Clin Cancer Res. 2020 Jul 24:clincanres.1825.2020. doi: 10.1158/1078-0432.CCR-20-1825. Online ahead of print.
PURPOSE: SMARCA4 mutations are among the most common recurrent alterations in NSCLC, but the relationship to other genomic abnormalities and clinical impact has not been established.
EXPERIMENTAL DESIGN: To characterize SMARCA4 alterations in NSCLC, we analyzed the genomic, protein expression, and clinical outcome data of patients with SMARCA4 alterations treated at Memorial Sloan Kettering.
RESULTS: In 4813 tumors from patients with NSCLC, we identified 8% (n= 407) patients with SMARCA4-mutant lung cancer. We describe two categories of SMARCA4 mutations: Class 1 mutations (truncating mutations, fusions and homozygous deletion) and Class 2 mutations (missense mutations). Protein expression loss was associated with Class 1 mutation (81% vs 0%, (P < 0.001)). Both classes of mutation co-occured more frequently with KRAS, STK11, and KEAP1 mutations compared to SMARCA4 wildtype tumors (P < 0.001). In patients with metastatic NSCLC, SMARCA4 alterations were associated with shorter overall survival, with Class 1 alterations associated with shortest survival times (P < 0.001). Conversely, we found that treatment with immune checkpoint inhibitors was associated with improved outcomes in patients with SMARCA4-mutant tumors (P = 0.01), with Class 1 mutations having the best response to ICIs (p = 0.027).
CONCLUSIONS: SMARCA4 alterations can be divided into two clinically relevant genomic classes associated with differential protein expression as well as distinct prognostic and treatment implications. Both classes co-occur with KEAP1, STK11, and KRAS mutations, but individually represent independent predictors of poor prognosis. Despite association with poor outcomes, SMARCA4-mutant lung cancers may be more sensitive to immunotherapy.