The study was designed to evaluate the efficacy of perioperative FLOT chemotherapy in combination with perioperative hyperthermic intraperitoneal chemotherapy (HIPEC) in patients with advanced gastric cancer at high risk of peritoneal metastases. The impact of treatment on peritoneal recurrence and survival over 6 months, 1, 3 and 5 years will be assessed.

This is a randomized, multicenter, clinical trial in which 598 patients with advanced gastric cancer at high risk of peritoneal metastases are randomly allocated to receive either preoperative hyperthermic intraperitoneal chemotherapy (HIPEC) plus gastrectomy (experimental group) or gastrectomy alone (control group). All patients, regardless of allocation, will additionally receive 4 cycles of FLOT chemotherapy (docetaxel 50 mg/m2, oxaliplatin 85 mg/m2, leucovorin 200 mg/m2 and 5-fluorouracil 2600 mg/m2) before surgery ± HIPEC and 4 cycles of FLOT chemotherapy after gastrectomy. The main outcome is frequency of peritoneal recurrence by 6-months post-operative. Patients will be followed for 5 years and undergo additional evaluations at 6 months, 1 year, 3 and 5 years.

The study will take place at 7 hospitals across Poland. All participating centers have the equipment and skills to perform all necessary procedures in this study. The below centers specialize in the treatment of stomach cancer with many documented years of experience. They are trained in the maintenance of a register, possess the skills to conduct appropriate research analyses and are equipped with a system for assessing the quality of both surgical and oncological treatment.

Inclusion Criteria:

• Gastric cancer confirmed histopathologically in tumor specimens.
• Age 18-75 years.
• Advanced gastric cancer cT3 / cT4a / N0-3b.
• No distant metastases on computed tomography (CT) scan of the chest, abdomen and pelvis (cM0).
• Written consent to participate in the study.

Exclusion Criteria:

• No clear histopathological confirmation of gastric cancer.
• Age > 75 years.
• Poor general condition (Performance Status 3 or more on the Eastern Cooperative Oncology Group (ECOG)/World Health Organization scale).
• Previous abdominal surgery (including oncological surgery), other than laparoscopic cholecystectomy or appendectomy (open or laparoscopic).
• Pregnancy and lactation.
• Refusal to participate or an inability to provide written consent.
• Coexisting cancer in another location.
• Systemic treatment or radiotherapy for another cancer.
• Dysphagia requiring surgical treatment (gastric resection or nutritional jejunostomy) before starting neoadjuvant treatment and indication for accelerated surgery for other reasons.
• Disqualification for perioperative FLOT4 chemotherapy as decided by a multi-specialist consultation.