The role of preoperative immunonutrition on morbidity and immune response after cystectomy: protocol of a multicenter randomized controlled trial (INCyst Trial).

Introduction: Cancer, malnutrition, and surgery negatively impact patient's immune system. Despite standardized surgical technique and the development of new perioperative care protocols, morbidity after cystectomy remains a serious challenge for urologists. Most common postoperative complications, such as infections and ileus, often lead to longer length of stay and worse survival. The immune system and its interaction with the gut microbiota play a pivotal role in cancer immunosurveillance and in patient's response to surgical stress. Malnutrition has been identified as an independent and modifiable risk factor for both mortality and morbidity. Immunonutrition (IN) may improve the nutritional status, immunological function, and clinical outcome of surgical patients. Aims of the study are (1) to evaluate the impact of IN on morbidity and mortality at 30 and 90 days after cystectomy and (2) to determine immune and microbiota signature that would predict IN effect.

Methods: This is a randomized, multicentric, controlled, pragmatic, parallel-group comparative study, supported by the Swiss National Science Foundation. A total of 232 patients is planned to be enrolled between April 2023 and June 2026. Three participating centers (Lausanne, Bern, and Riviera-Chablais) have been selected. All patients undergoing elective radical and simple cystectomy will be randomly assigned to receive 7 days of preoperative IN (Oral Impact^®, Nestlé, Switzerland) versus standard of care (control group) and followed for 90 days after surgery. For the exploratory outcomes, blood, serum, urine, and stool samples will be collected in patients treated at Lausanne. In order to determine the impact of IN on immune fitness, patients enrolled at Lausanne will be vaccinated against influenza and the establishment of the vaccine-specific immune response will be followed. Analysis of the microbiota and expression of argininosuccinate synthetase 1 as potential biomarker will also be performed.

Discussion and conclusion: Strengths of the INCyst study include the randomized, multicenter, prospective design, the large number of patients studied, and the translational investigation. This study will challenge the added value of preoperative IN in patients undergoing cystectomy, assessing the clinical effect of IN on the onset of postoperative morbidity and mortality after cystectomy. Furthermore, it will provide invaluable data on the host immune response and microbiota composition.

Trial registration: ClinicalTrials.gov NCT05726786. Registered on March 9, 2023.