Long-term Results of a Phase II Study of Neoadjuvant SOX for Advanced Gastric Cancer

Background/Aim: This study aimed to evaluate the long-term survival outcomes from our previous study: a phase II study of neoadjuvant chemotherapy with S-1 plus oxaliplatin for cT4 or N2-3 advanced gastric cancer. Patients and Methods: The patients with clinical T4 and/or N2 or more lymph nodes received two cycles (3 weeks per cycle) of neoadjuvant chemotherapy with S-1 plus oxaliplatin (oxaliplatin at 130 mg/m2 on day 1 and S-1 at 80-120 mg/day on days 1 to 14), followed by gastrectomy with D2 lymphadenectomy. The final preplanned analysis of long-term outcomes, including overall and relapse-free survival, was performed. This trial has been completed and registered with the University Hospital Medical Information Network Clinical Trials Registry under number UMIN 000024656. Results: Between May 2016 and March 2019, 30 patients were enrolled. All patients completed the protocol. After a median follow-up of 50 months for surviving patients, the 3-year overall and recurrence-free survival rates were 80.0% and 76.7%, respectively, at the last follow-up in March 2023, whereas the 5-year overall and recurrence-free survival rates were 72.7% and 73.0%, respectively. Conclusion: The administration of two cycles of neoadjuvant chemotherapy with S-1 plus oxaliplatin, followed by D2 gastrectomy, was associated with relatively good long-term oncologic outcomes for patients with high-risk gastric cancer.