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PURPOSE The primary objective of the Children’s Oncology Group study ANBL0531 (ClinicalTrials.gov identifier: NCT00499616 ) was to reduce therapy for subsets of patients with intermediate-risk neuroblastoma using a biology- and response-based algorithm to assign treatment duration while maintaining a 3-year overall survival (OS) of 95% or more for the entire cohort. PATIENTS AND METHODS Children younger than age 12 years with intermediate-risk stage 2A/2B or stage 3 tumors with favorable histology; infants younger than age 365 days with stage 3, 4 or 4S disease; and toddlers from 365 to younger than 547 days with favorable histology, hyperdiploid stage 4, or unfavorable histology stage 3 tumors were eligible. Patients with MYCN-amplified tumors were excluded. Patients were assigned to initially receive two (group 2), four (group 3), or eight (group 4) cycles of chemotherapy with or without surgery on the basis of prognostic markers, including allelic status of chromosomes 1p and 11q; ultimate duration of therapy was determined by overall response. RESULTS Between 2007 and 2011, 404 evaluable patients were enrolled. Compared with legacy Children’s Oncology Group studies, subsets of patients had a reduction in treatment. The 3-year event-free survival and OS rates were 83.2% (95% CI, 79.4% to 87.0%) and 94.9% (95% CI, 92.7% to 97.2%), respectively. Infants with stage 4 tumors with favorable biology (n = 61) had superior 3-year event-free survival compared with patients with one or more unfavorable biologic features (n = 47; 86.9% [95% CI, 78.3% to 95.4%] v 66.8% [95% CI, 53.1% to 80.6%]; P = .02), with a trend toward OS advantage (95.0% [95% CI, 89.5% to 100%] v 86.7% [95% CI, 76.6% to 96.7%], respectively; P = .08). OS for patients with localized disease was 100%. CONCLUSION Excellent survival was achieved with this treatment algorithm, with reduction of therapy for subsets of patients. More-effective treatment strategies still are needed for infants with unfavorable biology stage 4 disease.

Purpose Infants with stage 4S neuroblastoma usually have favorable outcomes with observation or minimal chemotherapy. However, young infants with symptoms secondary to massive hepatomegaly or with unfavorable tumor biology are at high risk of death. Our aim was to improve outcomes for patients with symptomatic and/or unfavorable biology 4S neuroblastoma with a uniform treatment approach using a biology- and response-based algorithm. Patients and Methods The subset of patients with 4S disease with MYCN-not amplified tumors with impaired or impending organ dysfunction, or with unfavorable histology and/or diploid DNA index, were eligible. Patients were assigned to receive two, four, or eight cycles of chemotherapy on the basis of histology, diploid DNA index, chromosome arm 1p or 11q loss of heterozygosity (LOH) status, and symptoms. Results Forty-nine eligible patients were enrolled: 41 were symptomatic and 28 had unfavorable biology. Seventeen patients (symptomatic, favorable biology) were assigned two cycles, 21 patients (any unfavorable biologic feature without 1p or 11q LOH) were assigned four cycles, and 11 patients (unfavorable biology including 1p and/or 11q LOH [n = 7] or symptomatic with unknown biology [n = 4]), were assigned eight cycles. The 3-year overall survival was 81.4% ± 5.8%. Eight of nine deaths were in patients younger than 2 months of age at diagnosis (median, 9 days [range, 1 to 68 days]): five acute deaths were a result of hepatomegaly and associated toxicities; two were a result of late relapse in patients with unfavorable biology; and two were a result of treatment complications. No deaths occurred after protocol-mandated pre-emptive treatment of infants younger than 2 months with hepatomegaly, regardless of symptoms. A new scoring algorithm for emergent chemotherapy in patients with 4S disease was developed on the basis of this experience. Conclusion The outcome for 4S neuroblastoma can be improved with pre-emptive chemotherapy for evolving hepatomegaly or other baseline comorbidities in infants younger than 2 months of age.

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 (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

10026 Background: 131I-metaiodobenzylguanidine (131I-MIBG) has demonstrated efficacy as a single agent for patients with neuroblastoma. Recent trials have focused on 131I-MIBG combination strategies, though little is known about the impact of combination agents on markers of radiation exposure. Methods: NANT11-01 (NCT02035137) was a multicenter, open label, randomized phase II clinical trial that evaluated 131I-MIBG therapy alone (Arm A) or in combination with vincristine/irinotecan (Arm B) or vorinostat (Arm C) for patients with resistant/relapsed neuroblastoma. We collected blood samples at baseline, 72 hours, 96 hours, and 15 days after 131I-MIBG infusion and determined levels of plasma FLT3 ligand, serum amylase, and gene expression for selected RNA transcripts (apoptosis, DNA damage response and cell cycle related). We evaluated marker association with treatment arm, clinical response using NANT response criteria, toxicity, and whole-body radiation dose. Results: The cohort included 99 patients who had at least one biomarker available for analysis (32 Arm A; 35 Arm B; 32 Arm C). We observed both positive and negative significant modulation in most biomarkers between baseline, 72 hours, and 96 hours following 131I-MIBG. Patients in Arm C had the lowest degree of modulation in FLT3 ligand. Elevated baseline levels of FLT3 ligand were significantly associated with improved Curie response but not overall response. Lower baseline BCL2 levels were associated with higher overall and Curie response. Patients with increased FLT3 ligand at 96 hours after 131I-MIBG therapy were significantly more likely to have grade 4 thrombocytopenia.Peripheral blood gene expression of the BCL2 family of apoptotic markers (BCL2/L1 and BAX) was significantly associated with grade 4 hematological toxicity. Whole-body radiation dose and PRKDC fold change at 72 hours were significantly correlated. No other individual biomarkers were correlated with whole body radiation dose at 72 or 96 hours post 131I-MIBG. Conclusions: Peripheral blood biomarkers relevant to radiation exposure demonstrate significant modulation over time after 131I-MIBG treatment. Biomarkers related to hematopoietic damage and apoptosis were associated with hematological toxicity. Patients treated with vorinostat and 31I-MIBG had differential modulation of FLT3-ligand Further use of these biomarkers may improve our ability to care for patients treated with 131I-MIBG.

10041 Background: Lorlatinib, a macrocyclic ATP-competitive ALK inhibitor, exerts potent activity against neuroblastoma (NB) xenograftsharboring the most common ALK mutations. We performed a first-in-child phase 1 study of lorlatinib for patients with refractory/relapsed (R/R) ALK aberrant high-risk NB. We previously reported on Part A of the study, where safety of single agent lorlatinib was determined, showing complete responses (CR) to lorlatinib at the recommended phase 2 dose (RP2D) of 115 mg/m2 in pts < 18 years and 150 mg in pts > 18 yrs. Part B of the study aimed to determine the safety, pharmacokinetics (PK), RP2D, and explore the anti-tumor activity of lorlatinib in combination with topotecan and cyclophosphamide in pts with R/R ALK-driven NB. Methods: Patients with R/R NB ages 1-17 years with ALK mutations or amplification were eligible; prior ALK inhibitor (ALKi) treatment was allowed. Lorlatinib was orally administered once daily on days 1-28 with topotecan (0.75 mg/m2/day) and cyclophosphamide (250 mg/m2/day) administered intravenously days 1-5 and GCSF starting day 6. Two lorlatinib dose levels (DL) of 95 mg/m2/day (DL4B) and 115 mg/m2/day (DL5B) were assessed using a 3+3 dose escalation design with the primary endpoint of dose limiting toxicity (DLT) in Course 1. We report lorlatinib safety, PK, and objective response rate (ORR) for patients enrolled on Part B. Results: Between 10FEB2020 and 03DEC2021,9 eligible pts enrolled on Part B with a median age of 6.7 years (3.7-12.7). Three pts were enrolled onto DL4B and six onto DL5B (2/3 pts on DL4B and 4/6 pts on DL5B had received prior ALKi therapy) with no DLT’s observed in course 1. One patient on DL5B experienced a neuropsychological DLT in Course 3. Most common treatment-related adverse events were hematological, febrile neutropenia, high cholesterol, hypertriglyceridemia, and neuropsychological effects. The median number of courses received was 6 with a range of 1-8 on DL4B and 1-7 on DL5B. Of the 8 patients evaluable for response, ORR was 50%: 2/3 pts on DL4B and 2/5 pts on DL5B. Preliminary PK data demonstrate comparable dose level-associated lorlatinib steady state exposure between Part B chemotherapy combination and Part A monotherapy cohorts, supporting that chemotherapy had no effect on lorlatinib exposure that there are no overlapping toxicities. Conclusions: Lorlatinib in combination with topotecan and cyclophosphamide is well tolerated, and early data suggest encouraging objective anti-tumor activity. These data support the current integration of lorlatinib into up-front high risk neuroblastoma therapy for patients with ALK-driven neuroblastoma. Clinical trial information: NCT03107988.

