Immuno-PET of Cancer: A Revival of Antibody Imaging With

the identification of tumor-associated antigens more than 30 y ago and the development of hybrid-oma technology in 1975, investigators realized that Paul Ehrlich’s vision to effectively target drugs to diseased tis-sues could be tested. It was shown that monoclonal antibodies could specifi-cally target tumors (1,2), and it was hypothesized that cancer could be treated with naked antibodies by in-ducing antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, or apoptosis or with anti-bodies tagged with cytotoxic drugs or radionuclides. Indeed, in the early See page 1173 1980s, clinical studies provided the proof of principle that tumors could be visualized using radiolabeled anti-bodies. As a result, a few labeled antibody products were marketed for scintigraphic imaging of tumors: sat-umomab pendetide (OncoScint; Cyto-gen Corp.) for colorectal and ovarian carcinoma, arcitumomab (CEA scan) for colorectal cancers, nofetumomab merpetan (Verluma; Boehringer-Ingelheim Pharma KG) for small cell lung carcinoma, and capromab pen-tetide (ProstaScint; EUSA Pharma) for prostate cancer. However, the diagnostic accuracy of these antibody-based scans was limited, and when 18F-FDG PET was introduced in the clinic, antibody-based imaging for staging and restaging of cancer patients became obsolete. In most groups of cancer patients, the sen-sitivity and specificity of 18F-FDG PET was superior and the resolution of the images was higher. Moreover, quantita-tive analysis of the images provided valuable information about tumor metab-olism and response to therapy