ASPO Abstracts
Risk of keratinocyte carcinomas in a randomized clinical trial of vitamin D and calcium for the prevention of colorectal adenomas
Category: Lifestyles Behavior, Energy Balance & Chemoprevention
Conference Year: 2019
Abstract Body:
Purpose: Observational studies linking blood levels of 25-hydroxyvitamin D to keratinocyte carcinoma (KC) risk have been inconsistent, and often suffer from confounding because ultraviolet radiation is both the primary risk factor for KC and involved in the production of vitamin D in skin. A large clinical trial of daily supplementation with 400 IU vitamin D3 and 1,000 mg calcium for the prevention of hip fracture in postmenopausal women found no treatment effect in a secondary analysis of KC without considering subtype.Methods: We evaluated the incidence of KC (basal cell carcinoma, BCC, and cutaneous squamous cell carcinoma, SCC) in the Vitamin D/Calcium Polyp Prevention Study, a multicenter, randomized, double-blind, placebo-controlled, partial 2x2 factorial clinical trial of vitamin D, calcium, or both for the prevention of colorectal adenomas. Between 2004-2008, a total of 2,259 men and women, 45-75 years of age, recently diagnosed with a colorectal adenoma, were randomized to 1,000 IU of vitamin D3 daily and/or 1,200 mg of calcium carbonate daily. Women could elect to receive calcium and be randomized only to vitamin D. Treatment continued until a 3- or 5-year surveillance colonoscopy. Self-reported KC diagnoses were ascertained every 6 months during treatment and annually afterwards. Pathology reports were obtained for 94% of self-reported KC diagnoses, and a centralized, blinded review verified lesion histology and diagnosis date. Treatment effects were estimated using proportional hazards regression.Results: During a median follow-up of 8.3 years, 200 (8.9%) participants developed BCC and 68 (3.0%) participants developed SCC. BCC occurrence was unrelated to treatment (hazard ratio, HR [95% confidence interval], for vitamin D versus no vitamin D = 0.96 [0.73-1.26]; HR for calcium versus no calcium = 1.01 [0.74-1.39]; and HR for both versus neither = 0.99 [0.65-1.51]). There was suggestive evidence of treatment effects for SCC (HR for vitamin D versus no vitamin D = 0.79 [0.49-1.27]; HR for calcium versus no calcium = 0.60 [0.36-1.00]; and HR for both versus neither = 0.42 [0.19-0.92]).Conclusions: This secondary analysis of a randomized clinical trial suggests vitamin D and calcium supplementation reduces the incidence of SCC, but not BCC.
Keywords: vitamin D, calcium, skin cancer