Effects of High-Dose Vitamin D Supplementation on Phase Angle and Physical Function in Patients with Prostate Cancer on ADT

Purpose Androgen deprivation therapy (ADT) is commonly used to treat patients with advanced prostate cancer but is associated with functional decline. Bioelectrical impedance analysis (BIA)-derived phase angle may reflect frailty and functional decline in cancer patients. High-dose vitamin D supplementation may improve phase angle values and physical function. Methods We conducted an exploratory analysis from a phase II randomized controlled trial investigating the efficacy of high-dose vitamin D supplementation in prostate cancer patients (age >= 60 yrs). Fifty-nine patients were randomized to high-dose vitamin D (600 IU/day plus 50,000 IU/week) or low-dose: RDA for vitamin D (600 IU/day plus placebo weekly) for 24 weeks. Phase angle was measured by BIA. Physical function measures included handgrip strength, 6-minute walk test, Short Performance Physical Battery and leg extension. All testing was completed at baseline, week 12 and week 24. Results Phase angle values were wider over the entire study in the high-dose vitamin D arm indicating healthier muscle cells. The low-dose vitamin D arm had phase angle values consistent with frailty cutoffs in older men (<5.7 degrees). Conclusion Patients in the high-dose vitamin D arm experienced wider phase angle values over the course of the study which may indicate less frailty. ClinicalTrials.gov ID: NCT02064946.