Effect of immunonutrition on postoperative infectious complications and survival after colon cancer surgery: long-term follow up of randomized clinical trial

Background: A previous randomized clinical trial (RCT) in patients undergoing elective colon cancer surgery showed that preoperative immunonutrition did not reduce short-term postoperative infectious complications. This study reports the long-term follow-up of that RCT, evaluating the impact of preoperative immunonutrition and the association of postoperative infectious complications with survival outcomes. Methods: This secondary analysis used prospectively collected survival data from a prior RCT in which patients were randomized 1:1 to receive either preoperative immunonutrition plus a normal diet or a normal diet alone (control) for 7 days before surgery. The primary endpoints were disease-free survival (DFS) and overall survival (OS). Survival outcomes were analysed in relation to randomized treatment allocation and clinicopathological variables, including postoperative complications, using Kaplan–Meier methods and Cox proportional hazards models. Results: A total of 161 patients were included, with 79 randomized to immunonutrition and 82 to control. The mean age was 65.3 years, and 65.8% were male, with similar baseline characteristics between groups. After a median follow-up of 57 months (range 4–65), preoperative immunonutrition did not affect 5-year DFS (80% versus 86% in controls; P = 0.474) or 5-year OS (88% versus 90%; P = 0.761). In contrast, postoperative infectious complications were associated with lower 5-year OS (74% versus 92%; P = 0.013) and showed a trend towards worse DFS (71% versus 86%; P = 0.065). On multivariable analysis, advanced T category and postoperative infectious complications remained independently associated with poorer DFS (HR 2.53; P = 0.041) and OS (HR 4.14; P = 0.007). The adverse prognostic effect of infectious complications was evident primarily in patients with advanced T category disease. Conclusion: Preoperative immunonutrition did not improve long-term survival after colon cancer surgery. Postoperative infectious complications were independently associated with worse long-term outcomes, providing prospective evidence that supports previous observational findings. © The Author(s) 2026. Published by Oxford University Press on behalf of BJS Foundation Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.