Abstract P2-13-04: Risk of osteoporosis and osteoporotic fracture in breast cancer survivors: A nation-wide study

Abstract

Abstract Background: Referring to American Society of Clinical Oncology (ASCO) 2015 guidelines, they recommend bone screening every two years for premenopausal women receiving tamoxifen, considering it as a risk factor for developing osteoporosis. This nationwide study aimed to investigate the incidence of osteoporosis and osteoporotic fractures, and to assess whether the known factors increase the risk of osteoporosis and/or osteoporotic fractures among breast cancer survivors in South Korea. Methods: A nationwide retrospective study was conducted using the Health Insurance Review and Assessment Service (HIRA) data. The incidence rates of osteoporosis and osteoporotic fracture were calculated by dividing the number of incident cases by the total follow-up period (person-years). The risk factors for osteoporosis and osteoporotic fracture were investigated using Cox proportional hazard regression models. Results: From Jan 2009 to Dec 2014, a total of 47,649 breast cancer survivors were included in this analysis. During the study period, 5,955 osteoporosis events were observed from 252,396 person-year. The incidence rate of osteoporosis in breast cancer survivors was 23.59 per 1000 person-year (95% CI 23.00 - 24.20). Osteoporotic fracture incidence was assessed 2.40 per 1000 person-year (95% CI 2.23 - 2.60), with 647 events out of 269,075 person-years. In age<40 subgroup, use of ovarian function suppression (OFS) was significantly related to incidence of osteoporosis (Incidence rate 7.06 95% CI 5.47 - 9.11). However, the use of tamoxifen did not show an increased risk of osteoporosis (HR 1.24, 95% CI 0.85 - 1.82). Nine osteoporotic fracture was found in 7,121 patients in age under 40. In 40-49 age group, use of chemotherapy (HR 1.41, 95% CI 1.24-1.60, p<.0001), aromatase inhibitor (HR 2.45, 95% C.I. 2.05- 2.92, p<.0001), and OFS (HR 1.19, 95% CI 1.01-1.40, p =.0113) showed a significant increase of osteoporosis. Osteoporotic fracture were associated with use of AI and OFS in 40-49. Use of tamoxifen significantly decreased osteoporosis diagnosis in age 40-49, 50-59, and 60-69. Tamoxifen was also related to decreased incidence of osteoporotic fracture in age 40-49 (HR 0.49, 95% CI 0.31-0.76, p<.0001) and 50-59 (HR 0.37, 95% CI 0.23-0.60, p<.0001). Conclusions: Tamoxifen is not associated with the increased risk of osteoporosis and osteoporotic fracture in breast cancer survivors. Keywords: Breast Neoplasms, Survivorship, Osteoporosis, Bone Fractures, adverse effects Citation Format: Il Yong Chung, Jihyoun Lee, Heba Alqudaihi, Jong Won Lee, Byung Ho Son, Sei Hyun Ahn, Ji Sung Lee. Risk of osteoporosis and osteoporotic fracture in breast cancer survivors: A nation-wide study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-13-04.