Vitamin D Receptor Genotype, Vitamin D3 Supplementation, and Risk of Colorectal Adenomas: A Randomized Clinical Trial.

TLDR: It is suggested that benefits from vitamin D3 supplementation for the prevention of advanced colorectal adenomas may vary according to vitamin D receptor genotype, and the effect of vitamin D2 supplementation on advanced adenoma risk overall, significantly varied according to genotype at 2 VDR SNPs.

Abstract: Importance Despite epidemiological and preclinical evidence suggesting that vitamin D and calcium inhibit colorectal carcinogenesis, daily supplementation with these nutrients for 3 to 5 years was not found to significantly reduce the risk of recurrent colorectal adenomas in a recent randomized clinical trial. Objective To investigate whether common variants in 7 vitamin D and calcium pathway genes (VDR,GC,DHCR7,CYP2R1,CYP27B1,CYP24A1, andCASR) modify the effects of vitamin D3or calcium supplementation on colorectal adenoma recurrence. Design, Setting, and Participants We examined 41 candidate single-nucleotide polymorphisms (SNPs) in 2259 participants in a randomized, double-blind, placebo-controlled trial conducted at 11 clinical centers in the United States. Eligibility criteria included a recently diagnosed adenoma and no remaining colorectal polyps after complete colonoscopy. The study’s treatment phase ended on August 31, 2013, and the analysis for the present study took place from July 28, 2014, to October 19, 2016. Interventions Daily oral supplementation with vitamin D3(1000 IU) or calcium carbonate (1200 mg elemental calcium) or both or neither. Main Outcomes and Measures The outcomes assessed were the occurrence of 1 or more adenomas or advanced adenomas (estimated diameter, ≥1 cm; or with villous histologic findings, high-grade dysplasia, or cancer) during follow-up. Treatment effects and genotype associations and interactions were estimated as adjusted risk ratios (RRs) and 95% confidence intervals (CIs). The effective number of independent SNPs was calculated to correct for multiple testing. Results Among the 2259 participants randomized, 1702 were non-Hispanic whites who completed the trial and had genotype data for analysis (1101 men; mean [SD] age 58.1 [6.8] years). The effect of vitamin D3supplementation on advanced adenomas, but not on adenoma risk overall, significantly varied according to genotype at 2VDRSNPs (rs7968585andrs731236) in linkage disequilibrium (D′ = 0.98;r2 = 0.6). Forrs7968585, among individuals with the AA genotype (26%), vitamin D3supplementation reduced risk by 64% (RR, 0.36; 95% CI, 0.19-0.69;P = .002; absolute risk decreased from 14.4% to 5.1%). Among individuals with 1 or 2 G alleles (74%), vitamin D3supplementation increased risk by 41% (RR, 1.41; 95% CI, 0.99-2.00;P = .05; absolute risk increased from 7.7% to 11.1%;P  Conclusions and Relevance Our findings suggest that benefits from vitamin D3supplementation for the prevention of advanced colorectal adenomas may vary according to vitamin D receptor genotype. Trial Registration clinicaltrials.gov Identifier:NCT00153816