Decompositions of the Contribution of Treatment Disparities to Survival Disparities in Stage I-II Pancreatic Adenocarcinoma

Background: Higher socioeconomic status (SES) and non-Hispanic White (NHW) race/ethnicity are associated with higher treatment rates and longer overall survival (OS) among US patients with stage I-II pancreatic ductal adenocarcinoma. The proportion of OS disparities mediated through treatment disparities (PM) and the proportion predicted to be eliminated (PE) if treatment disparities were eliminated are unknown.

Methods: We analyzed 2007-2015 data from the Surveillance, Epidemiology, and End Results (SEER) census tract-level database and the National Cancer Database (NCDB) using causal mediation analysis methods to understand the extent to which treatment disparities mediate OS disparities. In the first set of decompositions, race/ethnicity was controlled for as a covariate proximal to SES, and lower SES strata were compared with the highest SES stratum. In the second set, an intersectional perspective was taken and each SES-race/ethnicity combination was compared with highest SES-NHW patients, who had the highest treatment rates and longest OS.

Results: The SEER and NCDB cohorts contained 16,921 patients and 44,638 patients, respectively. When race/ethnicity was controlled for, PMs ranged from 43 to 48% and PEs ranged from 46 to 50% for various lower SES strata. When separately comparing each SES-race/ethnicity combination with the highest SES-NHW patients, results were similar for lower SES-NHW patients but differed markedly for non-Hispanic Black and Hispanic patients, for whom PMs ranged from 60 to 80% and PEs ranged from 55 to 75% for most lower SES strata.

Conclusions: These results suggest that efforts to reduce treatment disparities are worthwhile, particularly for NHB and Hispanic patients, and simultaneously point to the importance of non-treatment-related causal pathways.