10038 Background: 131I-metaiodobenzylguanidine (MIBG) is one of the most active salvage therapies for patients with relapsed or refractory (R/R) high-risk neuroblastoma (HRNB). Preclinical neuroblastoma studies show cooperative effects when radiation is combined with anti-GD2 monoclonal antibody (mAb). We hypothesized that MIBG would synergize with the anti-GD2 mAb dinutuximab to provide improved anti-tumor responses. The primary aims of Part A of this study were to determine the maximum tolerated dose (MTD) and/or recommended Phase II dose (RP2D) of MIBG administered with dinutuximab in children with R/R HRNB and to define and describe the toxicities. Methods: Patients 1-29 years of age with R/R HRNB who had MIBG uptake in ≥ 1 site were eligible. Prior anti-GD2 mAb therapy was allowed provided it was not administered with MIBG and not permanently discontinued due to toxicity. One prior MIBG therapy was allowed. MIBG was administered on day 1 at one of three dose levels (DLs): 12, 15, and 18 mCi/kg (DL1-DL3, respectively) with an expansion cohort at the RP2D. Doses were escalated using a rolling six design starting at DL1. The primary endpoint was dose-limiting toxicity (DLT) during course 1. Dinutuximab (17.5 mg/m2/dose) was administered intravenously on days 8-11 and 29-32 and GM-CSF (250 mcg/m2/dose) subcutaneously on days 8-17 and 29-38. Autologous peripheral blood stem cells were infused to all patients on day 15 (+/- 2 days). A maximum of 2 courses per patient were allowed. Response rate was defined as the proportion of patients with a complete or partial response. Results: Thirty-one patients were enrolled. Fourteen were evaluable for dose escalation (4 on DL1, 4 on DL2, and 6 on DL3); 5 evaluable patients were treated in the DL3 expansion. The median age was 7.4 years (range: 3.1 – 22.0) and 20 (65%) were male. Twenty-seven (87%) patients had previously received a median of 8.5 cycles of chemoimmunotherapy (range: 2 – 21). Eight patients previously progressed while receiving anti-GD2 mAb including 7 in DL3. Five (16%) patients had previously received MIBG. No patient at any dose level experienced DLT. Common grade 3/4 treatment-related toxicities were expected hematologic toxicities attributable to MIBG and non-hematologic toxicities attributable to dinutuximab or GM-CSF. Among 26 response-evaluable patients, the centrally-confirmed response rate was 31% across all dose levels: 2/6 (33%) in DL1, 3/5 (60%) in DL2, and 3/15 (20%) in DL3. There were 3 minor responses, 1 in DL2 and 2 in DL3. Conclusions: The RP2D of MIBG in combination with standard doses of dinutuximab and GM-CSF is 18 mCi/kg. This radioimmunotherapy regimen is well-tolerated without additive toxicity. Preliminary efficacy data are encouraging in this heavily pre-treated patient population. A phase 2 trial of this regimen is planned in patients with R/R HRNB. Clinical trial information: NCT03332667.

e22003 Background: 131I-metaiodobenzylguanidine (MIBG) remains one of the most active agents for neuroblastoma. The clinical and biologic predictors of response to MIBG therapy have not been systematically characterized in a recent era trial. Methods: Patients 1-30 years were enrolled on the randomized phase 2 trial of MIBG vs. MIBG/vincristine/irinotecan vs. MIBG/vorinostat for relapsed/refractory neuroblastoma (NANT2011-01, NCT02035137) between 2014-2019. Data were compared between those who had an objective response (partial response or better using NANT response criteria) to MIBG after the first cycle and those who did not according to clinical features (age at study enrollment; sex; response to prior therapy; prior receipt of MIBG therapy; bone marrow involvement at study enrollment; and measurable disease status at study enrollment) and MYCN status. Univariate analyses were performed using odds ratio and Fisher exact tests. Multivariate logistic regression analysis was used to identify predictors of response to MIBG therapy while controlling for key confounders. Results: 105 response-evaluable patients were included in the analytic cohort. Across the 3 study arms, 20% (21/105) had an objective response to the treatment. Only measurable disease status was statistically significantly associated with response to therapy, with higher rates of response among patients without measurable disease at study enrollment (30% vs. 13%, p = 0.049). Response to prior therapy, sex, MYCN status, and measurable disease status showed univariate odds ratios of 2 or greater (Table). Only measurable disease status remained statistically significant in the multivariate analysis (p = 0.043, Table). Conclusions: Patients without measurable disease have a higher rate of objective responses to MIBG therapy. Understanding these differences based upon predictors of response may help to inform stratification methods for future MIBG clinical trials.[Table: see text]

10012 Background: Circulating tumor DNA (ctDNA) is detectable in children with neuroblastoma. Less is known about how levels change during treatment and the implications of these changes. We evaluated ctDNA pre- and post- 131I-metaiodobenzylguanidine (MIBG) therapy. Methods: We utilized plasma samples from NANT11-01 (NCT02035137), a multi-center, open label, randomized phase II clinical trial evaluating MIBG with or without radiation sensitizers for patients with relapsed or refractory neuroblastoma. Plasma was collected at Baseline prior to MIBG, 72 hours (Hr72), 96 hours (Hr96), 15 days after MIBG (D15), and prior to a second course among patients without progression who received a second course (C2). Samples were analyzed for percent ctDNA levels using ultra-low passage whole genome sequencing. We evaluated associations between ctDNA findings with baseline disease measures of percent involvement in bone marrow, Curie score, and RECIST disease sum of diameters as well as overall response by NANT Response Criteria v1.2 (complete response or partial response coded as responders). Results: Eighty-four patients had a baseline sample and were included in this analysis. Of the 37 patients (44%) with detectable ctDNA at baseline, the median ctDNA level was 32% (range 3.9-91%). Baseline ctDNA levels showed a significant positive correlation with percent involvement in bone marrow (r=0.37; p=0.0004) and Curie score (r=0.26; p = 0.018), but not RECIST sum of diameters for soft tissue sites (r=0.065; p=0.56). Following therapy, the proportions of patients with detectable ctDNA were: Hr72 47% (34/73; median level 28%); Hr96 50% (26/52; median 28%); D15 33% (7/21; median 4%); and C2 14% (3/21; median 50%). Rate of ctDNA detection was similar between responders and non-responders at baseline, Hr72, and Hr96, but lower among responders at D15 and C2 (Table). Among the 21 patients with C2 data, ctDNA levels were either undetectable (n=18) or lower than Cycle 1 Baseline (n=3). Among patients with detectable baseline ctDNA, the median relative ctDNA level at Hr72 (Hr72 ctDNA/baseline ctDNA) for non-responders was 0.87 (n=24) vs. 1.16 for responders (n=7). In contrast, the median relative ctDNA level at C2 for non-responders was 0.56 (n=4) vs. 0 for responders (n=4). Conclusions: ctDNA is detectable in a substantial proportion of patients with relapsed / refractory neuroblastoma, with levels correlated with conventional measures of disease burden. Following MIBG therapy, early timepoints (Hr72 and Hr96) are less informative, whereas ctDNA becomes undetectable at D15 and C2 more commonly in patients with clinical response.[Table: see text]

