The combined use of sunitinib and other tyrosine kinase inhibitors (TKIs) is discouraged because of the increased risk of adverse events (AEs). Furthermore, plasma sunitinib levels are affected by drugs that affect CYP3A4 activity
therefore, caution should be exercised when using CYP3A4 inhibitors. In the present study, a 59-year-old Japanese man with metastatic renal cell carcinoma (RCC) was diagnosed with chronic myeloid leukemia (CML) while on sunitinib treatment and was simultaneously treated with sunitinib and dasatinib, a multi-TKI used for CML with moderate CYP3A4 inhibitory activity. The trough levels of sunitinib and