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BackgroundPancreatic cancer is expected to be the third deadliest cancer in the US in 2021. Evaluation of treatment response in patients with mPDAC necessitates scheduled clinical and radiographic assessments along with monitoring serum CA 19-9 levels. Currently available single-institution data examining the importance of CA 19-9 monitoring cannot be generalized to real-world settings. We investigated the impact of serum CA 19-9 monitoring and its association with clinical outcomes in patients with mPDAC in a population-based setting.MethodsData were extracted from the Flatiron Health electronic health record (EHR)-derived de-identified database for patients diagnosed with mPDAC between January 1, 2015, and June 30, 2020. Serum CA 19-9 levels at baseline – defined as the values obtained ≤ 60 days prior to treatment initiation - and during treatment were extracted. CA 19-9 levels > 40 IU/mL were considered elevated. Survival outcomes were compared based on testing frequency, baseline CA 19-9 levels, and change in CA 19-9.Results6,118 patients with mPDAC who received treatment were included in the analysis. The median age at diagnosis was 68 years (IQR: 61-75). Patients with normal baseline CA 19-9 experienced longer median survival than patients with elevated levels [1L: 8.8 months (95% CI: 7.9 - 10) vs. 7.2 months (6.8 – 7.5), p < 0.001; 2L: 7.2 months (6.1 – 9.2) vs. 5.2 months (4.9 – 5.6), p < 0.001; 3L: 6.1 months (5.4 – 9.1) vs. 3.9 months (3.4 – 4.3), p < 0.001]. Patients with decreasing/stable CA 19-9 during treatment experienced longer survival than patients who experienced an increase in CA 19-9 levels [1L: 10.9 months (10.5 – 11.3) vs. 5.4 months (5.1 – 5.9), p < 0.0001; 2L: 8.2 months (7.7 – 8.5) vs. 4.3 months (4.1 – 4.7), p < 0.001; 3L: 7.5 months (6.6 – 9.2) vs. 3.7 months (3.4 – 4.3), p < 0.001].ConclusionsIn one of the largest, contemporary, real-world studies of patients with mPDAC, elevated CA 19-9 level at treatment initiation demonstrated a prognostic impact. Routine serial monitoring of CA 19-9 levels during treatment may be warranted, in addition to clinical and radiographic assessment, and may translate into better patient outcomes. Further validation studies are needed to understand the generalizability of these results.

580 Background: Subgroup analyses of the NAPOLI-1 study identified that among patients who were IRI naïve prior to entering the clinical trial, a survival benefit was observed between the study arm and control arm (overall survival (OS): 6.7 months vs 4.2 months). This treatment benefit was not observed among those previously exposed to IRI (OS: 4.6 months in study arm vs 4.8 months in control arm). This study sought to understand the impact of prior exposure to IRI on clinical outcomes among patients treated with liposomal irinotecan in the real-world setting. Methods: This retrospective observational study utilized the Flatiron Health EHR database. Data were analyzed for adult patients with mPDAC treated with liposomal irinotecan -based regimens between January 2016 and October 2020. Patient characteristics, OS and progression-free survival (PFS) were assessed. Prior IRI was defined as IRI given in a prior regimen in the metastatic setting. Cox proportional hazard (PH) methods were used to calculate hazard ratios (HRs). HRs were adjusted to account for demographics and relevant clinical covariates. Patients without prior exposure to IRI were used as the reference population for the Cox PH model (an HR < 1 represents worse survival for unexposed patients relative to the exposed). Results: 675 patients with mPDAC treated with a liposomal irinotecan-based regimen were included. Median age at treatment initiation was 69 (IQR: 62 – 75) years and among patients with available ECOG performance status (PS), 77.4% had a PS of 0-1. 