The effect of aromatase inhibitors on bone mineral density measured by serial DXA scans

Abstract

11065 Background: We are now using aromatase inhibitors (AI) in increasing numbers of women as treatment in the breast cancer care pathway. Studies have reported a loss of bone mineral density (BMD) with use of all AIs. It has been shown in our unit that 5 years of tamoxifen (T) in post-menopausal women prior to commencing an AI does not offer sufficient protection to prevent significant BMD loss when an AI is introduced, with 25% requiring concurrent bisphosphonate (BP) therapy. The aim of this study was to determine changes in serial DXA scan results over a 12month period in women taking AIs. Method: 62 women being considered for or in early stages of use of an AI attended for a DXA scan and re-scan at 12 months. Vertebral morphometry and fracture rate were assessed and risk factors for osteoporosis noted. Scan results were compared ( Table 1 ). Results: Mean age was 67yrs [standard deviation (SD) 9yrs]. The patients were grouped according to initial endocrine therapy. 13 (21%) switched from tamoxifen to arimidex after 2years, 3 (4.8%) switched from tamoxifen to exemestane after 3 years and 30 (48.4%) switched from tamoxifen to letrozole after 5 years. 11 (17.7%) had been on arimidex as first line endocrine therapy for <=2 years and 5 (8.1%) had been on letrozole as first line endocrine therapy for <=1 year. Mean t-score and SD was calculated at each site and results categorised by lowest t-score at any site. The overall decrease in BMD measured at 1.66% over the 12 months. Conclusion: We have demonstrated a decrease in BMD with AI treatment of 1.66% per year as well as an increase in fracture incidence and increased need for bisphosphonate therapy whilst on an AI. We would recommend that all patients on any AI receive annual DXA scans. [Table: see text] No significant financial relationships to disclose.