Physiological reserve and early recovery across oncologic and non-oncologic abdominal surgery: a prospective multicenter interaction analysis

Frailty and low handgrip strength are established markers of limited physiological reserve, but it is uncertain whether their prognostic meaning differs between oncologic and non-oncologic surgery. We examined whether oncologic indication modifies the associations of preoperative frailty and baseline handgrip strength with early postoperative outcomes.

This secondary analysis used a prospective cohort conducted at participating surgical centers between January 2023 and June 2025. Frailty was classified using the Fried phenotype, and handgrip strength was measured at admission. The primary outcome was prolonged length of stay (LOS >10 days); secondary outcomes were any postoperative complication, major complications, and log-transformed LOS. Effect modification was evaluated using interaction terms in multivariable logistic models adjusted for age and sex. Because no prolonged stays occurred among fit patients in the non-oncologic stratum, categorical frailty models used Firth penalized logistic regression.

Among 222 clinically characterized participants, 118 (53.2%) underwent oncologic surgery. Prolonged LOS occurred in 41/118 (34.7%) oncologic and 7/104 (6.7%) non-oncologic patients. The complete-case primary analysis included 216 patients and 45 events. In an additional ordinal main-effects model, increasing frailty [odds ratio (OR) 2.91 per category, 95% confidence interval (CI) 1.57-5.38], lower handgrip strength (OR 0.95 per kg, 95% CI 0.90-0.99), and oncologic indication (OR 8.97, 95% CI 3.47-23.19) were associated with prolonged LOS. However, categorical frailty-by-oncology interaction was not supported (global p = 0.341), nor was handgrip-strength-by-oncology interaction (p = 0.739); the joint interaction test was not statistically significant (p = 0.525). No convincing effect modification was observed for complications or continuous LOS.

Oncologic surgery was associated with a substantially higher early postoperative burden, while frailty and handgrip strength retained prognostic relevance. No clear evidence of multiplicative interaction by oncologic indication was detected, but clinically meaningful effect modification cannot be excluded. Physiological reserve assessment should therefore be considered across elective abdominal surgery rather than restricted to the oncologic setting.