10526 Background: Pro-angiogenic factors may represent therapeutic targets in sarcoma. Preclinical studies have demonstrated a potential additive or synergistic interaction between anti-angiogenic agents and chemotherapy. The purpose of this study was to determine the maximum tolerated dose (MTD), toxicities, pharmacokinetic (PK) and pharmacodynamics (PD) effects of PAZIT in patients with advanced sarcoma. Methods: Patients 6-30 years of age with relapsed/refractory sarcomas were eligible. In the initial dose escalation plan (A), patients received pazopanib PO (225-450 mg/m2/dose) on Days 1-21 of 21-day cycles. Pazopanib was combined with fixed doses of irinotecan (IV 50 or PO 90 mg/m2/dose) and temozolomide PO 100 mg/m2/dose on Days 1-5. Due to DLTs, an amendment was made to the dose escalation plan (B) and patients received fixed doses of pazopanib PO (225 mg/m2/dose) on Days 1-21 of 21-day cycles and reduced irinotecan doses (IV 25-37.5 or PO 45-67.5 mg/m2/dose) and temozolomide PO 100 mg/m2/dose on Days 1-5. Oral cephalosporin diarrhea prophylaxis was required. Dose escalation followed a 3+3 design. Correlative studies included PK (pazopanib, irinotecan) and PD (angiogenic factors, ctDNA) effects. Results: Sixteen patients were treated (median age 16 years, range 7-21). The dose levels in the table were evaluated. First cycle DLTs occurred at all dose levels (Table) and included diarrhea, pancreatitis, colitis, neutropenia, hypertension, deep vein thrombosis, and ALT increase. Due to excessive toxicity, an MTD could not be established. One patient with osteosarcoma had a partial response. Four patients had prolonged stable disease > 4 cycles, including 2 patients with Ewing sarcoma (5 and 6 cycles), rhabdomyosarcoma (9 cycles), and desmoplastic small round cell tumor (6 cycles). Mean±SD plasma exposures to pazopanib, irinotecan, and SN-38 in patients treated on dose level 1B (n = 4) on Day 4 were 601±83, 1.4±0.2 and 0.1±0.04 ug/mL*hr, respectively. Analyses of correlative studies are ongoing. Conclusions: Combination PAZIT therapy is not tolerable as evaluated at these doses/schedules. This study provides important toxicity data to inform future clinical trials using combination anti-angiogenic strategies in sarcoma. Clinical trial information: NCT03139331. [Table: see text]

10523 Background: Immunotherapy with the anti-GD2 antibody dinutuximab plus sargramostim (GM-CSF), aldesleukin (IL-2) and isotretinoin following consolidation therapy improved outcome for high-risk neuroblastoma (HRNBL) pts enrolled on COG ANBL0032. Randomization was halted in 2009; subsequent pts were non-randomly assigned to immunotherapy. Toxicities and survival were evaluated. Methods: HRNBL pts < 31 years old with a pre-autologous stem cell transplant (ASCT) response of ≥ partial response (PR) were eligible. Demographics, INSS stage, tumor biology, 1993 INRC pre-ASCT response and toxicities were summarized using descriptive statistics. Five-year (yr) EFS and OS from time of study enrollment were estimated. Results: From 2009-2015, 1,183 pts were non-randomly assigned to immunotherapy. 96.7% (n = 1,144) were ≥18 months old and 83.1% (n = 765/921) had stage 4 disease. 45.1% (n = 363/805) of tumors with known biology were MYCN amplified, 94.5% (n = 749/793) had unfavorable histology, and 54.9% (n = 397/723) were diploid. Pre-ASCT, 352 (29.8%) pts had complete response (CR), 418 (35.3%) had very good partial response (VGPR), and 413 (34.9%) had PR. 1,042 (88.1%) pts underwent a single and 141 (11.9%) underwent tandem ASCT. For the entire cohort, 5-yr EFS was 61.1±1.9% and 5-yr OS was 71.9±1.7%. 5-yr EFS and OS for pts ≥18 months of age with stage 4 disease (n = 746) were 58.4±2.3% and 71.0±2.1%. 5-yr EFS and OS were 82.3±4.8% and 86.7±4.2% among pts with stage 3 disease (n = 110). EFS but not OS was superior for those with a CR/VGPR pre-ASCT vs. PR (5-yr EFS: 64.2±2.2% vs. 55.4±3.2%, p = 0.0133; OS: 72.7±2.1% vs. 70.5±2.9%, p = 0.3811). There was a trend toward improved OS for those treated with tandem vs. single transplant (5-yr EFS: 65.9±4.3% vs. 60.4±2.1%, p = 0.1282; OS: 76.5±3.8% vs. 71.2±1.9%, p = 0.0704). Grade ≥3 toxicities ( > 10% of pts) during GM-CSF and IL-2-containing cycles, respectively, included pain (15.6/11.4%), fever (15.1/32.7%), anemia (18.9/21.7%), thrombocytopenia (13.9/17.4%), lymphopenia (12.3/16.0%), and hypokalemia (13.3/25.2%). Additional Grade ≥3 toxicities ( > 10% of pts) included hypoxia (10.1%) during GM-CSF-containing cycles, and anaphylaxis (12.0%), neutropenia (16.1%), hyponatremia (16.5%), and hypotension (13.8%) during IL-2-containing cycles. Conclusions: In this large cohort of HRNBL pts treated with immunotherapy, 5-yr EFS was 61.1%. Superior EFS was observed for pts with stage 3 disease and for those with CR/VGPR pre-ASCT. IL-2-containing cycles were associated with increased toxicity. Clinical trial information: NCT00026312.

10504 Background: Lorlatinib, a potent ALK inhibitor, exerts unprecedented activity against neuroblastoma (NB) derived xenografts harboring common crizotinib-resistant ALK mutations, leading to a first in child phase I study. Methods: R/R NB patients (pts) > 12 months, with ALK mutations/amplification and prior ALK inhibitor (ALKi) treatment were eligible. Lorlatinib was administered in 28-day courses (C). For pts < 18 years, 5 dose levels (DL) (45, 60, 75, 95, 115 mg/m2/day) were assessed. DL5 (115 mg/m2/day) expansion is enrolling (cohort A1). For patients > 18 years, two DL (DL3a the adult RP2D of 100 mg/day and DL4a at 150mg/day) were assessed (cohort A2). Primary endpoint was dose-limiting toxicity (DLT) during C1 and neurocognitive toxicity through C2. Blood samples for circulating tumor DNA (ctDNA) were matched to radiologic restaging. Results: From 9/2017 to 1/2019, 33 eligible patients enrolled (13 with prior ALKi therapy), with median age (range) 5.5 years (2-17) on A1, 21.5 years (15-50) on A2. In A1, 3 pts each enrolled onto DL1-3, with no DLT’s. 5/10 pts enrolled on DL4, with no DLT’s. 1/3 on DL5 had a DLT of grade 3 diarrhea, with expansion ongoing. In cohort A2, 5 patients enrolled at 100 mg/day with no DLT’s; 6 enrolled at 150 mg/day, with one DLT (grade 4 reversible psychosis). Most common treatment-related adverse events were weight gain (90%, grade 1-3), hyperlipidemia (90%, grade 1-3), concentration/memory impairment (23%, grade 1-2), peripheral neuropathy (13%; grade 1-2, A2 only), and peripheral edema (10%; grade 1, A2 only). Lorlatinib steady state exposure at DL3 and DL4 was in the range of exposures seen in adult lung cancer patients at the 100 mg and 200 mg DLs. In A1, 1/18 had partial response (PR), 3/18 had minor responses (MR), and 4/18 had stable disease (SD). Of pts with MR, 2/3 had PR of soft tissue and 1/3 had complete response (CR) by MIBG. In A2 pts, 1/10 had CR, 3/10 PR, and 3/10 MR; Notably, 2/3 with PR had CR by MIBG. Of the pts with MR, one had PR and one CR by MIBG. Responses occurred across dose levels, ALK mutations, and in ALKi pre-treated pts with median courses of 2 (1-24) on A1 and 10.5 (2-28) on A2. Serial ctDNA results showed mutant ALK variant allele frequency trajectories that correlated with clinical response and emergence of novel ALK mutations in cis that corresponded with disease progression. Conclusions: Inhibition of ALK-driven NB with lorlatinib occurs with manageable toxicity and objective anti-tumor activity. Prospective ctDNA allows for monitoring of disease and evolution of resistance. Clinical trial information: NCT03107988.

