Long-term Outcomes of OGSG1108: A Supplemental Study of Oral Nutritional Supplementation During Adjuvant S-1 Chemotherapy

Abstract

Background/Aim: The OGSG1108 trial evaluated the effect of oral elemental nutritional supplementation (ONS) on one-year compliance with adjuvant S-1 chemotherapy after gastrectomy for pathological stage II/III gastric cancer. It remains unknown whether intervention with ONS affords survival benefits, along with enhanced compliance with adjuvant chemotherapy. Patients and Methods: Two groups of patients registered in the OGSG1108 trial were compared. The on-protocol group included 81 patients with pathological stage II/III gastric cancer and good acceptability (≥60%) in an ONS compliance test, who were eligible for the second registration and received protocol-based treatment with adjuvant S-1 and ONS. The off-protocol group included 24 patients with pathological stage II/III gastric cancer and poor acceptability (<60%) in an ONS compliance test, who were ineligible for the second registration and received optional adjuvant S-1 as an off-protocol treatment. Supplemental data were collected for both groups. Patient characteristics, biochemical and oncological factors, postoperative complications, number of S-1 chemotherapy courses, overall survival (OS), and relapse-free survival (RFS) were compared and prognostic factors were analyzed. Results: The number of S-1 courses was comparable between the two groups (on-protocol vs. off-protocol: 6.3±2.5 vs. 5.9±3.3). No significant differences were observed in 5-year OS (71.9% vs. 66.7%, p=0.700) or RFS (58.4% vs. 62.5%, p=0.972). A multivariate analysis identified pathological stage and number of S-1 courses as independent prognostic factors, but not acceptability of ONS. Conclusion: Postoperative intervention with ONS did not seem to improve the prognosis of patients receiving adjuvant S-1 treatment. The number of S-1 courses was a prognostic factor.