DISIALOGANGLIOSIDE G(D2) LOSS FOLLOWING MONOCLONAL-ANTIBODY THERAPY IS RARE IN NEUROBLASTOMA

Ganglioside G(D2) is abundant on human neuroblastoma (NB). Monoclonal antibody 3F8 targeted to G(D2) may have imaging and therapeutic potent ial. Antigen-negative clones can escape immune-mediated attack, leadin g to clinical resistance or recurrence. Among 95 evaluable patients tr eated i.v. with 3F8 (94 stage 4 and 1 stage 3), 66 received nonradiola beled 3F8, II received I-131-labeled 3F8 (8-28 mCi/kg) with autologous hone marrow rescue, and 18 received bath forms of treatment, Prior to treatment, 91 patients tested positive for G(D2) reactivity by bone m arrow immunofluorescence (n = 68), tumor immunohistochemistry (n = 20) , or diagnostic radioimmunoscintigraphy only (il = 3), Of 62 patients who had refractory or recurrent NB following 3F8 treatment, 61 (98%) t ested positive for G(D2) reactivity by bone marrow immunofluorescence (II = 51) or tumor immunohistochemistry (rt = 10), The sole tumor that lost G(D2) expression underwent phenotypic transformation into a pheo chromocytoma-like tumor. The persistence of G(D2) expression in refrac tory or recurrent NE suggests that complete antigen loss is an uncommo n event and cannot account for treatment failure.