A Phase 2 Study of Induction Chemotherapy Using Docetaxel, Cisplatin, and S-1 for Gastric Cancer with Peritoneal Metastasis (KUGC06).

Background: The authors previously showed the significant efficacy of S-1 plus cisplatin for gastric cancer with limited peritoneal metastasis. They conducted a phase 2 study to evaluate the safety and efficacy of induction chemotherapy using a docetaxel, cisplatin, and S-1 (DCS) triplet regimen to treat gastric cancer with peritoneal metastasis.
Methods: The key eligibility criteria were gastric cancer with peritoneal metastasis or positive peritoneal cytology but no other distant metastases and capability of oral administration. The patients received three 28-day cycles of DCS (60 mg/m ² of cisplatin, 40 mg/m ² of docetaxel on day 1, and 80 mg/m ² of S-1 from day 1 to day 14), then underwent D2 gastrectomy if R0 was possible. The primary end point was the R0 resection rate. The sample size was determined to have 80% power for detecting a 20% improvement in the R0 resection rate over a 45% baseline for a one-tailed alpha of 0.1.
Results: Among 30 enrolled patients, 24 completed three cycles of DCS. The most frequent grade 3 or 4 toxicity was neutropenia (60%). A complete response of peritoneal metastasis was observed in 16 patients, and 14 patients achieved R0 resection (47%; 95% confidence interval 28-66%). When the extent of peritoneal metastasis was classified as P0CY1, P1, P2, and P3 according to the Japanese classification, the R0 resection rates were respectively 63%, 60%, 46% and 0%.
Conclusions: Induction chemotherapy with DCS is safe and can achieve R0 resection for some patients with limited peritoneal metastasis or positive peritoneal cytology. The efficacy, however, appears similar to that of S-1 plus cisplatin.