FDG PET characterization of renal masses: Preliminary experience

Objective: This study was undertaken to evaluate the potential efficacy of fluorine-18 2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) to detect renal tumours and to characterize indeterminate renal cysts. Subjects and methods: Twenty-six PET scans mere performed in 21 patients (14 PET scans in 10 patients with malignant renal tumours and 12 PET scans in 11 patients with Bosniak type 3 indeterminate renal cysts). Pathological proof was obtained in 18 of 21 patients (10 with solid neoplasms, eight with indeterminate cysts). Imaging was performed 1 h after injection of 5-10 mCi of FDG with IV administration of Lasix (10 mg) 20 mins after injection. Two consecutive 9.7-cm image segments mere scanned to cover the entire renal areas. Results: PET accurately depicted solid neoplasms as areas of increased uptake in nine of 10 patients. Bilateral renal cell carcinomas mere missed in one diabetic patient. All but one indeterminate renal cysts mere correctly classified as benign (photopenic areas), but an indeterminate cyst with a 4-mm papillary neoplasm was wrongly classified as benign. There mere no false positive PET interpretations. The mean tumour-to-kidney ratio was 3.0 for malignant lesions. Conclusion: We conclude that FDG PET scanning shows promise in the evaluation of indeterminate renal cysts. A positive PET scan in the appropriate clinical setting obviates the need for cyst aspiration. A negative PET scan in conjunction with a negative cyst aspiration offers confirmatory evidence of benignity. Our preliminary results are encouraging and further work is ongoing.