Routine EGFR molecular analysis in non-small-cell lung cancer patients is feasible: exons 18-21 sequencing results of 753 patients and subsequent clinical outcomes

Abstract

Background: Epidermal growth factor receptor (EGFR)-targeting therapies dramatically modified the prognosis of stage 4 non-small-cell lung cancer. Sensitizing EGFR mutations are the best efficacy factor of these treatments. In 2006, the French National Cancer Institute launched a network of 28 centers for EGFR molecular analysis in routine practice. The aim of this retrospective study was to describe the results of routine EGFR analysis in one of these centers (Lyon University Hospital) and to assess outcomes in patients with the mutation.

Methods: EGFR mutations were analyzed for exons 18-21 by direct sequencing. The characteristics of each sample were retrospectively collected from the lab archives. Subsequent outcomes for patients harboring at least one mutation were retrospectively collected from each referring physician.

Results: During 1 year, 792 samples were analyzed, corresponding to 753 patients. A total of 133 mutations were diagnosed in 124 samples (15.7 %), corresponding to 121 patients. Most of them (77.4 %) were sensitizing mutations and were located in exons 19 and 21. Others were resistance mutations (8.3 %) or rare mutations (14.3 %) for which effects on tyrosine kinase inhibitor (TKI) sensitivity are unknown. The rate of indeterminate results (i.e., no sequencing of the entire exon 19 or 21) was 6.3 % (n = 50 samples). The only factor statistically associated with a risk of failure was sample from bone tissue: 13.7 % gave incomplete results (i.e., no whole sequencing of exons 18-21).

Conclusions: Eighty-five of the 121 patients with EGFR mutations were treated with TKI. There were no differences in progression free survival (PFS) according to the type of molecule (erlotinib or gefitinib) or to the line of prescription of TKI. By contrast, exon 18 sensitizing mutations showed a worse PFS than exon 19 or 21 mutations. Finally, dose reduction was significantly more frequent in the erlotinib group than in the gefitinib group.