Bone mineral density fall during aromatase inhibitor treatment may predict lower breast cancer recurrence

Purpose: Aromatase inhibitors (AIs) are associated with reduction in bone mineral density (BMD). The use of bone strengthening agents zoledronic acid and denosumab are associated with improved breast cancer outcomes for post-menopausal patients treated with AIs. This study investigates whether change in BMD with AI therapy is associated with breast cancer recurrence. Methods: A cohort of patients treated at a single institution diagnosed with hormone receptor-positive breast cancer with baseline BMD and subsequent BMD test while receiving adjuvant aromatase inhibitor therapy were studied. Demographic, treatment and outcome data was obtained. Simple and multiple linear regression analysis was performed to investigate predictors of annual percent BMD change at the LS and hip. Univariate and multivariate Cox proportional hazards modelling were undertaken to investigate predictors of breast cancer recurrence. Results: 353 patients eligible patients were identified. In multivariate analysis of lumbar spine BMD change, the difference between those in quartile 1, which showed the greatest reduction in BMD, and quartile 3, with substantially less reduction, was significant (HR = 3.02, 95% CI 1.15–7.90 p = 0.025). Hip BMD reduction was also not significantly associated with breast cancer recurrence. The two quartiles with the least reduction in hip BMD showing a non-significant reduced risk of recurrence relative to the quartile with the greatest (p = 0.10). Conclusions: The findings suggest an association may exist between lumbar spine BMD change and breast cancer recurrence for patients treated with adjuvant AI. Further research is required to determine whether BMD change can be utilised as a biomarker.