The importance of postoperative rehabilitation on physical performance and recovery is well-recognized. However, the preoperative period constitutes a unique opportunity to address comorbidities and modifiable risk factors, improve functional capacity and address deficiencies in physiologic reserve, which might otherwise preclude surgery or significantly impede recovery.

Therefore, the aim of this study is to evaluate the efficacy of a multimodal program of prehabilitation in patients undergoing major oncological gastrointestinal surgery. The hypothesis is that severe post-operative complications within 30 days will be reduced in the treatment group compared to the control group.

This is a 2-arm randomized multicentric controlled trial to test the efficacy of a personalized, multidisciplinary, preoperative conditioning program to reduce severe complications and facilitate recovery in patients undergoing major oncological gastrointestinal surgery.

400 patients will be randomized (ratio 1:1) and allocated either to the intervention group (Prehabilitation), or to the control group (which will be treated according to usual standard of care within Enhanced Recovery After Surgery (ERAS) pathways).

Multimodal prehabilitation is a preoperative intervention which includes exercise training, nutritional therapy and anxiety reducing techniques, aimed at preventing or attenuating surgery-driven functional decline.

The primary objective is to evaluate the effect of a multimodal program of prehabilitation on postoperative severe complications.

Secondary outcomes include time to functional recovery, length of hospital stay, complication severity, proportion of patients returning to preoperative functional walking capacity and self-reported activity status and generic health related quality of life at 30 days after surgery.

Included patients will be randomized and allocated either to the intervention group, which will receive 4 weeks of prehabilitation, or to the control group, which will receive no prehabilitation. All patients will be reassessed the day before surgery, 30 days and 3 months after surgery.

Patients enrolled in treatment group will not receive any additional medication but only a multimodal program to optimize their preoperative functional capacity.

Within 30 days prior to scheduled surgery, participants of both groups will undergo a specialized multidisciplinary assessment with a physician, a certified physiotherapist, registered dietitian and psychology trained personnel. All tests will be performed following international guidelines and standardized verbal instructions. A tailored intervention will be prescribed if specific physical, nutritional or psychological impairments will be identified during the assessment phase. Based on the data obtained during the multimodal assessment, different domains and levels of care will be prescribed, focusing on exercise training, and/or nutrition optimization, and/or distress-coping techniques. Different combinations of three domains will be utilized to maximize their synergistic anabolic effect.

Statistical analysis will be performed according to study sites, type of surgery (esophageal, gastric, colonic, rectal) and neoadjuvant treatment.

Inclusion Criteria:

• All adult patients (age > 18 years) scheduled for elective gastrointestinal surgery for cancer.
• Signed informed consent

Exclusion Criteria:

Co-morbid medical, physical, and mental conditions interfering with the ability to complete study procedures, such as:

• acute or unstable cardio-respiratory conditions (e.g., unstable angina or symptomatic severe aortic stenosis)
• severe/end-stage organ diseases (e.g., cardiac failure NYHA functional classes III-IV, COPD FEV1 <50% pred, end-stage kidney or liver disease);
• American Society of Anesthesiologists (ASA) physical status classes 4-5.
• disabling orthopedic and neuromuscular disease.
• psychosis, dementia;
• symptomatic anemia.
• Pregnancy