Correlation of plasma crizotinib trough concentration with adverse events in patients with anaplastic lymphoma kinase positive non-small-cell lung cancer

BACKGROUND Crizotinib, an ATP-competitive receptor tyrosine kinase inhibitor of both anaplastic lymphoma kinase (ALK) and the hepatocyte growth factor receptor, commonly causes several adverse events (AEs). The clinical utility of measuring the plasma concentration of crizotinib in patients with non-small-cell lung cancer (NSCLC) has not been fully elucidated. The aim of this study was to evaluate the variability in the crizotinib trough concentration and its relationship with the occurrence of AEs in NSCLC patients. FINDINGS Plasma samples were collected from 9 ALK fusion gene-positive NSCLC Japanese patients at day 14 after the first administration of crizotinib. We assessed crizotinib-induced AEs on days 7, 14, 21, and 28. The crizotinib trough concentration on day 14 ranged from 243.5 to 847.8 ng/mL, and all of the patients achieved stable disease based on assessment of the tumor response on day 28. The cumulative number of AEs on day 28 in the higher trough concentration group was approximately 3-fold greater than that in the lower trough concentration group. AEs of grade 3 or 4 were observed only in patients in the higher trough concentration group. CONCLUSIONS The occurrence of several AEs may correlate with the increase in the crizotinib trough concentration. Monitoring of the crizotinib trough concentration could predict the risk of development of several AEs and provide guidance for determining the optimal dose of crizotinib.