This is a phase III randomized, multicenter study with two different arm:

• experimental: prophylactic surgery plus HIPEC CO2 performed with mitomycin and cisplatin
• comparator: standard surgery

Adjuvant treatment after surgery is mandatory except for documented cases of non-eligibility in both arms.

Patient will be randomized in a 1:1 ratio. Randomization will be performed during surgery if the total resection of tumor will be reached according to center and neoadjuvant chemotherapy as stratification variables.

This is a phase III randomized, multicenter study with two different arm:

• experimental: prophylactic surgery plus HIPEC CO2 performed with mitomycin and cisplatin
• comparator: standard surgery Adjuvant treatment after surgery is mandatory except for documented cases of non-eligibility.

Patient will be randomized in a 1:1 ratio. Randomization will be performed during surgery if the total resection of tumor will be reached according to center and neoadjuvant chemotherapy as stratification variables.

The primary objective of the study is to compare the efficacy of prophylactic surgery (radical gastric resection, appendectomy, round ligament of the liver resection and bilateral adnexectomy) plus HIPEC CO2 versus standard surgery in terms of disease free survival (DFS).

Patients affected by gastric carcinoma at high risk of developing peritoneal carcinomatosis will be randomized in this study.

Inclusion Criteria:

1. Patients with histologically documented gastric carcinoma (diffuse/intestinal histotype) eligibile for R0.

   1. Presurgical or intraoperative stage T3-T4 N0-N+ primary tumour (TNM 8 th).
   2. Urgent presentation: perforation without purulent generalized peritonitis
   3. Positive cytology of peritoneal fluid (if previously obtained)

2. Age ≥ 18 years and ≤75 years.

3. Written informed consent.

Exclusion Criteria:

1. Gastroesophageal Junction (GEJ) cancer
2. Distant metastatic disease (even if limited and completely resected)
3. Peritoneal carcinomatosis
4. History of tumor diagnosed in the 3 years before entering the study, except for topical and healed pathologies that do not need further treatment (e.g. non-melanoma skin carcinomas, superficial bladder carcinomas or in situ carcinoma of the breast or cervix).
5. Psychological, family or social conditions which may negatively affect the treatment and follow-up protocol.
6. Poor general conditions (ECOG > 2).
7. Impaired cardiac function (history of congestive heart failure or FE <40%). Clinically significant cardiovascular disease: cerebral vascular accident/stroke (< 6 months prior to enrolment), unstable angina, congestive heart failure (New York Heart Association Classification Class > II) or serious uncontrolled cardiac Arrhythmia requiring medication
8. Impaired renal function (creatinine> 1.5 upper limit of normal or creatinine clearance <60 mL / min).
9. Impaired hepatic function (AST, ALT >2.5 upper limit of normal, bilirubin > 1.5 upper limit of normal).
10. Impaired hematopoietic function (leucocytes <4000 / mm3, neutrophils <1500 / mm 3, platelets <100000 / mm3).
11. Impaired pulmonary function (presence of COPD or other pulmonary restrictive conditions with FEV1 <50% or DLCO <40% of normal age value).
12. History or presence of other disease, metabolic dysfunction, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates use of HIPEC or chemotherapy or patient at high risk from treatment complications.
13. Pregnancy.
14. Krukenberg tumor
15. Refusal to join the study.