Prognosis of patients with advanced gastric cancer by HER2 status and trastuzumab treatment

The purpose of this study was to evaluate the impact of human epidermal growth factor receptor 2 (HER2) status and trastuzumab treatment on the prognosis of patients with advanced gastric cancer (AGC). We retrospectively analyzed 364 AGC patients who received systemic chemotherapy. To evaluate the impact of trastuzumab exposure during any type of chemotherapy, our analysis used time-varying covariates to avoid a possible lead-time bias. Among the 364 patients, 58 (15.9 %) were HER2-positive. The median overall survival of the HER2-positive patients treated with trastuzumab (n = 43) was significantly longer than that of the HER2-negative patients [n = 306; 24.7 vs. 13.9 months, with an adjusted hazard ratio (HR) of 0.58; 95 % confidence interval (CI), 0.36-0.95; P = 0.03]. Notably, 22 patients continued with trastuzumab beyond the date of progression. By contrast, the HER2-positive patients not treated with trastuzumab (n = 15) showed survival similar to that of the HER2-negative patients (13.5 vs. 13.9 months, with an adjusted HR of 1.04; 95 % CI, 0.52-2.11; P = 0.91). According to the multivariate analysis, exposure to trastuzumab was independently associated with a better prognosis (HR 0.56; 95 % CI; 0.33-0.93; P = 0.026). Recent HER2-positive AGC patients have a better prognosis than HER2-negative patients, particularly when treated with trastuzumab.