Aromatase inhibitors (AIs) are standard adjuvant therapy for post menopausal women with hormone receptor positive breast cancer . AIs increase the risk of osteoporosis and fracture, with an estimated 9% fracture rate after 5 years of therapy.  This causes morbidity and mortality in patients with an otherwise excellent prognosis. There is no standard or guideline for bone health monitoring of patients on AIs. The prevalence of investigation and treatment is unknown. We aim to review the patterns of investigation and treatment of osteoporosis in breast cancer patients on AIs at our centre.
We identified postmenopausal women receiving AIs for early hormone receptor positive breast cancer in our area health service in 2009 to 2011. Bone mineral density (BMD) and Vitamin D assessment was retrieved through Computerised Provider Order Entry or the oncology electronic medical record. A multivariate analysis using 14 co-variates is planned in the final analysis, including age at diagnosis, BMI, BMDs throughout therapy, and commencement of bisphosphonate therapy.
We identified 880 consecutive early breast cancer cases. A random selection of 275 cases were reviewed in the preliminary assessment. Of these, 74 patients (25%) were eligible for inclusion. The main reasons for exclusion were treatment with tamoxifen (N=60, 29%) or did not receive any endocrine therapy for any reason (N=101, 50%). Of the included patients, 54 (72%) had baseline BMI recorded, 54 (72%) had baseline BMD recorded, 46 (61%) had vitamin D recorded. Women who had chemo were more likely to commence osteoporosis therapy (HR 1.375). Of included patients, 20 (26%) commenced osteoporosis therapy during the follow up period. Alendronate (10) and zolendronic acid (6) were the most frequently used agent.
Our preliminary analysis suggests sufficient numbers of events to conduct a larger retrospective study at our centre. We anticipate that 22 of the 880 cases would have developed insufficiency fractures for our study period, with a larger number developing osteoporosis. Our study to inform patterns of assessment and risk factors for osteoporosis in our population could be developed into a tool to ensure relevant bone health investigations and management of osteoporosis.