10500 Background: 131I-metaiodobenzylguanidine (MIBG) remains one of the most active agents for neuroblastoma. It is not clear if putative radiation sensitizers improve upon this activity. The primary aim of this trial was to identify the MIBG treatment regimen with highest response rate among: MIBG monotherapy (Arm A); MIBG/Vincristine/Irinotecan (Arm B); MIBG/Vorinostat (Arm C). The secondary aim was to compare toxicity across arms. Methods: We conducted a multicenter, randomized phase II trial. Patients 1-30 years with relapsed/refractory high-risk neuroblastoma were eligible with at least one MIBG-avid site and adequate autologous stem cells (ASCs). All patients received MIBG 18 mCi/kg on Day 1 and ASC on day 15. Patients on Arm A received only MIBG; patients on Arm B also received vincristine (2 mg/m2) IV on Day 0 and irinotecan (50 mg/m2) IV daily on Days 0-4; patients on Arm C also received vorinostat (180 mg/m2) orally once daily on days -1 to 12. The primary endpoint was response after one course according to NANT response criteria. The trial was designed as a pick-the-winner study with a maximum of 105 eligible and evaluable patients to ensure an 80% chance that the arm with highest response rate is selected, if that response rate is at least 15% higher than the other arms. Results: 114 patients enrolled. Three patients were ineligible and 6 eligible patients never received MIBG, leaving 105 eligible and evaluable patients (36 Arm A; 35 Arm B; and 34 Arm C; 55 boys; median age 6.5 years). 9 patients had received prior MIBG monotherapy, 65 prior irinotecan, and 7 prior vorinostat. After one course, the response rates (Partial Response or better) on Arms A, B, and C were 17% (95% CI 7-33%), 14% (5-31%), and 32% (18-51%). An additional 4, 4, and 7 patients met NANT Minor Response criteria [partial response in one disease category (e.g., bone marrow) and stable disease in other categories] on Arms A, B, and C, respectively. On Arms A, B, and C, rates of any grade 3+ non-hematologic toxicity were 19%, 49% and 32%; rates of grade 3+ diarrhea were 0%, 11%, 0%; and rates of grade 3+ febrile neutropenia were 6%, 11%, and 0%. Conclusions: The combination of vorinostat/MIBG had the highest response rate, with manageable toxicity. Vincristine and irinotecan do not improve the response rate to MIBG and are associated with increased toxicity. These data provide response rates for MIBG monotherapy in a contemporary patient population assessed with current response criteria. Clinical trial information: NCT02035137.

388 Background: Iobenguane scan positive cancers include pheochromocytoma and paraganglioma (PPGL), neuroblastoma, and gastroenteropancreatic neuroendocrine tumors. A pooled analysis was conducted to assess the safety profile of high-specific-activity I-131 metaiodobenzylguanidine (HSA I-131 MIBG [AZEDRA]) in PPGL and neuroblastoma. Methods: Safety data were pooled from four clinical studies with 118 subjects who received HSA I-131 MIBG. Adverse events (AEs) were described by age, gender, race, number of HSA I-131 MIBG doses, temporal association of AEs within 12 weeks after therapeutic dose 1, vital signs, laboratory values, hematological events of Grade 3/4 or serious AEs, and changes in mean hematology values over a period of 12 months. Results: Out of 118 subjects, mean age was 47.0 ± 18.9 years (range 3-76); 57.6% were males and 74.6% were white. A total of 102 (86.4%) subjects had at least one AE assessed as treatment-related. The incidences of most AEs were similar among both genders and all racial groups. The most common toxicities associated with HSA I-131 MIBG were gastrointestinal disorders, with nausea the most prevalent. The incidences of nausea and salivary gland pain showed decreasing trends with age while dyspnea, asthenia, and peripheral edema showed increasing trends. The second most common toxicities were hematologic. Following each therapeutic dose, mean hemoglobin, leukocytes, neutrophils, and platelets decreased. Most hematological AEs resolved within 12 weeks, and recovery to pre-therapeutic dose values was apparent 6 months after each therapeutic dose. After therapeutic dose 1, higher percentages of subjects experienced AEs in the first 2 weeks, and the incidence decreased beyond 6 weeks. No notable changes were observed in clinical chemistry tests. The incidence of Grade 3/4 AEs was similar following each therapeutic dose. Conclusions: HSA I-131 MIBG was safe and well-tolerated among subjects with iobenguane scan positive cancers. No trends were discerned between baseline characteristics and AEs. Hematology results reflected toxicity profile expected in a population of subjects administered a radiopharmaceutical. Clinical trial information: Pooled Safety.

Purpose The primary objective of Children's Oncology Group study P9641 was to demonstrate that surgery alone would achieve 3-year overall survival (OS) ≥ 95% for patients with asymptomatic International Neuroblastoma Staging System stages 2a and 2b neuroblastoma (NBL). Secondary objectives focused on other low-risk patients with NBL and on those who required chemotherapy according to protocol-defined criteria. Patients and Methods Patients underwent maximally safe resection of tumor. Chemotherapy was reserved for patients with, or at risk for, symptomatic disease, with less than 50% tumor resection at diagnosis, or with unresectable progressive disease after surgery alone. Results For all 915 eligible patients, 5-year event-free survival (EFS) and OS were 89% ± 1% and 97% ± 1%, respectively. For patients with asymptomatic stage 2a or 2b disease, 5-year EFS and OS were 87% ± 2% and 96% ± 1%, respectively. Among patients with stage 2b disease, EFS and OS were significantly lower for those with unfavorable histology or diploid tumors, and OS was significantly lower for those ≥ 18 months old. For patients with stage 1 and 4s NBL, 5-year OS rates were 99% ± 1% and 91% ± 1%, respectively. Patients who required chemotherapy at diagnosis achieved 5-year OS of 98% ± 1%. Of all patients observed after surgery, 11.1% experienced recurrence or progression of disease. Conclusion Excellent survival rates can be achieved in asymptomatic low-risk patients with stages 2a and 2b NBL after surgery alone. Immediate use of chemotherapy may be restricted to a minority of patients with low-risk NBL. Patients with stage 2b disease who are older or have diploid or unfavorable histology tumors fare less well. Future studies will seek to refine risk classification.

TPS10576Background: Sarcomas express pro-angiogenic factors that may represent therapeutic targets. Pazopanib, an oral multi-kinase inhibitor of VEGFR-(1-3), c-kit, and PDGFR, is FDA-approved for t...

10558Background: MYC drives polyamine expansion to support its oncogenic functions. Ornithine decarboxylase (Odc) is a direct MYC target that is rate-limiting for polyamine synthesis, and is itself...

10522Background: Ch14.18 (dinutuximab) increases event free and overall survival in patients with high-risk NB when given in a regimen with GM-CSF/IL-2. However, this therapy has significant toxici...

Purpose Iodine-131—metaiodobenzylguanidine (131I-MIBG) provides targeted radiotherapy with more than 30% response rate in refractory neuroblastoma, but activity infused is limited by radiation safety and hematologic toxicity. The goal was to determine the maximum-tolerated dose of 131I-MIBG in two consecutive infusions at a 2-week interval, supported by autologous stem-cell rescue (ASCR) 2 weeks after the second dose. Patients and Methods The 131I-MIBG dose was escalated using a 3 + 3 phase I trial design, with levels calculated by cumulative red marrow radiation index (RMI) from both infusions. Using dosimetry, the second infusion was adjusted to achieve the target RMI, except at level 4, where the second infusion was capped at 21 mCi/kg. Results Twenty-one patients were enrolled onto the study at levels 1 to 4, with 18 patients assessable for toxicity and 20 patients assessable for response. Cumulative 131I-MIBG given to achieve the target RMI ranged from 22 to 50 mCi/kg, with cumulative RMI of 3.2 to 8.92 Gy. No patient had a dose-limiting toxicity. Reversible grade 3 nonhematologic toxicity occurred in six patients at level 4, establishing the recommended cumulative dose as 36 mCi/kg. The median time to absolute neutrophil count more than 500/μL after ASCR was 13 days (4 to 27 days) and to platelet independence was 17 days (6 to 47 days). Responses included two partial responses, eight mixed responses, three stable disease, and seven progressive disease. Responses by semiquantitative MIBG score occurred in eight patients, soft tissue responses occurred in five of 11 patients, but bone marrow responses occurred in only two of 13 patients. Conclusion The lack of toxicity with this approach allowed dramatic dose intensification of 131I-MIBG, with minimal toxicity and promising activity.

