Abstract PS9-23: Second-generation HR-pQCT analysis of bone mineral density and microstructure in women with breast cancer who underwent adjuvant endocrine therapy

Background: Adjuvant endocrine therapy for 5-10 years reduces breast cancer (BC) mortality in women with hormone receptor-positive BC. However, aromatase inhibitors (AIs) decrease bone mineral density (BMD), and increase fractures, joint stiffness, and joint pain. Although dual energy X-ray absorptiometry (DXA) is widely used to assess BMD, it is a two-dimensional method and thus cannot analyze trabecular and cortical bone microstructure. High-resolution peripheral quantitative computed tomography (HR-pQCT) allows in vivo analysis of peripheral bone microarchitecture with high spatial resolution and low radiation exposure. We used HR-pQCT to evaluate changes in volumetric bone density and microstructure consisting of trabecular and cortical bone associated with AI treatment in patients with early BC. Methods: This was a prospective single-center observational study of nonosteoporotic, postmenopausal women with hormone receptor-positive BC, whose baseline DXA lumber spine and femoral neck T-scores were > −2.5. All patients were scheduled to receive DXA and HR-pQCT at baseline and at 6 and 12 months after starting AI therapy. The primary endpoint was to examine changes in total volumetric BMD (Tt. vBMD), trabecular volumetric BMD (Tb. vBMD), cortical volumetric BMD (Ct. vBMD) change at the distal radius and the distal radius between baseline and 6 and 12 months after starting endocrine therapy. Results: Of the 20 women in the study (median age: 57.5 years; range: 55-72 years), 8 had undergone chemotherapy before registration. Their mean change in Tt. vBMD between baseline and 1 year were distal radius: −5.7% (SD: 2.5%, P Citation Format: Sayaka Kuba, Konosuke Watanabe, Megumi Matsumoto, Ko Chiba, Kosho Yamanouchi, Ayako Fukushima, Michi Morita, Ryota Otsubo, Hiroshi Yano, Kengo Kanetaka, Makoto Osaki, Takeshi Nagayasu, Susumu Eguchi. Second-generation HR-pQCT analysis of bone mineral density and microstructure in women with breast cancer who underwent adjuvant endocrine therapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS9-23.