The Continuum of Metastatic Prostate Cancer: Interpreting PSMA PET Findings in Recurrent Prostate Cancer

SIMPLE SUMMARY: Molecular imaging with PSMA PET–CT is more accurate and sensitive than conventional imaging with CT, MRI, and a Technetium-99 bone scan. This new imaging modality will result in more advanced disease being diagnosed earlier which may improve survival, however, it could also lead to overtreatment. Since molecular imaging has the potential to identify disease prior to its detection on conventional imaging, this highlights that advanced prostate cancer exists on a continuum. This review discusses how PSMA PET–CT can be used in managing prostate cancer using clinical scenarios. ABSTRACT: Conventional imaging has been the standard imaging modality for assessing prostate cancer recurrence and is utilized to determine treatment response to therapy. Molecular imaging with PSMA PET–CT has proven to be more accurate, sensitive, and specific at identifying pelvic or distant metastatic disease, resulting in earlier diagnosis of advanced disease. Since advanced disease may not be seen on conventional imaging, due to its lower sensitivity, but can be identified by molecular imaging, this reveals that metastatic prostate cancer occurs on a continuum from negative PSMA PET–CT and negative conventional imaging to positive PSMA PET–CT and positive conventional imaging. Understanding this continuum, the accuracy of these modalities, and treatment related outcomes based on imaging, will allow the clinician to counsel patients on management. This review will highlight the differences in conventional and molecular imaging in prostate cancer and how PSMA PET–CT can be used for the management of prostate cancer patients in different clinical scenarios, while providing cautionary notes for overtreatment.