Prevalence of EGFR mutations in newly diagnosed locally advanced or metastatic non-small cell lung cancer Spanish patients and its association with histological subtypes and clinical features: The Spanish REASON study

Background and objectives: The aim of the REASON study is to determine the frequency of EGFR mutation in advanced non-small cell lung cancer (aNSCLC) patients in Spain (all histologies), and to better understand the clinical factors (gender, smoking habits and histological subtypes) that may be associated with EGFR mutations, in an unselected sample of aNSCLC patients.

Methods: All newly diagnosed aNSCLC patients from 40 selected centers in Spain were prospectively included for a 6-month period. Patient characteristics were obtained from clinical records. Mutation testing was performed on available tumor samples. Exploratory analyses were performed to characterize the clinico-pathological factors associated with presence of EGFR mutations.

Results: From March 2010 to March 2011, 1113 patients were included in the study, of which 1009 patients provided sample for EGFR mutation analysis (90.7%). Mutation analysis was not feasible in 146/1113 patients (13.1%) due to either sample unavailability (79/1113; 7.1%) or sample inadequacy (67/1113; 6.0%). Twenty-five out of 1113 patients (2.3%) were excluded due to unavailable information. Most patients (99.5%) were Caucasian, 74.5% were male, and predominantly were current (38.1%) or former smokers (44.0%). Median age was 66 years (range 25-90) and 70.7% of patients had non-squamous histology (57.8% adenocarcinoma, 1.8% bronchoalveolar, 11.1% large-cell carcinoma). Exon 19 deletions and the exon 21 L858R point mutation were analyzed in 942/1009 (93.4%) samples. Mutation rate was 11.6% (82.6% exon 19 dels and 17.4% L858R). To be never smoker (38.1%), female (25.4%), with bronchioloalveolar carcinoma (22.2%) or adenocarcinoma (15.4%) histology was associated with a higher prevalence of EGFR mutations. Exons 18, 20 and 21 (excluding L858R) were analyzed in 505/942 samples, and EGFR mutations were found in 22/505 samples (4.4%).

Conclusion: The estimated prevalence of sensitizing EGFR mutations (exon 19 del, exon 21 L858R) in an unselected samples of newly diagnosed aNSCLC patients in Spain (all histologies) is consistent with previous published data in Caucasian patients. When a sample is available, EGFR mutation testing is feasible in over 90% of cases, and may therefore be suitable for routine clinical practice. CLINICALTRIALS.

Gov identifier: NCT01081496.