External validation of a predictive system from the Swedish colorectal cancer registry to predict the risk of permanent stoma after rectal cancer surgery: A multicenter study in Spain.

BACKGROUND Sphincter-preserving surgery in rectal cancer aims to avoid permanent stoma formation, yet this remains a frequent outcome. Although several predictive models for permanent stoma have been proposed, few have undergone external validation. This study aimed to externally validate a Swedish registry-based model for predicting permanent stoma in patients undergoing anterior rectal resection.

METHODS This multicentre retrospective study included six high-volume colorectal surgery units in Spain. A total of 837 patients who underwent sphincter-preserving resection for rectal cancer between January 2016 and January 2020 were initially assessed. Of these, 549 patients met the inclusion criteria defined in the original prediction study. Discriminative ability of the online risk calculator was assessed using the area under the receiver operating characteristic curve (AUC).

RESULTS Among the 549 included patients, 57 (10.4%) had a permanent stoma two years after surgery. In accordance with the original study, male sex, low tumour height, and synchronous metastases were identified as preoperative factors associated with permanent stoma. When the online risk calculator was applied to our cohort, the model showed an AUC of 0.6345 (95% CI: 0.559-0.709; p < 0.001).

CONCLUSION External validation of a Swedish registry-based prediction model showed limited discriminative ability in predicting permanent stoma. These results highlight the need for improved, patient-centred predictive tools. Better-performing models could support shared decision-making by providing individualized risk estimates and help clinicians and patients weigh surgical options with greater confidence, ultimately contributing to improved long-term quality of life.