Background Two reversible tyrosine-kinase inhibitors of the epidermal growth factor receptor (EGFR-TKI) (A and B) were approved for the treatment of EGFR-mutant advanced non-small cell lung cancer (aNSCLC), with similar activity and results. Pharmacovigilance detected efficacy differences between A and B in our centre.

Purpose To define and possibly correct the cause of this finding.

Material and methods Drug A was considered our standard treatment for EGFR-mutant aNSCLC from April 2011 to March 2013, and was replaced with B from April 2013 to the present. EGFR-mutant patients were sequentially diagnosed in two different external platforms (PA and PB) during the same periods of time. We retrospectively reviewed the medical charts of TKI-treated EGFR-mutant aNSCLC patients from April 2011 to March 2014. Progression free survival (PFS) was analysed in any, first, and second line of treatment by Kaplan-Meier curves and Cox regression. The finding of significant differences in PFS between A and B led to the retrospective review of all EGFR-analysed aNSCLC patients.

Results Fifteen EGFR-mutant aNSCLC patients were treated with A (7 s line), and 16 with B (10 s line). Mean age of the series was 65 years (44–82), and 74.2% were women. PFS benefited A in any (11.43 vs. 4.96 months; p = 0.000), first (13.3 vs. 3.98 months; p = 0.014), and second line of treatment (9.5 vs. 5.53 months; p = 0.023). PA analysed 108 aNSCLC, patients detecting 12.1% EGFR-mutant and 15% non-analysable tissue samples. PB analysed 85 aNSCLC, patients finding 20% EGFR-mutant and 3.5% non-analysable tissue samples.

Conclusion The lower PFS of B-treated aNSCLC patients was attributed to an excessive sensitivity of PB in detecting EGFR-mutation. Re-calibration of the technique modified the current percentage of EGFR-mutant and non-analysable samples to 15.5% and 10% of 129, respectively. Periodic monitoring of selected drugs helps to correct protocol defects, to improve quality of treatments, and to reduce costs.

References and/or acknowledgements Conflict of interest