Interventions associated with a decreased risk of colorectal cancer: Benefits and harms
Nonsteroidal anti-inflammatory drugs
One large cohort study (301,240 people with 3,894 colorectal cancer cases) found an association between daily or weekly nonaspirin (non-acetylsalicylic acid [non-ASA]) nonsteroidal anti-inflammatory drug (NSAID) use and reduced 10-year incidence of proximal and distal colon cancer, but not rectal cancer, with a hazard ratio (HR) of 0.67 (95% CI, 0.58-0.77) for daily use for colon cancer. Because exposure to non-ASA NSAIDs was assessed only once, assessment was by self-report, and there is no information on dose or duration of use, the certainty of this single study must be rated low. Further research is needed before this finding can be accepted.
Although evidence is currently inadequate to determine whether NSAIDs reduce CRC incidence, proponents suggest that any effect of these drugs results from their ability to inhibit the activity of cyclooxygenase (COX). COX is important in the transformation of arachidonic acid into prostanoids, prostaglandins, and thromboxane A2. NSAIDs include not only aspirin (ASA, which is considered separately here) and other, first-generation nonselective inhibitors of the two functional isoforms of COX, termed COX-1 and COX-2, but also newer second-generation drugs that inhibit primarily COX-2. Normally, COX-1 is expressed in most tissues and primarily plays a housekeeping role (e.g., gastrointestinal mucosal protection and platelet aggregation). COX-2 activity is crucial in stress responses and in mediating and propagating the pain and inflammation that are characteristic of arthritis.
Nonselective COX inhibitors include indomethacin (Indocin); sulindac (Clinoril); piroxicam (Feldene); diflunisal (Dolobid); ibuprofen (Advil, Motrin); ketoprofen (Orudis); naproxen (Naprosyn); and naproxen sodium (Aleve, Anaprox). Selective COX-2 inhibitors include celecoxib (Celebrex), rofecoxib (Vioxx), and valdecoxib (Bextra). Rofecoxib and valdecoxib are no longer marketed because of an associated increased risk of serious cardiovascular events.
Both celecoxib and rofecoxib have been associated with serious cardiovascular events including dose-related death from cardiovascular causes, myocardial infarction, stroke, or heart failure.[39,40,41,42] Four trials that demonstrated this increased risk are summarized in the Table. In addition, a network meta-analysis of all large scale randomized, controlled trials (RCTs) comparing any NSAID to any other NSAID or placebo found that there is little evidence to suggest that any of the investigated drugs are safe in terms of cardiovascular effects. Naproxen seemed least harmful.