Post-hoc biomarker analyses of T4a/T4b gastric cancer from patients recruited into SAMIT, a phase III randomized controlled trial

Biomarkers for selecting gastric cancer (GC) patients likely to benefit from sequential paclitaxel treatment followed by fluorinated-pyrimidine-based adjuvant chemotherapy were searched for using samples of patients recruited into SAMIT, a phase III randomized controlled trial. Total RNA was extracted from 556 GC patients and the expression of 105 genes were quantified using real-time PCR. Genes predicting positive effects of sequential paclitaxel on overall survival (OS), disease-free survival (DFS), or cumulative incidence of relapse were identified based on p-values associated with the interaction between the biomarker and sequential paclitaxel or monotherapy group. Low VSNL1 and CD44v expression predicted the positive effects of sequential paclitaxel in all above three endpoints. In the patient subgroup with combined low expression of both genes, sequential paclitaxel therapy was associated with a significantly improved OS (hazard ratio [HR] = 0.48 [95% confidence interval (CI), 0.30–0.78]; p < 0.01; interaction p-value < 0.01), particularly in patients with stage IIIB GC (HR = 0.39 [95% CI, 0.20–0.75]; p < 0.01; interaction p-value < 0.01). In this study, two biomarkers were identified. Our findings might open up the way for clinical trials on biomarker-oriented postoperative adjuvant chemotherapy for locally advanced cancer.