To determine the feasibility of using serial injections of monoclonal antibodies (MoAbs; 96.5 and ZME 018) to evaluate metastases of malignant melanoma, 11 patients were studied. Each patient received two injections of antibody 7 days apart and were imaged 7 days after injection. Serum for human antimouse antibody (HAMA) was obtained immediately prior to injection of MoAb and 7-10 days after the second injection. Six patients were evaluated with both planar and single photon emission computed tomography (SPECT) images. Planar imaging alone was compared with SPECT alone and with planar and SPECT imaging in combination. In seven patients with 19 lesions, 96.5 and ZME 018 each identified eight lesions. In no case did one antibody identify a lesion missed by the other. In the six patients on whom SPECT imaging was performed, 14 confirmed and six suspected lesions were identified. Using planar imaging alone, only 12 confirmed and one suspected lesion were identified. HAMA titers rose significantly (0.32 optical density (O.D.) units prior to injection to 1.28 O.D. units on day 14, P less than 0.001). Allergic reactions occurred during the second injection in two patients. One of these demonstrated elevated HAMA titers and one did not. The preliminary data suggest that monoclonal antibody imaging may be aided by SPECT and that a normal HAMA titer does not preclude an allergic reaction.

Resolution of abnormal foci of increased radiotracer deposition on bone imaging occurs commonly. Photopenic areas due to avascular necrosis and infarcts have been reported to resolve. This report describes serial changes in a photopenic lesion due to metastatic disease and demonstrates that such lesions can resolve following chemotherapy.