Racial disparities in lung adenocarcinoma: The contribution of African ancestry.

Abstract

8516 Background: Racial disparities in lung cancer are well-known with African Americans disproportionally affected by lung cancer in terms of incidence and survival. Previous comparative analyses of molecular features of lung cancer revealed racial differences in genomic profiles, which supports somatic differences arising from genetic ancestry. Using The Cancer Genome Atlas (TCGA), we investigated the genetic alterations in lung adenocarcinomas (LUAD) on individuals of African (AFR) ancestry. Methods: The genomic and clinical data of TCGA PanCancer Atlas LUAD were downloaded through the GDC Data Portal. Given that substantial proportion of the US population consist of genetically admixed populations, we utilized The Cancer Genome Ancestry Atlas (TCGAA) and LAMP for estimates of genetic ancestry and quantitative ancestral compositions. This dataset contains 518 samples, including 393 self-reported whites and 52 African Americans. For each case the proportion of European, AFR, East Asian, native American ancestry was estimated. The dominant ancestry was defined as ≥50% of admixture from one reference population. Differences in gene mutation frequency were analyzed based on AFR ancestry proportion. The Kaplan-Meier curves were generated, and Cox regression analyses were performed. Results: Global ancestry analysis identified 50 AFR ancestry cases with mean ancestry of 78.3%. The dominant AFR ancestry group matched the self-reported race with 96% accuracy. We identified 9 subjects with ≥90% AFR ancestry, 22 subjects with 80-90% AFR ancestry, 12 subjects with 70-80% AFR ancestry, and 7 subjects with 50-70% AFR ancestry. TP53 was the most frequently mutated gene, and ≥90% AFR ancestry had the highest rate of mutations (77.8%) compared with 80-90% AFR ancestry (68.2%), and 70-80% AFR ancestry (66.8%). We evaluated classic driver gene mutations (EGFR, KRAS, NRAS, PIK3CA, ALK) and found only 33% of ≥90% AFR ancestry subjects carry a known driver mutation, compared to 58-77% in lower proportion of AFR ancestry subjects. Higher AFR ancestry was associated with worse overall survival (OS) and progression free survival (PFS). Median OS was 14.5 months for ≥90% AFR ancestry compared to 71.47 months in 70-80% AFR ancestry (P = 0.048). ≥90% AFR ancestry had median PFS of 12.8 months compared to 33.5 months in 80-90% AFR ancestry, and 47.1 months in 70-80% AFR ancestry (P = 0.002). Conclusions: This study demonstrates the power of genomic study to investigate the etiology of health disparities by analyzing the effect of ancestry on genetic alterations in LUAD. Our results reveal different mutation loads even among AFR ancestry patients. We observed that AFR ancestry is associated with worse OS, suggesting possible influence of germline ancestry in subsequent somatic alterations. Further work is needed to explore how genetic ancestry impacts tumorigenesis and cancer progression to eliminate lung cancer disparities.