Scragg R, et al. - Researchers investigated a possible association between high-dose vitamin D supplementation received monthly, without calcium, and cancer incidence and mortality in the general population. According to findings, high-dose vitamin D supplementation prescribed monthly for up to 4 years without calcium may not protect against the development of cancer.

Methods

• In this post hoc analysis including adult community residents aged 50 to 84 years, researchers used data from the Vitamin D Assessment (ViDA) study, a randomized, double-blind, placebo-controlled trial that recruited participants from family practices and community groups in Auckland, New Zealand, from April 5, 2011 through November 6, 2012, with follow-up completed December 31, 2015.
• Of 47,905 adults invited from family practices and 163 from community groups, randomization of 5110 participants to vitamin D₃ (n = 2558) or placebo (n = 2552) was carried out.
• Consent was withdrawn by two participants, and primary analysis was performed including all others (n = 5,108).
• Data analysis was by intention to treat.
• They implemented the intervention that involved administration of oral vitamin D₃, in an initial bolus dose of 200,000 IU, followed by monthly doses of 100,000 IU or placebo for a median of 3.3 years (range, 2.5-4.2 years).
• The number of all primary invasive and in situ malignant neoplasms (excluding nonmelanoma skin cancers) diagnosed from randomization until study medication was discontinued on July 31, 2015 was included as post hoc primary outcome.

Results

• A total of 5,108 participants were included in the analysis.
• The participants were of mean (SD) age 65.9 (8.3) years, 58.1% were male, and 4,253 (83.3%) were of European or another race/ethnicity, with the remainder being Polynesian or South Asian.
• As per data, mean (SD) baseline deseasonalized 25-hydroxyvitamin D concentration was 26.5 (9.0) ng/mL.
• In a random sample of 438 participants, the vitamin D group vs the placebo group had the mean follow-up 25-hydroxyvitamin D concentration consistently greater than 20 ng/mL higher.
• Findings revealed that the primary outcome of cancer included 328 total cases of cancer (259 invasive and 69 in situ malignant neoplasms).
• The occurrence of the primary outcome of cancer was observed in 165 of 2,558 participants (6.5%) in the vitamin D group and 163 of 2550 (6.4%) in the placebo group, yielding an adjusted hazard ratio of 1.01 (95% CI, 0.81-1.25; P=.95).