Abstract
The aim of this study was to describe the characteristics of positron emission tomography (PET) molecular imaging combined with low-dose computed tomography (CT) in small renal mass (SRM) treated with cryoablation (CA). Currently, treatment success is defined by the absence of contrast enhancement at CT. However, the use of contrast is relatively contraindicated in patients with renal function impairment, mandating alternative follow-up strategies. Several reasons were identified as criteria for performing PET-CT before and/or after SRM-CA in 9 patients, and the results were retrospectively studied. The histology revealed renal cell carcinoma in 7 patients and oncocytoma in 2 patients. In 6 patients, a PET-CT was performed before and after CA. In one patient, the PET-CT was performed only before CA and in 2 patients only after CA. Before CA, clearly there was metabolic uptake of fluorine-18 fluorodeoxyglucose (18F-FDG) in the SRM in all patients. Following CA, the absence of 18F-FDG uptakes in the SRM could clearly be noticed. However, the tracer cannot always be distinguished from focal recurrence or reactive inflammatory tissue. In one patient, asymptomatic metastatic bone lesions were noticed when performing PET-CT at follow-up. This pilot study with 18F-FDG PET-CT for the follow-up of SRM cryosurgery showed that 18F-FDG PET-CT imaging could be used to characterize cryoablative tissue injury at different times after CA.
Highlights
The number of new renal cancer cases in the Netherlands was estimated to be 2000 in the year 2007 and is expected to increase to 2300 new cases by the year2020
A total of 9 patients treated with cryosurgery, between July 2007 and January 2012, were retrospectively studied in case preoperative workup and/or followup consisted of an 18F-FDG positron emission tomography (PET)-computed tomography (CT)
Indications for PET-CT before and/or after laparoscopic CA (LCA) were renal function impairment (n=6), suspicion for local recurrence following LCA (n=1), and contraindication for intravenous contrast-medium use (n=1), and in one patient, a preoperative PET-CT was performed at the referring center for staging purposes
Summary
The number of new renal cancer cases in the Netherlands was estimated to be 2000 in the year 2007 and is expected to increase to 2300 new cases by the year. This increase may be due in part to an increase in the discovery of small incidental solid renal masses (RMs) using cross-sectional imaging [1]. Cryoablation (CA) has been added as a viable treatment option for patients with small RM and for those who are at high surgical risk [2,3,4]. Patients who can benefit from thermal ablation procedures are those who are poor surgical candidates because of compromised renal function and/or comorbid disease. Patients with impaired renal function who are candidates for ablation can be poor subjects for the typical investigational methods used at follow-up
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