Abstract only 297 Background: There is limited research evaluating the share of patients (pts) with metastatic pancreatic cancer (m-PANC) treated according to NCCN guidelines. Methods: We identified pts with m-PANC using ICD-10 diagnosis codes in the 2016-2019 Medicare Parts A/B/D 100% Research Identifiable Files. Study pts had 2+ claims with a pancreatic cancer diagnosis and Medicare FFS coverage for 6 months pre- and 3 months post-metastatic disease diagnosis. A line of therapy (LOT) was assigned based on the order and number of therapies used. Pts with one, two, or three LOTs were defined as treated according to NCCN Category 1 guidelines if, in each LOT, pts used one of the following regimens: FOLFIRINOX (FFX), gemcitabine/nab-paclitaxel (gem/nab), gemcitabine + erlotinib, gemcitabine monotherapy, or 5-FU + leucovorin + liposomal irinotecan. Multi-drug LOTs were excluded from the analysis. Results: We identified 31,782 pts with m-PANC. 21,304 received one LOT, 7,352 received two LOTs, and 3,126 received three LOTs between 2016 and 2019. Among pts who received one or two LOTs, a higher portion were treated according to NCCN Category 1 guidelines in 2019 (72% and 43%, respectively) than in 2016 (64% and 33%, respectively). Among pts who received three LOTs, a higher portion were treated according to NCCN Category 1 guidelines in 2019 (17%) than in 2017 (12%); too few pts were treated in 2016 to make a comparison. From 2016 to 2019, FFX had the largest increase in share of pts receiving only one NCCN Category 1 LOT (11% to 27%) and gem-mono had the largest decrease (30% to 17%). Among pts receiving two NCCN Category 1 LOTs, gem/nab to liposomal irinotecan sequences had the largest increase in share of pts (18% to 32%) and gem/nab to FFX had the largest decrease (17% to 10%). Among pts receiving three NCCN Category 1 LOTs, patient share for FFX to gem/nab to Liposomal irinotecan was 35% in 2019, while gem/nab to FFX to Liposomal was 8%; pt counts in earlier years were too small to calculate patient share. Conclusions: The use of NCCN Category 1 therapies increased consistently from 2016 to 2019 among pts that received one, two, and three lines of therapy. FFX drove increases in NCCN Category 1 utilization among patients receiving one line of therapy, and gem/nab to liposomal irinotecan sequences were the primary drivers of the increase among patients receiving two lines of therapy. FFX to gem/nab to liposomal irinotecan was the primary driver of increase among patients receiving three lines of therapy.