Survival of patients with KRAS G12C mutated stage IV non-small cell lung cancer with and without brain metastases treated with immune checkpoint inhibitors

Introduction: Few data is available on whether brain metastases (BM) influence survival in patients with stage IV KRAS G12C mutated (KRAS G12C+ ) non-small cell lung cancer (NSCLC) treated with first-line immune checkpoint inhibitor (ICI) +/- chemotherapy ([chemo]-ICI). Methods: Data was retrospectively collected from the population-based Netherlands Cancer Registry. The cumulative incidence of intracranial progression, overall survival (OS) and progression free survival (PFS) was determined for patients with KRAS G12C+ stage IV NSCLC diagnosed January 1 - June 30, 2019, treated with first-line (chemo)-ICI. OS and PFS were estimated using Kaplan-Meier methods and BM+ and BM- groups were compared using log-rank tests. Results: Of 2489 patients with stage IV NSCLC, 153 patients had KRAS G12C+ and received first-line (chemo)-ICI. Of those patients, 35% (54/153) underwent brain imaging (CT and/or MRI), of which 85% (46/54) MRI. Half of the patients with brain imaging (56%; 30/54) had BM, concerning one-fifth (20%; 30/153) of all patients, of which 67% was symptomatic. Compared to BM-, patients with BM+ were younger and had more organs affected with metastasis. Around one-third (30%) of patients with BM+ had & GE;5 BM at diagnosis. Three quarters of patients with BM+ received cranial radiotherapy prior to start of (chemo)-ICI. The 1-year cumulative incidence of intracranial progression was 33% for patients with known baseline BM and 7% for those without (p = 0.0001). Median PFS was 6.6 (95% CI 3.0-15.9) and 6.7 (95% CI 5.1-8.5) months for BM+ and BM- (p = 0.80), respectively. Median OS was 15.7 (95% CI 6.2-27.3) and 17.8 (95% CI 13.4-22.0) months for BM+ and BM- (p = 0.77), respectively. Conclusion: Baseline BM are common in patients with metastatic KRAS G12C+ NSCLC. During (chemo)-ICI treatment, intracranial progression was more frequent in patients with known baseline BM, justifying regular imaging during treatment. In our study, presence of known baseline BM did n