Contributions of nuclear medicine to the therapy of malignant tumors.

The diagnostic and therapeutic application of radionuclides in oncology has led to an increased efficiency in the treatment of malignant tumors. Regarding diagnosis, measuring metabolic reactions in tumor tissue, especially by positron emission tomography, opened the potential for assaying tumor response to different treatment modalities and thus eventually for tailoring effective treatment of a given tumor in the individual patient. Regarding treatment, attention is given to the choice of the radionuclide for optimal deposition of the desired radiation in tumor cells avoiding exposure of normal cells; in this context microdosimetric considerations are essential with respect to beta-emitters, alpha-emitters, the Auger-effect and neutron capture therapy. Examples of therapeutic uses of radionuclides in the inorganic form are 131-I for thyroid cancer and 32-P for polycythemia vera; organically bound radionuclides are employed with precursors for tumor cell metabolism or with receptor seeking agents, such as MIBG and monoclonal antibodies which presently enjoy a particular interest and bear great promise. Stable nuclides, if properly accumulated within tumors, may be activated for therapy in situ, for example by thermal neutrons, as in neutron capture therapy using the 10-B (n, alpha)7-Li reaction. Treatment planning and execution with radionuclides have gained momentum over the past decade, yet much more needs to be done.