Understanding extended duration of therapy (DOT) among patients with metastatic pancreatic ductal adenocarcinoma (mPDAC) treated with liposomal irinotecan-based regimens.

Abstract

579 Background: Few analyses have identified characteristics associated with extended DOT (eDOT) among a large group of patients (pts) treated with liposomal irinotecan. This study examines the characteristics associated with eDOT among pts with mPDAC treated with liposomal irinotecan in a real-world setting. Methods: This retrospective observational study utilized the Flatiron Health EHR database from over 280 cancer clinics in the US. Data were analyzed for adult pts with mPDAC treated with liposomal irinotecan-based regimens between January 2016 and October 2020. eDOT was defined as a DOT > 2 standard deviations (SD) above the mean. Demographic and clinical characteristics evaluated included age, sex, stage at diagnosis, ECOG performance score (PS), and the number of prior lines of therapy at the time of treatment initiation. Dose delays and dose reductions during treatment were assessed. Additionally, changes in lymphocyte counts during treatment were described. Chi-squared test and Fisher’s exact test were used to test for significance for categorical variables and the t-test was used for continuous variables. Results: 675 pts with mPDAC treated with a liposomal irinotecan-based regimen were included. The overall mean DOT was 14.6 weeks (SD: 22.1). There were 30 pts (4.4%) that met the definition for eDOT. Patient sex and median age at treatment initiation were similar between those with eDOT and non-eDOT: male, 46.7% vs. 51.9% (p = 0.582); age, median 70 years vs 69 years (p = 0.923), respectively. A higher proportion of pts with eDOT had ECOG PS of 0-1 compared to those with non-eDOT, 73.3% vs 57.7%, respectively (p = 0.397). At treatment initiation 80.0% of pts who had eDOT had a serum albumin level of ≥ 35g/L versus 55.2% of pts with non-eDOT (p = 0.013). On average, those with eDOT experienced a 55.1% reduction in lymphocyte count (baseline to nadir) during treatment compared to a 34.7% reduction among pts with non-eDOT (p < 0.0001). Pts who experienced eDOT were more likely to be treated in earlier lines of therapy than those with non-eDOT: 33.3% vs 14.1% received 0 prior lines and 46.7% vs 47.3% received 1 prior line, respectively (p = 0.008). 53.3% of pts with eDOT experienced a dose reduction (of at least 7mg/m2) compared to 24.7% pts with non-eDOT (p = 0.0005). All pts with eDOT experienced a dose delay of > 16 days during treatment versus 45.3% of pts with non-eDOT (p < 0.0001). Conclusions: This real-world study identified pts treated earlier in their disease course with a liposomal irinotecan-based regimen and normal baseline serum albumin were more likely experience extended DOT. Treatment modifications and delays appear to have enabled longer treatment duration with liposomal irinotecan-based regimens. Further prospective studies should be considered to characterize factors that may predict extended DOT.