Abstract PR03: Somatic mutations and ancestry markers in Hispanic lung cancer patients

Introduction: Hispanics are projected to constitute 23% of the U.S. population by 2050. However, large-scale sequencing projects, such as The Cancer Genome Atlas (TCGA), provide little information on this ethnic population. In fact, only seven out of over 500 lung adenocarcinoma tumors sequenced in the TCGA database are reported to be Hispanic. To address the lack of genomic data from Hispanic/Latino patients with lung cancer, the Latino Lung Cancer Registry was established to collect patient data and biospecimens from these patients.

Methods: This retrospective observational study examined lung cancer tumor samples from 163 Hispanic/Latino patients, and tumor-derived DNA was subjected to targeted-exome sequencing (>1000 genes, including EGFR, KRAS, STK11, and TP53) and ancestry analysis. Mutation frequencies in this Hispanic/Latino cohort were compared with those in a similar cohort of non-Hispanic white (NHW) patients. Novel mutations in EGFR were functionally characterized, and mutation rates were correlated with ancestry, patient sex, smoking status, and tumor histology.

Results: Among adenocarcinomas (n=120) in the Hispanic/Latino cohort, 31% had EGFR mutations versus 17% in the NHW control group (p < 0.001). The EGFR mutations in Hispanic/Latino patients included well-characterized activating mutations, such as L858R, and uncharacterized EGFR variants. A rare exon 19 mutation, W731R, was identified that conferred resistance to both erlotinib and AZD9291. KRAS (20% vs. 38%; p=0.002) and STK11 (8% vs. 16%; p=0.065) mutations occurred at lower frequency, and mutations in TP53 occurred at similar frequency (46% vs. 40%; p=0.355) in Hispanic/Latino and NHW patients, respectively. Within the Hispanic cohort, ancestry influenced the rate of TP53 mutations (p=0.009) and may influence the rate of EGFR, KRAS, and STK11 mutations.

Conclusions: Driver mutations in Hispanic/Latino lung adenocarcinoma patients differ in frequency from those in NHWs associated with their Indigenous American ancestry. The spectrum of driver mutations needs to be further assessed in the Hispanic/Latino population.

Citation Format: William D. Cress, Nicholas T. Gimbrone, Bhaswati Sarcar, Edna Gordian, Jason I. Rivera, Christian Lopez, Jamie K. Teer, Eric A. Welsh, Alberto A. Chiappori, Matthew B. Schabath, Gary W. Reuther, Pedro G. Santiago-Cardona. Somatic mutations and ancestry markers in Hispanic lung cancer patients [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr PR03.

Somatic Mutations and Ancestry Markers in Hispanic Lung Cancer Patients

INTRODUCTION

To address the lack of genomic data from Hispanic/Latino (H/L) patients with lung cancer, the Latino Lung Cancer Registry was established to collect patient data and biospecimens from H/L patients.

METHODS

This retrospective observational study examined lung cancer tumor samples from 163 H/L patients, and tumor-derived DNA was subjected to targeted-exome sequencing (>1000 genes, including EGFR, KRAS, serine/threonine kinase 11 gene [STK11], and tumor protein p53 gene [TP53]) and ancestry analysis. Mutation frequencies in this H/L cohort were compared with those in a similar cohort of non-Hispanic white (NHW) patients and correlated with ancestry, sex, smoking status, and tumor histologic type.

RESULTS

Of the adenocarcinomas in the H/L cohort (n = 120), 31% had EGFR mutations, versus 17% in the NHW control group (p < 0.001). KRAS (20% versus 38% [p = 0.002]) and STK11 (8% versus 16% [p = 0.065]) mutations occurred at lower frequency, and mutations in TP53 occurred at similar frequency (46% versus 40% [p = 0.355]) in H/L and NHW patients, respectively. Within the Hispanic cohort, ancestry influenced the rate of TP53 mutations (p = 0.009) and may have influenced the rate of EGFR, KRAS, and STK11 mutations.

CONCLUSIONS

Driver mutations in H/L patients with lung adenocarcinoma differ in frequency from those in NHW patients associated with their indigenous American ancestry. The spectrum of driver mutations needs to be further assessed in the H/L population.

Early2 factor (E2F) deregulation is a prognostic and predictive biomarker in lung adenocarcinoma

Clinicians routinely prescribe adjuvant chemotherapy (ACT) for resected non-small cell lung cancer patients. However, ACT only improves five-year disease-free survival in stage I-III non-small cell lung cancer by 5-15%, with most patients deriving no benefit. Herein, deregulation of the E2F pathway was explored as a biomarker in lung adenocarcinoma patients. An E2F pathway scoring system, based on 74 E2F-regulated genes, was trained for RNA from two platforms: fresh-frozen (FF) or formalin-fixed paraffin-embedded (FFPE) tissues. The E2F score was tested as a prognostic biomarker in five FF-based cohorts and two FFPE-based cohorts. The E2F score was tested as a predictive biomarker in two randomized clinical trials; JBR10 and the NATCH (Neo-Adjuvant Taxol-Carboplatin Hope) trial. The E2F score was prognostic in untreated patients in all seven datasets examined (p < 0.05). Stage-specific analysis of combined cohorts demonstrated that the E2F score was prognostic in stage I patients (p = 0.0495 to <0.001; hazard ratio, HR, =2.04- 2.22) with a similar trend in other stages. The E2F score was strongly predictive in stage II patients from the two combined randomized clinical trials with a significant differential treatment effect (p = 0.015). Specifically, ACT improved survival in stage II patients with high E2F (p = 0.01; HR= 0.21). The 5-year survival increased from 18% to 81%. In contrast, in patients with low E2F, 5-year survival was 57% in untreated patients and 41% in ACT-treated patients with a HR of 1.55 (p = 0.47). In summary, the E2F score provides valuable prognostic information for Stage I and predictive information for Stage II lung adenocarcinoma patients and should be further explored as a decision support tool for their treatment.