A meta-analysis of randomized controlled trials comparing the efficacy and safety of anastrozole versus tamoxifen for breast cancer

Whether anastrozole has superior effects to tamoxifen for breast cancer remains controversial. Therefore, we conducted this meta-analysis of randomized controlled trials (RCTs) to compare the efficacy and safety of anastrozole versus tamoxifen as adjuvant therapy in breast cancer. A systematic literature search of PubMed, Web of Science, Embase, and Cochrane library were performed to evaluate the survival benefits and toxicity profiles of patients with breast cancer who were treated with anastrozole or tamoxifen. The main outcome measures included disease-free survival (DFS), recurrence-free survival (RFS), overall survival (OS), overall response rate (ORR), and adverse events. Hazard ratios (HRs) or risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using a fixed-effects model or random-effects model. Nine RCTs with a total of 15,300 patients met the inclusion criteria and were included in this meta-analysis. Pooled estimates suggested that, anastrozole was associated with a significantly improvement in DFS (HR=0.72, 95%CI: 0.55-0.94; P=0.016), and ORR (RR=1.21, 95% CI: 1.05-1.39; P=0.009) than tamoxifen. But it did not prolong OS (HR=0.96, 95%CI: 0.77-1.21; P=0.751). Compared with tamoxifen, anastrozole induced a higher incidence of arthralgia (RR=1.55, 95%CI: 1.20-1.99; P=0.001) and bone pain (RR=1.31, 95%CI: 1.05-1.62; P=0.015), as well as a lower incidence of vaginal bleeding (RR=0.51, 95%CI: 0.28-0.93; P=0.029), vaginal discharge (RR=0.31, 95%CI: 0.12-0.82; P=0.017), and thromboembolic events (RR=0.39, 95%CI: 0.28-0.55; P<0.001). Based on the current evidence, patients with breast cancer would benefit from the anastrozole treatment.