Clinical characteristics and outcomes of non-small cell lung cancer patients with HER2 alterations in Korea

Purpose Human epidermal growth factor receptor 2 (HER2) alterations are found in approximately 1%-3% of non-small cell lung cancers (NSCLCs). We evaluated the clinical features and outcomes of NSCLC harboring HER2 alteration detected by next-generation sequencing (NGS) in Korea. Materials and Methods A total of 1,108 patients who were diagnosed with NSCLC between December 2015 and December 2017 were screened and analyzed by NGS. Medical records were reviewed retrospectively to analyze the clinical characteristics and outcomes from various treatments. Results HER2 alterations were identified in 36 NSCLC patients. Of the patients, 22 (61.1%) had an exon 20 in-frame insertion mutation, 15 (41.7%) had HER2 amplification, and one had both. The median patient age was 58 years, 55.6% were male, and 50.0% were never-smokers. Adenocarcinoma was predominant (88.9%). The most common metastatic site was bone (58.3%), and 66.7% of patients were stage IV at initial diagnosis. Six patients (16.7%) had a coexistent sensitizing epidermal growth factor receptor (EGFR) mutation, and two patients (5.6%) had anaplastic lymphoma kinase (ALK) rearrangement. With a median 14 months of follow-up, the median progression-free survival of first-line treatment was 6 months (95% confidence interval, 4.172 to 7.828), and median overall survival was not reached. The proportions of adenocarcinoma, never-smokers, and metastasis to the liver were higher in the exon 20 in-frame insertion mutation group, whereas coexistence of EGFR mutation was more frequently found in the HER2 amplification group. Conclusion HER2-altered NSCLC showed distinct clinical features. Moreover, different characteristics were identified between the HER2 in-frame insertion mutation group and the HER2 amplification group.