However, as the ACTS-GC had the control group of patients who had received surgery alone without adjuvant chemotherapy, the ACTS-GC investigators showed that the benefit of adjuvant S-1 therapy is mostly confined to GC patients with high intratumoral DPD mRNA expression [surgery followed by adjuvant S-1 therapy vs. surgery alone; HR on OS, 0.52 (95% CI; 0.38–0.72)]; in contrast, in patients with low intratumoral DPD expression, adjuvant S-1 therapy seemed to have less benefit [surgery followed by adjuvant S-1 therapy vs. surgery alone; HR on OS, 0.85 (95% CI; 0.56–1.28)] [32]. This evidence concerns the gene DPYD and gastric cancer.