Optimizing measurement of EGFR mutation status in NSCLC.

e18120 Background: Improved clinical benefit from EGFR tyrosine kinase inhibitors (TKIs) in non-small cell cancer (NSCLC) patients (pts) with sensitizing mutations (mu) of the EGFR, along with European licence prescribing restrictions, make it important to optimize the accuracy of mu analysis. The association of TKI resistance with KRAS mu at codons 12, 13 and 61, and their mutual exclusion with activating EGFR mutations, make it appropriate to measure both in the usually small samples where tumour content has been evaluated and maximised. Methods: EGFR and KRAS mu status are sought on all nonsquamous NSCLC diagnosed in our Cancer Centre and samples referred from other UK institutions. Formalin fixed paraffin embedded tumour samples are assessed by one specialist thoracic pathologist and macro-dissected to enrich for tumour content. Mu screening by direct sequencing has been the core analytical technique employed but lacks the required sensitivity to detect mu in samples with low mu content. Earlier work ...