This study will evaluate the effect of preoperative oral immunonutrition on postoperative complications in patients undergoing radical cystectomy for bladder cancer. Patients receiving preoperative immunonutrition will be compared to controls receiving a standard high-calorie, high-protein oral nutritional supplement.

Radical cystectomy with pelvic lymph node dissection and urinary reconstruction is a major surgical procedure performed for bladder cancer. The literature reports an incidence of 50-88% and 30-42% for any grade complications (Clavier-Dindo grade I-IV) and severe complications (Clavier-Dindo grade ≥III), respectively. Nutritional status prior to radical cystectomy has been shown to be a strong predictor of 90-day mortality. The term "immunonutrition" refers to the oral or enteral administration of specific substrates such as omega-3 fatty acids, arginine, and nucleotides. These substrates have been shown to upregulate the host immune response, modulate inflammatory responses and improve protein synthesis after surgery, with a favorable impact on postoperative infection rates and length of hospital stay in major abdominal surgery. Data on patients undergoing radical cystectomy are scarce, mainly due to the small sample size of the studies. However, the available evidence suggests a potential beneficial effect of this nutritional intervention in patients undergoing radical cystectomy. Several aspects remain largely unclear, including the dosage and timing of immunonutrition and the impact of preoperative malnutrition risk on the efficacy of immunonutrition. This study will evaluate the effect of 7 days of preoperative immunonutrition on postoperative complications compared to patients receiving standard high-calorie, high-protein oral nutritional supplements.

Inclusion Criteria:

• Surgical indication to radical cystectomy with diagnosis of muscle invasive bladder cancer (any N, any M), BCG (Bacillus Calmette-Guerin)-unresponsive non-muscle invasive bladder cancer or extensive non-muscle invasive bladder cancer that cannot be treated with endoscopic surgery alone;
• Willingness to participate by signing written informed consent.

Exclusion Criteria:

• Age < 18 years;
• Pregnant or lactating women;
• Participation in another study with nutritional supplements within the 30 days preceding and during the present study
• Known hypersensitivity or allergy to components of immunonutrition or standard high-calorie high-protein oral nutritional supplement;
• Need for artificial nutrition support due to totally compromised spontaneous food intake;
• Diarrhoea with suspected malabsorption syndrome;
• Inability to consume oral supplements as a consequence of pre-existing disease (e.g. dysphagia) or other factors (e.g. language barrier, psychological disorders, absence of a home caregiver in dependent or elderly patients);
• Kidney failure with need for renal replacement therapy;
• Type 1 diabetes mellitus;
• Type 2 diabetes mellitus requiring insulin therapy and/or inadequate glycaemic control (glycosylated haemoglobin ≥7% and/or fasting plasma glucose ≥150 mg/dL);
• Inability to give an informed consent.