Participants
digestive tract cancers
Of 417 patients with digestive tract cancers who were randomly assigned to receive vitamin D supplements (251 patients [60.2%]) or placebo (166 patients [39.8%]) and who were followed up for a median (IQR; maximum) period of 3.5 (2.5-5.3; 7.6) years, 392 participants (94.0%) had available serum samples and were eligible for this post hoc analysis. Serum samples were not obtained for 25 patients (6.0%). Details of inclusion and exclusion criteria are described in the original report.