Predictive Value of the nProfiler 1 Assay for the Efficacy of Adjuvant S-1-Based Doublet Chemotherapy in Stage III Gastric Cancer: A Post-Hoc Analysis of a Randomized Phase III Trial.

Purpose: The nProfiler 1 Stomach Cancer Assay (nProfiler1), designed to predict responses to fluorouracil-based adjuvant chemotherapy, measures the expression of four gastric cancer target genes (GZMB, WARS, SFRP4, and CDX1). The randomized phase III POST trial aimed to compare the efficacies of two adjuvant S-1-based doublet chemotherapies: S-1 plus cisplatin (SP) and S-1 plus docetaxel (DS). This study aimed to validate the nProfiler1 assay using a distinct cohort from the POST trial.

Materials and methods: The nProfiler1 assay stratifies patients into three groups (low-risk, intermediate-risk, and high-risk) using the prognostic single-patient classifier and two groups (chemotherapy-benefit and no-benefit) using the predictive single-patient classifier. The nProfiler1 assay was applied to formalin-fixed paraffin-embedded slides obtained from the POST trial. Disease-free survival (DFS) and overall survival (OS), including 5-year survival rates, were calculated for the enrolled patients.

Results: Of the 153 patients in the POST trial, 118 were included in the post-hoc analysis. With a median follow-up of 57.9 months, no significant difference in DFS or OS was observed between the SP and DS groups. The prognostic single-patient classifier predicted the OS in the SP group (p=0.0425) but not in the DS group (p=0.5940). The chemotherapy-benefit group exhibited numerically longer DFS than the no-benefit group in the SP and DS groups.

Conclusion: The nProfiler1 assay offers valuable insights into the prognosis and efficacy of adjuvant chemotherapy based on fluorouracil plus platinum doublet regimens but not docetaxel-containing regimens. Further validation with larger patient cohorts and different regimens is warranted.