Risk Factors and Development of a Prediction Model for Unplanned Reoperation Within 30 Days After Skin Flap Repair in Patients With Basal Cell Carcinoma

BACKGROUND: Basal cell carcinoma (BCC) is the most common malignant skin tumor worldwide. Unplanned reoperation may occur after local flap repair, increasing patient suffering and medical burden. At present, evidence regarding the risk factors for and prediction models of unplanned reoperation after flap repair for BCC remains insufficient. The aim of this study was to explore the influencing factors associated with unplanned reoperation after flap repair for BCC and to construct a prediction model, thereby providing a basis for clinical risk assessment and individualized treatment. METHODS: A retrospective cohort study was conducted. A total of 455 patients with BCC who underwent local flap repair at Jiangnan University Medical Center from January 2020 to December 2025 were enrolled. The patients were divided into a reoperation group (45 cases, 9.9%) and a non-reoperation group (410 cases, 90.1%) according to whether unplanned reoperation occurred within 30 days after surgery. Demographic characteristics, tumor-related characteristics, and surgery-related characteristics were collected. Univariate and multivariate logistic regression analyses were used to identify independent influencing factors, and a prediction model was constructed. Receiver operating characteristic (ROC) curve analysis, calibration curves and decision curve analysis (DCA) were used to evaluate the discrimination, calibration and clinical utility of the model. Model performance was internally validated using 1000 bootstrap resampling iterations. RESULTS: Multivariate logistic regression analysis showed that preoperative fasting glucose, infiltration depth, systemic immune-inflammation index (SII; per 10-unit increase), and flap aspect ratio were independent influencing factors for unplanned reoperation. The AUC of the prediction model was 0.852 (95% CI: 0.792–0.912), with a sensitivity of 0.80 and a specificity of 0.79 at the optimal cut-off value. The calibration curve (Hosmer-Lemeshow test, p = 0.17) and decision curve analysis showed that the model had a good fit and provided a net clinical benefit. Internal validation using 1000 bootstrap resampling iterations yielded an optimism-corrected AUC of 0.841. CONCLUSIONS: Preoperative fasting glucose, infiltration depth, SII, and flap aspect ratio are independent risk factors for unplanned reoperation after BCC flap repair. The prediction model based on these variables demonstrated good discrimination and calibration in this single-center cohort, with potential clinical utility. Further external validation is needed before its application in clinical decision-making. However, as this study focused solely on reoperations occurring within the 30-day postoperative period, late reoperations due to positive margins or residual tumors beyond this period were not captured. Studies with extended follow-up are warranted to comprehensively assess the full spectrum of reoperation risk.