Introduction: Surgical resection continues to be a central tenant of multimodal cancer care for patients with gastrointestinal malignancies treated with curative intent. However, several studies have shown that surgical complications can often interfere with the completion of chemotherapy. This highlights the need for better patient selection. We compared the predictive ability of various frailty tools for 30-day outcomes in patients undergoing elective surgical oncology procedures for gastric and hepatopancreatic-biliary malignancies within the VA system. Methods: Using the Veteran Affairs Surgical Quality Improvement Program database, we performed a retrospective study of patients who underwent gastrectomy, pancreatectomy, hepatectomy, or laparoscopic cholecystectomy for malignant indications from 1999-2019. Emergency cases were excluded. RAI-rev, mFI-5, MFI-11, MELD, Childs-Pugh, and Whipple-ABACUS scores were calculated. Pearson's χ2 tests, one-way ANOVA, ROC, and C-statistics were used to assess the predictive accuracy of each frailty index for 30-day mortality. Results: In the cohort, 3,976 surgeries were performed for malignancy. 49.1% were hepatectomies, 38.6% were pancreatectomies, 6.5% were cholecystectomies, and 5.8% were gastrectomies. RAI performed the best overall, C-statistic 0.688. RAI outperformed all other frailty indices, as determined by comparing the AUC of the respective ROC curves (p <0.001). In analyzing each surgery independently, RAI remained superior for pancreatectomy (C-statistic 0.673), gastrectomy (C-statistic 0.727), and laparoscopic cholecystectomy (C-statistic 0.823). However, Childs-Pugh performed the best for hepatectomies (C-statistic 0.633). Conclusion: RAI-rev is a good predictor of 30-day mortality when applied to pancreatectomy, gastrectomy, and laparoscopic cholecystectomy for cancer indications. However, Childs-Pugh performed better than RAI-rev in patients undergoing hepatectomy for malignancy.Tabled 1Frailty Index ComparisonC-statisticAUC DifferenceP-valueRAI0.688refrefMELD0.605-0.083<0.001Childs-Pugh0.632-0.053<0.001MFI-110.592-0.096<0.001MFI-50.590-0.098<0.001Whipple-ABACUS0.645-0.043<0.001 Open table in a new tab