Impact of HER2 gene and protein status on the treatment outcome of cisplatin-based chemoradiotherapy for locally advanced non-small cell lung cancer

BACKGROUND: 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. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.