Clinical Evidence of Chemotherapy or Endocrine Therapy Maintenance in Patients With Metastatic Breast Cancer After First-Line Chemotherapy

Background: The clinical benefit of chemotherapy or endocrine therapy maintenance in patients with metastatic breast cancer (MBC) after first-line chemotherapy, specifically hormone receptor (HR) positive MBC patients remain inconclusive. This study aims to comprehensively evaluate the clinical efficacy of chemotherapy or endocrine therapy maintenance in MBC patients. Methods: The meta-analysis of randomized clinical trials (RCTs) and propensity score matched analysis of multicentre cohort study in China were evaluated MBC patients who underwent first-line chemotherapy or endocrine therapy maintenance. The GRADE approach was used to assess quality of evidence in meta-analysis. The primary endpoints were progression-free survival (PFS) and overall survival (OS). Findings: A total of 2,867 patients from 15 RCTs and 760 patients from multicentre cohort were included. The results from meta-analysis showed that chemotherapy maintenance significantly improved PFS (hazard ratio [HR], 0·63; 95% confidence interval (CI) 0·54-0·73; P 0·05). Additionally, treatment effect sizes were greater for OS than for PFS, and a moderate correlation between PFS and OS was identified. Interpretation: This study provided a high evidence for PFS and OS benefits of longer first-line chemotherapy and endocrine therapy maintenance in MBC patients, and there were no difference efficacy between chemotherapy and endocrine therapy maintenance for HR-positive patients. We also suggested that both PFS and OS should be evaluated to determine the effectiveness of maintenance therapy in future clinical trials. Trial Registration: This study is registered with PROSPERO Identifier: CRD42017071858, and ClinicalTrials.gov Identifier: NCT04258163. Funding Statement: This study was supported by grant 2020ZX09201021 from the National Science and Technology Major Project, grant YXRGZN201902 from the Medical Artificial Intelligence Project of Sun Yat-Sen Memorial Hospital, grants 81572596, 81972471, U1601223, 82073408, 81802656, and 82071754 from the National Natural Science Foundation of China, grant 2017A030313828 from the Natural Science Foundation of Guangdong Province, grant 201704020131 from the Guangzhou Science and Technology Major Program, grant 2017B030314026 from the Guangdong Science and Technology Department, grant 2018007 from the Sun Yat-Sen University Clinical Research 5010 Program, grant SYS-C-201801 from the Sun Yat-Sen Clinical Research Cultivating Program, and A2020558 from the Medical Scientific Research Foundation of Guangdong Province. Declaration of Interests: The authors have no conflicts of interest to declare. Ethics Approval Statement: The study protocol was approved by the ethics committee of the Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China and was conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines.