Background The use of aromatase inhibitors (AIs), given after breast cancer, has been associated with a low bone mineral density (BMD) and as a risk factor for fragility fractures. We have reported on the risk factor for low BMD in a previous abstract and it showed that the use of AIs significantly reduced lumbar spine BMD and femoral neck BMD (1). The FRAX ™ tool uses the femoral neck BMD to predict fractures on a population basis but ignores the lumbar spine. Some patients who have undergone bilateral hip replacements would not be able to estimate their FRAX ™ risk accurately.

Objectives To determine the predictors of fragility fractures in an observational cohort of female patients on aromatase inhibitors.

Methods Female patients referred for BMD estimation in a scanner in the North West of England between 2004 and 2014 on aromatase inhibitors were identified from a dual X-ray absorptiometry database. Demographics and other risk factors, as well as fragility fractures, were recorded. Initially, those who had sustained a fracture were compared to those who had not sustained a fracture using chi-squared tests for categorical variables and T-tests for continuous variables. Following that, univariate and multivariate logistic regression models were fitted looking at the predictors of fracture. Variables included age at scan, height, weight, alcohol, smoking, family history, rheumatoid arthritis, secondary osteoporosis as defined by FRAX™, body mass index and steroid exposure, in addition to BMD in the lumbar spine and femoral neck.

Results 2029 female patients were scanned in the referral period. The mean age at scan was 66 (SD 10.46). 356/2029 (17.55%) had sustained a fracture. Results of the univariate analysis are shown in table 1, significant predictors are indicated with an asterisk (*).

In the multivariate model, the variables that predicted fractures in this cohort were age at scan (OR 1.03 95% CI 1.02,1.05), femoral neck BMD (OR 0.74 95% CI 0.02,0.29) and lumbar spine BMD (OR 0.34 95% CI 0.14,0.80). Using the femoral neck multivariate model resulted in an area under the curve of 0.6720 and using the lumbar spine was 0.6653.

Conclusions In the univariate analysis, many risk factors are associated with fractures within this cohort of female patients on aromatase inhibitors but both univariate analysis and multivariate analysis showed that lumbar spine BMD is a good predictor of fractures. This is not included in the FRAX ™ tool and would enable fracture risk to be calculated in patients who have undergone hip replacements.

References

1. Ann Rheum Dis 2014;73 Suppl3 SAT0472.

References

Disclosure of Interest None declared