Preliminary studies of radiolabeled monoclonal antibody lymphoscintigraphy in malignant melanoma

Studies have been initiated to examine the ability of I-131 anti-melanoma antibody (Fab) to delineate metastases in regional lymp nodes. 500 μgm of I-131 Fab (48.7) directed against HMW antigen of melanoma and I-125 non-specific Fab were injected subcutaneously distal to sites of node resection in 5 patients 20 hours prior to surgery. 3 additional injections were made distal to non-diseased inguinal nodes. 3 pts had no palpable nodes (class 1) and 2 did (class II). Gamma imaging of nodes at 3 and 18 hrs was negative in non-diseased areas and was positive in Pts 1-3; Pt 1 had only micrometastases occupying less than 1% of node volume. In-vitro counting of nodes showed concentrations of I-131 of % .0015 dose/gm of whole node and presumably much higher on tumor cells per se. Autoradiography of I-131 specific Fab in tumored nodes showed high discrete concentration on tumor compared to normal areas. Autoradiography of non-specific I-125 is currently underrway. The authors conclude these preliminary data show considerable promise for pre-surgical delineation of metastatic disease by radiommuno- lymphoscintigraphy