Radioimmunolocalization of primary and metastatic breast cancer

The appropriate therapy for breast cancer depends mainly upon early and reliable tumor detection, correct tumor staging and accurate re-staging after therapy. Current radiological imaging methods are based primarily on morphology resulting in high sensitivity but lacking specificity. Established nuclear medicine techniques are sensitive but not very specific. To improve specificity, a number of monoclonal antibodies, selected against a particular tumor-associated antigen expressed on the surface of breast cancer cells, have been radiolabeled for imaging in vivo tumor localizations. In theory, radioimmunodetection offers the potential to demonstrate cancer cells even in subradiological disease, or when anatomy-based imaging methods may be unable to distinguish the nature of an evident mass, making the differential diagnosis between an inflammatory reaction, a postsurgical fibrosis, or a truly viable tumor impossible. Suspected tumor recurrence indicated by increasing tumor marker levels could be another clinical indication for radioimmunolocalization, even if standard imaging modalities are negative. A large number of antibodies against different epitopes of human neoplastic breast tissue have been investigated previously. However, a highly specific and sensitive monoclonal antibody for immunoscintigraphy and radioimmunotherapy has not yet been found. This review addresses tumor-biological considerations, radioisotopes and radiolabeling methods, tumor targets and different monoclonal antibodies used for immunoscintigraphy (incl. SPECT amd PET) of breast cancer.