KRAS mutational status and sensitivity to a reversible epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) in EGFR wild type (WT) advanced non-small cell lung cancer (NSCLC) patients (pts).

Abstract

e18023 Background: Treatment with a reversible EGFR-TKI may benefit pts with EGFR WT advanced NSCLC, though to a much lesser extent than pts carrying an activating mutation in the EGFR gene. We assessed whether KRAS mutational status would help predict sensitivity to gefitinib or erlotinib in EGFR WT advanced NSCLC pts. Methods: Sixty-seven EGFR WT, advanced NSCLC pts treated with a reversible EGFR-TKI in any line setting were included. Pts were treated from May 2005 to March 2011 at the Medical Oncology of the Perugia Hospital. EGFR (exons 18 to 21) and KRAS (codons 12, 13 and 61) genes were amplified by nested PCR and sequenced in both sense and antisense directions. Results: Median age was 60 years (39-84); 52 pts (77.6%) were PS 0 or 1; 58 pts (86.6%) belonged to the non-squamous subtype and 22 pts (32.8%) were never-smokers. Eighteen pts (26.8%) were KRAS mutant (MUT), of which 14 pts at codon 12 (COD 12 MUT) and 4 pts at codon 13 (COD 13 MUT). Overall, 11 pts (16.4%) responded to treatment and 8 pts (11.9%) achieved stable disease, for a disease control rate of 28.3%. At a median follow-up of 25.2 months, median progression-free survival (PFS) and overall survival (OS) were 2.9 and 29.5 months, respectively. When analyzed according to KRAS status, a significantly shorter PFS was noted for the EGFR WT/KRAS MUT subgroup (N=18) compared with the EGFR WT/KRAS WT population (N=49) (1.6 vs. 3.0 months, respectively, p=0.04). However, no significant difference was observed between the two groups in terms of OS (18.0 vs. 34.8 months, respectively, p=0.42). Within the EGFR WT/KRAS MUT subrgoup a significantly longer PFS was reported for COD 12 MUT pts compared with COD 13 MUT pts (1.7 vs 0.7 months, respectively, p=0.04). Similarly, KRAS COD 12 MUT pts experienced a statistically significant superior OS compared with COD 13 MUT pts (36.2 vs 7.4 months, respectively, p=0.003). Conclusions: EGFR WT/KRAS MUT pts appear to be more resistant to treatment with a reversible EGFR-TKI, the greatest resistance occurring in COD 13 MUT pts. KRAS COD 12 MUT pts may represent a clinically distinct subgroup of KRAS mutants with a particularly favorable prognosis.