EGFR mutation frequency and effectiveness of erlotinib: a prospective observational study in Danish patients with non-small cell lung cancer

In 2008, we initiated a prospective study to explore the frequency and predictive value of epidermal growth factor receptor (EGFR) mutations in an unselected population of Danish patients with non-small cell lung cancer offered treatment with erlotinib, mainly in second-line.

Four hundred and eighty eight patients with advanced NSCLC were included. The mutation status was assessed using the cobas EGFR Mutation Test. Erlotinib was administrated (150 mg/d) until disease progression or unacceptable toxicities occurred. The primary endpoint was progression-free survival. Secondary endpoints were overall survival and response.

Biopsies were retrieved from 467 patients, and mutation results obtained for 462. We identified 57 (12%) patients with EGFR mutations: 33 exon 19 deletions, 13 exon 21 mutations, 5 exon 18 mutations, 3 exon 20 insertions, 1 exon 20 point mutation (S768I), and two complex mutations. Seven percent of the patients were never smokers. The differences in median progression-free survival and overall survival between the mutated group and the wild-type group were 8.0 vs. 2.5 months, p<0.001 and 12.1 vs. 3.9 months, p<0.001. Performance status (0-1 vs. 2-3) and line of treatment (1st vs. 2nd and 3rd) had no influence on outcome in EGFR-mutated patients.

We found a higher frequency of EGFR mutations than expected in a cohort with less than 10% never smokers. The outcome after treatment with erlotinib was much better in patients with EGFR mutations than in patients with wild-type EGFR and was independent of performance status and treatment line in EGFR-mutated patients.