Effect of Intensity Modulated Radiotherapy Combined with S-1-Based Chemotherapy in Locally Advanced Gastric Cancer Patients

Background: The optimal radiotherapy technique and combination with systemic therapy in locally advanced gastric cancer patients are far from being resolved despite the fact that radiochemotherapy is becoming more attractive in contemporary clinical practice. Patients and Methods: 40 patients with locally advanced gastric cancer received intensity-modulated radiotherapy (IMRT) at a dosage of 45-50.4 Gy concurrent with chemotherapy using S-1 solely or with a combination of oxaliplatin. Surgery was recommended for those who were evaluated as resectable. Sequential chemotherapy with various regimens was adopted based on the efficacy and tolerance of radiochemotherapy. Results: The overall response rate was 75% according to Response Evaluation Criteria in Solid Tumors and Japanese Gastric Cancer Association criteria. 24 finally underwent surgery, with 22 (91.7%) receiving an R0 resection (resection for cure or complete remission). The overall pathological response rate was 37.5% (9/24). Patients receiving an R0 resection had a higher 2-year overall survival rate (64.7 vs. 16.2%, p = 0.001) and local relapse-free survival rate (90.2 vs. 29.3%, p = 0.000), while there was no difference in distant metastasis-free survival rate (66.1 and 48.1% p = 0.231). Hematological and gastrointestinal toxicities of grade 1 or grade 2 were relatively common. Conclusion: The high rate of R0 resections and low rate of locoregional recurrence suggest that IMRT combined with S-1-based chemotherapy is an effective treatment for locally advanced gastric cancer patients.