EGFR mutation testing is now well established as a means of selecting the optimal first-line therapy for patients with advanced non-small-cell lung cancer (NSCLC). However, deciding on the correct treatment for EGFR wild-type NSCLC remains a challenge. EGFR fluorescence in-situ hybridization (FISH) testing of gene copy number has been a promising marker, but has provided mixed results despite attempts to standardize the reading and scoring process. The novel ReadMax reading and scoring system focuses on the most aberrant cells, to identify oncogene addiction, rather than taking a representative reading as in the Colorado method. The methodology was developed using historical samples from the TRUST and MERIT studies, followed by re-reading of the samples from the SATURN trial. Analysis of samples using the ReadMax methodology revealed that progression-free survival (PFS) and overall survival (OS) were improved in patients with ReadMax FISH-positive (RM FISH+) tumours, compared with those whose tumours were not RM FISH+: PFS hazard ratios (HRs) were 0.52 for RM FISH+ versus 0.93 for not RM FISH+; OS HRs were 0.69 and 0.92, respectively. For PFS, HR for RM FISH+ versus not RM FISH+ in the SATURN erlotinib group was 0.53 (p = 0.003). The PFS and OS results were also similar in the EGFR wild-type population (PFS HRs were 0.63 and 0.96; OS HRs were 0.61 and 0.84, respectively), although amplification of the EGFR gene in patients with EGFR wild-type disease was not found to be predictive of treatment outcomes, which was unexpected but not unprecedented. KRAS status was not found to affect outcomes. Further experience is required to refine the ReadMax methodology and fully establish its validity and robustness. In conclusion, the ReadMax scoring system to identify patients with EGFR FISH-positive NSCLC is a promising technique, which could improve treatment options and outcomes for patients with advanced NSCLC, in particular for EGFR wild-type tumours.
Keywords: EGFR; FISH; ReadMax; biomarkers; gene expression; non‐small‐cell lung cancer.