Pharmacokinetically guided dosing has the potential to improve real-world outcomes of pazopanib.

It remains unclear whether therapeutic drug monitoring (TDM) of pazopanib improves treatment outcomes in routine clinical practice. We did a prospective cohort study to evaluate the benefits of TDM for pazopanib therapy in real-world practice. Among 25 patients with pharmacokinetically guided dosing, only 5 (20%, 95% confidence interval 6.8-40.7%) discontinued treatment because of adverse events. However, 5 (41.7%, 95% confidence interval 15.2-72.3%) of historical controls including 12 patients not receiving such a strategy experienced adverse events leading to early termination. PK-guided dosing significantly increased median time-to-treatment discontinuation (252 vs 74 days, P = .012) with reduced toxicity and improved overall survival (not reached vs 313 days, P = .002) relative to conventional dosing in the control group. In conclusion, PK-guided dose adaptation through the use of TDM has the potential to improve treatment outcomes of pazopanib in routine clinical practice, warranting larger, randomized studies.