Disparities in the impact of the AJCC 8th edition staging system on differentiated thyroid cancer outcomes

Background: The impact of AJCC8 among self-reported racial/ethnic groups on differentiated thyroid cancer (DTC) outcomes is unknown. Methods: Multivariate-regression evaluated the association between AJCC7 to AJCC8 stage change and race/ethnicity in patients with DTC in the NCDB. Cox-proportional-regression evaluated whether AJCC7 to AJCC8 stage change affects overall survival (OS) differently based on reported race/ethnicity. Results: After adjusting for confounders, Hispanics and Asian-Pacific-Islanders (APIs) were 27% and 12% less likely to be down-staged compared to white-non-Hispanics (WNHs) (p < 0.001); black-non-Hispanics (BNHs) had no significant down-staging difference. Down-staged patients had an increased risk of death compared to patients with unchanged staging, regardless of race/ethnicity. However, based on two-way interaction, the magnitude of this negative change on survival from down-staging was only different between WNHs (HR = 2.64) and BNHs (HR = 1.77), (p = 0.04). Conclusions: Outcome disparities persist among self-reported racial/ethnic groups with AJCC8. Down-staged patients across all racial/ethnic groups had decreased survival compared to those with unchanged stage, with the least impact in BNHs.