Bisphosphonate therapy requirement during adjuvant aromatase inhibitor therapy in early breast cancer patients according to UK bone health guidelines

Abstract

e11612 Background: Adjuvant aromatase inhibitor (AI) therapy increases bone loss and incidence of bone fracture. Recently published UK bone health guidelines recommend to prescribe bisphosphonate (BPN) during adjuvant AI therapy for T score of -2 or less, or annual loss of bone density >4%, or known vertebral fracture, or patients over the age of 75 with one or more clinical risk factors (previous low-trauma fracture after age 50, previous hip fracture, alcohol intake of >4 units/ day, diseases associated with secondary osteoporosis, prior corticosteroids for >6 months, BMI <22). We evaluated the impact of BPN therapy requirement using UK guidelines on adjuvant AI therapy patients. Methods: Patients who were commencing adjuvant AI therapy for early breast cancer underwent Dual energy X-ray Absorptiometry (DXA) bone density assessment, with a baseline scan and 2 subsequent scans. Results: A total of 91 patients were eligible and included in this study (median age 59). Different AIs included anastrozole(68), exemestane (7) and letrozole (16). Patients received AI therapy in up-front (56), sequential (15) and extended adjuvant (20) therapy settings. Median duration of AI therapy was 35 months, with 85 patients having received therapy for more than 24 months. BPN was prescribed to 35 patients during AI therapy as per local practice. According to WHO classification, 11 patients were found to have osteoporosis at the 1st scan, and 4 & 2 patients were found to develop osteoporosis at 2nd & 3rd scans, respectively. According to UK guidelines, however, BPN therapy would be indicated in 56 patients (62%): after 1st scan 22 patients, after 2nd scan another 26 patients and following the 3rd scan an additional 8 patients. Factors predictive of BPN indication during AI therapy are hyperthyroidism (p = 0.009), previous fracture (p = 0.001) and smoking (p = <0.001). Patients who took tamoxifen for more than one year are less likely to require BPN compared to those who did not take tamoxifen (p = 0.028) Conclusions: Majority of patients (up to 62% in our study) will require BPN during adjuvant AI for breast cancer. Therefore the cost of BPN and potential drug side effects need to be taken into account in the use of adjuvant AI, and it's health economic analysis. No significant financial relationships to disclose.