Diagnosis of ovarian cancer with radiolabelled monoclonal antibodies: our experience using 131I-B72.3.

Radioimmunoscintigraphy (RIS) using 131I-labelled B72.3, a monoclonal antibody (MoAb) reacting against a tumor associated antigen (TAA) called TAG-72, has been performed in 36 patients with epithelial ovarian cancer. The patients were divided in three groups as follows: 17 patients with primary cancer before any therapy (Group 1); 10 patients studied after a partial therapeutic approach, having either bulky or minimal disease (Group 2); 9 patients with microscopic disease or in clinical remission at the moment of the study (Group 3). All the most important epithelial histotypes, including mucinous, were present. Results were confirmed at surgery and/or by other diagnostic procedures. Immunocytochemical (ICC) and immunocytofluorimetric (ICF) studies on ascitic collections were performed in order to demonstrate specificity of B72.3 and TAG-72 distribution on neoplastic cells. Immunohistochemistry (IHC) on tissue sections was also obtained. No cross reactions between B72.3 and mesothelial cells in the presence of specific uptake by neoplastic cells was found. Moreover, a non-homogeneous distribution of TAG-72 in the neoplastic population was demonstrated by ICF. RIS proved the intraperitoneal presence of disease in 15 out of 17 and in 5 out of 10 patients in Groups 1 and 2, respectively. One out of four (Group 1) and two out of four (Group 2) extraperitoneal metastases were also seen. False negative results were explained by lack of expression of the antigen, size and location of the lesion, and patho-physiological conditions. One false positive due to an aspecific uptake by a post-surgical active scar was also observed in a disease-free patient.