Purpose: This study was performed to predict individualized treatment strategies in ruptured abdominal aortic aneurysm (rAAA) by estimating the survival benefit of endovascular aneurysm repair (EVAR) and open surgical repair (OSR) based on anatomical and physiological features using a causal inference model. Methods: This retrospective study included 45 patients with de novo rAAA who underwent EVAR or OSR between 2012 and 2024. Thirty-three variables were analyzed. The model estimated individualized treatment effects (ITE) for 30-day survival.Model interpretability was assessed using Shapley Additive Explanations (SHAP) analysis. Five-fold cross-validation, receiver operating characteristic (ROC) analysis, and calibration plots were used for model evaluation. A clinical decision tree was developed to derive simplified decision rules. Results: The mean ITE was 0.22 ± 0.42, with 33% of patients classified as OSR-benefit candidates. SHAP analysis revealed that suprarenal angle, infrarenal angle, iliac anatomy, and proximal neck characteristics strongly influenced treatment effects. However, some predictors, such as low hemoglobin and systolic blood pressure favoring OSR, conflicted with clinical intuition. ROC analysis showed an area under the curve of 1.00, but calibration suggested overfitting due to a small sample size. Treatment-matched patients had a higher 30-day mortality rate than mismatched patients, suggesting potential bias or unmeasured confounding. The decision tree identified clinically relevant features but displayed structural inconsistencies and impractical cutoff values due to the limited sample size. Conclusion The X-learner model demonstrated the feasibility of individualized treatment prediction in rAAA but suffered from overfitting and limited generalizability. Validation with larger multicenter cohorts is necessary to confirm clinical applicability.

PURPOSE: Breast cancer rates are expected to rise with an increasingly aging society. However, research on breast cancer among elderly women is scarce. In the present study, we aimed to investigate the clinicopathological features of elderly women with breast cancer and assess their clinical outcomes following adjuvant chemotherapy. METHODS: Patients who underwent curative surgery for breast cancer between January 1, 2009 and December 31, 2014 were retrospectively reviewed (n=1,865). The clinicopathological features, comorbidities, and survival outcomes were compared among three age groups (<55, 55–64, and ≥65 years). Subgroup analyses were also performed according to adjuvant chemotherapy status (i.e., administered or forgone) and need. RESULTS: The median age of the patients (n=1,865) was 51.7 years, and 231 (12.3%) patients were ≥65 years of age (defined as elderly). The median follow-up period was 56 months. The tumor characteristics were similar among the three age groups, except for tumor size and progesterone receptor status. The five-year overall survival rate was significantly poorer in elderly patients (87.5%) than in the younger groups (<55 years: 94.1%; 55–64 years: 93.2%) (p=0.002). Elderly patients received significantly less frequent adjuvant chemotherapy than the younger patients (p<0.001). Not all elderly patients in need of adjuvant chemotherapy were administered chemotherapy. Those administered adjuvant chemotherapy had significantly higher five-year overall survival rates than that of the non-administered patients (86.5% vs. 66.5%, p=0.014) and marginally longer breast cancer-specific survival (87.9% vs. 73.5%, p=0.07). Elderly patients who did not undergo chemotherapy had a higher prevalence of diabetes mellitus than those who did. CONCLUSION Adjuvant chemotherapy in elderly breast cancer patients improved overall survival, and marginally extended breast cancer-specific survival. Therefore, standard adjuvant chemotherapy should be considered in elderly patients who require it.