Genomic and immune characteristics of HER2‐mutated non‐small‐cell lung cancer and response to immune checkpoint inhibitor‐based therapy

The efficacy of immunotherapy in advanced HER2‐mutated non‐small‐cell lung cancer (NSCLC) remains incomprehensively studied. A total of 107 NSCLC patients with de novo HER2 mutations were retrospectively studied at Guangdong Lung Cancer Institute [GLCI cohort, exon 20 insertions (ex20ins): 71.0%] to compare clinical/molecular features and immune checkpoint inhibitor (ICI)‐based therapy efficacy between patients with ex20ins and non‐ex20ins. Two external cohorts (TCGA, n = 21; META‐ICI, n = 30) were used for validation. In the GLCI cohort, 68.2% of patients displayed programmed death‐ligand 1 (PD‐L1) expression < 1%. Compared with ex20ins patients, non‐ex20ins patients had more concurrent mutations in the GLCI cohort (P < 0.01) and a higher tumour mutation burden in the TCGA cohort (P = 0.03). Under ICI‐based therapy, advanced NSCLC patients with non‐ex20ins had potentially superior progression‐free survival [median: 13.0 vs. 3.6 months, adjusted hazard ratio (HR): 0.31, 95% confidence interval (CI): 0.11–0.83] and overall survival (median: 27.5 vs. 8.1 months, adjusted HR: 0.39, 95% CI: 0.13–1.18) to ex20ins patients, consistent with findings in the META‐ICI cohort. ICI‐based therapy may serve as an option for advanced HER2‐mutated NSCLC, with potentially better efficacy in non‐ex20ins patients. Further investigations are warranted in clinical practice.