Abstract only 531 Background: Medicare Advantage accounts for almost 40% of Medicare beneficiaries in 2021. There is limited research evaluating utilization and cost for Medicare Advantage patients with metastatic pancreatic cancer (m-PANC) receiving various NCCN Category 1 preferred regimens. Methods: We used ICD-10 diagnosis codes to identify patients with m-PANC without end-stage renal disease in the 2016-2019 Milliman Consolidated Health Cost Guidelines Sources Database (CHSD) claims files. Study patients had 2+ claims with a pancreatic cancer diagnosis and Medicare Advantage coverage for 3 months pre- and 1 month post-metastasis diagnosis. Patients with stand-alone Part D plan coverage or aged<65 years were excluded. Total cost of care (TCOC) was the sum of the average paid by the insurer and patient. Study patients were treated with NCCN Category 1 preferred regimens: 1L gemcitabine/nab-paclitaxel (gem/nab), 1L gemcitabine monotherapy (gem mono), 1L FOLFIRINOX (FFX), and 2L+ liposomal irinotecan (5FU was not included in this analysis; see Limitations for further details). Results: Of the approximately 2.5 million patients covered by Medicare Advantage in CHSD, there were 946 patients that received an NCCN Category 1 chemotherapy regimen between 2016 and 2019. Among NCCN Category 1 preferred regimens, patients receiving 2L+ liposomal irinotecan had the lowest mean admissions per beneficiary and mean readmission rate (0.5 and 8%) compared to patients receiving gem/nab (0.8 and 12%), gem mono (0.6 and 8%), or FFX (0.6 and 9%). Patients receiving 2L+ liposomal irinotecan also had the shortest length of stay per inpatient admission in days (2.9) compared to patients receiving gem/nab (5.1), gem mono (3.6), or FFX (4.3). Mean claims per beneficiary for emergency department observations was lowest among patients receiving 2L+ liposomal irinotecan (0.7), compared to patients receiving gem/nab (0.9), gem mono (1.0), or FFX (0.89). Patients receiving 2L+ liposomal irinotecan had lower median TCOC ($31,885) than patients receiving gem/nab ($39,479) or FFX ($32,632). Conclusions: Patients with Medicare Advantage receiving 2L+ liposomal irinotecan-based regimens to treat m-PANC had lower healthcare resource utilization in key categories and lower median total costs than patients receiving other NCCN Category 1 preferred regimens. Limitations: Analysis of different populations or time periods may yield different results. Our study used claims data and not electronic health records (EHRs), so we could not control for clinical covariates. Patient characteristics and regimen performance might influence which regimens patients receive. We did not adjust TCOC or utilization for LOT durations. We did not study whether liposomal irinotecan-based therapy patients received concomitant 5FU or prior gemcitabine-based therapy.