Adjuvant Endocrine Therapy Effects on Bone Mineral Density and Microstructure in Women with Breast Cancer.

Although aromatase inhibitors (AIs) are typical drugs for cancer treatment-induced bone loss, their effects on the bone microstructure remain unclear. In this study, we evaluated changes in the bone mineral density (BMD) and bone microstructure associated with AI treatment using high-resolution peripheral quantitative computed tomography (HR-pQCT) in patients with early breast cancer. This prospective, single-arm, observational study included non-osteoporotic, postmenopausal women with hormone receptor-positive breast cancer. Patients underwent dual-energy X-ray absorptiometry (DXA), HR-pQCT, and tartrate-resistant acid phosphatase-5b (TRACP-5b) or procollagen type-I N-terminal propeptide measurements at baseline and 6 and 12 months after AI therapy. The primary endpoint was changes in the total volumetric BMD (Tt.vBMD), trabecular vBMD (Tb.vBMD), and cortical vBMD (Ct.vBMD) longitudinally at the distal radius and tibia. Twenty women were included (median age 57.5 years; range 55–72 years). At 12 months, HR-pQCT indicated a significant decrease in the Tt.vBMD (median distal radius − 5.3%, p < 0.01; distal tibia − 3.2%, p < 0.01), Tb.vBMD (− 3.2%, p < 0.01; − 1.0%, p < 0.05, respectively), and Ct.vBMD (− 3.2%, p < 0.01; − 2.7%, p < 0.01, respectively). Estimated bone strength was also significantly decreased. The DXA BMD value in the total hip (p < 0.01) and femoral neck (p = 0.03), but not in the lumbar spine, was significantly decreased. The TRACP-5b levels was significantly negatively associated with changes in the Tt.vBMD in both the distal radius and tibia (r =  − 0.53, r =  − 0.47, respectively) Postmenopausal women who received AIs for early breast cancer experienced significant trabecular and cortical bone deterioration and a decrease in estimated bone strength within only 1 year.