Radioimmunotargeting: diagnosis and therapeutic use

Monoclonal antibodies labeled with a radionuclide make feasible the in vivo radioimmunotargeting of tumor cells. This targeting could be performed for diagnosis, using gamma emitters, or for the therapeutic purpose when antib odies are labeled with beta- and in the future alpha-emitters. Diagnosis ap plications (tumor detection and caracterization), i.e. immunoscintigraphy, have been widely investigated during 20 last years. This technic appeared q uite interesting, complementary of morphological imaging, and clinically us eful, but difficult on a practical point of view because of several pharmac ological and immunological limitations. For these reasons, despite several consequent improvements (especially two-steps or pre-targeting methods), im munoscintigraphy is currently not widely used; furthermore, other scintigra phic methods, mainly positron emission tomography with F-18-fluorodeoxygluc ose, are efficient and easier to perform. On the other hand, knowledge of t he biodistribution of radiolabeled antibodies allows the development of the ir therapeutic use, i.e. radioimmunotherapy, which represents a new method of cancer treatment. Radioimmunotherapy has several particular radiobiologi cal and dosimetric aspects, which remain widely under investigation. Unders tanding of these aspects, together with a better delineation of the indicat ions, allow to be really optimist concerning this new way of cancer treatme nts, as shown by clinical results that have been obtained in non Hodgkin's lymphoma. Radiolabeled immunoconjugates appears as a growing field in nucle ar medicine, which sustains numerous preclinical and clinical studies.