High-dose vitamin D supplementation and prostate cancer progression: a phase II randomised trial in localised prostate cancer cases with intermediate risk of progression (ProsD)

Background: The ProsD trial aimed to determine if oral vitamin D supplementation could prevent prostate cancer (PC) progression in men on active surveillance (AS). Methods: ProsD is a phase-II double-blinded randomized trial of newly diagnosed, low-intermediate risk PC cases, aged between 50 and 80 years and on AS. The intervention was a monthly oral dose of cholecalciferol (50,000IU; Vitamin D) or placebo. Primary and secondary endpoints were active therapy-free (ATFS) and progression-free (PFS) survival, respectively. Blood samples were analysed for vitamin D metabolites and cytokinesis-block micronucleus cytome (CBMN) markers for lymphocytic genome damage. Results: There were 123 randomised participants (81 vitamin D and 42 placebo) included in this analysis. Mean (SD) for age was 66.5 (6.6) years and for 25(OH)D levels were 72.0 (19.9) and 66.4 (18.4) nmol/L at baseline (p = 0.1), and 91.9 (19.9) and 60.4 (24.4) nmol/L at 24 months, in the vitamin D and placebo arms respectively. There were no appreciable differences in ATFS (p_log-rank = 0.44), PFS (p p_log-rank = 0.60) and occurrence of adverse events, in each trial arm. There were declines in some of the lymphocytic CBMN markers in the vitamin D arm. Conclusion: Vitamin D supplementation did not prevent PC progression, although reduced prevalence of CBMN markers may indicate a benefit of vitamin D supplementation. Trial registration: Australia New Zealand Clinical Trials Registry (ACTRN12616001707459).