Evaluation of the accuracy of FDG-/FLT-PET for early prediction of non-progression in patients with advanced non-small cell lung cancer (NSCLC) treated with erlotinib

e19054 Background: EGFR mutations predict response to erlotinib treatment in advanced NSCLC. However, also a subgroup of patients with wildtype EGFR benefits from erlotinib treatment. This subgroup could not yet be defined by molecular means. In this trial we set out to prospectively evaluate the accuracy of [18F]FDG-/[18F]FLT-PET analyses for early prediction of non-progression in chemo-naive patients with advanced NSCLC treated with erlotinib. Methods: Patients with NSCLC stage IIIB/IV without prior systemic treatment for NSCLC were eligible and treated for 6 weeks with erlotinib in this single centre diagnostic pilot trial. Primary endpoint was the accuracy of [18F]FDG/18F[FLT] PET after 1 week of treatment to predict non-progression as defined by RECIST criteria in CT scans after 6 weeks of treatment. Here we present the evaluation of 20 patients of this ongoing trial in accordance with the data monitoring board (EudraCT number 2005–005393–73; NCT00568841 ). Results: Twenty patients were recruited from 9/07 to 9/08. Seventeen patients were eligible for final analysis. The AUC for [18F]FDG PET at week 1 to predict non-progression was 0.857 ±0.105 (p=0.013) and 0.643±0.137 (p=0.32) for [18F]FLT PET. Using [18F]FDG PET specificity was 1 and sensitivity 0.71 for prediction of non- progression after six weeks (p=0.006 Fishers exact). In addition, [18F]FDG PET after 1 week of treatment clearly predicted tumor non- progression after 18 weeks of treatment with a predefined cut-off of -20% change in sSUVmax. (p=0.0004, Fisher´s exact). Finally, using this cut-off value [18F]FDG-PET after one week of treatment, predicted progression free survival (p=0.001, log rank test), with differences in median PFS of 45 days vs 320 days. Using univariable Cox regression, both [18F]FDG and [18F]FLT PET predicted PFS [hazard ratio 2.1 (p=0.006, Wald test) and 2.3 (p=0.011), respectively, per standard deviation]. Conclusions: Our observations indicate that early [18F]FDG but not [18F]FLT PET analysis predicts non-progression after 6 weeks of first-line erlotinib treatment in patients with advanced NSCLC. In addition, early [18F]FDG PET predicts non-progression after 18 weeks of treatment and progression free survival. [Table: see text]