e23106 Background: Androgen deprivation therapy (ADT) is standard treatment for prostate cancer but may cause changes in body composition that lead to decreased physical function. Low vitamin D status is also associated with decreased functionality. The Short Physical Performance Battery (SPPB) is an objective assessment tool for evaluating functionality. The bioelectrical impedance analysis (BIA) is a portable tool for assessing lean mass and phase angle, a measure of nutrition status and frailty in chronic disease. Methods: This was a secondary analysis of a randomized controlled trial to assess the impact of high dose vitamin D in older patients (≥60 yrs) with prostate cancer on ADT. Patients with prostate cancer (N = 59, age 67.6 ± 5.4) with vitamin D insufficiency ( < 32 ng/ml) were randomized to high-dose vitamin D (n = 29, 600 IU/daily plus 50,000 IU/weekly) or low-dose vitamin D (n = 30, 600 IU/daily plus placebo weekly) for 24 weeks. SPPB tests and BIA were assessed at baseline, 12 weeks and 24 weeks. Phase angle values were calculated using atan(reactance/resistance) x (180°/π). A phase angle value < 5.7° is a valid cutoff for frailty in older men. Results: Serum analyses showed compliance with vitamin D intake (25-OH vitamin D change: high vitamin D = +32.0 ng/ml vs low dose RDA vitamin D = +4.3 ng/ml; p < .01). There were no difference at all three assessments for SPPB or lean mass between arms. The high-dose vitamin D group had wider phase angle values at 12 weeks (5.81º vs. 5.32º; p = .018) and 24 weeks (5.89º vs. 5.40º; p = .030). The low-dose group had phase angle values < 5.7º over the course of the study. At baseline, over 18% of patients had phase angle values below the 10th percentile of the general population matched on age and BMI. As vitamin D levels increased throughout the study, fewer patients fell below the 10th percentile. Conclusions: The high-dose vitamin D group maintained wider phase angle values over 24 weeks, while phase angle for the low-dose group decreased from baseline. High-dose vitamin D supplementation may impact factors related to phase angle and frailty in patients receiving ADT. Funding: NCI UGCA189961, R21CA175793, K07CA168911, and GR501293.
A Phase 2 Trial on the Effect of Low-Dose versus High-Dose Vitamin D Supplementation on Bone Mass in Adults with Neurofibromatosis 1 (NF1)