Abstract C035: Chemotherapy plus HER2-targeted therapy versus endocrine therapy plus HER2-targeted therapy as first-line treatment in patients with HR+/HER2+advanced breast cancer: A real-world trial
Authors: Liang Yuehua , Li Hui Ping , Yun Zehui 
Published: December 2023

Abstract
Purpose:This study is a real-world research to compare the efficacy of using chemotherapy plus anti-HER2 therapy versus endocrine therapy plus anti-HER2 therapy as first-line treatment for HR+/HER+ advanced breast cancer patients, aiming at providing a better treatment option for patients.
Patients and methods: This study enrolled patients with advanced breast cancer who had complete medical records and were treated in the breast oncology department of Peking University Cancer Hospital from October 2010 to October 2022. These patients were pathologically confirmed with HR+/HER2+ and underwent first-line treatment with anti-HER2 therapy + endocrine therapy (HE group) or anti-HER2 therapy + chemotherapy (with/without endocrine maintenance therapy) (HC group). HER2 positive was defined as HER2+++ or HER2++ on immunohistochemical staining of tumor tissue and fluorescence in situ hybridization (FISH) testing showing HER2 gene amplification in patients. HR+ was considered when more than 1% of tumor cells expressed estrogen receptor (ER) and/or progesterone receptor (PR). The primary endpoints being investigated are progression-free survival (PFS) and overall survival (OS). The second endpoint is objective response rate (ORR) and clinical benefit rate (CBR).
Results:From October 2010 to October 2022, a total of 181 patients who met the inclusion criteria were enrolled in the study. Among them, 18 patients received endocrine therapy + anti-HER2 therapy in the first-line treatment stage, while 163 patients received chemotherapy + anti-HER2 therapy (70 patients underwent endocrine maintenance therapy). The median follow-up time was 67 months. The median PFS (mPFS) of the patients in HC group and the HE group were 14.32 months (95% confidence interval (CI) 12.83-15.81) and 9.78 months (95%CI 4.48-15.8), respectively (p=0.299), and no significant statistical difference was observed. Similarly, no significant statistical difference was achieved in the median OS (mOS) of the HC group and the HE group patients, with 126.87 months (95%CI 102.08-151.658) versus 96.00 months (95%CI 78.41-113.59) (p=0.076). In the HC group, the mPFS of patients who received endocrine maintenance therapy and those who did not receive endocrine therapy were 16.24 months (95%CI 12.11-20.37) and 12.36 months (95%CI 10.26-14.46), respectively. The ORR of the two groups of patients were 46.6% and 16.7% (p=0.0015), respectively.
Conclusion: The analysis demonstrated that the combination of anti-HER2 therapy with endocrine therapy is not inferior to the combination of anti-HER2 therapy with chemotherapy as first-line treatment for HR+/HER2+ advanced breast cancer. It provides compelling evidence to support the selection of endocrine therapy plus HER2-targeted therapy as a first-line treatment strategy that that enhances the quality of life for patients without shortening their survival time.
Citation Format: Yuehua Liang, Hui Ping Li, Zehui Yun. Chemotherapy plus HER2-targeted therapy versus endocrine therapy plus HER2-targeted therapy as first-line treatment in patients with HR+/HER2+advanced breast cancer: A real-world trial [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C035.