Prognostic impact of human epidermal growth factor-2 (HER2) status on overall survival (OS) of advanced gastric cancer (AGC) patients (pts) treated with standard chemotherapy without trastuzumab as a first-line treatment: A Japanese multicenter collaborative retrospective study.

Abstract

4075 Background: The prognostic impact of HER2 status on OS of AGC pts treated with standard chemotherapy without trastuzumab for first-line treatment remains controversial. This study investigated whether HER2 status is an independent prognostic factor for AGC pts. Methods: Formalin-fixed paraffin-embedded tumor samples from 293 eligible pts were examined for HER2 by immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). Eligible criteria included: 1) histologically confirmed gastric or gastroesophageal junction adenocarcinoma, 2) unresectable or recurrent cancer, 3) treated with S-1 plus cisplatin as first-line chemotherapy, 4) age: ≥20, 5) ECOG performance status score: 0-2 and 6) with archived tumor sample. HER2+ was defined as IHC 3+ or IHC 2+/FISH+. Results: Of 293 pts, 43 (15%) were HER2+. Baseline pt characteristics between HER2+ and HER2- pts were significantly different by histology (intestinal/diffuse, 65%/35% vs. 39%/61%; p=0.001), measurable disease by RECIST v1.0 (91% vs. 69%; p=0.003), No. of metastatic sites (≥2, 72% vs. 46%; p=0.003) and presence of liver metastasis (56% vs. 31%; p=0.003). After median follow-up time of 48.9 months with 270 (92%) death events, there was no significant difference in OS between HER2+ and HER2- pts (median, 11.7 vs. 13.7 months; hazard ratio [HR] 1.11, 95% CI 0.79–1.55; log rank p=0.550). After adjusting other prognostic factors with Cox hazard model, HER2+ was still not prognostic for OS (HR 0.890, 95% CI 0.627–1.262, p=0.513). Conclusions: HER2 status has no significant prognostic impact on OS of AGC pts treated with S-1 plus cisplatin without trastuzumab as a first-line treatment.