Development and internal validation of a Cox-based recurrence risk prediction model after endovenous laser treatment for lower-extremity varicose veins

Background Recurrence after endovenous laser treatment (EVLT) remains clinically important. We therefore developed and internally validated a Cox-based model for medium- to long-term recurrence after EVLT. Methods This single-center retrospective cohort included 183 patients treated between March 2017 and December 2023; 78 experienced recurrence and 105 did not. The primary Cox proportional hazards model retained age, sex, body mass index (BMI), disease duration, family history, perforator vein incompetence, preoperative great saphenous vein (GSV) diameter, and Venous Clinical Severity Score (VCSS). Perforator vein incompetence was coded as Yes = present and No = absent, with No as the reference category. A nomogram estimated 12, 24, and 36 month recurrence risk. Model performance was evaluated using ROC analysis, calibration plots, bootstrap internal validation, and decision curve analysis (DCA). Results In the multivariable Cox model, BMI (HR 1.122, 95% CI 1.013–1.242; P = 0.027), disease duration (HR 1.024, 95% CI 1.000–1.048; P = 0.046), and family history (HR 1.635, 95% CI 1.017–2.628; P = 0.042) were associated with higher recurrence hazard, whereas perforator vein incompetence (Yes = present vs. No = absent) was inversely associated with recurrence hazard (HR 0.351, 95% CI 0.193–0.639; P < 0.001). Age did not reach conventional significance after adjustment (HR 1.024, 95% CI 0.999–1.050; P = 0.064). The model ROC AUC was 0.799 (95% CI 0.734–0.864). The original and bootstrap-corrected C-indices were 0.727 and 0.694, respectively. Detailed bootstrap validation yielded a corrected calibration slope of 0.807, indicating some optimism. The supplied 36 month DCA showed the model curve overlapping the treat-none strategy across the displayed threshold range, so incremental net benefit was not demonstrated in this analysis. Conclusions The revised Cox-based model provides moderate discrimination and generally reasonable calibration after internal validation, but its performance attenuates after optimism correction and clinical net benefit was not demonstrated by the supplied 36 month DCA. External validation is required before clinical implementation, and the inverse association observed for perforator vein incompetence should be interpreted cautiously and confirmed in independent cohorts.