Testing the Addition of Paclitaxel Administered Into the Abdominal Cavity Combined With Chemotherapy for Patients With Gastric Cancer Spread to the Abdominal Cavity

The most common regimens are FOLFOX, CAPOX, FLOT, CF, and CX. Other local institutional standard of care regimens as well as targeted agents for gastric/GEJ adenocarcinoma are allowed.

Plasma is to be submitted at baseline and every three months for the first year or until progression, whichever comes first. For patients who have progression, their last plasma sample should be at time of progression.

Restaging imaging with CT and/or diffusion weighted MRI with contrast will be obtained after completion of 12 weeks (+/- 2 weeks) of assigned treatment (restaging will occur at this timepoint, regardless of if the patient completed all 4 cycles or not). At this point, patients with stable disease or a response will continue assigned treatment. In the absence of radiological or clinical progression, if clinically indicated by treatment team, patients may undergo diagnostic laparoscopy to assess surgical candidacy at which time a PCI assessment and biopsies of peritoneal nodules, peritoneal lavage could be performed. Cytoreduction can be offered to patients with a PCI \< 7 and if complete cytoreduction is feasible based on treating surgeon's discretion. If deemed a candidate for surgical cytoreduction, surgery should be performed within 6 weeks of the last study treatment in both arms.

After induction of general anesthesia, administration of preoperative antibiotics and placement of appropriate laparoscopic ports, peritoneal lavage will be performed by instillation of 200 ml of normal saline in the left upper quadrant and allowed to dwell for 5 minutes after which it will be aspirated for cytology. Extent of peritoneal disease burden will be ascertained as per the Peritoneal Cancer Index (PCI) scoring system as outlined in Appendix V.

Patients assigned to Arm B will undergo placement of indwelling tunneled intraperitoneal port with Teflon cuff following Step 1 randomization and during the diagnostic laparoscopy procedure.

Restaging imaging with CT and/or diffusion weighted MRI with contrast will be obtained after completion of 12 weeks (+/- 2 weeks) of assigned treatment (restaging will occur at this timepoint, regardless of if the patient completed all 4 cycles or not). At this point, patients with stable disease or a response will continue assigned treatment. In the absence of radiological or clinical progression, if clinically indicated by treatment team, patients may undergo diagnostic laparoscopy to assess surgical candidacy at which time a PCI assessment and biopsies of peritoneal nodules, peritoneal lavage could be performed. Cytoreduction can be offered to patients with a PCI \< 7 and if complete cytoreduction is feasible based on treating surgeon's discretion. If deemed a candidate for surgical cytoreduction, surgery should be performed within 6 weeks of the last study treatment in both arms.

"Patients on Arm B will start systemic therapy + intraperitoneal paclitaxel as early as the day after Step 1 randomization and must start within 30 calendar days (including holidays) after Step 1 randomization as per the schedule shown in the table below.~Therapy will be administered on Days 1 and 8 of a 21-day cycle for 4 cycles."