DDDR-20. CLINICAL EFFICACY OF PYROTINIB COMBINING WITH STEREOTACTIC RADIOSURGERY IN HER2-POSITIVE BREAST CANCER BRAIN METASTASES

Abstract BACKGROUND Up to 50% of patients with breast cancer (BC) and human epidermal growth factor receptor 2 (HER2) positive present with disease progression in brain metastases (BM). Pyrotinib, an oral irreversible pan-HER receptor tyrosine kinase inhibitor, has shown efficacy in active central nervous system (CNS) metastases. However, clinical efficacy of pyrotinib combining with stereotactic radiosurgery (SRS) in BCBM is unclear. METHODS This retrospective, observational study collected data from 52 HER2+ BC patients with brain metastasis who received pyrotinib-based therapy in Guang dong Sanjiu brain hospital from 2019 to 2023. Among these patients, 36 received pyrotinib-based therapy combining with SRS concurrently, or within 1 months. Age, stage at diagnosis, dates of BM, primary tumor subtypes, prior systemic therapy, CNS-directed local therapy, the objective response and survival status were collected. The assessment of adverse effects was based on CTCAE 4.0. RESULTS 34 patients were evaluable for efficacy (median age: 51.5). With a median follow-up duration of 19.6 months, 1 patient (0.3%) achieved CR, while 27 patients (79.4%) had PR, resulting in an ORR of 82.3%. The median CNS PFS was 13.2 months (95% CI, 4.9-21.7). Median overall survival (OS) was 22.6 months (95% CI, 17.5-27.6). The most common grade 3 or worse treatment-emergent adverse event was diarrhea (6 [17.6%]). CONCLUSIONS Our results suggest that pyrotinib combining with SRS is associated with promising efficacy and a satisfactory safety profile for Her2+ breast cancer brain metastases.