Background: Optimum therapy for prostate carcinoma patients requires accurate staging, but computed tomography (CT) and magnetic resonance imaging (MRI) have limitations as methods for detecting soft tissue metastases. In this study, radioimmunoscintigraphy (RIS) was evaluated for its ability to identify sites of metastatic disease in lymph nodes.
Methods: RIS was evaluated in 51 prostate carcinoma patients at high risk for metastatic disease. An intravenous infusion of indium-111 capromab pendetide was given, followed by nuclear medicine imaging on two separate dates. Bilateral, open pelvic lymph node dissection was performed with additional exploration and biopsy of scan positive extraprostatic regions. Histologic evaluation of removed tissue confirmed the accuracy of RIS. In addition, results were compared with other standard methods for diagnosing patients prior to surgery.
Results: Nineteen patients (37%) had evidence of lymph node involvement with RIS. Fifteen of the 19 positive patients had pathologic evidence of cancer in the biopsied lymph nodes. Sensitivity, specificity, accuracy, and the positive predictive value for detection of extraprostatic disease were 75%, 86%, 81%, and 79%, respectively. CT, MRI, and ultrasound of the pelvis demonstrated a combined accuracy of only 48% in detecting lymph node disease. Twenty-five previously undetected sites were deemed positive with RIS. Fourteen of these were biopsy-proven tumor sites, seven were probable tumor sites, and four were assumed to be false-positive.
Conclusions: RIS had an impact on patient management through its detection of occult disease in more than 50% of prostate carcinoma patients studied, and it provided information concerning the likelihood that lymph node metastases would be found during surgery.