Impact of HER2 Gene and Protein Status on the Treatment Outcome of Cisplatin-Based Chemoradiotherapy for Locally Advanced Non-small Cell Lung Cancer

Abstract

It has not been fully evaluated whether both HER2 gene copy number and HER2 protein expression are related to the outcome of chemoradiotherapy in patients with locally advanced non-small cell lung cancer (LA-NSCLC). The aim of this study was to evaluate their relationships. HER2 gene copy number determined by fluorescence in situ hybridization (FISH) and HER2 protein expression determined by immunohistochemistry (IHC) were assessed in 68 patients with LA-NSCLC enrolled in our previous phase II trials of concurrent cisplatin-based chemoradiotherapy, and a multivariate analysis was conducted for response and survival. HER2-IHC-positive tumors were detected in 23 patients (34%), and the median ratio of HER2 to chromosome 17 copy number was 0.93 (range, 0.55-2.00). The HER2-FISH results were marginally correlated with the IHC results (p = 0.0715). When the median ratio in the FISH analysis was used as a cut-off level for its positivity, there was no association between either HER2-FISH or IHC status and objective response to chemoradiotherapy. Contrary, a multivariate analysis revealed HER2-FISH result but not IHC result was an independent poor prognostic factor for both overall survival and progression-free survival (hazard ratio = 2.568, 95% confidence interval [CI] = 1.117-5.903, p = 0.0264 and hazard ratio = 2.283, 95% CI = 1.005-5.189, p = 0.0487, respectively). Patients with HER2 FISH-positive LA-NSCLC had a poorer outcome even when treated with cisplatin-based chemoradiotherapy, despite the strong need for validation assessment of these observations. Development of more effective treatment for these high-risk patients is needed to improve their poor prognosis.