Randomized phase II trial of S-1 plus irinotecan versus S-1 plus paclitaxel as first-line treatment for advanced gastric cancer (OGSG0402).

Background: S-1-based regimens are commonly used for advanced gastric cancer (AGC) in Japan. We performed this trial to evaluate the efficacy and safety of S-1 plus irinotecan (SIri) and S-1 plus paclitaxel (SPac) as first-line treatments for AGC in order to select the optimal regimen for a subsequent phase III trial.
Patients and Methods: Patients with previously untreated, locally advanced or metastatic measurable gastric adenocarcinoma were randomly assigned to receive SIri (irinotecan 80 mg/m(2) was administered intravenously (i.v.) on day 1 and 15, while 40 mg/m(2) S-1 was orally administered twice daily for three weeks from days 1-21 followed by a two-week pause) or SPac (paclitaxel 50 mg/m(2) was administered i.v. on day 1 and 8, while 40 mg/m(2) S-1 was orally administered twice daily for two weeks from day 1-14 followed by a one-week pause) regimen. The primary end-point was the overall response rate (ORR), and the secondary end-points were progression-free survival (PFS), overall survival (OS), and toxicity.
Results: A total of 102 patients were enrolled. The ORR was 33.3% for SIri and 31.4% for SPac, which did not achieved the predicted ORR in either group. PFS and OS were 5.7 and 12.4 months for SIri, 4.6 and 11.9 months for SPac respectively. No treatment-related deaths occurred during the study. Although grade 3/4 neutropenia and anemia were more frequent in the Siri group, both regimens were well-tolerated.
Conclusion: Both regimens were well-tolerated in patients with AGC, but we conclude that neither regimen was optimal for a phase III trial.