Abstract A23: Detection of K ras mutations in Korean non small cell lung cancer patients

Background: Point mutation of the K ras gene is known to be a poor prognostic marker of an adenocarcinoma of the lung. This study aims to define frequency of K ras mutations and evaluate clinical features of patients with Non small cell lung cancer (NSCLC) who harbor K ras mutation. Methods: NSCLC patient who were diagnosed from Sep. 2005 to Aug. 2011 at Konkuk University Hospital were included in this retrospective study. K ras mutation was assessed by pyrosequencing on biopsy or cytology specimen. Medial chart review was performed and clinical characteristics were compared according to K ras mutation status of their tumors. Results: K ras mutation was found in 25 (9.0%) of 277 patients and which was similar to those in East Asian countries, but lower than those in western countries. Fifteen mutations (60.0%) were point mutation at codon 12 (GGT), 7 mutations (28.0%) were point mutation at codon 61 (CAA), and 3 mutations (12.0%) were found at codon 13 (GGC) in exon 2. Median age of 25 patients with KRAS mutation was 6 years (range 43–85 years). There were 20 males (80.0%) and 3 never-smokers (12.0%). The majority of histological diagnoses were adenocarcinomas (21 cases; 84.0%) and squamous cell carcinomas were followed (3 cases; 12.0%). Interestingly, 2 patients had both mutations of EGFR and KRAS unlike previous studies, they showed favorable response to EGFRTKIs. Conclusions: The data indicate that KRAS mutation is less frequent in Korean than Caucasian patients. Although it is suggested that EGFR and KRAS mutations occur in mutually exclusive, very few of the patients with KRAS mutation showed also EGFR mutation and relatively favorable response to EGFR-TKIs. Additional large scale prospective studies are needed in order to validate the clinical significance of Kras mutation in Asian patients.