Phase 1 Study of Combined Chemotherapy of Nab-Paclitaxel, S-1, and Oxaliplatin for Gastric Cancer with Peritoneal Metastasis (NSOX Study)

Objectives: A regimen of S-1 combined with oxaliplatin (SOX) has been widely used as the first-line regimen for advanced gastric cancer. To further improve the antitumor efficacy for gastric cancer patients with peritoneal metastasis, we added nab-paclitaxel to the established SOX regimen (NSOX). Nab-paclitaxel (nanoparticle albumin-bound paclitaxel) has effective transferability to tumor tissues and strong antitumor effects for peritoneal metastasis. We performed a phase 1 study of this regimen to determine the maximum tolerated dose (MTD) and the recommended dose (RD) in patients with gastric cancer with peritoneal metastasis. Methods: The NSOX regimen involved 21-day cycles with escalated doses of nab-paclitaxel (50 [level 1] to 80 [level 4] mg/m2 on days 1 and 8) and fixed doses of oxaliplatin (100 mg/m2 on day 1) and S-1 (80 mg/m2/day for 2 weeks). Results: Six patients with gastric cancer with peritoneal metastasis were enrolled. The MTD was determined to be dose level 2, as 2 of 3 patients experienced dose-limiting toxicities (DLTs), grade 4 non-hematological toxicities. One patient experienced acute myocardial infarction, and the other patient developed jejunal perforation. There were no treatment-related deaths. No patients experienced DLTs, so the RD was determined to be dose level 1. Conclusions: The NSOX regimen was shown to be a tolerable regimen and may be a promising triplet therapy for patients with gastric cancer with peritoneal metastasis.