Yang J, et al. - Given that mitogen-activated protein kinase (MAPK) pathway represents a core pathway that modulates the efficacy of anticancer drugs, researchers focused on the clinical importance of MAP3K1 rs889312 (one pivotal functional gene polymorphism in the MAPK pathway) in patients with stage II gastric cancer (GC) to stage III GC. In 591 GC patients who had received radical gastrectomy, they analyzed genotypes of MAP3K1 rs889312. Postsurgery, adjuvant chemotherapy based on platinum and fluorouracil (PF) regimens was received by 204 patients. In patients who took adjuvant chemotherapy only, MAP3K1 rs889312 AC/CC vs AA genotype [mean overall survival (OS) of 68.12 months] significantly attenuated the mean OS of 56.83 months. Patients with tumors smaller than or equal to 5 cm in size, poorly differentiated tumors and intestinal tumors experienced a significant reduction of OS due to MAP3K1 rs889312 AC/CC. Overall, the possible role of MAP3K1 rs889312 single-nucleotide polymorphism as a biomarker for adjuvant chemotherapy reaction was suggested. Its ability to predict the prognosis of GC patients managed with PF-based therapy was also shown.