Computed Tomography‐Derived Abdominal Aortic Calcification Independently Predicts Survival in Rectal Cancer Surgery: A Retrospective Cohort Study

Background Contemporary rectal cancer treatment pathways remain predominantly guided by tumour‐related characteristics, including stage and histopathology, with comparatively limited objective assessment of physiological reserve for treatment planning. Aortic calcification represents a potential imaging biomarker reflecting systemic vascular disease, chronic inflammation and physiological reserve. We evaluated computed tomography (CT)‐derived abdominal aortic calcification as a prognostic imaging biomarker for postoperative outcomes and long‐term survival. Methods A retrospective cohort study was conducted using the prospectively maintained Australian Comprehensive Cancer Outcomes and Research Database (ACCORD) of rectal cancer patients treated between 2013 and 2022. Pre‐treatment staging CT was subjected to semi‐automated volumetric quantification of calcium using 3D Slicer software. Calcification volume was assessed segmentally at vertebral levels L1–L4 and at the iliac vessels. Primary outcomes were major postoperative complications (Clavien–Dindo ≥ III) and overall survival. Cox proportional hazards modelling was performed using a prespecified parsimonious multivariable model. Results A total of 174 patients were included in the analysis. Increasing calcification burden demonstrated no statistically significant association with major postoperative complications (OR 1.09 per 1000‐unit increase; 95% CI 0.99–1.19; p = 0.07). Increasing calcification independently predicted worse 5‐year survival after multivariable adjustment (HR 1.17 per 1000‐unit increase ([CI 1.08–1.28, p = 0.001]). Kaplan–Meier analyses showed separation between calcification groups, although dichotomised analyses did not reach statistical significance. Conclusion Aortic calcification independently predicts long‐term survival following rectal cancer surgery but not short‐term postoperative complications. Quantitative CT‐derived calcification assessment may provide a rapid, objective imaging biomarker that reflects physiological reserve and represents a potential adjunct to future risk stratification pathways.