Radioimmunoscintigraphy of pelvic lymph nodes with ¹¹¹indium-labeled monoclonal antibody CYT-356

In an attempt to define the possible role of radioimmunoscintigraphy to assess noninvasively the pelvic lymph nodes, we studied 19 patients with prostate cancer. All 19 men underwent conventional radiographic imaging of the pelvis with computerized tomography or magnetic resonance imaging before bilateral pelvic lymph node dissection. In addition, radioimmunological scanning with ¹¹¹indium-labeled monoclonal antibody CYT-356 was performed. Pathologically 8 of the 19 patients had histological confirmation of metastatic nodal disease ranging from 1 to 15 mm. The monoclonal scan was positive at a site corresponding to the histologically confirmed nodal foci in 4 of the 8 patients. Since each hemipelvis could be independently assessed for pathological disease and imaging status, we report site-specific analysis of the monoclonal antibody scan in 38 hemipelves. The overall accuracy was 76% with a sensitivity and specificity of 44% and 86%, respectively. The negative predictive value was 83% and the positive predictive value was 50%. The administration of a single dose of CYT-356 antibody is safe, feasible and capable of detecting soft tissue nodal disease. A negative scan enables the physician to predict noninvasively a low probability of nodal disease for individuals at high risk. The detection threshold of this antibody scan appears to be disease foci 5 mm. or greater.