Vitamin D and calcium supplementation and one-year change in mammographic density in the Women's Health Initiative Calcium and Vitamin D Trial
Menée sur 330 femmes ménopausées, cette étude randomisée évalue l'effet d'une supplémentation en calcium et vitamine D pendant un an sur la densité mammaire
Background: Calcium and vitamin D may be inversely related to breast cancer risk, in part by affecting mammographic density. However, results from previous, mostly cross-sectional studies have been mixed, and there have been few randomized clinical trials of the effect of calcium and vitamin D supplementation on change in mammographic density. Methods: We assessed the effect of one year of supplementation on mammographic density in 330 postmenopausal women enrolled in the Women's Health Initiative Hormone Therapy (HT) and Calcium and Vitamin D (CaD) trials. Women were randomized to receive 1000 mg/day of elemental calcium carbonate plus 400 IU/day of vitamin D3 or placebo. Results: After approximately one year, mammographic density decreased 2% in the CaD supplementation group and increased 1% in the placebo group (ratio of means = 0.97; 95% confidence interval (CI) = 0.81-1.17). Results suggested potential interaction by HT use (P = 0.08). Among women randomized to HT placebo, the ratio of mean density comparing CaD supplementation and placebo groups was 0.82 (95%CI = 0.61-1.11) vs. 1.16 (95%CI = 0.92-1.45) in women randomized to active HT. In sensitivity analyses limited to women taking ≥80% of study supplements, ratios were 0.67 (95%CI = 0.41-1.07) in women not assigned to HT and 1.07 (95%CI = 0.79-1.47) women assigned to HT. Conclusions: We observed no overall effect of vitamin D and calcium supplementation on mammographic density after one year. Impact: Potential interaction between these nutrients and estrogen as related to mammographic density warrants further study.