11C-acetate PET for early prediction of sunitinib response in metastatic renal cell carcinoma.

Sunitinib is an oral multitargeted tyrosine kinase inhibitor with antiangiogenic properties used for treatment of renal cell carcinoma and gastrointestinal stromal tumors at a dose of 50 mg/day consecutively for 4 weeks followed by 2 weeks off per cycle. At present, no data are available on the early prediction of sunitinib response in renal cell carcinoma. We report a clinical case of a patient with metastatic renal cell carcinoma diagnosed with 11C-acetate PET and conventional CT and treated with sunitinib. Partial and complete remission documented by CT was preceded by early functional tumor inhibition shown by 11C-acetate-PET after only 14 days of therapy. This case report highlights some interesting points related to the potential role of a novel non-FDG PET tracer, 11C-acetate, in the early prediction of the response to targeted therapies in metastatic renal cell carcinoma.