Pharmacokinetic exposure and treatment outcomes of lenvatinib in patients with renal cell carcinoma and differentiated thyroid carcinoma

Purpose: After initial approval of lenvatinib for radioiodine-refractory differentiated thyroid cancer (DTC), it has also shown promising outcomes in among others metastatic renal cell carcinoma (mRCC). Given that trial populations typically do not represent routine clinical care populations, questions arise about how applicable trial outcomes are in clinical practice. This study aims to compare the pharmacokinetics (PK), toxicity patterns, and survival data of lenvatinib in a real-world cohort with DTC and mRCC to those observed in pivotal clinical trials. Materials and methods: Patients were included when diagnosed with DTC or mRCC, had received current or prior treatment with lenvatinib, and had at least one available lenvatinib plasma concentration measurement. A descriptive comparison was made between the baseline characteristics, PK data, toxicity and survival data in this real-world cohort and those described in the phase III trials. Results: Overall, 29 patients with mRCC and 35 patients with DTC were included. For mRCC, median time to treatment discontinuation (mTTD) was shorter than observed in the phase III trial (7.5 versus 11.0 months) with fewer dose-limiting toxicities, likely because 66% of the patients started with a reduced dose. mRCC patients were more pretreated and had a worse performance status than trial participants. This was resembled in overall lower PK exposure in mRCC patients. For DTC, mTTD was longer in our cohort (17.1 versus 13.8 months), with similar toxicity patterns and PK exposure as in the phase III trial. Conclusions: Our data suggests that patient characteristics and outcomes in routine clinical care deviate from clinical trials and show the need for alternative treatment strategies to manage tolerability to lenvatinib.