Incidence of molecular targets (EGFR-mutation, EML4-ALK, BRAF and KRAS) in metastatic NSCLC in a certified lung cancer hospital

Background: NSCLC has become a molecularly defined disease with the discovery of activating mutations within the EGFR gene, inversions of EML4 -ALK as well as the description of B-RAF and k-ras mutations. The incidence of these targets is not well known in the Caucasian population. Therefore, we have in part retrospectively, in part prospectively screened patients with predominantly non-squamous cell NSLCLC with a tumor stage M1a or M1b for the occurrence of these molecular alterations. Methods: Archived formalin fixed paraffin embedded tumor material was microdissected and studied for activating mutations in EGFR exons 18-21 using Sanger sequencing. Direct sequencing (Sanger method) was also used to evaluate codons 13, 13, and 61 of the KRAS gene for mutations. The BRAF mutation V600E was detected using a PCR based allelic discrimination assay and screening for EML4-ALK translocation was done by RT-PCR assays spanning all 12 relevant exons of EML4 and exon 20 of ALK. Smoking status was defined according to the criteria in the IPASS trial (Mok et al., NEJM 2009). Results: 88 patients were screened for the genetic alterations. Patient characteristics were: male/female: 42/46, median age: 62, non-squamous/squamous: 80/8, never smoker/light smoker vs. smoker:37/42 . In 8 patients, the amount of tumor material was not sufficient to carry out the molecular analyses. In 18/80 patients, EGFR mutations were found, in 5/80 patients, EML4-ALK inversions were detected, in 0/59 patients, B-RAF mutations and in 5/53 patients, k-ras mutations were found. Patient characteristics of the EGFR mutated patients were: male/female:4/14, non-squamous vs. squamous: 17/1, never/light smoker vs. smoker:14/4. Median age of the EGFRMT group was 66, the distribution of e19 mutations/ L858R mutations/vs. other mutations was: 8/7/3. Median time to progression in e19/e21 EGFRMT pts was 14 months (6-24 months). Patient characteristics in the EML4-ALK positive group were: male/female 1/4, median age 77 years (33- 80) and never/light smoker vs. smoker: 4/1. Patient characteristics of the KRAS mt patients were male/ female 3/2, never/light smoker vs smoker: 2/2, and median age was 66 years. EGFR mutations did not occur in combination with k-ras, BRAF or EML4- ALK alterations. Within the group of 35 never/light smokers, successfully analyzed for the molecular targets, the incidence of EGFR mutations was 14/35 (40%), of EML4-ALK 4/35 (16%) and KRAS 2/35 (8%). Conclusion: Recurrent mutations were detected in this screened population diagnosed and treated at a certified lung cancer center with an incidence of 23% (EGFR-MT), 6% (EML4-ALK) and 9% (KRAS). An association with smoking status, gender and histology was found for EGFR and EML4-ALK alterations. The EML4-ALK population had a higher median age than the EGFR-MT group and seemed to be more frequently detected than in most reported series.