Positron-emission tomography imaging in urological oncology: Current aspects and developments

Positron-emission tomography/computed tomography combining both functional and morphological information has emerged as a powerful tool in oncological imaging within the past decades. The most commonly used radiotracer in oncology visualizing metabolic information is 2-[18F]fluoro-2-deoxy-d-glucose. However, the use of 2-[18F]fluoro-2-deoxy-d-glucose in urological oncology is challenging, as it is limited by physiological excretion through the urinary system. Therefore, it is only useful when applied to specific indications in selected patients with urological malignancy; for example, for detection of residual disease in the post-chemotherapy management of patients with seminoma. Despite initial promising results in bladder cancer, no relevant additional diagnostic value with positron-emission tomography using 2-[18F]fluoro-2-deoxy-d-glucose or choline-based tracers could be obtained, and should therefore be used with caution or only within clinical trials. In prostate cancer, however, a paradigm shift in imaging can be observed after development of new tracers that target the prostate-specific membrane antigen. Biochemical recurrent prostate cancer has become a clinically widely accepted indication for prostate-specific membrane antigen ligand positron-emission tomography/computed tomography, with several studies showing superior detection efficacy compared with conventional imaging. For primary high-risk prostate cancer, growing evidence suggests well-improved staging. The present review aimed to provide an overview of the current status of positron-emission tomography imaging in cancer of the urogenital system including the latest advances in ⁶⁸ Ga-labeled and ¹⁸ F-labeled positron-emission tomography agents targeting the prostate-specific membrane antigen for positron-emission tomography imaging of prostate cancer.