Pharmacokinetics of gefitinib in elderly patients with EGFR-mutated advanced non-small cell lung cancer: a prospective study.

BACKGROUND: Gefitinib is recommended as a first-line treatment option for elderly patients with non-small cell lung cancer (NSCLC). Because no pharmacokinetics of gefitinib have been examined, we prospectively assessed the pharmacokinetics of gefitinib in patients with epidermal growth factor receptor gene-mutated advanced NSCLC who were 75 years or older. METHODS: Gefitinib was orally administered once daily at a dose of 250 mg. The concentrations of gefitinib and its major metabolite O-desmethyl gefitinib in plasma were measured by high-performance liquid chromatography. The area under the plasma concentration-time curve from time 0 to 48 h (AUC0-48) was calculated. Polymorphisms in CYP3A5, CYP2D6, ABCG2, ABCB1, and OATP1B1 were analyzed by direct sequencing. RESULTS: Eighteen patients with a median age of 80.5 years (range, 75-89) with adequate liver and kidney functions were examined. AUC0-48 values of gefitinib and O-desmethyl gefitinib in this population were 9.49 ± 3.5 and 10.6 ± 14 µM h, respectively. Compared to the gefitinib pharmacokinetics observed in a previous phase I study in Japan, systemic exposure to gefitinib in elderly patients was slightly higher than that in younger patients. Three patients experienced grade 3 diarrhea, increases in alanine aminotransferase, and aspartate aminotransferase levels 30 days after starting gefitinib treatment. The CYP2D6 genotype was associated with CYP2D6-mediated metabolism of gefitinib to O-desmethyl gefitinib. CONCLUSIONS: We demonstrated for the first time the systemic exposure to gefitinib in elderly patients with NSCLC. TRIAL REGISTRATION: The study was registered with the University Hospital Medical Information Network-Clinical Trials Registry Japan (UMIN000026409) on November 8, 2013.