Background and objectives: Aromatase inhibitors (AIs) provide an alternative to tamoxifen as adjuvant therapy for post-menopausal breast cancer (BC) patients. Large trials resulted better outcomes with AIs. Adjuvant therapy with AIs reduced risk of relapse than tamoxifen. Systemic therapies for BC can interfere with bone turnover, either through their effects on gonadal steroid hormone production or by inhibiting peripheral aromatization into estrogen. Comparative studies of AIs are lacking. We aimed to evaluate safety profile of bone related events by comparing three AIs against tamoxifen and placebo.
Methods: PRSIMA guidelines were used for network meta-analyses. Searches were performed from PubMed, Embase/Medline, Cochrane, Ovid databases. Randomized controlled trials in BC patients treated with steroidal or non-steroidal AIs compared against tamoxifen and placebo or other AIs, with reported bone-related safety events were included. Network meta-analysis by Bayesian approach was performed by R software (ver 3.2), GemtC package.
Results: 17 studies reporting 4 different bone-related endpoints were included. Treatment with exemestane lowered incidence of bone pain (odds ratio (OR) Vs anastrozole and letrozole: 0.63, 0.54), fracture episodes (OR Vs anastrozole and letrozole: 0.84, 0.80), and osteoporosis (OR) Vs anastrozole and letrozole: 0.85, 0.73) than letrozole and anastrozole, although there was no statistical significance. Reduction in bone mineral density was lesser in exemestane than anastrozole (mean reduction in hip: 1.05; lumbar spine: 1.25). Treatment ranking with the Surface Under the Cumulative ranking curve, exemestane was found to reduce incidence of bone-related adverse events.
Conclusion: Lower incidence of bone-related safety events in patients treated with exemestane was observed. Further head-on studies are confirmation.