Purpose To evaluate the effect of disease sites and prior therapy on response and toxicity after iodine-131-metaiodobenzylguanidine (131I-MIBG) treatment of patients with resistant neuroblastoma. Patients and Methods One hundred sixty-four patients with progressive, refractory or relapsed high-risk neuroblastoma, age 2 to 30 years, were treated in a limited institution phase II study. Patients with cryopreserved hematopoietic stem cells (n = 148) were treated with 18 mCi/kg of 131I-MIBG. Those without hematopoietic stem cells (n = 16) received 12 mCi/kg. Patients were stratified according to prior myeloablative therapy and whether they had measurable soft tissue involvement or only bone and/or bone marrow disease. Results Hematologic toxicity was common, with 33% of patients receiving autologous hematopoietic stem cell support. Nonhematologic grade 3 or 4 toxicity was rare, with 5% of patients experiencing hepatic, 3.6% pulmonary, 10.9% infectious toxicity, and 9.7% with febrile neutropenia. The overall complete plus partial response rate was 36%. The response rate was significantly higher for patients with disease limited either to bone and bone marrow, or to soft tissue (compared with patients with both) for patients with fewer than three prior treatment regimens and for patients older than 12 years. The event-free survival (EFS) and overall survival (OS) times were significantly longer for patients achieving response, for those older than 12 years and with fewer than three prior treatment regimens. The OS was 49% at 1 year and 29% at 2 years; EFS was 18% at 1 year. Conclusion The high response rate and low nonhematologic toxicity with 131I-MIBG suggest incorporation of this agent into initial multimodal therapy of neuroblastoma.

Purpose To determine the maximum-tolerated dose (MTD) and toxicity of iodine-131–metaiodobenzylguanidine (131I-MIBG) with carboplatin, etoposide, melphalan (CEM) and autologous stem-cell transplantation (ASCT) in refractory neuroblastoma. Patients and Methods Twenty-four children with primary refractory neuroblastoma and no prior ASCT were entered; 22 were assessable for toxicity and response. 131I-MIBG was administered on day −21, CEM was administered on days −7 to −4, and ASCT was performed on day 0, followed by 13-cis-retinoic acid. 131I-MIBG was escalated in groups of three to six patients, stratified by corrected glomerular filtration rate (GFR). Results The MTD for patients with normal GFR (≥ 100 mL/min/1.73 m2) was 131I-MIBG 12 mCi/kg, carboplatin 1,500 mg/m2, etoposide 1,200 mg/m2, and melphalan 210 mg/m2. In the low-GFR cohort, at the initial dose level using 12 mCi/kg of 131I-MIBG and reduced chemotherapy, one in six patients had dose limiting toxicity (DLT), including veno-occlusive disease (VOD). Three more patients in this group had grade 3 or 4 hepatotoxicity, and two had VOD, without meeting DLT criteria. There was only one death as a result of toxicity among all 24 patients. All assessable patients engrafted, with median time for neutrophils ≥ 500/μL of 10 days and median time for platelets ≥ 20,000/μL of 26 days. Six of 22 assessable patients had complete or partial response, and 15 patients had mixed response or stable disease. The estimated probability of event-free survival and survival from the day of MIBG infusion for all patients at 3 years was 0.31 ± 0.10 and 0.58 ± 0.10, respectively. Conclusion 131I-MIBG with myeloablative chemotherapy is feasible and effective for patients with neuroblastoma exhibiting de novo resistance to chemotherapy.

Purpose In the Children's Oncology Group, risk group assignment for neuroblastoma is critical for therapeutic decisions, and patients are stratified by International Neuroblastoma Staging System stage, MYCN status, ploidy, Shimada histopathology, and diagnosis age. Age less than 365 days has been associated with favorable outcome, but recent studies suggest that older age cutoff may improve prognostic precision. Methods To identify the optimal age cutoff, we retrospectively analyzed data from the Pediatric Oncology Group biology study 9047 and Children's Cancer Group studies 321p1-p4, 3881, 3891, and B973 on 3,666 patients (1986 to 2001) with documented ages and follow-up data. Twenty-seven separate analyses, one for each different age cutoff (adjusting for MYCN and stage), tested age influence on outcome. The cutoff that maximized outcome difference between younger and older patients was selected. Results Thirty-seven percent of patients were younger than 365 days, and 64% were ≥ 365 days old (4-year event-free survival [EFS] rate ± SE: 83% ± 1% [n = 1,339] and 45% ± 1% [n = 2,327], respectively; P < .0001). Graphical analyses revealed the continuous nature of the prognostic contribution of age to outcome. The optimal 460-day cutoff we selected maximized the outcome difference between younger and older patients. Forty-three percent were younger than 460 days, and 57% were ≥ 460 days old (4-year EFS rate ± SE: 82% ± 1% [n = 1,589] and 42% ± 1% [n = 2,077], respectively; P < .0001). Using a 460-day cutoff (assuming stage 4, MYCN-amplified patients remain high-risk), 5% of patients (365 to 460 days: 4-year EFS 92% ± 3%; n = 135) fell into a lower risk group. Conclusion The prognostic contribution of age to outcome is continuous in nature. Within clinically relevant risk stratification, statistical support exists for an age cutoff of 460 days.

Purpose The long-term survival of children between age 12 and 24 months with stage 4 neuroblastoma and nonamplified MYCN (MYCN-NA) has not been defined previously. Patients and Methods Survival for stage 4 MYCN-NA neuroblastoma patients enrolled onto Children's Cancer Group (CCG) protocols 321P2 (1986 to 1991) and 3891 (1991 to 1996) was analyzed. Treatment consisted of intensive alkylator-based induction chemotherapy with or without autologous bone marrow transplantation (ABMT) with or without 13 cis-retinoic acid. Survival was analyzed by age strata less than 12, 12 to 18, 18 to 24, and more than 24 months at diagnosis. Patients younger than 12 months were treated on the moderate-intensity CCG protocol 3881. Results Forty-three patients with stage 4 MYCN-NA disease enrolled onto CCG-321P2 (n = 17) or CCG-3891 (n = 26) were between 12 and 24 months of age at diagnosis. After a median follow-up of 94 months (range, 4 to 140 months), the 6-year event-free survival (EFS) for the 12- to 18-month age group was superior to that of the 18- to 24-month age group (74% ± 8% v 31% ± 12%; P = .008). The EFS for children older than 24 months with stage 4 MYCN-NA neuroblastoma was 23% ± 3%, and for children younger than 12 months was 92% ± 3%. Conclusion Children diagnosed with stage 4 MYCN-NA neuroblastoma in the second year of life form a transitional group between infants and older children in terms of prognosis. Patients between 12 and 18 months of age have significantly better long-term survival than that of older children treated with intensive chemotherapy with or without ABMT. These patients may not benefit from additional intensification of therapy beyond that provided in earlier clinical trials and may even maintain this high survival rate with less intensive therapy.

