Variability of Sorafenib Toxicity and Exposure over Time: A Pharmacokinetic/Pharmacodynamic Analysis

Background. Sorafenib displays major interpatient pharmacokinetic variability. It is unknown whether the pharmacokinetics of sorafenib influence its toxicity. Methods. We analyzed the severity and kinetics of sorafenib-induced toxicities in unselected consecutive patients with cancer, as well as their relationship with biological, clinical, and pharmacokinetic parameters. Toxicity was recorded bimonthly. Sorafenib plasma concentrations were assessed by liquid chromatography. Results. For 83 patients (median age, 62 years; range, 21-84 years), median sorafenib 12-hour area under the curve (AUC(0-12)) was 52.8 mg.h/L (range: 11.8-199.6). A total of 51 patients (61%) experienced grade 3-4 toxicities, including hand-foot skin reactions (23%), asthenia (18%), and diarrhea (11%). Sorafenib AUC(0-12) preceding grade 3-4 toxicities was significantly higher than that observed in the remaining population (61.9 mg.h/L vs. 53 mg.h/L). In 25 patients treated with fixed doses of sorafenib for the first 4 months, median dose-normalized AUC(0-12) on day 120 was significantly lower than on day 15 (63 vs. 102 mg.h/L). The incidence of hypertension and hand-foot skin reactions significantly decreased over time. Conclusion. Sorafenib AUC(0-12) decreases over time, similarly to the incidence of hypertension and hand-foot skin reactions. Monitoring of sorafenib plasma concentrations may help to prevent acute severe toxicities and detect patients with suboptimal exposure at disease progression. The Oncologist 2012;17:1204-1212