Molecular characteristics and clinical outcomes of ERBB2-activating mutation-positive non-small cell lung cancer: A Japanese nationwide real-world cohort

Background: Erb-b2 receptor tyrosine kinase 2 (ERBB2)-activating mutations are well-documented oncogenic drivers in non-small cell lung cancer (NSCLC), occurring in approximately 1–4% of cases. These alterations include a heterogeneous spectrum of variant subtypes; however, the clinicogenomic characteristics and clinical significance of the individual variants have yet to be elucidated.
Methods: We searched the nationwide Center for Cancer Genomics and Advanced Therapeutics database, which integrates comprehensive genome profiling data generated in routine clinical practice across Japan, to investigate the molecular landscape and clinical outcomes of patients with ERBB2-mutated NSCLC.
Results: A total of 319 patients with ERBB2-activating mutations were included in this retrospective analysis. Although 74% of the patients harbored canonical tyrosine kinase domain (TKD) in-frame insertions, 26% carried noncanonical variants, including TKD missense (8%), transmembrane/juxtamembrane domain (10%), and extracellular domain (ECD) mutations (8%). Co-occurring oncogenic driver alterations were identified in only 18 cases (5.6%) and were largely restricted to noncanonical variants, whereas no co-occurring driver alterations were detected among patients with TKD in-frame mutations. Noncanonical variants—TKD missense and ECD mutations in particular—were associated with an increased tumor mutational burden. Among 288 patients with available survival data, 78 (27%) received trastuzumab deruxtecan (T-DXd) during their clinical course. After excluding patients who had started treatment with T-DXd before undergoing comprehensive genome profiling testing, time-dependent T-DXd exposure was associated with a reduced risk of death (adjusted hazard ratio, 0.63; 95% confidence interval, 0.39–1.01; P = 0.057).
Conclusions: ERBB2-mutated NSCLC exhibited substantial molecular heterogeneity, with canonical TKD in-frame insertions characterized by a low frequency of co-occurring oncogenic driver alterations. Among patients harboring ERBB2-activating mutations, exposure to T-DXd was associated with improved overall survival.