Abstract 72 Background: Neuroblastoma is the most common extracranial solid tumor of childhood, accounting for 10% of childhood cancers in high-income countries (HIC), with an unknown incidence in most low- and middle-income countries (LMIC). A multidisciplinary approach to the treatment of high-risk (HR) neuroblastoma consisting of a combination of chemotherapy, surgery, radiation and immunotherapy, has lead to improvements in survival in HICs, approaching 40-50%. Morocco, a LMIC, has historically had a survival rate for HR neuroblastoma of 10-15% at three years, with almost no survival at five years from diagnosis, due to a combination of limited availability of accurate diagnosis, staging, and risk stratification, as well as lack of some of the necessary treatment modalities and high abandonment rates. The International Society for Pediatric Oncology (SIOP) Pediatric Oncology in Developing Countries (PODC) committee developed adapted risk stratification and treatment guidelines using locally available chemotherapeutic agents in doses that limit toxicity. This approach was implemented at the four cancer treatment centers in Morocco beginning in January of 2012. This study aims to describe HR neuroblastoma patients presenting in Rabat, Morocco, in the last four years; test feasibility of an intensive induction regimen for HR neuroblastoma; and assess response to a novel intensive induction chemotherapy regimen adapted for a LMIC setting. Methods: This treatment protocol was first implemented in January of 2012 with approval of the local ethics board. Chart review was performed on patients with high risk neuroblastoma enrolled on the protocol at Pediatric Hematology and Oncology Center of Rabat between January of 2012 and September of 2015. Data regarding demographics, toxicity, and outcomes was collected and descriptive statistics were performed. Results: 40 patients were diagnosed with high risk neuroblastoma between January of 2012 and September of 2015 in Rabat. There were 14 females (35%) and 26 males (65%) with a median age of 40 months (age range 13m to 11y5m). With regards to diagnostic testing, 100% of patients underwent CT scan, while 47.5% (19/40) of patients underwent MIBG and 47.5% underwent bone scintigraphy. Only 9 patients (22.5%) had MYCN status determined, however MYCN testing increased over time during this protocol, as 53.8% (7/13) of patients diagnosed with HR neuroblastoma in the past year had MYCN testing performed. 82.5% of patients (33/40) completed all five cycles of induction chemotherapy, with 9/40 (22.5%) experiencing delays of 1 or 2 cycles (delay defined as >5 weeks) due to toxicity. Of the 33 patients who completed induction, 60.6% (20 patients) experienced a PR or VGPR, continuing on to local control with surgery or consolidation therapy. Only one patient was lost to follow up due to abandonment. Conclusion: Adapted risk stratification and treatment guidelines for LMICs allow for more accurate diagnosis and systematic treatment. Standardizing a protocol for high risk patients has led to more consistent MYCN evaluation, performed by immunohistochemistry, as well as the introduction of MIBG to the Rabat Children's Hospital. While this is a multi-center study (a known study obstacle in LMICs), this protocol has led to a decrease in the barriers to accurate diagnosis and optimal treatment. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST: No COIs from the authors.

Purpose: Metaiodobenzylguanidine (MIBG), specifically taken up in cells of sympathetic origin, provides a highly sensitive and specific indicator for the detection of metastases in neuroblastoma. The aim of this study was to correlate early response to therapy by MIBG scan, using a semiquantitative scoring method, with the end induction response and event-free survival (EFS) rate in stage IV neuroblastoma. Patients and Methods: Seventy-five children older than 1 year and with stage IV neuroblastoma had 123I-MIBG scans at diagnosis, after two and four cycles of induction therapy, and before autologous stem-cell transplantation. The scans were read by two independent observers (concordance > 95%) using a semiquantitative method. Absolute and relative (score divided by initial score) MIBG scores were then correlated with overall pretransplantation response, bone marrow response, and EFS. Results: The pretransplantation response rate was 81%, and the 3-year EFS rate was 32%, similar to a concomitant group of 375 stage IV patients. The median relative MIBG scores after two, four, and six cycles were 0.5, 0.24, and 0.12, respectively. The probability of having a complete response or very good partial response before transplantation was significantly higher if the relative score after two cycles was ≤ 0.5, or, if after four cycles, the relative score was ≤ 0.24. Patients with a relative score of ≤ 0.5 after two cycles or a score of ≤ 0.24 after four cycles had an improved EFS rate (P = .053 and .045, respectively). Conclusion: Semiquantitative MIBG score early in therapy provides valuable prognostic information for overall response and EFS, which may be useful in tailoring treatment.

PURPOSE: To determine the independent prognostic significance of 1p36 loss of heterozygosity (LOH) in a representative group of neuroblastoma patients. PATIENTS AND METHODS: Diagnostic tumor specimens from 238 patients registered onto the most recent Children’s Cancer Group phase III clinical trials were assayed for LOH with 13 microsatellite polymorphic markers spanning chromosome band 1p36. Allelic status at 1p36 was correlated with other prognostic variables and disease outcome. RESULTS: LOH at 1p36 was detected in 83 (35%) of 238 neuroblastomas. There was a correlation of 1p36 LOH with age at diagnosis greater than 1 year (P = .026), metastatic disease (P < .001), elevated serum ferritin level (P < .001), unfavorable histopathology (P < .001), and MYCN oncogene amplification (P < .001). LOH at 1p36 was associated with decreased event-free survival (EFS) and overall survival (OS) probabilities (P < .0001). For the 180 cases with single-copy MYCN, 1p36 LOH status was highly correlated with decreased EFS (P = .0002) but not OS (P = .1212). Entering 1p36 LOH into a multivariate regression model suggested a trend toward an independent association with decreased EFS (P = .0558) but not with decreased OS (P = .3687). Furthermore, allelic status at 1p36 was the only prognostic variable that was significantly associated with decreased EFS in low-risk neuroblastoma patients (P = .0148). CONCLUSION: LOH at 1p36 is independently associated with decreased EFS, but not OS, in neuroblastoma patients. Determination of 1p36 allelic status may be useful for predicting which neuroblastoma patients with otherwise favorable clinical and biologic features are more likely to have disease progression.

PURPOSE: A prospective Children’s Cancer Group study, CCG-3881, has been completed to determine if a more accurate prediction of prognosis by biologic features can identify subgroups of infants with stage IV neuroblastoma (NBL) who require differing intensities of treatment. PATIENTS AND METHODS: One hundred thirty-four infants were registered from June 1989 to August 1995, with a median follow-up of 47.1 months (range, 0 to 88 months). The biologic factors examined were tumor MYCN copy number, Shimada histopathologic classification, serum ferritin, and bone marrow immunocytology (sensitivity, one tumor cell per 105 bone marrow cells). Patients treated on CCG-3881 (n = 116) received four-drug chemotherapy for 9 months (cisplatin, cyclophosphamide, doxorubicin, and etoposide), with surgery and local radiation to residual disease. After January 1991, all subsequent infants with tumor MYCN amplification (n = 18) were transferred after one cycle of therapy to the high-risk CCG-3891 protocol (open January 1991 to April 1996) for more intensive treatment. RESULTS: The 3-year event-free survival (EFS) and overall survival (mean ± SD) for the 134 infants were 63% ± 5% and 71% ± 5%, respectively. Patients whose tumors were without MYCN amplification had a 93% ± 4% 3-year EFS, whereas those with amplified MYCN had a 10% ± 7% 3-year EFS (P < .0001). Each of the other biologic features studied had prognostic significance in univariate analysis but not after stratifying by MYCN copy number. CONCLUSION: Infants less than 1 year of age at diagnosis with stage IV NBL have a much improved outcome compared with children ≥ 1 year of age. Nonamplified MYCN tumors identify a group of infants with a 93% ± 4% EFS, whereas amplified MYCN copy number clearly identifies patients who are unlikely to survive despite intensive chemotherapy.

PURPOSE To identify a biologically favorable and unfavorable subset of patients with Evans stage III neuroblastoma and to determine whether treatment stratification would improve the event-free survival (EFS) for high-risk patients and maintain excellent EFS for the lower-risk patients. PATIENTS AND METHODS Risk stratification was performed by age, MYCN gene copy number, Shimada histopathologic classification, and serum ferritin level. Lower-risk patients were treated on the less intensive Children's Cancer Group (CCG)-3881, whereas high-risk patients were treated on CCG-3891, which included more intensive multimodality therapy and, in some cases, autologous bone marrow transplantation (ABMT). RESULTS Of 228 Evans stage III patients entered onto the study, 92% also met the definition of International Neuroblastoma Staging System (INSS) stage 3. One hundred forty-three patients met the lower-risk criteria, which included 89 patients less than 1 year of age and 54 patients 1 year of age or greater, and favorable biology, whereas 85 patients were 1 year of age or greater and biologically unfavorable. Biologically unfavorable patients 1 year of age or greater who underwent gross surgical resection had improved survival, whereas the outcome of infants or biologically favorable older patients did not change according to resection. The EFS rate at 4 years was 100% for the patients with favorable biology of any age, 90% for those less than 1 year of age but with at least one unfavorable characteristic, and 54% for Evans stage III patients 1 year of age or greater with unfavorable biology. Age, ferritin level, MYCN copy number, Shimada histopathology, primary site, and intraspinal extension were significant univariate prognostic factors for all patients, but only MYCN copy number and age were independent factors in multivariate analyses. CONCLUSION The excellent survival of the biologically favorable group and the historically improved EFS of the biologically unfavorable group suggest that biologic staging should be used to define the prognosis and treatment of stage III neuroblastoma.

