Association between Clonorchis sinensis infection and postoperative recurrence in colorectal cancer: a retrospective cohort study

<title>Abstract</title> <p>Background Clonorchis sinensis infection is a well-established Group 1 carcinogen; however, its role in colorectal cancer (CRC) progression remains unclear. This study aimed to investigate the association between C. sinensis infection and postoperative recurrence/metastasis in CRC and to develop a clinically applicable predictive model. Methods In this single-center retrospective cohort study, 155 patients with stage I–III CRC who underwent curative resection between August 2022 and August 2024 were enrolled. Patients were stratified according to C. sinensis infection status. Logistic regression analysis was performed to identify factors associated with postoperative recurrence or metastasis, with inverse probability of treatment weighting (IPTW) applied to minimize confounding. A combined predictive model was constructed and evaluated using receiver operating characteristic (ROC) curves, calibration plots, Brier scores, and decision curve analysis (DCA), with bootstrap validation. Results Among the 155 patients, 91 (58.7%) were positive for C. sinensis infection. The infection-positive group exhibited significantly higher proportions of male sex, ulcerative tumor phenotype, and aberrant p53 expression (all P &lt; 0.05). Recurrence or metastasis occurred more frequently in infected patients than in non-infected patients (20.9% vs. 7.8%, P = 0.027). In multivariable analysis, C. sinensis infection (OR = 3.37, P = 0.028) and TNM stage (OR = 5.06, P = 0.001) were independently associated with postoperative recurrence or metastasis. This association remained significant after IPTW adjustment (OR = 3.90, P = 0.016). The combined model incorporating infection status, TNM stage, and CA19-9 showed good discriminative performance (AUC = 0.822), calibration (Brier score = 0.097), and net clinical benefit over a threshold probability range of 0.10–0.60. Conclusion C. sinensis infection was independently associated with postoperative recurrence and metastasis in CRC. The combined model incorporating infection status, TNM stage, and CA19-9 demonstrated good discriminative performance and may be useful for individualized postoperative risk stratification in endemic areas.</p>