Smoking status and self-reported race affect the frequency of clinically relevant oncogenic alterations in non-small-cell lung cancers at a United States-based academic medical practice

Abstract

Introduction: The identification of somatic genomic aberrations in non-small-cell lung cancer (NSCLC) is part of evidence-based practice guidelines for care of patients with NSCLC. We sought to establish the frequency and correlates with these changes in routine patient-tumor sample pairs.

Methods: Clinicopathologic data and tumor genotype were retrospectively compiled and analyzed from an overall cohort of 381 patient-tumor samples.

Results: Of these patients, 75.9% self-reported White race, 13.1% Asian, 6.5% Black, 27.8% were never-smokers, 54.9% former-smokers and 17.3% current-smokers. The frequency of EGFR mutations was 23.9% (86/359), KRAS mutations 34.2% (71/207) and ALK FISH positivity 9.1% (23/252) in tumor samples, and almost all had mutually exclusive results for these oncogenes. In tumors from White, Black and Asian patients, the frequencies of EGFR mutations were 18.4%, 18.2% and 62%, respectively; of ALK FISH positivity 7.81%, 0% and 14.8%, respectively; and of KRAS mutations 41.6%, 20% and 0%. These patterns changed significant with increasing pack-year history of smoking. In White patients, the frequencies of EGFR mutations and ALK FISH positivity decreased with increasing pack-year cohorts; while the frequencies of KRAS mutations increased. Interestingly, in Asian patients the frequencies of EGFR mutations were similar in never smokers and in the cohorts with less than 45pack-year histories of smoking and only decreased in the 45pack-year plus cohort.

Conclusions: The frequencies of somatic EGFR, KRAS, and ALK gene abnormalities using routine lung cancer tissue samples from our United States-based academic medical practice reflect the diverse ethnicity (with a higher frequency of EGFR mutations in Asian patients) and smoking patterns (with an inverse correlation between EGFR mutation and ALK rearrangement) of our tested population. These results may help other medical practices appreciate the expected results from introduction of routine tumor genotyping techniques into their day-to-day care of NSCLC.

Keywords: ALK; Anaplastic lymphoma kinase; EGFR; Epidermal growth factor receptor; KRAS; Lung cancer; Never smokers; Non-small-cell lung cancer.

FIGURE 1

Frequencies of EGFR mutations (A), ALK FISH positivity (B) and KRAS mutations within increasing cohorts of smoking history (from never smokers to >45 pack-years history of smoking). Concurrent frequency of EGFR mutations, ALK FISH positivity and KRAS mutations in never smokers and smokers (D) successfully tested for all three tumor genotypes.

FIGURE 2

Frequencies of EGFR mutations (A), ALK FISH positivity (B) and KRAS mutations (C) within increasing cohorts of smoking history (from never smokers to >45 pack-years history of smoking) by self-reported race (White, Asian or Black).