Clinical radioimmunolocalization with a rat monoclonal antibody directed against c-erbB-2

Lymph node status is still the single most important prognostic factor in breast cancer and surgery remains the only reliable means of providing this information. This study evaluates using a highly specific radiolabeled monoclonal antibody to provide equivalent information. The optimum labeling conditions for radiolabeling a monoclonal antibody against the gene product of the protooncogene c-erbB-2 with Tc99m were established. This immunoconjugate was next evaluated in a mouse model system and averaged 20% localization of the total injected dose per gram of tumor at 24 h. Ten patients have had this immunoconjugate, with planar and tomographic reconstructed images being obtained at 24 h. The resulting images were compared to histopathological examination of the surgical specimens. Three patients acted as normal controls, two patients were selected on the basis of inappropriate sampling of adjacent ductal carcinoma in situ, three patients demonstrated only moderate antigen expression, and two patients demonstrated excellent tumor localization in both breast primary and regional node metastases. The high specificity of this antibody, ease of labeling, and excellent localization performance with a good antigen target encourage the development of this system as a method of localization and a potential means of antibody-guided therapy.