusers and a 34% reduction among current users (RR = 0.66; 95% CI, 0.59–0.74).

Study Design: Evidence obtained from a RCT and meta-analysis of 18 observational studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.
1|2|3|4

WebMD Public Information from the National Cancer Institute

Last Updated: February 25, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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