No Evidence for Post-Treatment Effects of Vitamin D and Calcium Supplementation on Risk of Colorectal Adenomas in a Randomized Trial
Mené sur 1 121 patients bénéficiant d'une surveillance médicale par coloscopie (durée moyenne de suivi post-traitement : 55 mois), cet essai randomisé met en évidence l'absence d'effet d'une supplémentation en calcium et/ou en vitamine D sur le risque d'adénome colorectal
Vitamin D and calcium supplementation are postulated to have chemopreventive effects against colorectal neoplasia, yet in our previously-reported randomized trial, there was no overall efficacy of calcium and/or vitamin D3 against colorectal adenoma recurrence. It is possible vitamin D3 and calcium chemopreventive effects are not detectable until beyond the 3-5 year follow-up captured in that trial. Accordingly, we explored possible vitamin D and calcium effects on post-treatment (observational) adenoma occurrence. In this secondary analysis of the observational follow-up phase of the Vitamin D/Calcium Polyp Prevention Study, participants who completed the treatment phase were invited to be followed for one additional surveillance colonoscopy cycle. We evaluated adenoma occurrence risk at surveillance colonoscopy, with a mean of 55 ± 15 months post-treatment follow-up, according to randomized treatment with vitamin D vs. no vitamin D, calcium vs. no calcium, and calcium plus vitamin D vs. calcium alone. Secondary outcomes included advanced and multiple adenomas. Among the 1121 participants with observational follow-up, the relative risk (95% confidence interval, CI) of any adenoma was 1.04 (0.93-1.17) for vitamin D vs. no vitamin D; 0.95 (0.84-1.08) for calcium vs. no calcium; 1.07 (0.91-1.25) for calcium plus vitamin D vs. calcium; and 0.96 (0.81-1.15) for calcium plus vitamin D vs. neither. Risks of advanced or multiple adenomas also did not differ by treatment. Our results do not support an association between supplemental calcium and/or vitamin D3 for 3-5 years and risk of recurrent colorectal adenoma at an average of 4.6 years post-treatment.