Effects of piroxicam on prostaglandin E2 levels in rectal mucosa of adenomatous polyp patients: a randomized phase IIb trial.

Prostaglandin E2 (PGE2) has served as a surrogate end point biomarker in colorectal tumor progression. Colonic mucosa PGE2 levels of patients with colorectal adenomas or carcinomas have been shown to be higher than in control subjects. Our dose-finding study on piroxicam, a nonsteroidal anti-inflammatory drug with chemopreventive effects in preclinical colon carcinoma models, suggested that 7.5 mg/day was well tolerated and associated with significant depression of rectal mucosa PGE2 concentrations in comparison with baseline values. We therefore conducted a randomized Phase IIb cancer prevention clinical trial to investigate the chemopreventive properties of piroxicam in patients with a history of resected colorectal adenomatous polyps. After a 2-month run-in period, 47 participants were randomized to piroxicam at a dose of 7.5 mg/day, and 49 were randomized to a placebo. Rectal biopsy specimens were taken at the initial visit, at 2 months later during the run-in period, and at 6, 12, and 24 months after the start of the interventions. Mean PGE2 concentrations in the rectal mucosa of the piroxicam-treated patients differed significantly between visits (P < 0.001), and the values at the 6-month visit (P < 0.001) and 12-month visit (P = 0.005) differed significantly from the average baseline value. Unfortunately, we observed an incidence of adverse gastrointestinal side effects in patients treated with 7.5 mg/day of piroxicam similar to that seen for arthritis patients treated with 20 mg/day. Consequently, the gastrointestinal toxicities appear to override the potential benefit that piroxicam may offer as a long-term colon cancer chemopreventive agent.