Because the contemporary diagnosis of prostate cancer is largely based on the measurement of serum prostate-specific antigen (PSA) levels, the disease has been identified at progressively earlier points in its natural history. Early diagnosis, at small volumes of cancer, brings about inherent difficulties in staging and identification of relapse. To this end, recent attempts to refine imaging have focused on molecular techniques that take advantage of the biologic characteristics of prostate cancer.
a radiolabeled monoclonal antibody to prostate-specific membrane antigen (PSMA), offers a potential means of localizing sites of soft tissue metastasis. The test is approved by the US Food and Drug Administration for the imaging of prostate cancer patients. Patients receive an intravenous infusion of 5.0 mCi of radiolabeled antibody, followed by planar and cross-sectional single photon emission computed tomography (SPECT). Repeat images are obtained 4 to 5 days later to allow wash-out of the isotope from the blood vessels and bowel. Simultaneous technetium-99m-labelled red blood cell (RBC) scanning allows assessment of the RBC pool to provide anatomic alignment of the blood vessels