Endocrine Abstracts

Introduction: Adjuvant therapy with aromatase-inhibitors (AIs) increases bone loss and fracture risk. Concomitant antiresorptive treatment is currently recommended. The aim of this study was to evaluate the effects of AIs on bone metabolism and mineral density at 12 and 24 months.

Methods: Among 400 women on AIs who attended our Endocrinology Unit from 2014 to 2016, we retrospectively evaluated those who initially refused antiresorptive and took cholecalciferol supplements only. Laboratory parameters of bone metabolism were assessed before starting AIs, after 12 and 24 months. BMD was measured at baseline and after 24 months.

Results: A total of 54 women were selected. When starting AIs, age was 65±9 years, menopausal age 50±4 years, BMI 26.2±4.1 kg/m². Sixteen had a normal BMD at DXA baseline measurement, 25 were osteopenic and 13 osteoporotic. Twelve months after starting AIs, 15 patients began bisphosphonates (BP), while the remaining 39 continued cholecalciferol supplements only, according to their choice. A BMD loss at both neck (−5.27%) and total hip (−4.24%) was observed in all patients on cholecalciferol supplements alone (P<0,001), while spine BMD decrease (−3.14%) did not reach significance (P=0.053). In the group starting BP at 12 months, 24-month BMD at both neck (−3.59%) and total hip (−3.27%) did not significantly change (P=0.153 and P=0.338), whereas spine BMD showed a significant decrease (−3.50%; P=0.049). Considering the group taking cholecalciferol alone, univariate analysis was performed to evaluate if bone metabolism indexes after 12-month were predictive of BMD decline at 24 months for each DXA site. Percentage spine BMD loss was independently associated with CTX percent variation (P<0.001) and BAP percent variation (P<0.001). Percentage BMD loss at the femoral neck was independently associated with CTX percent variation (P<0.021), PTH and 25OH vitamin D levels (P<0.001 and P=0.002, respectively). Percentage BMD loss at the total hip was independently associated with CTX percent variation (P=0.006), PTH (P<0.001) and 25OH vitamin levels (P=0.002). On a multivariate analysis including spine, neck and total hip BMD along with bone metabolic parameters, only percent CTX change (P<0.001) at 12 months was associated to spine BMD loss at 24 months (P=0.002). Four new morphometric vertebral fractures were observed in the group on cholecalciferol supplements alone. No fractures were reported in the group starting BP 12 months after AIs.

Conclusions: Increase of bone turnover markers 12 months after starting AIs predicts BMD loss. Delayed antiresorptive treatment appears to be only partially effective in preserving BMD.