Sunitinib is an inhibitor of multiple receptor tyrosine kinases and is a standard-of-care treatment for advanced and metastatic renal clear-cell carcinoma and a second line treatment in locally advanced inoperable and metastatic gastrointestinal stromal tumors. A fixed dose of the drug, however, does not produce a uniform therapeutic outcome in all patients and many face adverse effects and/or toxicity. One of the possible causes of the inter-individual variability in the efficacy and toxicity response is the highly variable systemic exposure to sunitinib and its active metabolite.

This review aims to summarize all available clinical evidence of the treatment of adult patients using sunitinib in approved indications, addressing the necessity to introduce proper and robust therapeutic drug monitoring (TDM) of sunitinib and its major metabolite, N-desethylsunitinib.

The authors performed a systematic search of the available scientific literature using the PubMed online database. The search terms were “sunitinib” AND “therapeutic drug monitoring” OR “TDM” OR “plasma levels” OR “concentration” OR “exposure.” The search yielded 520 journal articles. In total, 447 publications were excluded because they lacked sufficient relevance to the reviewed topic. The remaining 73 articles were, together with currently valid guidelines, thoroughly reviewed.

and discussion: There is sufficient evidence confirming the concentration-efficacy and concentration-toxicity relationship in the indications of gastrointestinal stromal tumors and metastatic renal clear-cell carcinoma. For optimal therapeutic response, total (sunitinib + N-desethylsunitinib) trough levels of 50-100 ng/mL serve as a reasonable target therapeutic range. In order to avoid toxicity, the total trough levels should not exceed 100 ng/mL. According to the current evidence presented in this review, a TDM-guided dose modification of sunitinib in selected groups of patients could provide a better treatment outcome while simultaneously preventing sunitinib toxicity.

Therapeutic drug monitoring. 2019 Jun 26 [Epub ahead of print]

Regina Demlová, Miroslav Turjap, Ondřej Peš, Katarína Kostolanská, Jan Juřica

Medical Faculty, Masaryk University, Czech Republic., Dpt. of Clinical Pharmacy, University Hospital Ostrava, Czech Republic., Dpt. of Biochemistry, Medical Faculty, Masaryk University, Czech Republic., Dpt. of Pharmacology, Medical Faculty, Masaryk University, Masaryk memorial cancer institute, University of Veterinary and Pharmaceutical sciences, Czech Republic.