ABSTRACT
Assessment of the stage of prostate cancer is critical in determining optimal therapy for the disease. Accurate staging is more important in patients with a high likelihood of extraprostatic spread, such as those with a prostate-specific antigen (PSA) greater than 10 ng/mL, Gleason 8 to 10 tumors, or with clinical stage T3 disease. Nuclear scintigraphy (bone scan) has been routinely utilized to assess bone involvement, while computed tomography (CT) scans and, more recently, endorectal magnetic resonance imaging (MRI), has been used to assess lymph node and soft tissue involvement as well as periprostatic extension. Traditional imaging methods such as CT and MRI utilize size criteria (>1 cm) to designate a lymph node as clinically significant and substantively underestimate stage, which may lead to false-negative scans in many individuals with small volume nodal metastases. Hence, currently, there are few options available to confirm metastatic sites even in patients who have a high likelihood of extraprostatic disease as predicted by commonly used preoperative predictive algorithms.1 Identification of residual or recurrent disease following primary therapy such as radical prostatectomy or radiation therapy is also problematic. It is estimated that long-term biochemical failure after primary therapy can occur in as many as 40% of patients.2 Determination of the extent of disease (local versus nodal versus extrapelvic) is critical in this situation as it will direct further therapy and impact prognosis. Traditional staging using CT, MRI, or bone scan have not always been very accurate in this setting, particularly in patients with small volume recurrence or metastases. These shortcomings of traditional radiologic
techniques have prompted the search for better methods to image extraprostatic disease, both before primary therapy has been applied and to assess recurrent disease.
