Study of Sequential Systemic Therapy + Intraperitoneal Paclitaxel in Gastric/GEJ Peritoneal Carcinomatosis

This is a phase II clinical trial assessing the safety and efficacy of sequential systemic and intraperitoneal (IP) chemotherapy in patients with primary gastric/gastroesophageal junction cancer with cytology positive peritoneal lavage and/or peritoneal carcinomatosis.

Patients with histologically proven primary gastric or gastroesophageal junction (Siewert 3) adenocarcinoma with positive peritoneal cytology or peritoneal carcinomatosis detected by laparoscopy, laparotomy or imaging and without evidence of distant organ metastasis will be eligible for this study. Patients will undergo systemic therapy for 3-4 months at the discretion of the medical oncologist based on molecular makers (PD-L1, HER -2 neu, MSI). Patients without distant organ metastatic progression after completion of systemic chemotherapy, will undergo diagnostic laparoscopy and IP port placement. IP regimen will consist of IV Paclitaxel, 5- FU and Leucovorin and IP Paclitaxel. Paclitaxel 40 mg/m2 will be instilled into the peritoneal cavity through the IP port on days 1 and 8, repeated every 21 days for 3 months (3-4 cycles). Restaging imaging with CT and /or diffusion weighted MRI with contrast will be obtained 4-6 weeks after completion of IP chemotherapy. Based on response and extent of disease, patients will be triaged to one of the following treatment plans: stable disease or response and PCI \>10 - continue IP chemotherapy regimen, progression - switch to second line regimen, response with PCI ≤ 10 and complete cytoreduction is feasible - consider cytoreduction surgery (CRS) with intraperitoneal chemotherapy (IPEC).