Purpose: Conventional imaging modalities, such as computerized tomography and magnetic resonance imaging, lack sensitivity and specificity for detecting recurrent prostate cancer after radical surgery. We evaluated the role of the indium-capromab pendetide scan, otherwise known as the ProstaScint (Cytogen Corp., Princeton, New Jersey) scan, in this setting.
Materials and methods: A retrospective review was performed of 42 patients undergoing ProstaScint imaging for biochemical progression after radical prostatectomy. Of these patients 16 (38.1%) subsequently completed a course of salvage radiation therapy.
Results: Median prostate specific antigen (PSA) immediately prior to ProstaScint imaging was 1.2 ng/ml (range 0.2 to 4.8). Abnormal accumulation on the ProstaScint scan was detected in 36 patients (85.7%). Of the 16 patients undergoing salvage radiation therapy 15 had uptake isolated to the prostatic fossa on ProstaScint imaging. Ten of these 15 patients (66.7%) achieved undetectable PSA after radiation therapy, while 5 (33.3%) had little or no response. Using American Society for Therapeutic Radiology and Oncology criteria 3 of 10 responders had relapse after an average of 9 months. The remaining 7 patients remained biochemically free of disease at last followup.
Conclusions: ProstaScint imaging is capable of detecting recurrent prostate cancer at low PSA levels. However, only 7 of 15 men (46.7%) with ProstaScint uptake isolated to the prostatic fossa showed a durable response to salvage radiation therapy. Based on these findings patients might be better treated based on the rate of increase in PSA rather than on routine scanning with this test.