Efficacy and clinical outcome of chemotherapy and endocrine therapy as first-line treatment in patients with hormone receptor-positive HER2-negative metastatic breast cancer

Background:Endocrine therapy(ET)and ET-based regimens are the preferred first-line treatment options for hormone receptor(HR)-positive and human epidermal growth factor receptor 2(HER2)-negative metastatic breast cancer(HR+/HER2-MBC),while chemotherapy(CT)is commonly used in clinical practice.The aim of this study was to investigate the efficacy and clinical outcome of ET and CT as first-line treatment in Chinese patients with HR+/HER2-MBC.Methods:Patients diagnosed with HR+/HER2-MBC between January 1st,1996 and September 30th,2018 were screened from the Chinese Society of Clinical Oncology Breast Cancer database.The initial and maintenance first-line treatment,progression-free survival(PFS),and overall survival(OS)were analyzed.Results:Among the 1877 included patients,1215(64.7%)received CT and 662(35.3%)received ET as initial first-line treatment.There were no statistically significant differences in PFS and OS between patients receiving ET and CT as initial first-line treatment in the total population(PFS:12.0 vs.11.0 months,P=0.22;OS:54.0 vs.49.0 months,P=0.09)and propensity score matched population.For patients without disease progression after at least 3 months of initial therapy,maintenance ET following initial CT(CT-ET cohort,n=449)and continuous schedule of ET(ET cohort,n=527)had longer PFS than continuous schedule of CT(CT cohort,n=406)in the total population(CT-ET cohort vs.CT cohort:17.0 vs.8.5 months;P<0.01;ET cohort vs.CT cohort:14.0 vs.8.5 months;P<0.01)and propensity score matched population.OS in the three cohorts yielded the same results as PFS.Conclusions:ET was associated with similar clinical outcome to CT as initial first-line treatment.For patients without disease progression after initial CT,switching to maintenance ET showed superiority in clinical outcome over continuous schedule of CT.