Impact of systematic EGFR and KRAS mutation evaluation on progression-free survival and overall survival in patients with advanced non-small-cell lung cancer treated by erlotinib in a French prospective cohort (ERMETIC project--part 2).

BACKGROUND: Epidermal growth factor and v-Ki-ras2 Kirsten ras sarcoma (KRAS) mutation status, although associated with EGFR- tyrosine kinase inhibitor (TKI) efficacy, has not been used in clinical practice until recently. The prospective Evaluation of the EGFR Mutation status for the administration of EGFR-TKIs in non small cell lung Carcinoma (ERMETIC) study aimed to implement these biomarkers in France.
METHODS: Between March 2007 and April 2008, EGFR and KRAS were studied by sequencing DNA tumor specimens from 522 consecutive advanced non-small-cell lung cancer patients treated with EGFR-TKI, mostly in second- or third-line settings. Cox models were used to investigate the impact of patient characteristics and mutations on progression-free survival (PFS) and overall survival (OS). Added value from mutation status was evaluated using likelihood ratio (LR) tests. Classification and regression tree analysis aimed to identify homogeneous groups in terms of survival.
RESULTS: Among the 522 patients, 87% were white, 32% were women, and 18% were never-smokers, with 65% presenting with adenocarcinoma. Biological data were available for 307 patients, showing 44 EGFR mutations (14%) and 42 KRAS (14%) mutations. Median PFS was 2.4 months (interquartile range, 1.4-4.6) and median OS 5.6 months (interquartile range, 2.2-14.0). Factors independently associated with PFS were performance status 1 or 2 to 3 (hazards ratio [HR] = 1.5, 95% confidence interval [CI] 1.1-1.9; and HR = 2.3, CI 1.7-3.1, respectively; p < 0.001); former or current smoker status (HR = 1.8, CI 1.4-2.4 and 2.0,CI 1.4-2.8, respectively; p < 0.001); nonadenocarcinoma histology (squamous cell: HR = 0.9 CI 0.7-1.2]; others: HR = 1.6, 1.3-2.1; p < 0.001); at least two metastatic sites (HR = 1.3, CI 1.1-1.6 and 1.6, CI 1.3-2.1, respectively; p < 0.001); prior taxane-based chemotherapy (HR = 1.3, CI 1.0-1.3, p = 0.01); non-white (HR = 0.7, CI 0.5-0.9, p = 0.009). Similar results were found for OS. In addition, EGFR and KRAS mutations were significantly associated with PFS (HR = 0.5, CI 0.3-0.7 and HR = 1.2, CI 0.8-1.8, respectively, versus no mutation; LR p = 0.001). In the OS model, adjusted HR was 0.7 (0.4-1.0) for EGFR mutation and 1.7 (1.1-2.4) for KRAS (LR p = 0.004). Classification and regression tree analysis revealed EGFR mutation to be the primary factor for identifying homogeneous patient subgroups in terms of PFS.
CONCLUSIONS: EGFR and KRAS status independently impacts outcomes in advanced non-small-cell lung cancer patients treated with EGFR-TKI. However, EGFR status impacts both PFS and OS whereas KRAS only impacts OS. These findings support the nationwide use of EGFR status for patient selection before EGFR-TKI therapy. The role of KRAS mutations remains to be elucidated.