Abstract C115: Racial disparities in tumor profiling testing inferred from continental genetic ancestry determination of 100,000 cancer patients
Authors: De La Vega Francisco M. , Pouliot Yannick , Rhead Brooke , Guinney Justin 
Published: January 2023

Abstract
There are well documented disparities in the incidence of cancer and outcomes of treatment across patients of different races and ethnicities. This is credited to a variety of factors which include social, structural, and access to care inequities, as well as biological differences that may correlate with race/ethnicity. We aimed to measure racial differences in testing for cancer therapy decision support using real-world data (RWD) from 100,000 de-identified patients who underwent tumor genomic profiling with the Tempus xT next-generation sequencing assay (targeting 648 genes). A challenge for this analysis is that in RWD race/ethnicity is frequently missing from patients’ records. Instead, we used ancestry-informative markers overlapping assay capture regions to infer continental ancestry proportions: Africa, Americas, Europe, East Asia, and South Asia. Our data show that despite a majority of patients being of European descent (72%), our cohort includes 8 to 12-fold more patients with substantial (&gt;50%) non-European ancestry when compared to The Cancer Genome Atlas. Recognizing the complexity of ancestry and race relationships, we imputed several race/ethnicity categories using ancestry admixture thresholds based on literature and our own analysis, demonstrating less than 2% error with available race/ethnicity labels. With imputation, 85% more Black patients were identified within our cohort. Furthermore, Hispanics/Latinos were substantially overrepresented among those missing ethnicity metadata; using imputed ethnicity labels increased the numbers of this patient population by 150%. Patient subpopulation disparities were estimated through comparison of imputed race/ethnicity distributions with the expected overall cohort-level distributions. We observed significantly lower than expected percentages of Black patients with pancreatic (-18%) and urinary tract cancers (-42%), and White patients with breast (-7%) and colorectal (-5%) cancers, whereas higher than expected numbers of Hispanic/Latino patients with colorectal (+22%) and thyroid (+48%), and Asian patients with gallbladder cancer (+32%) were present (p&lt;0.05, chi-squared test). These disparities are unexpected as compared to the ranking of incidence rates in the SEER database by race/ethnicity. Our results show that genetic ancestry inference on genomic data from tumor profiling can partially compensate for the lack of race/ethnicity information in RWD and allow research on disparities and biological race differences in cancer etiology and outcomes.
Citation Format: Francisco M. De La Vega, Yannick Pouliot, Brooke Rhead, Justin Guinney. Racial disparities in tumor profiling testing inferred from continental genetic ancestry determination of 100,000 cancer patients [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr C115.