Background Aromatase inhibitors (AI) been related to an increased risk of bone loss and fractures in women receiving these drugs as adjuvant treatment, but few studies have assessed the impact of prior chemotherapy (CT) on bone mineral density (BMD) loss associated to AI.

Objectives To assess the impact of CT prior to the initiation of AI on BMD in postmenopausal patients with breast cancer (BC) seen at a Spanish tertiary care hospital.

Methods We perform a longitudinal study in patients who received AI after initial CT (CT group) or as adjuvant therapy without prior CT (non-CT group) followed up for 12 months. BMD was assessed by DXA in lumbar spine (LS) and femoral neck (FN) at baseline and after 12 months of AI treatment following the usual protocol of our center, with in vitro coefficient of variation of 1% in both locations and estimated minimal significant change (MSC) of 0.0223 g/cm² in LS and 0.0288 g/cm² in FN. Demographics, neoplastic disease data, and osteoporosis risk factors were also collected.

Results 69 patients (CT group 39, non-CT group 30) attended at our center between August 2011 and December 2014 were included. Mean age at diagnosis was 59.9±7.7 years, most of them have BC stages I-II (84%). Most frequent AI in both groups was letrozole (95%). Baseline characteristics were similar, except for age at diagnosis that was significantly higher in the non-CT group, these data are presented in the table. Mean BMD at the start of AI was significantly lower in LS in the CT group (0.7793 g/cm²) than in the non-CT group (0.8483 g/cm²) (p=0.018), but no difference in FN (CT 0.6764 g/cm² and non-CT 0.7077 g/cm², p=0.123). A significant difference in LS (CT 0.7685 g/cm², non-CT 0.8397 g/cm², p=0.003) was found in the comparison of BMD means between the two groups at 12 months but not in FN (CT 0.6598 g/cm², non-CT 0.6689 g/cm², p=0.369). After 12 months of treatment with AI, mean BMD change in the CT group in LS was -0.0107 g/cm² (95% confidence interval [CI] -0.0269, +0.0055, p=0.189) and in FN -0.0165 g/cm² (95% CI: -0.0339, +0.0009, p=0.063), while in the non-CT group the means changes were in LS -0.0085 g/cm² (95% CI -0.0416, +0.0244, p=0.599) and FN -0.0388 g/cm² (95% CI -0.0707, -0.0068, p=0.019). During the study period there was a fracture in each group (CT 2.6%, non-CT 3.3%).

Conclusions Our results do not demonstrate that CT prior to AI treatment significantly decreased BMD during the first year. Mean change in both LS and FN in CT group was not superior to MSC nor to the change in non-CT group, although they had a significantly lower mean BMD in LS than the latter group and this difference was maintained at the end of the study period.

Disclosure of Interest None declared