PURPOSE The purpose of our investigation was to correlate the extent and degree of organ involvement at presentation of Langerhans' cell histiocytosis (LCH) with subsequent disease course, survival, and late sequelae. MATERIALS AND METHODS The medical records of 71 patients with a pathologic diagnosis of LCH, age 0 to 21 years, who presented between January 1, 1969 and June 30, 1994, were reviewed for organ involvement at diagnosis, treatment, disease course, and late sequelae. Supplementary data were obtained by mailed questionnaire. RESULTS The median follow-up time from diagnosis for all patients was 8.1 years. Involvement at diagnosis included nine patients with skin-only disease, 22 with monostotic disease, 12 with polyostotic disease, and 28 with multisystem presentation. Treatment was surgery only in 17 and chemotherapy and/or radiotherapy in 54 patients. Recurrences were seen in 35 patients, with the highest rate in the polyostotic group. Ten patients died: seven with the multisystem presentation, two with monostotic disease, and one with skin-only disease. Causes included progressive LCH (n = 6) and late sequelae of either treatment (n = 3) or disease (n = 1). Late sequelae were seen in 64% of 51 patients with more than 3 years of follow-up data. The most common were skeletal defects in 42%, dental problems in 30%, diabetes insipidus in 25%, growth failure in 20%, sex hormone deficiency in 16%, hypothyroidism in 14%, hearing loss in 16%, and other CNS dysfunction in 14%. The overall estimated survival rates at 5, 15, and 20 years are 88%, 88%, and 77%, with an estimated event-free survival rate of only 30% at 15 years. CONCLUSION Despite the favorable survival, more than half of LCH patients will have further dissemination of disease or late sequelae, including even some patients with single-system disease at diagnosis. Future treatment needs to be designed to prevent disease progression and late sequelae.

PURPOSE Treatment of neuroblastoma cell lines with 13-cis-retinoic acid (cis-RA) can cause sustained inhibition of proliferation. Since cis-RA has demonstrated clinical responses in neuroblastoma patients, it may be effective in preventing relapse after cytotoxic therapy. This phase I trial was designed to determine the maximal-tolerated dosage (MTD), toxicities, and pharmacokinetics of cis-RA administered on an intermittent schedule in children with neuroblastoma following bone marrow transplantation (BMT). PATIENTS AND METHODS Fifty-one assessable patients, 2 to 12 years of age, were treated with oral cis-RA administered in two equally divided doses daily for 2 weeks, followed by a 2-week rest period, for up to 12 courses. The dose was escalated from 100 to 200 mg/m2/d until dose-limiting toxicity (DLT) was observed. A single intrapatient dose escalation was permitted. RESULTS The MTD of cis-RA was 160 mg/m2/d. Dose-limiting toxicities in six of nine patients at 200 mg/m2/d included hypercalcemia (n = 3), rash (n = 2), and anemia/thrombocytopenia/emesis/rash (n = 1). All toxicities resolved after cis-RA was discontinued. Three complete responses were observed in marrow metastases. Serum levels of 7.4 +/- 3.0 mumol/L (peak) and 4.0 +/- 2.8 mumol/L (trough) at the MTD were maintained during 14 days of therapy. The DLT correlated with serum levels > or = 10 mumol/L. CONCLUSION The MTD of cis-RA given on this intermittent schedule was 160 mg/m2/d. Serum levels known to be effective against neuroblastoma in vitro were achieved at this dose. The DLT included hypercalcemia, and may be predicted by serum cis-RA levels. Monitoring of serum calcium and cis-RA levels is indicated in future trials.

10526Background: Prior investigations suggest that neuroblastomas (NBL) that do not accumulate MIBG (MIBG non-avid) may have more favorable features compared to MIBG avid tumors. We compared clinic...

10556Background: In phase I testing in 22 patients with neuroblastoma, the maximum tolerated dose of alisertib tablets with irinotecan/temozolomide was 60 mg/m2/dose. This combination showed signif...

PURPOSE The goal of this investigation was to determine if comparing sites of neuroblastoma at relapse after myeloablative chemoradiotherapy and purged autologous bone marrow transplantation (ABMT) with sites of disease at diagnosis and before ABMT could provide insight to the reasons for treatment failure. PATIENTS AND METHODS Ninety-nine patients with high-risk neuroblastoma underwent ABMT after induction chemotherapy, surgery +/- local radiation (RT) and then myeloablative therapy with teniposide (or etoposide), melphalan, doxorubicin, cisplatin, and total-body irradiation (TBI). RESULTS Forty-one of 84 assessable patients (15 toxic deaths) developed progressive disease 1 to 44 months after ABMT. The overall probability of relapse 36 months after ABMT was 49%. Tumor recurred in primary (n = 22), bone (n = 20), bone marrow (n = 18), lung (n = 3), and other sites (n = 9). Eight patients relapsed in the primary site alone, 14 in primary and distant sites, and 19 in distant sites only. Of 41 patients with progressive disease, 33 have died, with a median interval from relapse to death of 4 months. Both bone and bone marrow involvement at diagnosis correlated with specific relapse in that site (P < .05). Bone marrow tumor content at harvest greater than 0.1% also correlated with bone marrow relapse (P = .001). There was an association between incomplete resection of the primary tumor at diagnosis and relapse in that site (P = .06). CONCLUSION Neuroblastoma normally recurs in multiple sites after ABMT, particularly in areas of previous disease. More intensive treatment to known areas of disease (aggressive early surgery, effective myeloablative consolidation therapy) and post-ABMT therapy for minimal residual disease should be studied for their potential to decrease the frequency of relapse.

PURPOSE This trial was undertaken to determine if a continuous infusion format with increased dose-intensity had antitumor activity with tolerable toxicity in patients with advanced neuroblastoma. PATIENTS AND METHODS Forty heavily pretreated patients with refractory or progressive neuroblastoma received continuous infusion doxorubicin, cisplatin, and etoposide along with bolus ifosfamide in a dose-escalation format. A total of 79 courses of chemotherapy were administered at five different dose levels. RESULTS Fifteen of 35 assessable patients (43%) achieved either a partial response (PR) or complete response (CR), including five patients with a CR, three with a very good PR (VGPR), and seven with a PR. Hematologic toxicity was severe, but reversible, and other toxicities, although significant, were tolerable and much less than that accepted in a bone marrow transplantation (BMT) setting. CONCLUSION This investigation illustrates that response is possible even in an extremely poor-prognosis group of patients, and it suggests that such a regimen may be effective if given before disease progression occurs.

10043 Background: Vesicular monoamine transporters 1 and 2 (VMAT1 and VMAT2) are thought to mediate MIBG uptake in adult neuroendocrine tumors. VMAT expression has not been comprehensively investig...

10033 Background: 131I-metaiodobenzylguanidine (MIBG) is a targeted radiopharmaceutical active in neuroblastoma. A previous study demonstrated that MIBG (18 mCi/kg) could be combined with vincristi...

10565 Background: Extraskeletal osteosarcoma (ESOS) is a rare subtype of osteosarcoma. We investigated patient characteristics, overall survival for ESOS as compared to skeletal osteosarcoma, and p...

10030 Background: Current methods for stratifying NB patients (pts) at diagnosis to INRG risk/pre-treatment groups are based on prognostic clinical, genomic, and histologic factors [Cohn et al, JCO...

