SUN-426 The Impact from AJCC 8(Th) Edition Staging System on Thyroid Cancer Outcomes by Race And Ethnicity

Background. Previous studies have demonstrated racial and ethnic outcome disparities among differentiated thyroid cancer (DTC) patients. However, the impact of the 8(th) edition of the American Joint Committee on Cancer staging system (AJCC8) on these disparities is unknown. Methods. DTC patients with sufficient tumor and survival data were identified in the National Cancer Database from 2004-2013. The 7(th) edition of the staging system (AJCC7) and AJCC8 criteria were compared. Multivariable logistic regression was used to evaluate the association between AJCC7 to AJCC8 staging change and race and ethnicity. Cox-proportional hazards regression was then used to evaluate the association between AJCC7 to AJCC8 staging change and overall survival. Results. Of 33,323 DTC patients, 76.7% were White/Non-Hispanics, 7.6% Blacks, 6.7% Hispanics, 5.4% Asian/Pacific-Islanders, and 3.6% Native-American/Other. Most were female (77%) with papillary DTC (90%). After adjusting for demographic, tumor, and treatment characteristics, Hispanics and Asian/Pacific-Islanders were 27% and 12% less likely to be AJCC7 to AJCC8 downstaged than White/Non-Hispanics (OR=0.73, 95%CI: 0.66-0.81; and OR=0.88, 95%CI: 0.79-0.99, respectively); Blacks had no significant downstaging difference compared to White/Non-Hispanics (OR=0.99, 95% CI: 0.90-1.09, p=0.79). Although AJCC8 was a better survival prognosticator than AJCC7, Cox-proportional hazards regression showed that all AJCC7 to AJCC8 downstaged patients had an increased risk of death compared to patients with unchanged staging, regardless of race and ethnicity: White/Non-Hispanics (HR=2.64, 95%CI: 2.34-2.98), Blacks (HR=1.77, 95%CI: 1.23-2.54), Hispanic (HR=3.27, 95%CI: 2.05-5.22), Asian/Pacific-Islanders (HR=2.31, 95%CI: 1.35-3.98), and Native-American/Other (HR=5.26, 95%CI: 2.10-13.19). However, based on two way interaction, the magnitude of negative change in survival from downstaging was only different between White/Non-Hispanics and Blacks (HR=2.64 vs. HR=1.77, respectively; p=0.04). Conclusions. Racial and ethnic outcome disparities persist with AJCC8. The proportion of downstaged DTC patients with AJCC8 varies by race and ethnicity, with the least impact found in Hispanics and Asian/Pacific-Islanders. Downstaged patients across all racial and ethnic groups had a decreased survival than those with unchanged stage, with the least impact in Blacks. These disparities should be taken into account when counseling patients about their prognosis with the new AJCC8.