Operative Stress Versus Physiologic Reserve: Distinct Predictors of Major Complications and Delirium in Older Adults Undergoing Cancer Surgery.

BackgroundWe prospectively compared the predictors of major postoperative complications (POCs) and postoperative delirium (POD) in older patients undergoing gastrointestinal and breast cancer surgery.MethodsThis single-center prospective cohort study included patients aged ≥65 years who underwent gastrointestinal or breast cancer surgery at our institution between 2021 and 2025. Of the 694 screened patients, 587 who underwent curative surgery were analyzed. Major POCs were defined as a Clavien-Dindo grade of IIIa or higher, and POD was diagnosed using the Confusion Assessment Method. Logistic regression was used to identify the independent predictors.ResultsMajor POCs occurred in 91 patients (16%) and POD in 49 patients (8%). Major POCs were associated with male sex, higher American Society of Anesthesiologists Physical Status and Charlson Comorbidity Index scores, hepato-biliary-pancreatic (HBP) cancer, longer operative time, and greater blood loss in univariate analyses. However, multivariate models identified independent associations with HBP cancer (odds ratio [OR], 2.07; P = 0.008), operative time (OR, 3.82; P = 0.001), and blood loss (OR, 3.69; P < 0.001). POD was broadly associated with geriatric vulnerability measures in univariate analyses; however, only older age (OR 3.03, P = 0.016) and impairment in activities of daily living (ADLs) (OR 2.29, P = 0.047) remained independent predictors.DiscussionMajor POCs and POD represent distinct perioperative risk phenotypes. Major POCs were predominantly driven by disease- and procedure-related factors, whereas POD was associated with diminished geriatric reserve. Preoperative functional assessment may improve delirium risk stratification and support individualized care in older patients undergoing cancer surgery.