Impact of dose reductions on clinical outcomes among patients (pts) with metastatic pancreatic cancer (mPC) treated with liposomal irinotecan (nal-IRI) in oncology clinics in the United States

665 Background: The recommended starting dose for nal-IRI is 70mg/m2 (free base, equivalent to 80 mg/m2 salt-based dosing). This study evaluates the impact of nal-IRI dose reductions on clinical outcomes. Methods: Using the nationwide Flatiron Health electronic health record-derived database, de-identified data were extracted and analyzed for adult mPC pts treated with nal-IRI Jan 2014-Jan 2019 and who initiated treatment at approximately the recommended dose (RD), 70mg/m2 +/- 5mg. Initial dose was derived from structured medication records, prioritizing administrations. The cumulative dose (CD) of nal-IRI over the first six weeks of treatment, the presence of dose reductions (DR) – (a decrease ≥ 7mg/m2), overall survival (OS) from treatment initiation, and duration of treatment (DoT) were assessed. Results: 257 mPC pts treated with nal-IRI (median age: 68y, IQR: 61 - 73) were identified initiating therapy at approximately the RD. 26.5% (N = 68) of pts experienced a DR during treatment. Mean 6-week CD was 175.8 mg/m2 (SD: 77.9) among pts with no DR. For pts with DR, mean CD was 191.8 mg/m2 (53.2). Median DoT was 6.1 wks (IQR: 2.1 – 15.3). Pts that experienced a DR had a longer median DoT: 15.1 wks (7.1 – 23.0) vs 4.3. wks (2.1 – 12.1) for pts with no DR. Overall Median OS (mOS) was 4.2 months (95% CI: 3.7 – 5.4). mOS for DR pts was 7.2 mos (95% CI: 5.5 – 9.7) and 3.7 mos (3.0 – 4.1) for pts who did not experience a DR. Conclusions: This real-world analysis suggests that reducing the dose of subsequent administrations of nal-IRI during treatment is associated with pts remaining on therapy longer, experiencing a larger CD, and a with longer OS. Additional real-world prospective studies are necessary to characterize the impact of nal-IRI dosing on clinical outcomes.