18F-RB390: innovative ligand for imaging the T877A androgen receptor mutant in prostate cancer via positron emission tomography (PET)

Prostate Cancer Imaging with Novel PET Tracers

Molecular imaging of prostate cancer is in a dynamic phase of development. Currently approved techniques are limited and researchers have been working on novel agents to improve accuracy in targeting and detecting prostate tumors. In addition, the complexity of various prostate cancer states also contributes to the challenges in evaluating suitable radiotracer candidates. We have highlighted nuclear medicine tracers that focus on mechanisms involved in bone metastasis, prostate cancer cell membrane synthesis, amino acid analogs, androgen analogs, and the prostate specific membrane antigen. Encouraging results with many of these innovative radiotracer compounds will not only advance diagnostic capabilities for prostate cancer but open opportunities for theranostic applications to treat this worldwide malignancy.

[Positron-emission tomography in urooncology]

The use of positron emission tomography (PET) is an established method for the diagnosis of urological malignancies. Several tracers are currently available to obtain metabolic information or directly detect molecular targets. While (18)F-FDG-PET is recognized in current guidelines for the staging of seminoma, PET is not used in clinical routine in renal malignancies due to the lack of specific tracers. Despite initial promising results in bladder cancer, no relevant additional diagnostic value with PET using (18)F-FDG or choline-based tracers could be obtained in most patients and therefore should be used with caution or only within clinical trials. In prostate cancer, however, after development of new tracers that, for example, target prostate-specific membrane antigen (PSMA), a paradigm shift in imaging can be recognized. Here, (68)Ga-PSMA-PET might be included in the future as part of standard imaging work-up.

PET Imaging of Steroid Hormone Receptor Expression

Steroid hormone receptor (SHR) expression and changes in SHR expression compared to basal levels, whether upregulated, downregulated, or mutated, form a distinguishing feature of some breast, ovarian, and prostate cancers. These receptors act to induce tumor proliferation. In the imaging context, total expression together with modulation of expression can yield predictive and prognostic information. Currently, biopsy for histologic assessment of SHR expression is routine for breast and prostate cancer; however, the technique is not well suited to the heterogeneous tumor environment and can lead to incorrect receptor expression assignment, which precludes effective treatment. The development of positron emission tomography (PET) radioligands to image receptor expression may overcome the difficulties associated with tumor heterogeneity and facilitate the assessment of metastatic disease.