Radioimmunoscintigraphy (RIS) as an imaging modality in oncology is in transition. In early experience with indium-111-labeled intact murine monoclonal antibodies (MoAbs) in colorectal cancer, RIS imaged hepatic metastases poorly and immunogenicity was frequent. Technetium-99m-labeled antibody fragments and human MoAbs provide significantly improved imaging efficacy, and lack of immune reactivity makes serial imaging possible. RIS is superior to computed tomography (CT) for detection of extrahepatic abdominal and pelvic colorectal carcinoma, and complements CT in imaging liver metastases. In surgical decision-making analyses, RIS improved the accuracy of predicting resectability and nonresectability as compared to CT. New MoAb moieties, manipulation of tumor cell antigen expression, and innovative tumor targeting strategies promise to bring RIS into the mainstream of diagnostic oncology, and, when used in conjunction with intraoperative gamma probes, may allow surgeons to localize and remove disease that can neither be visualized nor palpated.
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