52P Adjuvant endocrine therapy in HER2-positive breast cancer patients: Systematic review and meta-analysis

Abstract

Approximately 50% of HER2-positive breast cancer lesions express hormone receptors. These tumors present a unique therapeutic challenge, and the optimal endocrine therapeutic approach remains controversial. We aimed to study the optimal adjuvant endocrine therapy in this setting in order to better establish the bases for clinical recommendations in HER2-positive disease. We conducted a literature search up to May 2020 in which we identified randomized controlled trials (RCTs) that investigated the efficacy of various adjuvant hormonal therapies among premenopausal and postmenopausal patients with hormone receptor (HR)-positive HER2-positive early breast cancer. Disease-free survival (DFS) was calculated with the random effect model and hazard ratios (HRs) with 95% confidence intervals (CI). Six RCTs (n=5,390 patients) were included in the final analysis. There was no significant difference in DFS between adjuvant treatment with aromatase inhibitors and tamoxifen (HR 0.99, 95% CI 0.68-1.44, P=0.96). After omitting the ALTTO trial because it did not randomize patients to hormonal therapy, no significant difference was observed between the two protocols (HR 1.06, 95% CI 0.65-1.73, P=0.81). Our study demonstrates similar DFS with tamoxifen and aromatase inhibitors as adjuvant endocrine treatment in HER2-positive HR-positive early breast cancer patients. Future larger prospective studies focusing on the various contemporary endocrine regimens are warranted to validate our findings.