Effect Modification of Vitamin D Supplementation by Histopathological Characteristics on Survival of Patients with Digestive Tract Cancer: Post Hoc Analysis of the AMATERASU Randomized Clinical Trial

This is the authors' abstract. We don't add key points for this paper.

Some coauthors of this study previously performed the AMATERASU randomized, double-blind, placebo-controlled trial of postoperative oral vitamin D supplementation (2,000 IU/day) in 417 patients with stage I to III digestive tract cancer from the esophagus to the rectum who underwent curative surgery (UMIN000001977). We conducted a post-hoc analysis of the AMATERASU trial to explore the effects of modification of vitamin D supplementation by histopathological characteristics on survival. Among patients with poorly differentiated adenocarcinoma, the 5-year relapse-free survival rate of patients supplemented with vitamin D was 91% compared with 63% in the placebo group (hazard ratio [HR], 0.25; 95% confidence interval [CI], 0.08 to 0.78; P = 0.017; P for interaction = 0.023). Similarly, the 5-year overall survival rate was 92% in the vitamin D group compared with 72% in the placebo group (HR, 0.25; 95%CI, 0.07 to 0.94; P = 0.040; P for interaction = 0.012). In contrast, there were no significant effects in other histopathological characteristics between vitamin D and placebo groups. These findings generated the hypothesis that oral vitamin D supplementation may improve both relapse-free survival and overall survival in a subgroup of patients with poorly differentiated adenocarcinoma.