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S. Melemed

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    MINI 13 - Genetic Alterations and Testing (ID 120)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      MINI13.06 - Mutation Prevalence for Oncogenic Drivers in Lung Adenocarcinoma (ID 3279)

      10:45 - 12:15  |  Author(s): S. Melemed

      • Abstract
      • Presentation
      • Slides

      Identification of mutations which drive pulmonary adenocarcinomas (ADC) has rapidly moved from the research arena to clinical practice. The prevalence of these mutations has been suggested by a multitude of studies but here we describe the prevalence of mutations from a large study of patients with advanced ADC treated in the international phase III study INSPIRE (Lancet Oncology 2015) with all testing performed in one CLIA-certified laboratory under standardized conditions.

      Mutation testing was performed on 412 adenocarcinoma specimens using SNaPshot® methodology. Mutations were examined in the AKT, EGFR, KRAS, BRAF, NRAS, PIK3CA, TP53, PTEN, CTNNB1, and MEK1 genes. The relative frequencies of genetic alterations were calculated based on the total number of adequate specimens and specific consent for testing.

      Of the 412 adenocarcinoma specimens tested, 372 (90.3%) had evaluable results from mutation testing. A single mutation was detected in 157 (42.2%) specimens, whereas mutations in two genes were detected in an additional 20 (5.4%). The overall prevalence of mutations for each specific gene was as follows: KRAS (34.2%), EGFR (12.2%), TP53 (4.9%), PTEN (2.8%), PIK3CA (2.2%), CTNNB1 (2.2%), NRAS (1.8%), BRAF (1.2%), MEK1 (0.3%), and AKT (0%). Figure 1 Evaluation of smoking status identified a substantially higher percentage of KRAS mutations in ex-light smokers and current smokers (38.2% and 40.5%) combined compared to never smokers (7.6%, p<0.0001) , and a lower proportion of EGFR mutations in ex-light and current smokers (10.9% and 4.9%) combined compared to never smokers (39.7%, p<0.0001). Patients ≥70 years old had a higher proportion of both NRAS (7.1% vs. 0.7%, p=0.009) and TP53 mutations (12.5% vs. 3.3%, p=0.010). In addition, males had a lower incidence of EGFR mutation (8.6% vs. 19.0%, p=0.007) as compared to females. Patients from North America, Europe, and Australia/New Zealand demonstrated lower rates of mutation in CTNNB1 (1.4% vs. 8.6%, p=0.030) and PIK3CA (1.4% vs. 8.3%, p=0.032) compared to patients from Central/South America, South Africa and India. Finally, among specimens with two mutations, combinations involving KRAS were the most prevalent (70%, 14/20) followed by TP53 (50%, 10/20).

      These results demonstrate the wide spectrum of mutations that can be detected in adenocarcinoma specimens, with high prevalence rates in the EGFR and KRAS genes. Most patients had only one identified driver mutation. The study revealed age and geographical associations in some mutations. The clinical relevance of the studied mutations in relation to chemotherapy and the human EGFR antibody, Necitumumab, will be studied.

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