A separate study in colorectal cancer found that found that high dose vitamin D (4,000 units/day) did not improve PFS vs standard dose vitamin D (400 units/day) (13.0 vs 11.0 months, p=0.07), however a supportive statistical analysis of the data was statistically significant (HR for PFS or death 0.64, p=0.02).
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.