Aromatase inhibitors, bone microstructure, and estimated bone strength in postmenopausal women with breast cancer: a 5-year prospective study

Aromatase inhibitors (AIs) are the standard treatment for early breast cancer (EBC) and are typical causative agents of cancer treatment-induced bone loss. However, the effects of long-term treatment with these drugs on bone microstructure remain unclear.

This prospective, single-arm observational study included postmenopausal, non-osteoporotic women with hormone receptor-positive EBC. Patients who underwent dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and tartrate-resistant acid phosphatase-5b (TRACP-5b) or procollagen type I N-terminal propeptide levels were compared at baseline and at 60 months after commencing AI treatment.

Fifteen women were included in the study, with a median age of 58 years and a quartile range of 56.5–62.5 years. At 60 months, HR-pQCT revealed that the cortical area and thickness decreased with increased cortical porosity in the cortical bone. In addition, the number of trabeculae decreased and trabecular separation increased trabecular bones decreases, and trabecular bone separation opens, resulting in a decrease in the trabecular bone volume fraction. Total bone mineral density (BMD), trabecular volumetric BMD, and cortical volumetric BMD, and estimated bone strength significantly decreased. DXA BMD values significantly decreased in the total hip and femoral neck but not the lumbar spine. TRACP-5b values after 5 years of AI treatment showed a significant negative correlation with the rate of change in the total volumetric BMD in the distal tibia.

Postmenopausal women who received AIs for 5 years for EBC experienced significant deterioration in the bone microstructure, BMD, and estimated bone strength.