Background: Various monoclonal antibodies (MoAb) labeled with Iodine-131 or Indium-111 (In-111) have been investigated for radioimmunodetection of Hodgkin's and non-Hodgkin's lymphomas. Successful radioimmunotherapy also has been reported. The purpose of this pilot study was to stage non-Hodgkin's B-cell lymphomas (NHL) using whole body scintigraphy 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 and immunofluorescence. Initial clinical studies by others have demonstrated targeting of NHL with the Tc-99m-labeled LL2-Fab'.
Methods: One milligram of the antibody was injected intravenously after being radiolabeled with 30 mCi Tc-99m. Fifteen patients with high (n = 6), low (n = 2), and intermediate (n = 7) grade NHL were studied. No adverse effects 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 stage was altered in response to the scintigraphic findings. The physiologic biodistribution of the antibody demonstrated splenic uptake caused by antibody targeting of the white pulp and of normal B-cells, and renal uptake caused by urinary excretion. Lymph node and bone marrow involvement of known tumor sites were clearly seen. A number of previously unknown tumor sites were revealed by LL2-radioimmunodetection despite normal morphologic imaging results. Long-term follow-up of these patients is required to verify these findings. No human anti-mouse antibody elevations or adverse reactions were found in the patients studied.
Conclusion: These preliminary data suggest that Tc-99m-labeled LL2 Fab' yields useful clinical results, especially for the staging of patients with NHL before initial therapy or for the detection of early disease recurrence.