Somatic mutation spectrum of non-small cell lung cancers (NSCLCs) from African Americans (AAs).

Abstract

6038 Background: In the AA population, previous studies have presented conflicting data on the frequency of EGFR mutations (Reinersman JTO 2011;Leidner JCO 2009), while frequencies of other gene mutations and translocations, including anaplastic lymphoma kinase (ALK), have not been described. Methods: 161 archival FFPE tumor specimens from self reported AA patients with any stage NSCLC from 1997-2010 were collected from 3 sites in Tennessee (132 samples) and one site in Michigan (29 samples). Samples were evaluated for known recurrent driver mutations in EGFR, KRAS, BRAF, NRAS, AKT1, PI3KCA, PTEN, HER-2, MEK1 by standard SNaPshot/sizing assays, and translocations in ALK by FISH. Clinical data was collected on 119 patients. Chi-square was used to compare the frequency of mutations in subgroups and Kaplan-Meier and log rank were used to calculate and compare PFS between groups. Results: 5.0% of tumors had EGFR mutations, 14.9% had KRAS mutations, 0.6% had a BRAF, AKT1, PI3KCA, or HER2 mutation, and 0% had NRAS, PTEN, or MEK1 mutations. Of 35 ‘pan-negative’ non-squamous specimens, 0 had ALK translocations. PFS was the same in those with and without KRAS mutation (p=0.74) and showed a trend towards improvement in those with EGFR mutation (p=0.08). The frequency of EGFR mutations was higher in samples from Detroit versus those from Tennessee (17% vs 2.3%, p<0.01), as was the frequency of adenocarcinoma (62% vs 44%, p<0.05). The frequency of EGFR mutations in never smokers was higher in the samples from Detroit versus Tennessee (83% vs 7.1%, p<0.01). Conclusions: In the largest tumor mutational profiling study of NSCLC from AAs to date, EGFR mutations occurred less frequently than would be expected from a North American population. We noted a regional difference, with fewer EGFR mutations in Tennessee than in Michigan, a finding that may have been the result of more adenocarcinoma samples from Michigan. The rates of other mutations and translocations including ALK were low. While lung cancer tumors should continue to undergo routine molecular testing to prioritize therapy, future comprehensive genotyping efforts should focus on identifying novel driver mutations in this population. Funding: 5RC1CA162260 R01CA060691 R01CA87895.