Lung cancer is one of the most common cancers in men and women, and is the leading cause of cancer-related death (approximately 25% of all cancer deaths) worldwide. 1,2 Most cases of lung cancer are non-small-cell lung cancer (NSCLC) (approximately 85%), which can be further classified as adenocarcinoma, squamous cell carcinoma, or large cell carcinoma. 3 Although multiple strategies, including surgery, chemotherapy, radiotherapy, and immunotherapy, have been applied in the clinical treatment of NSCLC, the 5-year overall survival (OS) rate of NSCLC patients at all stages is only 16%. 4,5 Thus, studies that investigate the molecular mechanisms underlying the progression and metastasis of NSCLC would be valuable for development of novel therapeutic options for lung cancer in the clinic.

9080 Background: Patients (pts) with brain metastases (BM) were usually unrepresented in clinical trials assessing the efficacy of PD-(L) 1 inhibitors. Here, we investigated the efficacy and safety of tislelizumab (TIS) plus chemotherapy in NSCLC pts with asymptomatic untreated BM or with stable BM after local radiotherapy. Methods: This multicenter, prospective, open-label phase 2 study enrolled systemic treatment-naïve pts with stage IV non-squamous (nsq) NSCLC without EGFR or ALK mutations who had BM. Pts received TIS combined with pemetrexed and carboplatin for 4 cycles, followed by maintenance TIS and pemetrexed. RECIST v1.1 and RANO-BM were applied for assessment for systematic and brain disease, respectively. The primary endpoint was the investigator-assessed 1-year PFS rate per RECIST v1.1. Results: 36 pts were enrolled with 77.8% having stage IVB disease, 25.0% liver metastases and 41.7% bone metastases. 29 (80.6%) pts were with untreated, asymptomatic brain metastases, and the other 7 (19.4%) received radiotherapy for BM previously. As of 30 Nov 2022, the median follow-up was 12.3 months. 1-year systematic PFS rate was 36.8% (95% CI, 18.0-55.7), with median PFS of 7.5 months (95% CI, 5.1-NE). Systematic ORR was 50.0% (95% CI, 31.9-68.1%). Median OS was not reached, with 1-year OS rate of 70.5% (95% CI, 51.7-83.1). For intracranial efficacy assessment per RANO-BM, 1-year intracranial PFS (iPFS) rate was 56.6 % (95% CI, 31.7-75.5), with 45.5% (95% CI, 19.4, 68.5) and 100% in pts with untreated and pretreated BM, respectively. Intracranial ORR was 56.7% (95% CI, 37.4-74.5%), with 53.8% (95% CI, 33.4-73.4%) in pts with untreated BM and 75% (95% CI, 19.4-99.4%) in pretreated BM. No grade 5 toxicities were observed. Grade 3-4 TRAEs occurred in 33.3% (12/36) of pts. 13.9% of pts experienced irAEs; grade 3-4 irAEs occurred in 2 (5.6%) pts. Conclusions: TIS plus chemotherapy yielded promising systematic and intracranial PFS, and was generally well tolerated in nsq-NSCLC pts with untreated or pretreated BM. Clinical trial information: NCT04507217 . [Table: see text]