Radionuclide based imaging of prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths in American men. Early detection of PCa by blood tests for elevated levels of prostate-specific-antigen (PSA) has lead to early treatment and a reduction in death rates. However, PSA level alone does not distinguish between PCa and normal conditions that cause elevated PSA. Furthermore, because PCa can be a very slow growing cancer, even confirmation of PCa cells in a biopsy gives no indication whether the PCa will progress into active disease within the individual's lifetime. As a result many patients receive treatment that they may not need. Imaging is an attractive modality for the detection and characterization of disease because most techniques are non- or minimally invasive, nondestructive, provide dynamic real-time data, and allow for repeat measurements. In PCa, advanced imaging techniques could be useful for accurate staging of primary disease, restaging of recurrent disease, detection of metastatic lesions, and predicting the aggressiveness of the disease. This paper reviews the radionuclide based imaging agents for planar, single photon emission computed tomography (SPECT), and positron emission tomography (PET) imaging currently used in the clinic and those under development for PCa. The former includes the bone agents technetium diphosphonates and F-18 fluoride, the metabolic agents 2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG), and receptor targeted radiolabeled monoclonal antibodies including ProstaScint. The latter agents include C-11 acetate, C-11 and F-18 choline, C-11 and F-18 labeled 1-aminocyclobutane-1-carboxylic acid, radiolabeled androgen receptor binding compounds, radiolabeled peptides and small molecules for receptors over expressed either on prostate cancer itself or on the associated tumor neovasculature. Coregistration of PET or SPECT images with CT or MRI scans, improvements in imaging cameras, and image reconstruction algorithms have improved the quality of the images to the point where dual modality (radionuclide/CT or MRI) imaging with several agents can now be considered for staging of PCa. In addition, the high selectivity and rapid localization of many of the new agents under development portends promise for a greater use of radionuclide imaging for prostate cancer detection, characterization, and treatment monitoring.