Impact of diagnostic and end-of-induction Curie scores in tandem autologous hematopoietic cell transplant for patients with high-risk neuroblastoma: A report from the Children’s Oncology Group.

10027 Background: Diagnostic mIBG (meta-iodobenzylguanidine) scans are an integral component of response assessment in children with high-risk neuroblastoma. The role of end of induction (EOI) Curie Scores (CS) has been previously described in patients undergoing a single autologous hematopoietic cell transplant (AHCT) as consolidation therapy. We now examine the prognostic significance of CS in patients randomized to tandem or single AHCT on the Children’s Oncology Group (COG) trial ANBL0532. Methods: A retrospective analysis of mIBG scans obtained from patients enrolled in COG ANBL0532 (n = 652) was performed. Evaluable patients (n = 179) had mIBG-avid, International Neuroblastoma Staging System (INSS) stage 4 disease, did not progress during induction therapy, consented to consolidation randomization, and received either a single (n = 99) or tandem AHCT (n = 80). In addition, evaluable patients had paired mIBG scans at time of initial diagnosis and EOI. Optimal CS cut points maximized the outcome difference (≤ vs > CS cut-off) according to the Youden index. Log-rank tests compared EFS subgroups, with p < 0.05 considered statistically significant. 3-year EFS is presented ± standard error. EFS was estimated for relative reductions in CS of 50% and 75% from diagnosis to EOI. Results: For recipients of tandem AHCT, the optimal cut point at diagnosis was CS = 12, with superior EFS from study enrollment for patients with CS<12 (74.2±7.9%; n = 31) vs CS > 12 (59.2±7.1%; n = 49) (p = 0.002). At EOI, the optimal cut point was CS = 0, with superior EFS from EOI for patients with CS = 0 (72.9±6.4%; n = 48) vs CS > 0 (46.5±9.1%; n = 32) (p = 0.002). The cut point at diagnosis for recipients of single AHCT was CS = 21 (p = 0.04), while the EOI CS had an optimal cut point of 2, but without a significant difference in EFS (p = 0.29). Absolute CS at diagnosis and at EOI had a greater impact on outcome than the relative reduction in CS between diagnosis and EOI, for both single and tandem AHCT. Conclusions: In the setting of tandem transplantation for children with high-risk neuroblastoma, Curie scores at diagnosis and end-induction may identify a more favorable patient group. Patients treated with tandem AHCT who exhibited a CS<12 at diagnosis or CS = 0 at EOI had superior EFS compared to those with CS above these cut points. Similar to prior reports, a CS<2 was the optimal cut point for single transplant recipients. Clinical trial information: NCT00567567.