Positron Emission Tomography in Renal Cell Carcinoma

Abstract

IntroductionRenal cell carcinoma (RCC) is the most common solid kidney tumor. Contrast-enhanced computed tomography (CT) is the most frequently used imaging modality in the diagnosis, staging, and evaluation of recurrence and treatment response in patients with RCC. The overall success rate of CT for these indications is reported to be between 61% and 91% (1,2,3). However, as RCCs may appear isodense, hypodense, or hyperdense, it is difficult to distinguish benign and malignant renal masses by morphological methods (4). Magnetic resonance imaging (MRI) is recommended in cases where CT is contraindicated, such as patients who have contrast allergy or are pregnant. However, MRI is no more accurate than CT. This increases the importance of positron emission tomography (PET), which enables metabolic evaluation in addition to visualizing anatomic changes. In this review, we discuss currently available literature data regarding the use of PET applications with different radiopharmaceuticals in patients with RCC. Applications of Positron Emission Tomography in Renal Cell Carcinoma 18-Fluorine-Fluorodeoxyglucose Positron Emission TomographyPET is a metabolic imaging method that utilizes various positron-emitting radiopharmaceutical and can provide data on many different metabolic pathways. The most widely used radiopharmaceutical is a fluorodeoxyglucose molecule (FDG) labeled with 18-fluorine (18F). The modality is based on the principle of visualizing elevated glycolysis and glucose uptake in neoplastic tissues. Despite high success rates in many solid organ malignancies, the use of 18F-FDG for urinary system malignancies is limited due to excretion via the urinary tract. The first cases related to the use of 18F-FDG PET in RCC were described by Wahl et al. (5) in the early 1990s. The use of 18F-FDG PET in the detection of primary RCC is especially controversial (6,7,8,9,10). High and variable levels of background renal activity make it difficult to detect the primary focus. Forced diuresis with hydration may increase the sensitivity Renal cell carcinoma is the most common solid kidney tumor. Conventional methods such as computed tomography and magnetic resonance imaging are usually chosen for diagnosis, staging, and evaluating recurrence and treatment response. However, the sensitivity of these methods is limited in each indication. For this reason, metabolic evaluation with positron emission tomography has an important value in most solid tumors. However, the role of 18-fluorine-fluorodeoxyglucose (18F-FDG), which is the most commonly used positron emission tomography (PET) radiopharmaceutical, is limited in the evaluation of primary kidney lesions due to urinary excretion. Therefore, new radiopharmaceuticals with no or limited urinary excretion have been developed. In this paper, the application of PET imaging with the widely used 18F-FDG and the newly developed fluorothymidine and gallium-68/18F prostate-specific membrane antigen in renal cell carcinoma are reviewed.