181 (27%) patients were previously exposed to IRI in the metastatic setting (Table). The unadjusted OS HR was 1.3 (95% CI: 1.1 – 1.6, p < 0.001) and the unadjusted PFS HR was 1.4 (95%CI: 1.2 – 1.7, p < 0.001). After adjustment for baseline characteristics the adjusted OS HR was 1.0 (95% CI: 0.8 – 1.3, p = 0.8836) and the adjusted PFS HR was 1.1 (95%: 0.8 – 1.4, p = 0.5626). Conclusions: The results of this study suggest prior exposure to IRI is not a predictor of worse clinical outcomes for patients treated with liposomal irinotecan-based treatment when accounting for key clinical characteristics in a multivariable model. The results from this real-world study can be used to support treatment sequencing decisions for patients with mPDAC following first line therapy. This is the largest real-world evidence study to date of patients with mPDAC treated with liposomal irinotecan.[Table: see text]

Background: Pancreatic cancer is expected to be the third deadliest cancer in the US in 2020. Evaluation of treatment response in patients (pts) with mPDAC necessitates scheduled clinical and radiographic assessments along with monitoring serum CA 19-9 levels. Currently available single-institution data examining the importance of CA 19-9 monitoring cannot be generalized to real-world settings. We investigated the impact of serum CA19-9 monitoring and its association with clinical outcomes in pts with mPDAC in a population-based setting. Methods: Data were extracted from the nationwide Flatiron Health electronic health record (EHR)-derived de-identified database for pts diagnosed with mPDAC between January 1, 2014 and June 30, 2020. Serum CA19-9 levels at baseline – defined as the values obtained ≤ 60 days 1L initiation and during first-line (1L) treatment were extracted. CA 19-9 levels > 40 IU/mL were considered elevated. Data regarding patient exposure to second (2L) and third-line (3L) systemic therapies were collected. Survival analysis was performed using Kaplan-Meier methods. Categorical measures were compared with the chi-square test and survival outcomes with the log-rank test. Results: Among the 6,118 pts identified, median age at treatment initiation was 68 years (IQR: 61 – 75), 55% were male, 67% were white, and 73% had a baseline serum CA 19-9 level available. Among 4,486 pts with baseline CA 19-9 levels available, 701 (15%) had a normal (< 40 U/mL) level. Among 3,867 pts with elevated CA 19-9 at baseline, 534 (14%) had a single 1L assay and 2,448 (63%) had > 1 assay during 1L treatment. The proportions of pts who received 2L/3L treatment were 25%/7.6% among pts with no CA 19-9 assays performed at any time, 14%/3.7% among pts with only baseline CA 19-9 assays, 31%/9.7% among pts with a single CA 19-9 assay during 1L treatment (with or without a baseline assay), and 50%/17% if they had more than one CA 19-9 assay performed during the course of their 1L treatment (p < 0.001). Median OS (mOS) for pts who had no baseline serum CA 19-9 measurement, a normal baseline CA 19-9 level or an elevated baseline CA 19-9 level were 6.3 months, 8.8 months and 7.2 months, respectively (p < 0.001). The mOS of pts with no baseline CA 19-9 assay, only baseline assays, a single assay during 1L and > 1 assay during 1L was 3.8, 1.9, 4.2, and 11 months, respectively (p < 0.001). Conclusions: In one of the largest, contemporary, real-world studies of patients with mPDAC to date, elevated CA 19-9 level at diagnosis demonstrated a prognostic impact. Routine serial monitoring of CA 19-9 levels during 1L treatment may be warranted, in addition to clinical and radiographic assessment, and may translate into better patient outcomes. Further validation studies are needed to understand the generalizability of these results. Citation Format: Ben George, Matthew Kent, Andy Surinach, Neil Lamarre, Paul Cockrum, Aleksander Chudnovsky. Real-world serum CA19-9 level monitoring patterns and its association with clinical outcomes among patients with metastatic pancreatic ductal adenocarcinoma (mPDAC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 765.

