Peroperative radioimmunodetection of ovarian carcinoma using a hand-held gamma detection probe

Radioimmunoscintigraphy (RIS) can be used in the preoperative localisation of ovarian carcinoma to demonstrate uptake of radiolabelled monoclonal antibodies into neoplastic tissue. The tissue uptake of radiotracer was evaluated at laparotomy in 16 patients with suspected ovarian cancer who had preoperative RIS using technetium-99m-labelled monoclonal antibodies SM3 and H17E2. A gamma detection probe (gamma DP) was used to measure uptake in possible tumour deposits at operation and also the uptake in tissues resected for histology. The percentage uptake of the initial injected dose of radiotracer was also measured in resected tissues. Activity was found to be significantly higher in malignant than in non-neoplastic tissue by all three methods of evaluation. The gamma DP used peroperatively yielded a 82% sensitivity with a 72% specificity for an uptake ratio of 1.5:1. When tissue was examined immediately after resection, for a 100% specificity the sensitivity was 64%. In vitro measurements of monoclonal antibody uptake by tissue similarly gave a 65% sensitivity with a 100% specificity. Peroperative and immediate post-operative measurements of tissue radioactivity can be performed quickly and conveniently, and in some cases may be of benefit in the localisation of tumour at laparotomy and in providing extra information when tissue is examined by frozen section.