Design and baseline characteristics of participants in a phase III randomized trial of celecoxib and selenium for colorectal adenoma prevention

Abstract

Cyclooxygenase (COX) inhibitors reduce colorectal adenoma recurrence by up to 45% and selenium supplementation may prevent colorectal cancer. Following colonoscopic adenoma resection, 1,600 men and women aged 40-80 years were randomized to celecoxib (400 mg daily), a selective COX-2 inhibitor, and/or selenium (200 µg daily as selenized yeast), or double placebo. The trial was initiated in November, 2001. The primary trial endpoint is adenoma recurrence in each intervention group compared to placebo, as determined by surveillance colonoscopy performed 3-5 years after baseline. Randomization was stratified by use of low-dose aspirin (81 mg) and clinic site. Following reports of cardiovascular toxicity associated with COX-2 inhibitors, the celecoxib arm was discontinued in December, 2004 when 824 participants had been randomized. Accrual continued with randomization to selenium alone or placebo. Randomization of the originally planned cohort (n=1,621) was completed in November, 2008. A further 200 patients with 1+ advanced adenomas (denoting increased risk for colorectal cancer) were accrued to enhance statistical power for determining intervention efficacy in this higher-risk subgroup. Accrual of the total cohort (n=1,824) was completed in January, 2011. Baseline cohort characteristics include: mean age 62.9 years; 65% male; BMI 29.1 ±5.1; 47% taking low-dose aspirin while on trial; 20% with 3+ adenomas; and 38% with advanced adenomas. Intervention effects on adenoma recurrence will be determined, and their modification by genetic background and baseline selenium level. The effect of selenium supplementation on risk for type 2 diabetes will also be reported (Funded by the National Cancer Institute; ClinicalTrials.gov number, NCT00078897.)