Eldecalcitol Add-on to Risedronate Reduces Bone Loss From Aromatase Inhibitors in Postmenopausal Breast Cancer Patients.

Abstract

Aromatase inhibitors (AIs) cause bone loss and increase fracture risk in women with hormone receptor-positive early-stage breast cancer (HR + EBC). Bone antiresorptive agents are recommended for patients at risk of fragility fractures. Eldecalcitol, combined with bisphosphonate, increases bone mineral density (BMD) in primary osteoporosis. To determine the effect of eldecalcitol (0.75 ug/day) add-on therapy to risedronate (17.5 mg/week) on bone quantity and quality in women treated with AI. Open-label randomized control trial. Postmenopausal women with HR + EBC (TNM stage 0-3A) treated with risedronate for more than 12 months. Two hundred patients were enrolled; 196 patients were eligible for the full analysis set after excluding those without follow-up BMD data. Participants were advised to take vitamin D and calcium, yet many were vitamin D deficient or insufficient. Participants were randomly assigned in a 1:1 ratio to receive either eldecalcitol add-on therapy or risedronate monotherapy. The primary outcome was the group difference in the change of lumbar spine (LS)-BMD in 24 months. Secondary outcomes included femoral neck (FN)-BMD, total hip (TH)-BMD, trabecular bone score (TBS), and the incidence of vertebral and nonvertebral fractures. The increase at LS-, FN-, and TH-BMD at 24 months was larger in the add-on therapy group than in the monotherapy group, with a group difference (add-on therapy minus monotherapy) estimate of 0.020 g/cm2 [95% confidence interval (CI): 0.010-0.029 g/cm2, P < .001] for LS-BMD. The incidence rate ratio (add-on therapy/monotherapy) for morphometric vertebral fractures was 0.292 (95% CI: 0.080-1.061, P = .061). No group difference was detected in the change in TBS. Eldecalcitol add-on therapy increased LS-BMD in osteopenic to osteoporotic postmenopausal women treated with an AI and risedronate.