Effect of Vitamin D and Calcium Supplementation on Cancer Incidence in Postmenopausal Women
In a population-based trial reported in JAMA, Lappe et al found that dietary supplementation with vitamin D3 and calcium did not significantly reduce the incidence of all cancers over 4 years among postmenopausal women aged ≥ 55 years.
Study Details
In the double-blind trial, 2,303 healthy women from 31 rural Nebraska counties were randomized beginning in June 2009 to receive 2,000 IU/d of vitamin D3 and 1,500 mg/d of calcium (n = 1,156) or matching placebos (n = 1,147) for 4 years. The final date of follow-up was in August 2015. The primary outcome measure was the incidence of all-type cancer, excluding nonmelanoma skin cancer. Subjects had a mean age of 65.2 years, > 99% were white, and mean baseline serum 25-hydroxyvitamin D (vitamin D) level was 32.8 ng/mL.
Cancer Incidence
At year 1, vitamin D levels were 43.9 ng/mL in the intervention group and 31.6 ng/mL in the placebo group. On intent-to-treat analysis, a new diagnosis of cancer was made in 45 participants (3.89%) in the intervention group vs 64 (5.58%) in the placebo group (difference = 1.69%, P = .06). Kaplan-Meier incidence over 4 years was 0.042 (95% confidence interval [CI] = 0.032–0.056) in the intervention group vs 0.060 (95% CI = 0.048–0.076) in the placebo group (P = .06). In unadjusted Cox proportional hazards regression analysis, the hazard ratio (HR) was 0.70 (95% CI = 0.47–1.02). In proportional hazards modeling, age at baseline was significantly associated with cancer incidence (HR = 1.05), and use of estrogen agonists and antagonists during the study was significantly more common in the placebo group. With adjustment for age, the hazard ratio was 0.70 (95% CI = 0.48–1.02); with adjustment for estrogen agonist and antagonist use, the hazard ratio was 0.70 (95% CI = 0.47–1.02). Breast cancer was the most common cancer, occurring in 19 participants in the intervention group and 24 patients in the placebo group (difference in proportion = 0.005, 95% CI = −0.007 to 0.016).
Adverse Events
Renal calculi were reported by 16 participants (1.4%) in the intervention group and 10 patients (0.9%) in the placebo group. Serum calcium levels above normal were observed in 6 vs 2 patients.
The investigators concluded: “Among healthy postmenopausal older women with a mean baseline serum 25-hydroxyvitamin D level of 32.8 ng/mL, supplementation with vitamin D3 and calcium compared with placebo did not result in a significantly lower risk of all-type cancer at 4 years. Further research is necessary to assess the possible role of vitamin D in cancer prevention.”
The study was funded by the National Cancer Institute and Creighton University.
Joan Lappe, PhD, RN, of Creighton University College of Nursing and Creighton University School of Medicine, is the corresponding author of the JAMA article.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
