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SAT0473 Predictive Factors of Longitudinal Bone Loss in Patients Treated with Aromatase Inhibitors for Breast Cancer

Background It is well known that aromatase inhibitors (AIs) increase the rate of bone mineral density (BMD) loss in the human skeleton. Patient characteristics that have been found to predict an increased risk of BMD loss and fractures in longitudinal studies with those on AIs include increased age, prior fractures, diagnosis of osteoporosis at baseline, low BMI, >6months corticosteroid use, family history of osteoporosis and previous hormone therapy (1, 2). Other risk factors have not been investigated in longitudinal studies. Furthermore, the site of predicted loss could be important as the femoral neck is a better predictor for future fracture. Objectives The aim of this study was to investigate whether any more known risk factors influence the rate of bone loss of patients on AIs over time. Methods A cohort of patients referred between 2004 and 2011 to a dual energy x-ray absorptiometry scanner in the North West of England who were currently on or had had AI treatment were identified. Each of the selected cases had to have >2 scans so the bone loss could be assessed over time. The sites of bone that were scanned for BMD loss were the L1-L4 vertebrae and the left femoral neck. The risk factors that were being investigated included current smoking, family history of osteoporosis, rheumatoid arthritis, current corticosteroid use, age, current alcohol excess, BMI and weight. A regression model was then fitted to determine if there are any further predictors of bone loss over time. This was done at both the femoral neck and the lumbar vertebrae. Results 96 female patients on AI treatment were identified, with a median age of 63.9 years (IQR 59.2, 72.4) at the first scan. Difference in time between scans was 3.3 years (IQR 3.0, 4.1). There were two risk factors that had significant results; The regression model found that having a family history of osteoporosis gave a significant positive coefficient of 0.28 (95% CI 0.01 - 0.56) for lumbar spine BMD loss and 0.5 (95% CI 0.03 - 0.96) for femoral neck BMD loss. There was a significantly positive B coefficient of 0.36 (95% CI 0.13 - 0.61) for total femur BMD loss with rheumatoid arthritis. Other factors such as smoking, corticosteroid use, BMI, weight and alcohol excess did not show any significant influence on bone loss over time. Conclusions There is an association between having a family history of osteoporosis and increased BMD loss in the lumbar spine and femoral neck of the femur of patient on AIs. There is also an association between rheumatoid arthritis and increased BMD loss in the hip. Having a family history has already been identified as a risk factor for further BMD loss but rheumatoid arthritis is a novel finding in this analysis. The results from this study indicate that patient on AIs who either have a family history of osteoporosis or rheumatoid arthritis need to be intensely monitored for future fractures. thresholds for treatment could also be examined in patients with these two risk factors. References Annals of Oncology: Official Journal of the European Society for Medical Oncology/ESMO. 2011;22(12):2546-55. Epub 2011/03/19. Annals of Oncology: Official Journal of the European Society for Medical Oncology/ESMO. 2009;20(9):1489-98. Epub 2009/05/29. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.2415