Clinical outcomes of immune checkpoint inhibitors in HER2-amplified non-small cell lung cancers.

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e21098 Background: HER2 (ERBB2) amplification is a distinct actionable oncogenic driver in 2-3% of non-small cell lung cancer (NSCLC). While HER2-targeted agents are now in development for lung cancers harboring HER2 mutations, the therapeutic landscape for patients with HER2 amplification is not well elucidated. Although immune checkpoint inhibitors (ICIs) alone or in combination with chemotherapy are widely used as treatment for NSCLC, little is known about the impact of ICIs in patients with HER2-amplified NSCLC. This study aimed to assess the efficacy of ICIs in this patient population. Methods: Patients with HER2-amplified NSCLC were identified from January 2014 to October 2021. HER2 amplification was detected by next generation sequencing (NGS) on the MSK-IMPACT platform. Clinicopathologic and molecular features, as well as response to therapy with ICIs were assessed. Patients were excluded if they harbored concurrent HER2 mutations, had localized disease, or received concurrent chemotherapy. Patient records were reviewed to evaluate overall survival (OS), progression free survival (PFS) and overall response rate (ORR). Results: Eighteen patients with metastatic HER2-amplified NSCLC who received ICI alone as first line treatment or subsequent therapy after progression met inclusion criteria. Histologic subtypes included adenocarcinoma (78%) and squamous cell carcinoma (22%). PD-L1 expression was available for 16 patients, with 69% having no expression of PD-L1. The median tumor mutation burden (TMB) was 9.2 mutations/Mb (range 3.0-35.4). The median OS was 11 months (95% CI: 4 to 37), with 6-month and 12-month survival being 67% (95% CI: 40% to 83%) and 49% (95% CI: 25% to 70%), respectively. Median PFS was 2 months (95% CI: 1 to 7). In the 15 patients that were assessed for response, the ORR was 0% (95% CI 0% to 19%), including 3 cases with PD-L1 expression of ≥ 50% and 9 cases with TMB ≥ 10 mutation/Mb. Conclusions: Patients with HER2-amplified NSCLC showed minimal response to immunotherapy, regardless of PD-L1 status and TMB. These findings underscore the importance of developing novel HER2-targeted agents for these patients with unmet medical need.