Longitudinal cumulative dose: A novel measure to assess multiple dimensions of chemotherapy adherence over time.

Abstract

3522 Background: Adjuvant chemotherapy regimens take months to complete. Despite this, trials and observational studies evaluate chemotherapy adherence via measures assessed at the end of treatment (e.g. number of patients missing any dose, relative dose intensity [RDI]). This approach misses information that impacts outcomes, like treatment delays. We propose longitudinal cumulative dose (LCD) as a way to integrate the impact of dose reductions, missed doses, and dose delays at each cycle over time. Methods: We obtained data from the 2,246 participants in the Multicenter International Study of Oxaliplatin/5FU-LV in the Adjuvant Treatment of Colon Cancer (MOSAIC). We evaluated proportions of patients stopping treatment early and reducing (based on protocol), missing, or delaying a dose in each arm for each chemo agent at each visit. We obtained LCD, the fraction of the final standard dose a participant reached by a given day, for each participant and each chemo agent. We compared LCD medians over time and at the end of a standard regimen (24 weeks) between treatment arms and by age and performance status. We assessed agreement between oxaliplatin LCD and RDI with Fleiss’ kappa (Table). Results: Participants randomized to FOLFOX were more likely than those randomized to 5FU to stop treatment, reduce doses, miss doses, or delay visits; these differences increased over time. Median LCD for oxaliplatin in the FOLFOX arm at 24 weeks was 77%. Graphs of median LCD for 5FU showed a clear difference between arms (FOLFOX arm median LCD: 81%; 5FU arm median LCD, 96%). While 5FU LCD decreased with age in the FOLFOX arm (median LCD in those age <40: 85%; 40-64, 82%; 65-75, 76%), it was similar across ages in the 5FU arm (median LCD 94%, 96%, and 96%, respectively), with smaller performance status trends. RDI and LCD showed fair agreement (Fleiss’ kappa=0.34); 19% of those with RDI over 85% had LCD under 60%. Conclusions: Visualizing LCD highlighted the timing and scale of deviations from standard administration, with major differences in 5FU LCD across arms. Next steps include evaluating if LCD predicts clinical outcomes. [Table: see text]