A separate study in digestive tract cancer found that vitamin D supplementation (2,000 units per day) did not result in significant improvement in relapse free survival at 5 years vs placebo (77% vs 69%, HR for relapse or death = 0.76, 95% CI 0.50-1.14).
A related commentary discusses this research. It may be tempting to interpret the preliminary findings regarding recurrence- and progression-free survival as specific antineoplastic effects of vitamin D3 supplementation. However, higher vitamin D levels have been associated with substantially decreased mortality and morbidity among hospitalised patients with a range of non-neoplastic diseases as well as with cancer. These new studies provide new information regarding the potential use of vitamin D among patients with colorectal cancer and other luminal gastrointestinal malignancies. New research is however needed to ideally with longer follow-up to obtain better estimates of effects on potential survival as well as biological measurements to clarify any underlying mechanisms.