e16251 Background: Pancreatic cancer has an aggressive disease course, mandating close clinical monitoring while on treatment. Evaluation of treatment response in patients with mPDAC necessitates scheduled clinical and radiographic assessments along with monitoring serum CA 19-9 levels. We investigated the impact of serum CA 19-9 monitoring and its association with clinical outcomes in patients with mPDAC who received second- (2L) and third line (3L) in a population-based setting. Methods: Data were extracted from the nationwide Flatiron Health electronic health record (EHR)-derived de-identified database for patients diagnosed with mPDAC and subsequently treated in the 2L or 3L setting between January 1, 2014 and June 30, 2020. Serum CA 19-9 levels at baseline were extracted – defined as the values obtained ≤ 60 days of treatment initiation and during treatment. CA 19-9 levels > 40 IU/mL were considered elevated. Survival analysis was performed using Kaplan-Meier methods. Categorical measures were compared with a chi-square test and survival outcomes with a log-rank test. Results: There were 2,402 patients who received 2L and 790 patients who received 3L treatment included in the study. Among the 2L cohort, median age at treatment initiation was 67 years (IQR: 60 – 73), 54% were male, 57% had an ECOG score of 0-1, and 82% had a baseline serum CA 19-9 level available. Among the 3L cohort, median age at treatment initiation was 67 years (IQR: 60 – 73), 53% were male, 58% had an ECOG score of 0-1, and 84% had a baseline CA 19-9 level available. Most patients in the 2L and 3L cohorts had an elevated CA 19-9 at baseline, 85.2% and 82.0%, respectively. Among the 2L and 3L cohorts, 38.5% and 31.9% had CA 19-9 levels decrease/remain stable during treatment and 27.6% and 31.4% had levels increase during treatment, respectively. Patients with normal baseline CA 19-9 experienced longer survival than patients with elevated levels [2L: 7.2 months (95% CI: 6.1 – 9.2) vs 5.2 months (4.9 – 5.6), p < 0.001; 3L: 6.1 months (5.4 – 9.1) vs 3.9 months (3.4 – 4.3), p < 0.001]. Similarly, patients with decreasing/stable CA 19-9 during treatment had longer survival than patients who had their CA 19-9 levels increase [2L: 8.2 months (7.7 – 8.5) vs 4.3 months (4.1 – 4.7), p < 0.001; 3L: 7.5 months (6.6 – 9.2) vs 3.7 months (3.4 – 4.3), p < 0.001]. Conclusions: In this large, contemporary, real-world study of patients with mPDAC, CA 19-9 levels at treatment initiation had a prognostic value across later lines of therapy. Routine serial monitoring of CA 19-9 levels during treatment, in addition to clinical and radiographic assessment, may help with timely additional diagnostic testing and treatment intervention. Further validation studies are needed to understand the generalizability of these results.

e16250 Background: PDAC is a lethal malignancy which accounted for the third most cancer related deaths in 2020. Patients (pts) who are initially diagnosed with stage I-III PDAC have a 5-year relative survival of 13.3 – 39.4%; those with metastatic disease at diagnosis have a 5-year relative survival of 2.9%. Limited data are published comparing the outcomes of pts with stage I-III who develop metastases (recurrent) compared to pts with de novo mPDAC (de novo). This analysis seeks to compare demographic, clinical characteristics, and survival outcomes of pts with recurrent versus de novo mPDAC in a community oncology setting. Methods: Using the Flatiron Health database, a retrospective observational study was conducted abstracting deidentified data from ≥280 US cancer clinics. Pts with mPDAC diagnosed from 01/2016 to 08/2020 with a known stage at initial diagnosis were included. Pts were stratified based on initial stage at diagnosis. Median overall survival (OS) from time of metastasis was derived using Kaplan-Meier analysis. Unadjusted and multivariable Cox proportional hazards models were used to compare survival between recurrent and de novo cohorts. Results: N = 6,543 pts analyzed; 70.1% (n = 4,586) had de novo mPDAC and 29.9% (n = 1,957) had recurrent mPDAC. Median age at time of metastasis was similar for both cohorts: 69 years (IQR: 62 – 76). The most common site of primary tumor location was head for both cohorts (recurrent mPDAC: 69.8%; de novo mPDAC: 40.3%). Approximately 45% of pts with recurrent mPDAC underwent a Whipple procedure (pre diagnosis of metastasis). A similar proportion of pts in both cohorts received treatment in the metastatic setting (recurrent mPDAC: 74.3%; de novo mPDAC: 77.3%). Pts with recurrent mPDAC had a longer median OS compared to the de novo cohort: 8.0 months (95% CI: 7.5 – 8.6) versus 6.1 (95% CI: 5.7 – 6.4) [unadjusted hazard ratio (HR): 0.79 (95% CI: 0.74 – 0.84); adjusted HR: 0.73 (0.68 – 0.78), p < 0.0001]. Conclusions: The results of this real-world study indicate that pts with recurrent mPDAC are more likely to have a head primary and to experience longer OS from time of metastasis than those with de novo mPDAC. These data suggest stratification for clinical trial enrollment for recurrent vs de novo is necessitated.