Influence of ancestry in racial disparities of squamous cell lung cancer.

Abstract

e20554 Background: Significant progress has been made in the screening, diagnosis, and treatment of squamous cell carcinomas of the lung (LUSC). Despite the advancements, African American populations continue to experience worse disease burden and poorer overall survival, even after controlling for patient and tumor characteristics. While the interplay of various social determinants of health is well known to contribute to racial disparities in cancers, the molecular basis of racial disparity is less understood. Given the diversity of the US population that comprise of genetically admixed groups, understanding the role of ancestry and its influence on biology of cancers that drive incidence and prognosis is paramount to reducing racial disparities. Therefore, in this study, we aimed to investigate the influence of African (AFR) ancestry in genetic mutations of LUSC. Methods: We utilized The Cancer Genome Ancestry Atlas (TCGAA) to obtain data on the genetic ancestry and ancestral composition of 504 LUSC patients. The dataset contained 459 self-reported whites, 32 blacks, and 11 Asians. The percentage of each patient’s ancestral composition (European, AFR, Asian, and Native American) was revealed via the LAMP technique. The dominant ancestry was defined as those with genetic composition of ≥50% from one of four ancestral backgrounds. Genetic alteration profiles and clinical data of patients were obtained from LUSC TCGA PanCancer Atlas through GDC data portal. Of those with AFR dominant ancestry, we analyzed the differences in the gene mutation frequency based upon the proportion of AFR ancestry. Results: Ancestry analysis uncovered 30 AFR ancestry dominant cases with a mean AFR composition of 78.4%. We found 14 subjects with > 80% AFR ancestry and 16 subjects with 50-80% AFR ancestry. Two patients from the > 80% were excluded from the mutational analyses due to absence of genetic profiles in the data portal. TP53 was the most frequently mutated gene with a rate of 91.7% and 87.5% in > 80% and 50-80% AFR groups, respectively. Evaluation of the classic genetic mutations that drive disease pathology in LUSC (EGFR, ALK, PIK3CA, NRAS, KRAS) revealed 25% of > 80% AFR ancestry subjects carried mutations in at least one of these genes compared to 6.3% in the 50-80% AFR ancestry subjects. Also, a trend towards worse overall survival (OS) was seen in those with greater proportion of AFR ancestry (median OS of 27.2 months in > 80% group vs 43.9 months in 50-80% group). Conclusions: Despite the limited sample size, our study highlights substantial heterogeneity in tumor biology even within those of AFR ancestry and that genetic ancestry may impact tumor and host biology that contribute to disparities. Moving forward, engagement of the African American community into clinical trials and genomic studies are needed to explore ancestral influence on tumorigenesis, and to facilitate discovery of new actionable targets to help eradicate racial disparities in lung cancer.