INITIAL CLINICAL-RESULTS WITH TC-99M-LABELED LL2 MONOCLONAL-ANTIBODY FRAGMENT IN THE RADIOIMMUNODETECTION OF B-CELL LYMPHOMAS

Background. Various monoclonal antibodies (MoAb) labeled with Iodine-1 31 or Indium-111 (In-111) have been investigated for radioimmunodetect ion of Hodgkin's and non-Hodgkin's lymphomas. Successful radioimmunoth erapy also has been reported. The purpose of this pilot study was to s tage non-Hodgkin's B-cell lymphomas (NHL) using whole body scintigraph y with technetium-99m (Tc-99m)-labeled murine monoclonal antibody LL2 (EPB-2) Fab' (Immunomedics, Morris Plains, NJ), Others have shown this MoAb to have specific binding to B-cell lymphomas by flow cytometry a nd immunofluorescence. Initial clinical studies by others have demonst rated targeting of NHL with the Tc-99m-labeled LL2-Fab'. Methods. One milligram of the antibody was injected intravenously after being radio labeled with 30 mCi Tc-99m. Fifteen patients with high (n = 6), low (n = 2), and intermediate (n = 7) grade NHL were studied. No adverse eff ects were noted. Planar whole body imaging and single-photon emission computed tomography were performed at 2-6 h and 20-24 h postinjection. Human anti-mouse antibody levels were determined before injection and at 2 and 6 weeks. Results. In 4 of 15 patients (27%), the disease sta ge was altered in response to the scintigraphic findings. The physiolo gic biodistribution of the antibody demonstrated splenic uptake caused by antibody targeting of the white pulp and of normal B-cells, and re nal uptake caused by urinary excretion. Lymph node and bone marrow inv olvement of known tumor sites were clearly seen. A number of previousl y unknown tumor sites were revealed by LL2-radioimmunodetection despit e normal morphologic imaging results. Long-term follow-up of these pat ients is required to verify these findings. No human anti-mouse antibo dy elevations or adverse reactions were found in the patients studied. Conclusion. These preliminary data suggest that Tc-99m-labeled LL2 Fa b' yields useful clinical results, especially for the staging of patie nts with NHL before initial therapy or for the detection of early dise ase recurrence.