Exploratory analysis of EGFR FISH criteria in Japanese non-small cell lung cancer patients treated with gefitinib

7599 Background: In the phase III Iressa (gefitinib) Survival Evaluation in Lung cancer (ISEL) trial, high epidermal growth factor receptor (EGFR) gene copy number was a predictor of a gefitinib effect on survival in patients (pts) with refractory advanced non-small-cell lung cancer (NSCLC) (hazard ratio 0.61 vs 1.16 for high vs low copy number; p=0.045) [JCO 2006;24:5034–42]. Although EGFR mutation status may predict response to gefitinib in Japanese pts, there is insufficient data to clarify if high EGFR gene copy number assessed by fluorescence in situ hybridization (FISH) is predictive in these pts. This analysis investigated the applicability of both published Colorado FISH criteria (Colorado Univ) and new FISH criteria to Japanese NSCLC pts. Methods: 58 tumor specimens from gefitinib-treated Japanese pts were analyzed using Vysis LSI EGFR and CEP7 (chromosome 7 control) FISH probes. Specimens were classed as FISH+ or - using Colorado and exploratory (EGFR/cell; CEP7/cell; EGFR/CEP7; % of cells with various numbers of EGFR or CEP7 signals) criteria. Results: Of the 58 pts, 17 (29%) had an objective response (OR). Using Colorado criteria, OR was 50% in the 14 FISH+ pts vs 23% in the 44 FISH- pts (2-sided Fisher's exact test p=0.089). There was a trend for an association between FISH+ status and improved survival (log rank p=0.15). Defining FISH+ as specimens with =5% cells containing >5 EGFR signals, OR was significantly better among FISH+ pts vs FISH- pts (p=0.0030; 52% of the 23 FISH+ pts responding vs 14% of the 35 FISH- pts). A survival advantage was not indicated. Defining FISH+ as =74% of cells with EGFR or CEP7 loss (<2 signals) or gain (>2 signals), OR was significantly better among FISH+ pts vs FISH- pts (p=0.043; 45% of the 22 FISH+ pts responding vs 19% of the 36 FISH- pts). Association with survival had marginal significance (log rank p=0.061). Conclusions: These preliminary data have identified loss or gain of EGFR and CEP7 abnormality as promising biomarkers for response to gefitinib in Japanese NSCLC patients. Analysis of these markers for correlation with time to progression is ongoing. Investigation of these potential markers in other cohorts of patients is worthy of further evaluation. [Table: see text]