Comparison of the characteristics and clinical course of 677 patients with metastatic lung cancers with mutations in KRAS codons 12 and 13.

Abstract

8025 Background: Patients (pts) with KRAS mutant lung cancers have a shorter survival compared to pts with KRAS/EGFR wild type tumors (Johnson et al, Cancer 2012). Whether outcomes for patients with KRAS mutant metastatic lung cancers differ by smoking status or specific amino acid substitution is unknown. In order to understand the impact of KRAS mutation subtype in the metastatic setting, we analyzed a large cohort of patients with KRAS mutant metastatic lung cancer. Methods: We identified all pts with KRAS mutant metastatic or recurrent lung cancers from Feb 2005 to Aug 2011. KRAS mutation type, clinical characteristics, and outcomes from diagnosis were obtained from the medical record. A multivariate cox proportion hazard model was used to identify factors associated with overall survival. Results: KRAS mutations were identified in 677 pts (53 at codon 13, 624 at codon 12). Median age: 66 (range 31-89), women: 62%, never smokers: 7%. Pts with transition mutations (n=157) were more likely to be never-smokers (p<0.0001). There was no difference in outcome for pts with KRAS transition versus transversion mutations (p=1) or when comparing current/former smokers to never smokers (p=0.33). There was no difference in overall survival (OS) when comparing specific amino acid substitutions (G12C=366, G12V=141, G12D=114, G12A=68, G13C=27, G13D=23, G12S=19, G12F=11)(p=0.20). Pts with KRAS codon 13 mutant tumors had inferior OS compared to pts with codon 12 mutant tumors, median 13 months (mo) (95% CI 13-17 mo) and 16 mo (95% CI 9-16 mo), respectively (p=0.009). There was no difference in frequency of receiving platinum-based chemotherapy or chemotherapy of any kind between pts with codon 12 and 13 mutant tumors. In a multivariate Cox model which included age, gender and smoking status, KRAS codon 13 mutation was associated with worse overall survival than KRAS codon 12 mutation (HR 1.52 95% CI 1.11-2.08 p=0.008). Conclusions: Among pts with KRAS mutant metastatic lung cancers, smoking history, and specific amino acid substitution do not affect outcome. Patients with KRAS codon 13 mutant metastatic lung cancer have shorter survival compared to pts with KRAS codon 12 mutant lung cancer.