DXA assessment and fracture prevention in hormone positive breast cancer patients after treatment initiation with aromatase inhibitors: A registry-based cohort study.

Background: Several guidelines have been proposed to prevent aromatase inhibitors induced bone loss (AIBL), but there is scarce data on their endorsement in clinical practice. Aim: To assess bone health evaluation and fracture prevention in postmenopausal women with estrogen receptor (ER)-positive breast cancer after aromatase inhibitors (AI) initiation. Methods: An historical cohort analysis based on data from the cancer and osteoporosis Maccabi Health Services (MHS) registries from Jan 1st 2009 to Dec 31st 2020. Cases of estrogen receptor (ER)-positive breast cancer were extracted. Index date was set as the first aromatase inhibitors (AI) purchase. Variables such as age, BMI, smoking history, alcohol use, rheumatoid arthritis, diabetes, glucocorticosteroid use, previous fractures, BMD T-scores and purchases of AI and anti-resorptive agents were collected. Age under 50, previous cancer, prior major osteoporotic fractures and prior anti-resorptive treatment were exclusion criteria. Kaplan-Meier curves were generated to assess the time to outcomes. Multivariable Cox's proportional hazards survival model was performed. Results: A total of 8617 women initiating AI were eligible. The median follow up was 6.1 years. The mean (SD) age at index was 62.8 (9.2), the mean (SD) BMI was 29.1 (5.6). The mean (SD) T-score was -1.3 (1.2) at the lumbar spine, -1.5 (0.9) at the femoral neck and -1.0 (1.0) at the total hip. Twenty percent had type 2 diabetes, 8.1 % were active smokers, 3.8% had rheumatoid arthritis and 1.2% were exposed to glucocorticoids.A total of 37% and 53% underwent a DXA scan at 1 and 2 years from AI initiation, and 12% and 17% were prescribed an anti-resorptive agent at 1 and 2 years from index. Advanced age was associated with a higher rate of evaluation and treatment, while obesity and diabetes were associated with a lower rate. The cumulative incidence of a major osteoporotic fracture was 8.8 and 15.8 % at 5 and 10 years, respectively. Conclusions: Despite the excess risk of fractures, bone health assessment and preventive treatment are still partial and postponed in breast cancer AI treated patients. Strategies to ensure appropriate care are needed.