The radionuclide identification of tumors.

Tumor-seeking radiopharmaceuticals have been employed in the diagnosis of primary neoplasms, in the detection of distant disease, particularly in the localization of tumor foci to facilitate biopsies and the planning of radiation portals, and in assessing the response to tumor therapy. At the present, there is no ideal tumor-scanning agent. However, several approaches appear to be useful and offer promise for further study. The greatest experience has been with Gallium-67, which has major utility in the staging of Hodgkin's disease, in the diagnosis of bronchogenic carcinoma, in the detection of certain metastatic brain tumors, in the identification of recurrent disease, and in the noninvasive diagnosis of leukemic complications. A number of radiolabeled antibiotic and chemotherapeutic agents have shown promise, including tetracycline and bleomycin. A major drawback, however, of these agents which is shared with Gallium-67 is that they appear to be sequestered by inflammatory as well as neoplastic tissue. A most intriguing approach is the use of radiolabeled antibodies to tumor-associated antigens. Animal and clinical experiments have employed antifibrin, antifibrinogen, anticarcinoembryonic antigen, and antiferritin. Theoretically, agents such as these should allow for greater tumor specificity.