2.1. Trial Design
digestive tract cancer
This post hoc analysis was conducted using data from the AMATERASU trial (Trial Registration Identifier: UMIN000001977), which was performed in Japan from January 2010 to February 2018. Detailed information about the trial has been previously published [Patients who underwent surgical treatment for digestive tract cancer anywhere from the esophagus to the rectum at the International University of Health and Welfare Hospital were randomized to receive vitamin D supplementation or placebo during their first postoperative outpatient visit, which typically occurred between 2 and 4 weeks after the operation.The trial protocol received approval from the ethics committee of the International University of Health and Welfare Hospital (Otawara, Tochigi, Japan) on 4 December 2009 (code: 13-B-263), as well as from the Jikei University School of Medicine (Nishi-shimbashi, Tokyo, Japan) on 1 January 2010 (code: 21-216 [6094]). Written informed consent was obtained from each participating patient before surgery.