About 15% of non-small cell lung cancer (NSCLC) cases carry activating mutations in the EGFR gene which are associated with high sensitivity of the tumor to tyrosine kinase inhibitors. Frequency of the mutations positively correlates with adenocarcinoma (AdCa) histology, female gender, non-smoker status and Asian ethnicity. Most of activating mutations in EGFR gene (85-90%) are small in-frame deletions in exon 19 (del19), or missense mutation L858R. Population in Russia is composed of Caucasian and Asian ethnic groups which may have impact on frequency of EGFR mutations. Aim of the study was to evaluate frequency of EGFR mutations del19 and L858R in archive FFPE tumor tissue from NSCLC patients in Siberian part of Russia.
Archive FFPE samples were provided by clinics from 9 largest cities in East and West Siberia. DNA purification and EGFR mutation tests were done in one laboratory (Biolink Ltd, Novosibirsk). Mutation L858R was detected by allele-specific real-time PCR. Mutations del19 were detected by wild-type blocking (WTB) real-time PCR. Sequence of del19 mutations was determined by Sanger sequencing of the WTB PCR DNA.
Sensitivity of PCR tests was 1% mutant EGFR allele in 10ng of tissue DNA spiked with plasmid DNA with the mutation. A total of 400 FFPE samples were evaluated and DNA from 382 samples (95,5%) were suitable for the tests including 35 cases of squamous cell carcinoma (SCC), 249 AdCa and 96 cases with mixed histology. EGFR mutations were detected in 63 cases (16,5%) including 34 cases of del19 and 29 cases of L858R. EGFR mutations were much more frequent among female patients (39%) in comparison to male (6%). Mutations were also much more common in AdCa (22%) in comparison to SCC (3%).
Frequency of EGFR mutations in NSCLC cases in Siberia is in agreement with studies in Western Europe. Study was supported by FASIE grant 12594р/24404 and RSF grant 15-14-10004.
All authors have declared no conflicts of interest.