Résumé : Purpose: Patient-reported outcomes (PRO) of health-related quality of life (HRQoL) and time to worsening of clinical benefit parameters were evaluated as secondary end points in the phase 3 first-line advanced gastric cancer study (FLAGS) trial of cisplatin/S-1 versus cisplatin/5-fluorouracil (5-FU) in patients with previously untreated advanced gastric cancer. Methods: The primary PRO end point was the Trial Outcome Index of the Functional Assessment of Cancer Therapy-Gastric (FACT-Ga). FACT-Ga was completed at the beginning of the first 4 cycles, cycle 6, and then every 3 cycles thereafter. The Chemotherapy Convenience and Satisfaction Questionnaire (CCSQ) was administered before the first 4 cycles; clinical benefit parameters (performance status, weight loss, and anorexia) were assessed at baseline, prior to study drug administration on day 1 of each cycle after cycle 1, and at the end of study treatment. Results: Compliance to questionnaire fulfillment was more than 80 % through cycle 9. Significantly, fewer patients treated with cisplatin/S-1 reported worsened physical well-being (PWB) scores (45.1 versus 51.7 %, p = 0.044) and experienced significantly longer time to worsening in PWB scores, with a median of 4.5 months (95 % confidence interval (CI), 3.1–5.1) compared to 3.0 months (2.8–4.6) with cisplatin/5-FU (CF) (p = 0.01). Patients receiving cisplatin/S-1 also reported significantly higher best and worst score of PWB as well as CCSQ scores and a longer median time to worsening in clinical benefit parameters. Conclusions: Differences in secondary end points of PWB, CCSQ scores, and clinical benefit parameters favoring the cisplatin/S-1 arm provide further evidence for considering this combination a standard therapeutic option for first-line treatment of advanced gastric cancer.