Vitamin D deficiency and bone mineral density in postmenopausal women receiving aromatase inhibitors for early breast cancer

Abstract

Objective: Aromatase inhibitors (AI) treatment leads to an increased risk of bone loss and fractures. In a group of women with early breast cancer (EBC) and baseline Vitamin D deficiency (<30 ng/ml) who are treated with AI, we aim to describe: serum levels of Vitamin D, bone mineral density (BMD), calcium intake, and the increase of serum 25(OH)D accomplished in 3 months of treatment with Vitamin D supplements.

Study design: Prospective, non-randomized clinical trial.

Methods: In 232 consecutively included women with EBC in treatment with AI, we assessed baseline calcium intake, serum levels of 25(OH)D, BMD and, spine X-ray. All received Calcium and Vitamin D supplements, and those with vitamin deficiency received 16,000 IU Vitamin D every 2 weeks. Serum levels of 25(OH)D were newly assessed after treatment. All the baseline evaluation was performed before starting AI treatment.

Results: Mean age at baseline (+/-SD) was 63.2+/-8.8 years. In 150 (64.9%) cases, the women had been treated previously with tamoxifen; 101 (43.7%) started exemestane, 119 (51.5%) letrozole, and 11 (4.8%) anastrozole. The AI were initiated within 6 weeks after surgery or after the last cycle of chemotherapy. At baseline, 88.1% had 25(OH)D levels <30 ng/ml, 21.2% had severe deficiency (<10 ng/ml), and 25% of the participants had osteoporosis. Mean daily calcium intake was low (841+/-338). We found a significant association between 25(OH)D levels and BMD at baseline, which remained significant in femoral neck BMD after multivariate adjustment. Plasma 25(OH)D levels improved significantly at 3 months follow-up in those treated with high dose Vitamin D supplements: mean increase 32.55 ng/ml (95%CI 28.06-37.03).

Conclusions: Our study suggests a high prevalence of commonly unrecognized Vitamin D deficiency in women with EBC treated with AI, a known osteopenic agent. Our results support the need for a routine assessment of 25(OH)D levels and, when necessary, supplementation in these patients.