10195-MET-11 THE PREDICTIVE FACTORS OF EFFICACY OF PEMBROLIZUMAB IN BRAIN METASTASES OF LUNG CANER

Abstract The main treatment for metastatic brain tumors is radiation therapy or surgical removal. Since the pembrolizumab, an anti-PD1 monoclonal antibody, was revealed to be effective for brain metastases of lung cancer, it has been used as a therapeutic option. However, the predictive factors of its efficacy have been unclear. If the efficacy of pembrolizumab can be predicted prior to the treatment of metastatic brain tumors, it will have a significant impact on subsequent treatment strategies. In this study, we performed a retrospective analysis of patients with metastatic brain tumors from lung cancer treated with pembrolizumab to investigate predictive factors of pembrolizumab efficacy. From January 2018 to July 2023, 73 patients were treated with pembrolizumab for brain metastases of lung cancer at our institution. Among them, 16 patients who had received pembrolizumab for at least 1 year were included. Median age was 68 years (45-86), 10 were male (63%), and median period of pembrolizumab treatment was 105 months (49-319). Patients with brain metastasis which was well controlled for at least 2 years after starting pembrolizumab were defined as effective, and those who required new treatment were defined as invalid. There were 11 effective cases and 5 invalid cases. We compared clinical characteristics, genetic characteristics of the primary tumor, and imaging characteristics of metastatic brain tumors between the effective and ineffective cases, and identified predictive factors for efficacy of pembrolizumab.