KRAS mutation subtypes responded differently to combination immunotherapy via disturbing myeloid-derived suppressor cells in non-small cell lung cancer.

8635 Background: The combination of immune checkpoint inhibitors (ICIs) and chemotherapy has shown high efficacy in non-small cell lung cancer (NSCLC) patients, but further exploration of the predictive biomarkers is needed. KRAS is the most common driver oncogene in patients with NSCLC. However, the influence of different KRAS mutation subtypes on immunotherapy response remains controversial. We aimed to evaluate the value of KRAS mutation subtypes for predicting response to immunotherapy in NSCLC patients and to further analyze the related tumor immune microenvironment (TiME) phenotypes. Methods: In this retrospective study, clinical data were extracted from the medical records of patients with advanced NSCLC treated with ICIs and whose available molecular analysis included KRAS mutation information between January 2017 and December 2022. NSCLC tissue samples were collected for TiME analysis. Differences in immune cell subsets between different groups were analyzed using the Mann‒Whitney U test. Clinical characteristics, ICI treatment efficacy, progression-free survival (PFS), and overall survival (OS) were analyzed using multivariate Cox models. Results: A total of 1913 eligible KRAS-mutated NSCLC patients were screened, and 137 patients who received systemic immunotherapy were enrolled (108 males vs 29 females), with a median age of 62 (range, 39-84) years. Among them, 126 (92.0%) patients had adenocarcinoma, 99 (72.3%) patients were systemic therapy naïve, and 124 (90.5%) patients received combined immunotherapy. Among the patients with KRAS mutations, 48 (35.0%) had G12C, 20 (14.6%) had G12V, 27 (19.7%) had G12D and 42 (30.7%) had other subtypes. PFS was significantly longer in the G12C subgroup than in the other mutation subgroup (median PFS: 11.3 vs 6.8 months, P = 0.001). The median PFS times in the G12C/G12V subgroup and the other groups were 11.1 months and 6.5 months, respectively ( P= 0.0005). Multivariate analysis of the immunotherapy cohort revealed that G12C/G12V was an independent predictor of PFS ( P = 0.003, hazard ratio (HR): 2.021, 95% CI: 1.265-3.227). Further TiME analysis suggested that the infiltration of myeloid-derived suppressor cells (MDSCs, CD33+CD11b+) in the tumor and stromal areas in the G12C/G12V subgroup was significantly lower than that in the other subgroup (tumor area, P= 0.045; stroma area, P= 0.015). However, no significant difference in PD-L1 expression was found between the G12C/G12V group and the other groups. Conclusions: KRAS G12C and G12V were associated with favorable combined ICI treatment efficacy in patients with NSCLC. Patients with G12C or G12V mutations had longer PFS and lower infiltration of MDSCs. KRAS mutation subtypes are potential predictive biomarkers disturbed by MDSCs for combination therapy in NSCLC patients.