Effect of Vitamin D Supplements on Relapse or Death in a p53-Immunoreactive Subgroup With Digestive Tract Cancer: Post Hoc Analysis of the AMATERASU Randomized Clinical Trial

Abstract

Importance: Recent meta-analyses of randomized clinical trials found that daily vitamin D3 supplementation had beneficial effects on cancer mortality, although the results are still controversial.

Objective: To examine whether vitamin D supplementation reduces the risk of relapse or death in a supgroup of patients with digestive tract cancer who were p53 immunoreactive.

Design, setting, and participants: This was a post hoc subgroup analysis of the AMATERASU randomized, double-blind, placebo-controlled clinical trial. This trial included patients at a single university hospital in Japan with digestive tract cancers between January 2010 and February 2018 followed up for a median (IQR) of 3.5 (2.5-5.3) years to compare the effects of vitamin D supplementation with placebo and was reported in 2019. Patients from among 417 participants in the AMATERASU trial whose residual serum samples were available were included. Data were analyzed from October 20 to November 24, 2022.

Interventions: Vitamin D3 (2000 IU/d) supplementation or placebo.

Main outcomes and measures: The primary outcome was 5-year relapse or death. The subgroup of patients who were p53 immunoreactive was defined by positivity for anti-p53 antibodies in serum and nuclear accumulation of p53 oncosuppressor protein in more than 99% of cancer cells, which is considered a biomarker for p53 missense mutations. Anti-p53 antibody levels were measured using chemiluminescent enzyme immune assay. Immunohistochemical staining data of p53 protein in cancer tissue in pathologic specimens were obtained from a previous study and divided into 4 grades.

Results: Among 392 patients with digestive tract cancer (mean [SD] age, 66 [10.7] years; 260 males [66.3%]), there were 37 patients with esophageal cancer (9.4%), 170 patients with gastric cancer (43.4%), 2 patients with small bowel cancer (0.5%), and 183 patients with colorectal cancer (46.7%). Serum anti-p53 antibody was detectable in 142 patients (36.2%), and p53-immunohistochemistry grade showed a positive association with serum anti-p53 antibody levels (coefficient = 0.19; P < .001). In the p53-immunoreactive subgroup (80 patients), relapse or death occurred in 9 of 54 patients (16.7%) in the vitamin D group and 14 of 26 patients (53.8%) in the placebo group; 5-year relapse-free survival (RFS) was significantly higher in the vitamin D group (13 patients [80.9%]) than the placebo group (1 patient [30.6%]; hazard ratio [HR], 0.27; 95% CI, 0.11-0.61; P = .002). This was significantly different from 272 patients in the non-p53 immunoreactive subgroup, in which vitamin D had no effect on 5-year RFS (vitamin D: 35 of 158 patients [22.2%] vs placebo: 24 of 114 patients [21.1%]; HR, 1.09; 95% CI, 0.65-1.84) (P for interaction = .005).

Conclusions and relevance: This study found that vitamin D supplementation reduced the risk of relapse or death in the subgroup of patients with digestive tract cancer who were p53 immunoreactive.

Trial registration: Identifier: UMIN000001977.

Figure 1.. Study Flowchart

Figure 2.. Subgroup Analysis of Patients With and Without Serum Anti-p53 Antibody (p53-Ab)

Nelson-Aalen cumulative hazard curves for relapse or death in p53-Ab (+) and p53-Ab (−) groups, assessing patients taking vitamin D vs those taking placebo, were compared using hazard ratios and 95% CIs.

Figure 3.. Serum Anti-p53 Antibody (p53-Ab) Levels by p53 Immunohistochemistry (IHC) Protein Expression

IHC levels were 0 (<1% strong or faint p53 cells in cancerous region; p53-IHC [0]), 1 (1%-10% strong p53 cells in cancerous region; p53 IHC [1+]), 2 (>10%-99% strong p53 cells in cancerous region; p53 IHC [2+]), and 3 (>99% overexpressed p53 cells in cancerous region; p53 IHC [3+]).

Figure 4.. Analysis of p53-Immunoreactive Subgroup

IHC indicates immunohistochemistry; p53-Ab, anti-p53 antibody. Nelson-Aalen cumulative hazard curves are presented in the p53-Ab (+) and p53-IHC (3+) subgroup, p53-Ab (−) or p53-IHC (2+, 1+, or 0) subgroup, p53-Ab (+) and p53-IHC-positive subgroup, and p53-Ab (−) or p53-IHC-negative subgroup. Hazard curves for relapse or death in patients taking vitamin D were compared with those taking placebo.