Induction of Ab3 and Ab3' antibody was associated with long-term survival after anti-G(D2) antibody therapy of stage 4 neuroblastoma
Treatment with anti-G(D2) monoclonal antibody 3F8 (Ab1) at the time of remission may prolong survival for children with stage 4 neuroblastoma. A transient human antimouse antibody (HAMA) response was associated with significantly longer survival (Cheung et al., J. Clin. Oncol., 16: 3053-3060, 1998). Because this response was primarily anti-idiotypic (Ab2), we postulate that the subsequent induction of an idiotype network that included an elevation of anti-anti-idiotypic (Ab3) and anti-G(D2) (Ab3') antibody titers may be responsible for tumor control. Thirty-four patients with stage 4 neuroblastoma diagnosed at >1 year of age were treated with 3F8 at the end of chemotherapy. Most had either bone marrow (31 of 34) or distant bony (29 of 34) metastases at diagnosis. Thirteen patients were treated at second or subsequent remission, and 12 patients in this group had a history of progressive/persistent disease after bone marrow transplantation; 21 patients were treated in the first remission after N6 chemotherapy. Their serum HAMA, Ab3, and Ab3' titers prior to, at 6, and at 14 months after antibody treatment were measured by ELISA. Among these 34 patients, 14 are alive, and 13 (1.8-7.4 years at diagnosis) are progression free (53-143 months from the initiation of 3F8 treatment) without further systemic therapy. Long-term progression-free survival (PFS) and survival correlated significantly with Ab3' (anti-G(D2)) response at 6 months and with Ab3 response at 6 and 14 months. By defining Ab3 threshold ranging from the ratio of 1.1 to 2.6 above pretreatment level, the difference in PFS and survival between the high-Ab3 and low-Ab3 groups became markedly widened. Similarly, increasing the Ab3' threshold at either 6 or 14 months to 300% above pre-3F8 levels also increased the spread between the high versus low Ab3' groups for both PFS and survival curves. Non-idiotype antibody responses (anti-mouse-IgG3 or anti-tumor nuclear HUD antigen) had no apparent impact on PFS or survival. In conclusion, despite the high-risk nature of stage 4 neuroblastoma, long-term remission without myeloablative therapy can be achieved with 3F8 treatment. Ab3 and Ab3' antibody response correlated with prolonged PFS and survival. We postulate that successful induction of an idiotype network in patients may be responsible for long-term tumor control.