Abstract PS9-23: Second-generation HR-pQCT analysis of bone mineral density and microstructure in women with breast cancer who underwent adjuvant endocrine therapy
Authors: Kuba Sayaka , Watanabe Konosuke , Matsumoto Megumi , Chiba Ko , Yamanouchi Kosho , Fukushima Ayako , Morita Michi , Otsubo Ryota , Yano Hiroshi , Kanetaka Kengo , Osaki Makoto , Nagayasu Takeshi , Eguchi Susumu 
Published: February 2021

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 &gt; −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&lt;0.01); distal tibia: −3.8% (SD: 1.8%, P&lt;0.01), Tb. vBMD distal radius: −4.0% (SD: 3.9%, P&lt;0.01); distal tibia: −0.9% (SD: 2.4%, P&lt;0.05), Ct. vBMD distal radius: −3.1% (SD: 1.6%, P&lt;0.01); distal tibia: −2.9% (SD: 1.7%, P&lt;0.01). Furthermore, at 1 year in trabecular bone, mean trabecular bone volume fraction (p&lt;0.01), trabecular thickness (p&lt;0.05), and trabecular number (p&lt;0.01) were significantly decreased, and trabecular separation (p&lt;0.01) increased, in both the distal radius and tibia. At 1 year in cortical bone, mean changes in cortical thickness (p&lt;0.01) and cortical bone area (p&lt;0.01) were significantly decreased in both the distal radius and tibia; however, the endocortical perimeter of cortical bone did not significantly change and cortical porosity (p&lt;0.05) was significantly greater than that at baseline. At 1 year, DXA decreased at the total hip (−4.4%, P&lt;0.01) and femoral neck (−0.6%, P=0.03) compared with baseline. However, no significant difference was seen in median values for lumbar spine BMD at 1 year, or for tartrate-resistant acid phosphatase-5b (TRACP-5b) or procollagen type-I N-terminal propeptide (PINP). Conclusion: Postmenopausal women who took AIs for early BC experience volumetric bone density decline and both trabecular and cortical bone deterioration. A decade of AI treatment is a standard treatment for early BC; however, healthcare professionals should monitor bone health during and after these treatments.

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.