AUTORADIOGRAPHIC EVALUATION OF RADIOLABELED MONOCLONAL-ANTIBODY B72.3DISTRIBUTION IN TUMOR AND LYMPH-NODES OF ADENOCARCINOMA PATIENTS

Monoclonal antibody B72.3 recognizes a pancarcinoma antigen termed TAG -72 and is the MAb in ''OncoScint CR/OV''. Patients undergoing surgica l resection of primary or metastatic colorectal or breast carcinoma or pseudomyxoma peritonei were injected i.v. with I-125-labeled MAb B72. 3. Autoradiography identified the tissue distribution of the injected radiolabeled MAb B72.3. Immunohistochemical straining identified the c orresponding spatial distribution of the target antigen, TAG-72. The l abeling pattern seen using autoradiography closely matched the pattern that was observed using immunohistochemical techniques. This was espe cially notable in the mucin-containing compartments of the different t umors. The I-125-B72.3 was also found associated with the neoplastic c ells, demonstrating a good penetration and specificity of the radiopha rmaceutical through the tumor masses. The regional lymph nodes examine d were the only tissues in which autoradiography and immunoperoxidase gave different results. In these specimens, the presence of TAG-72 ant igen in the parafollicular area, as shown by immunoperoxidase, contras ted with the silver grain deposition, due to the I-125-B72.3, in germi nal centers. These findings suggest differences in the clearance pathw ays of the TAG-72 antigen and B72.3 MAb.