114Inm oxine-labelled lymphocytes--therapeutic applications

It has shown that, after intravenous administration of autologous lymphocytes labelled with the beta-emitting radionuclide 114Inm, the cells initially migrate normally before succumbing to the toxic effects of the radiation. The radioactive material is then released from the cell and taken up by neighbouring radioresistant macrophages, thereby localizing a field of radiation to the site of lymphocyte death. Using this technique, lymphocytopoenia has been produced in rats. We have measured the whole-body distribution and excretion of radioactivity in patients who received escalating activities of 114Inm-labelled lymphocytes. All patients had active non-Hodgkin's lymphoma involving the spleen and liver which proved resistant to combination chemotherapy and conventional radiotherapy. Following intravenous administration, the labelled cells cleared rapidly from the vasculature with only 15% remaining in the peripheral blood at 30 min. The radioactivity continued to fall over the next 5 days to approximately 3% and was maintained at approximately 2% for up to 90 days. There was an almost immediate uptake of radioactivity by the spleen and liver which reached approximately 85% of the injected dose by 48 h. The localization of radioactivity stabilized by 48 h and thereafter the whole-body content fell by approximately 0.8% per day. Up to 5% of the administered radioactivity accumulated in the bone marrow. The activities administered were too low to produce a therapeutic response and no toxicity was experienced by the patients. A therapeutic study at higher activities is now underway.