Bone Safety Profile of Steroidal Aromatase Inhibitor in Comparison to Nonsteroidal Aromatase Inhibitors in Postmenopausal Women with Breast Cancer: A Network Meta-Analysis

BACKGROUND AND OBJECTIVES: Aromatase inhibitors (AIs) provide an alternative to tamoxifen as an adjuvant therapy for postmenopausal patients with breast cancer (BC). Large trials resulted better outcomes with AIs. Adjuvant therapy with AIs reduced the risk of relapse compared with tamoxifen. Systemic therapies for BC can interfere with bone turnover, either by affecting gonadal steroid hormone production or by inhibiting peripheral aromatization into estrogen. We aimed to evaluate the safety profile of bone-related events by comparing 3 AIs with tamoxifen and a placebo. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were used for network meta-analyses (NMAs). Searches were performed using PubMed, Embase/Medline, Cochrane, and Ovid databases. Randomized controlled trials comparing tamoxifen and placebo or other AIs to steroidal or nonsteroidal AIs in patients with BC reporting bone-related safety events were included in NMA. NMA in a Bayesian approach was performed using R software (ver 3.2), Gemtc package. RESULTS: Seventeen studies reporting 4 different bone-related endpoints were included. Although there was no statistical significance, treatment with exemestane lowered the 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) compared with letrozole and anastrozole. Reduction in bone mineral density was lesser in exemestane than in anastrozole (mean reduction in hip: 1.05; lumbar spine: 1.25). Treatment ranking with the surface under the cumulative ranking curve showed that exemestane was found to reduce the incidence of bone-related adverse events. CONCLUSION: A lower incidence of bone-related safety events was observed in patients treated with exemestane.