Disialoganglioside G(D2) loss following monoclonal antibody therapy is rare in neuroblastoma

Background. Ganglioside G(D2) is abundant on human neuroblastoma (NBI. Mono clonal antibody 3F8 targeted to G(D2) may have imaging and therapeutic pote ntial. Antigen-negative clones can escape immune-mediated attack leading to clinical resistance or recurrence. Procedure. Among 95 evaluable patients treated intravenously with 3F8 (94 Stage 4, 1 Stage 3), 66 received nonradi olabeled 3F8, 11 received 131-iodine-labeled-3F8 (8-28 mCi/ kg] with autolo gous bone marrow rescue, and 18 received both forms of treatment. Prior to treatment, 90 patients tested positive for G(D2) reactivity by bone marrow immunofluorescence (n = 68), tumor immunohistochemistry (n = 20), or diagno stic radioimmunoscintigraphy (n = 2). Results. Of 62 patients who had refra ctory or recurrent neuroblastoma following 3F8 treatment, 61 (98%) tested p ositive for G(D2) reactivity by bone marrow immunofluorescence (n = 51) or tumor immunohistochemistry (n = 10). The sole tumor that lost G(D2) express ion underwent phenotypic transformation into a pheochromocytoma-like tumor. Conclusions. The persistence of G(D2) expression in refractory or recurren t NE suggests that complete antigen loss is an uncommon event and cannot ac count for treatment failure. Med. Pediatr. Oncol. 36. 194-196, 2001. (C) 20 01 Wiley-Liss, Inc.