Abstract P1-11-16: Treatment with tyrosine kinase inhibitors (TKIs) in HER2-positive metastatic breast cancer after trastuzumab emtansine (T-DM1) failure: A real-world study

Abstract

Abstract Background Trastuzumab emtansine (T-DM1) has shown great effectiveness in treating HER2-positive metastatic breast cancer, but therapies subsequent to T-DM1 failure remain controversial. Here, we investigated efficacy and safety of tyrosine kinase inhibitors (TKIs) based therapy in T-DM1 resistant HER2-positive metastatic breast cancer. Methods From August 2019 to April 2022, 53 HER2-positive metastatic breast cancer patients received TKIs-based therapy after T-DM1 failure in Jiangsu Province Hospital. Progression-free survival (PFS), overall survival (OS), objective response rate (ORR), clinical benefit rate (CBR), and safety profiles were reported. Results 53 patients received TKIs-based therapies as a second or later line therapy. 51 (96.2%) patients received a combined therapy, including TKIs plus capecitabine, vinorelbine or trastuzumab. 2 (3.7%) patients received TKIs alone. The median follow-up time was 19.7 months (95%CI 15.4-24.0). The median PFS was 11.9 months (95%CI 7.9-15.9). OS has not reached. ORR was 19.6% and CBR was 72.5%. For patients who had brain metastasis (n=12), the median PFS was 10.5 months (95%CI 7.5-13.5) and intracranial ORR was 33.3%. Compared with lapatinib (n=30), pyrotinib (n=21) provided a better PFS after T-DM1 progression (8.0 months vs. 19.0 months, P=0.033). The most common adverse events were thrombocytopenia (12, 23.6%), diarrhea (8, 15.7%), leucopenia (8, 15.7%) and hand-foot syndrome (8, 15.7%). Conclusion TKIs-based therapy could prolong the survival of HER2-positive metastatic breast cancer patients after T-DM1 failure, including those with brain metastases. Compared with lapatinib, pyrotinib might provide better outcomes for overcoming T-DM1 resistance. Citation Format: Yongmei Yin, Wei Li, Xiang huang, Chunxiao Sun, Yijia Hua, Nan Jin, Xinyu Wu. Treatment with tyrosine kinase inhibitors (TKIs) in HER2-positive metastatic breast cancer after trastuzumab emtansine (T-DM1) failure: A real-world study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-11-16.