Akutsu T, Okada S, Hirooka S, et al. - Given a potential advantage of vitamin D in a subgroup of patients with digestive tract cancer was shown in the AMATERASU randomized trial of vitamin D3 supplementation (2000 IU/day), researchers performed post hoc analyses of this trial to further know if subgroups stratified by expression levels of p53, vitamin D receptor (VDR), and Ki-67 alter the influence of vitamin D supplementation, with a special focus on relapse-free survival (RFS). They assessed the p53 status of 372 patients' pathological specimens. Among 226 patients with p53-positive cancer, constituting a subgroup, the observed 5-year RFS was 79% vs 57% in the vitamin D group vs in the placebo group. The 5-year RFS in the subgroup of patients with p53-negative cancer was estimated to be 72% vs 84% in the vitamin D group vs placebo group (not significantly different). There was significant effect modification by p53-positivity. However, they found no significant effect alteration by either VDR or Ki-67. Based on these findings, experts proposed a hypothesis that improved RFS may be achieved with vitamin D supplementation in patients with p53-positive digestive tract cancer.