Immunonutrition vs. Standard Oral Nutritional Supplements in Prehabilitation for Colorectal Cancer Surgery: A Randomized Clinical Trial Assessing Morbidity and Body Composition by Computed Tomography

Background/Objectives: Perioperative immunonutrition (IMN) has been proposed to improve outcomes after colorectal surgery. However, the evidence is heterogeneous, and few studies have assessed morbidity together with computed tomography (CT)-derived body composition. We compared IMN with standard oral nutritional supplementation (SONS) in patients undergoing colorectal cancer surgery, evaluating postoperative complications and changes in body composition. Methods: Two-arm open-label randomized clinical trial including sixty patients (SONS: n = 30; IMN: n = 30). Postoperative complications were assessed using the Clavien–Dindo classification, and the Comprehensive Complication Index (CCI). Body composition was quantified using pre- and postoperative CT scans, analyzing the skeletal muscle mass index (SMMI) and psoas area. Results: Baseline characteristics were comparable between groups, except for a higher age in the IMN group (p = 0.036). Overall morbidity was 40% in SONS and 50% in IMN (95%CI: −0.35 to 0.15). No differences were observed in the CCI (14.8 ± 23.1 vs. 15.7 ± 19.0, 95%CI: −11.8 to 10.0). Very major morbidity (Clavien ≥ IIIb) was comparable between groups (p = 0.687). At follow-up there was a decline in handgrip strength in SONS whereas it remained stable in IMN (p = 0.030 for the interaction). Also, there was a decrease in SMMI (−2.33, 95%CI: −1.19 to −3.48 cm2/m2) and psoas area (−1.15, 95%CI: −0.67 to −1.65 cm2) in SONS, whereas in IMN they remained stable: SMMI (−1.48, 95%CI: 1.04 to −3.99 cm2/m2), psoas area (−0.71, 95%CI: 0.36 to 1.78 cm2). Conclusions: IMN did not reduce morbidity compared with SONS when used as prehabilitation for colorectal cancer surgery. Exploratory findings suggested a possible attenuation of postoperative muscle loss with IMN.