Biochemical and Pathological Response of Prostate Cancer in a Patient with Metastatic Renal Cell Carcinoma on Sunitinib Treatment

Sunitinib is a small molecular inhibitor of tyrosine kinases and is used to treat advanced renal cell carcinoma and gastrointestinal stromal tumour after disease progression or intolerance to imatinib therapy. Here, we describe biochemical and pathological response of prostate cancer in a patient with metastatic renal cell carcinoma during sunitinib treatment. A 62-year-old man was referred to our hospital because of a mass in the scalp. He was diagnosed with left renal cell carcinoma with right renal and scalp metastases. In addition, synchronous prostate cancer involving less than one-half of the right lobe was found with a prostate-specific antigen (PSA) value of 23.4 ng/ml. Treatment was begun with sunitinib (50 mg daily, 4 weeks on and 2 weeks off). Regarding the prostate cancer, active monitoring was planned considering the far advanced renal cell carcinoma. Surprisingly, the PSA level was 3.4 ng/ml at week 6 and 0.2 ng/ml at week 12, and it subsequently remained normal. At the time of writing (cycle 6 of sunitinib therapy), the prostate nodule significantly decreased in size. Furthermore, a 12-core re-biopsy revealed pathological evidence of regression with sunitinib treatment, with control of his renal cell carcinoma.