Pharmacokinetic parameters of gefitinib predicts its progression-free survival and adverse events.

e19038 Background: Previously, through measuring plasma trough levels of gefitinib on days 3(D3) and 8 (D8), we reported that a high D8/D3 ratio was independently associated with better PFS in patients with advanced non-small cell lung cancer (NSCLC) treated with gefitinib. In this time, we also assessed the relationship between the biological half-life of gefitinib and its efficacy in patients with advanced NSCLC harboring Epidermal growth factor receptor (EGFR) mutations treated with gefitinib. Methods: Plasma trough levels of gefitinib were measured on days 2 (D2) and 8 (D8) by high-performance liquid chromatography in 30 patients. Additionally, We measured plasma concentration of gefitinib in 10 hours (10H) after first administration in 22 out of 30 patients to calculate the biological half-life of gefitinib using the values of 10H and D2. All patients were diagnosed pathologically with advanced NSCLC harboring EGFR mutations and 22 cases with values of 10H had no prior chemotherapy. Results: The medi...