The Modified Frailty Index Predicts Failure-to-Rescue Mortality After Pancreatoduodenectomy: A Comparison of the 11-Item and 5-Item Versions

Background: Frailty may influence outcomes after pancreatoduodenectomy (PD). We compared the prognostic performance of the 11-item modified Frailty Index (mFI-11) and the simplified 5-item version (mFI-5) and explored their link with post-pancreatectomy mortality (PPM). Methods: We retrospectively analyzed 1926 adults undergoing PD for periampullary lesions (2015-2023). Frailty was classified as non-frail, mildly frail, or severely frail. Co-primary outcomes were major complications, defined as Clavien-Dindo grade ≥ III, and 90-day mortality. Separate adjusted logistic models were fitted for each index; Firth regression was used for mortality sensitivity analyses. Discrimination was assessed by AUC and compared using DeLong tests. Deaths were independently adjudicated as PPM1, PPM2, or PPM3. Results: Major complications occurred in 350 patients (18.2%), and 90-day mortality was 52 (2.7%). Both indices showed a stepwise increase in event rates across frailty strata. In adjusted models, severe frailty was independently associated with mortality (mFI-11: OR 4.1, 95% CI 1.6-10.3, p < 0.001; mFI-5: OR 2.8, 95% CI 1.4-5.6, p = 0.015 by Firth regression). Discrimination was modest and comparable between indices for major complications (AUC 0.629 vs. 0.630; DeLong p = 0.68) and good and comparable for mortality (AUC 0.761 vs. 0.757; DeLong p = 0.48). Severe frailty was independently associated with PPM2 deaths for both indices but not with PPM1 or PPM3, although the latter subgroups were underpowered. Conclusion: The mFI-5 performs similarly to the mFI-11 after PD and is preferable for routine use due to its simplicity. Frailty is more strongly linked to mortality, especially pancreas-specific failure-to-rescue trajectories, than to major morbidity alone.