Development and Internal Validation of the Si-AAA Prognostic Score for Five-Year Overall Survival after Endovascular Aneurysm Repair in Patients with Asymptomatic Abdominal Aortic Aneurysm

Background Although endovascular aneurysm repair is widely used for the treatment of asymptomatic abdominal aortic aneurysm, long-term survival is influenced by patient comorbidities and aneurysm-related characteristics. This study aimed to develop and internally validate a prognostic scoring system for predicting 5-year overall survival after endovascular aneurysm repair. Methods A retrospective cohort study was conducted in patients with asymptomatic abdominal aortic aneurysm undergoing endovascular aneurysm repair. Candidate predictors included demographic, clinical, aneurysm-related, and laboratory variables. Multivariable Cox proportional hazards regression was used to identify independent predictors of 5-year mortality. Continuous predictors were categorized using clinically interpretable thresholds derived from time-dependent receiver operating characteristic analysis, and a simplified point-based score was constructed from regression coefficients. Model performance was assessed using Harrell's concordance index, and internal validation was performed using 1,000 bootstrap resamples to obtain an optimism-corrected concordance index. Calibration was evaluated using bootstrap-based calibration plots. Results A total of 445 patients were screened, and 443 complete cases were included in the final analysis. During follow-up, 133 deaths (30.0%) occurred. The estimated 5-year overall survival rate was 62.8% (95% CI, 57.8%–68.0%). Independent predictors of 5-year mortality included age >70 years (adjusted hazard ratio [aHR] 1.66, 95% CI 1.06–2.62; P = .029), chronic obstructive pulmonary disease (aHR 1.70, 95% CI 1.08–2.69; P = .023), unfit status (aHR 2.32, 95% CI 1.58–3.39; P < .001), serum albumin ≤3.5 g/dL (aHR 2.80, 95% CI 1.97–3.98; P < .001), and abdominal aortic aneurysm diameter ≥7 cm (aHR 1.59, 95% CI 1.07–2.38; P = .023). The final score ranged from 0 to 7. The apparent concordance index was 0.721, with an optimism-corrected concordance index of 0.713 after bootstrap validation. Risk stratification showed clear separation between low-, intermediate-, and high-risk groups (5-year overall survival: 82.5%, 53.4%, and 23.8%, respectively; log-rank P < .001). Conclusions A simple prognostic scoring system incorporating age, chronic obstructive pulmonary disease, unfit status, serum albumin, and aneurysm diameter demonstrated acceptable discrimination and good calibration for predicting 5-year overall survival after endovascular aneurysm repair. This tool may assist in risk stratification and long-term clinical decision-making. As this score was derived and internally validated in a single-center cohort, external validation in independent cohorts is required before routine clinical implementation.