Purpose: The study aims to assess the usefulness of PET with 11C-acetate and 18F-FDG to differentiate renal cell carcinoma (RCC) from complicated renal cysts.
Methods: Thirty-one patients were enrolled, 14 patients with complicated renal cysts (12 with Bosniak III and 2 with Bosniak IV) and 17 patients with 19 solid renal tumors. The patients underwent both 11C-acetate PET and FDG PET. Nephrectomy or partial nephrectomy was performed after the PET scans.
Results: In 29 patients, 32 renal lesions were diagnosed as RCC. Twenty-three of the 32 RCCs (72%) had positive 11C-acetate PET findings, whereas only 7 FDG PET studies were positive (22%). Considering the relationship between tumor size measured by macroscopic appearance of resected tumors and PET results, 22 of 25 (88%) tumors more than 1.5 cm showed positive 11C-acetate PET findings. In 12 patients with Bosniak III renal cysts, 10 renal lesions were diagnosed as RCC. In this subgroup, 5 of the 10 RCCs (50%) had positive 11C-acetate PET findings, whereas 2 RCCs (20%) had positive FDG PET findings. None of the cases with benign findings had positive 11C-acetate PET or FDG PET scans.
Conclusions: 11C-acetate PET demonstrates a pronounced increase in tracer uptake in RCC, especially in renal tumors more than 1.5 cm, and displays a higher sensitivity than FDG PET. These preliminary data show that 11C-acetate may be a useful PET tracer to exclude RCC in complex renal cysts.