Impact of an Omega-3 Enriched Oral Nutritional Supplement on Improving Surgical Outcomes in Patients With Peritoneal Carcinomatosis Undergoing Cytoreductive Surgery

The OMNI study is a clinical trial investigating whether a nutritional supplement with added Omega-3 fatty acids can improve surgical outcomes for patients with peritoneal carcinomatosis. Peritoneal carcinomatosis is a type of cancer that affects the abdominal lining and often requires complex and extensive surgery called cytoreductive surgery (CRS). This procedure is associated with a high risk of postoperative complications, such as infections and long hospital stays. Omega-3 fatty acids are known for their anti-inflammatory and immune-modulating properties. The study's main goal is to see if a 21-day regimen of a pre-operative Omega-3 enriched oral nutritional supplement (ONS) can reduce postoperative complications, as measured by the Clavien-Dindo classification. Who can participate? The study is recruiting patients over 18 years old who have been diagnosed with non-gynecological peritoneal carcinomatosis and are scheduled to undergo cytoreductive surgery and HIPEC (hyperthermic intraperitoneal chemotherapy). What does participating involve? Upon joining the study, participants will be randomly assigned to one of two groups: * Intervention Group: Participants will receive an Omega-3 enriched nutritional supplement called Fortimel Forticare. * Control Group: Participants will receive a standard nutritional supplement called Fortimel Compact Protein. Both groups will be asked to consume two bottles of their assigned supplement per day for 21 days before the scheduled surgery. What will be measured? Throughout the study, the investigators will perform various assessments to monitor participant health and recovery: * Before and after surgery: The investigators will take body measurements, conduct a bioimpedance analysis (BIA) to check body composition, and perform a Hand Grip test to measure muscle strength. The investigators will also collect blood and stool samples. * During surgery: The investigators will collect tissue samples to study the tumor environment. * After surgery: The investigators will track patient recovery, including the length of the hospital stay and any complications that may occur. The investigators will also continue to monitor certain markers in the patients' blood. The study is expected to enroll a total of 28 patients.