Comparing the Safety and Efficacy of First-line Polychemotherapy and Polychemotherapy in Combination With PIPAC Sessions

Inclusion Criteria: 1. Availability of signed informed voluntary consent of the patient 2. Age ≥18 years and ≤75 years 3. ECOG ≤1 4. Histological verification of gastric cancer and esophageal-gastric junction Siewert III (adenocarcinoma, ring-cell carcinoma) 5. Her2-neu negative tumor status 6. The presence of a preserved informative block of the primary tumor in the histological archive of the NOCOD (performing a biopsy and/or providing archival material - with the consent of the patient) 7. Verified gastric cancer (adenocarcinoma, ring-cell carcinoma) with the presence of M1 (with the only manifestation of M1 in the form of - Cy+ in initial peritoneal lavage and/or peritoneal dissemination PCI \<16) 8. Peritoneal adhesion index PAI \<16 9. Absence of active infectious, mental diseases, pronounced allergic conditions, as well as other concomitant pathology that may interfere with the implementation of the therapeutic and diagnostic measures provided for in the protocol 10. Adequate organ function (evaluation by laboratory parameters at screening - evaluation of hemoglobin, neutrophils, platelets, AST, ALT, total bilirubin, urea, creatinine) 11. Consent of men and women with preserved childbearing potential to use highly effective methods of contraception. Exclusion Criteria: 1. Lack of informed voluntary consent of the patient 2. Age \<18 years and \>75 years 3. ECOG ≥2 4. Histological forms other than adenocarcinoma and ring-cell carcinoma of the stomach and esophageal-gastric junction Siewert III 5. Her2-neu positive tumor status 6. The absence of a preserved informative block of the primary tumor in the histological archive of the NOCOD 7. M1 with the exception of Cy+ in initial peritoneal lavage and/or peritoneal dissemination PCI \<16 (Distant metastases, including mts in supraclavicular, mediastinal, paraaortic (16 collector), ovarian metastases. Note - MTS in peripheral lymph nodes require a fine needle puncture with cytological examination for verification. In case of mts lesions of intracorporeal lymph nodes, the criteria of mts will be - dimensions of more than 15 mm along the short axis or mts-altered structure of the lymph node, regardless of size; PCI ≥16) 8. Peritoneal adhesion index PAI ≥16 9. Contraindications to performing diagnostic laparoscopy 10. Complicated primary tumor (bleeding, decompensated stenosis, dysphagia III-IV) if not corrected. 11. Decompensated concomitant pathology 12. Primary multiple tumors (except basal cell skin cancer and cervical cancer in situ - provided there are no signs of relapse of the disease) 13. Any specific antitumor treatment for stomach cancer and /or other malignant tumor in the anamnesis (except basal cell skin cancer and cervical cancer in situ - provided there are no signs of relapse of the disease) 14. Previous specialized treatment for stomach cancer 15. Known individual intolerance to drugs included in the protocol 16. Pregnancy, breast-feeding