10015 Background: Patients with metastatic NB typically have a poor prognosis; however case series have suggested that those with 4N disease may have improved outcomes. Methods: Retrospective analysis of data from INRG database for patients diagnosed 1990–2002. 4N patients (INSS stage 4 disease confined to distant lymph nodes) were compared to the balance of stage 4 patients (‘non-4N’), excluding those with missing metastatic site data. 5-yr estimates of overall (OS) and event-free survival (EFS) were calculated ± standard error (Kaplan-Meier method). Patient characteristics were compared by Mann-Whitney or Fisher’s exact/Chi-square tests. Results: 2,250 INSS stage 4 patients with complete data were identified, of whom 146 (6%) had 4N disease. For 4N patients, EFS and OS (5-yr: 77% ± 4%, 85% ± 3%), were significantly better than EFS and OS (5-yr: 35% ± 1%, 42% ± 1%) for non-4N stage 4 patients (p

10060 Background: Neuroblastoma (NB) is the most common solid extra-cranial tumor of childhood. 131I-mIBG is a targeted radiopharmaceutical for patients with advanced NB and is one of the most active agents in this treatment resistant population. To date, no clinically relevant biomarkers of response or toxicity have been reported in patients treated with 131I-mIBG. Methods: Patients with relapsed or refractory NB who received 131I-mIBG at UCSF were eligible to participate in this prospective correlative study. Blood samples were obtained at baseline and 72 hours after 131I-mIBG infusion. We quantified a panel of biomarkers shown to be effected in patients receiving other forms of radiation, including: serum amylase; plasma Flt-3 ligand; plasma monocyte colony stimulating factor (MCSF); and CDKN1A mRNA in mononuclear cells. Extent of modulation of each marker was evaluated using paired t-tests at hour 0 and 72. We assessed potential differential modulation between groups based on response (PR/CR vs SD/PD), toxicity (grade 3 non-hematologic toxicity; grade 4 neutropenia or thrombocytopenia) or administration of combination therapy (131I-mIBG alone vs in combination with vincristine/irinotecan or vorinostat) using unpaired t-tests. Results: 26 patients (21 male; median age 7 years) participated and received a median 131I-mIBG dose of 18 mCi/kg. 16 patients received 131I-mIBG in combination. We observed robust modulation of amylase (median fold increase from baseline 3.1; p 131I-mIBG had more robust modulation of Flt-3 ligand (mean difference 296 pg/mL; p=0.02) compared to single agent 131I-mIBG. No correlations with clinical response or toxicity were found. Conclusions: Amylase, Flt-3 ligand, and CDKN1A mRNA all show robust modulation after 131I-mIBG treatment. Patients receiving 131I-mIBG in combination demonstrated the largest changes in plasma Flt-3 ligand. In this initial analysis, no associations were found between response or toxicity and the proposed biomarkers.

10039 Background: Accurate quantification of tumor burden in NBL patients is needed to define homogenous populations for therapy and establish response criteria that predict outcome. The 5-gene TLDA assay was developed for quantification of NBL cells in bone marrow (BM) and blood (BLD). Methods: Expression of CHGA, DCX, DDC, PHOX2B, and TH (NBL genes) was quantified with TLDA and reported as the geometric mean cycle threshold for the 5 genes (DGS=detection gene score; inversely related to tumor content, 40=negative). Sixty-three patients with recurrent/refractory NBL had TLDA performed on 107 BM and 99 BLD samples (66 paired) at 140 time points. Based on central review of reports, tumor longest diameter (LD) on CT/MRI (n=118), and number of 123I-MIBG avid sites (n=120) were recorded. Percentage of tumor cells in BM was from institutional reports of bilateral BM aspirates/biopsies (n=109). Overall response was assessed per NANT Response Criteria. Spearman rank correlation was performed. Results:TLDA detected tumor cells in 62/99(63%) BLD (average DGS=37.45) and 91/107(85%) BM samples (average DGS=33.42). 39/91(42%) with positive BM TLDA were negative by morphology. BLD and BM TLDA were correlated r = 0.6540, p< 0.0001 with stronger correlation with lower BM DGS scores. The BM and BLD DGS correlated with % BM involvement (BM r= -0.63, p

23 Background: Targeting the IGF-1R pathway has shown preclinical and clinical evidence of activity in EWS. Markers predictive of response to IGF-1R inhibition are required. The aims of the current study were to quantify surface IGF-1R expression and intracellular signaling proteins by flow cytometry. Methods: Flow cytometry for CD99 and CD45 was used to detect bone marrow micrometastatic tumor cells as CD99+CD45- events in patients with localized EWS. Surface IGF-1R was quantified on tumor cells and normal marrow cells using a commercially available antibody. RD-ES EWS cells were spiked into control PBMCs and starved for 1 hour. Cells were then treated with saline control, rapamycin 10 ng/mL, ADW742 5 uM (small molecule IGF-1R inhibitor), or alpha-IR3 0.5 ug/mL (anti-IGF-1R antibody) and levels of pS6, pAKT, and pERK quantified by phospho-flow cytometry 60 minutes later. All results were expressed as the mean fluorescent intensity (MFI) of staining using arbitrary units. Results: We detected bone marrow micrometastatic tumor cells in marrow samples from 16 patients with EWS. We observed heterogeneous levels of IGF-1R tumor cell surface expression between patients (range of IGF-1R MFI = 0 – 3355). IGF-1R levels were higher in CD99+CD45- tumor cells compared to normal marrow cells (mean MFI 840 for CD99+CD45- tumor cells vs.190 for normal marrow cells; p = 0.005). In RD-ES cells spiked into PBMCs, treatment with rapamycin resulted in 1.32 fold increase in pAKT MFI compared to saline control. Treatment with ADW742 or alpha-IR3 did not impact pAKT MFI. Treatment with rapamycin resulted in a 0.52 fold decrease and a 1.20 fold increase in pS6 and pERK, respectively. Treatment with ADW742 or alpha-IR3 each resulted in similar decreases in both pS6 (0.75-0.87 fold) and pERK (0.67-0.82 fold). In PBMCs, modest changes in pS6 in rapamycin treated cells were observed, without changes in pAKT or pERK. Neither ADW742 nor alpha-IR3 modulated pS6, pAKT, or pERK signaling in PBMCs. Conclusions: Flow cytometry detects a range of surface IGF-1R expression on bone marrow micrometastatic EWS cells. Phospho-flow cytometry detects modulation of pAKT, pS6, and pERK in EWS cells treated with IGF-1R or mTOR inhibitors.

9533 Background: Patients with non-high-risk neuroblastoma (low- and intermediate-risk) generally have an excellent event free (EFS) and overall (OS) survival with current therapy. However, within this heterogeneous patient population, there are patients that may benefit from further therapy reduction and patients that may benefit from augmented therapy. Methods: Survival tree regression analysis was performed in patients enrolled on P9641 and A3961 with OS the primary endpoint. Univariate Cox proportional hazards models determined statistically significant prognostic factors. Secondary analysis of cases with MYCN non-amplified, non-high-risk neuroblastoma classified patients by age, INSS stage, Shimada histology and genomic features to determine 5-year EFS and OS. Favorable genomics were defined as hyperdiploid tumors without 1p or 11q loss of heterozygosity (LOH). Those with LOH at 1p or 11q or with a diploid DNA index were considered unfavorable. Patients without genomic data were excluded. Results: In the survival tree analysis, ploidy and genomic features were found to be statistically significant. In the secondary analysis, patients

9559 Background: Metastatic neuroblastoma continues to carry a dismal prognosis. Radiation is an important part of the treatment for these patients and PARP inhibitors have been shown to radio-sensitize cancer cells. We hypothesize that the PARP inhibitor MK-4827 will radio-sensitize neuroblastoma cells and lead to a survival benefit in an in vivo model of metastatic neuroblastoma. Methods: Clonogenic survival assays were performed in four human neuroblastoma cell lines [Kelly, NB1691, SY5Y, Tet21(Myc-N expressed) and Tet21 (Myc-N suppressed)] with MK-4827 as a single agent and in combination with radiation. PARP activity in the presence of MK-4827 was assessed at varying concentrations and time points by a PARP activity assay (Trevigen, Inc.) as well as by western blot analysis of Poly-ADP-ribose. Phosphorylated H2AX, a marker of DNA strand breaks, was determined by FACS. In vivo activity of MK-4827 as a single agent and in combination with radiation was assessed in a murine metastatic neuroblastoma mode...

9513 Background: 131I-metaiodobenzylguanidine (MIBG) is a targeted radiopharmaceutical with activity in neuroblastoma. Irinotecan is a radiosensitizer with activity in neuroblastoma. This phase I s...

9512 Background: 131I-MIBG is specifically taken up in neuroblastoma, with a response rate >30% in relapsed disease. The presence of non-radioactive “carrier” MIBG molecules increases risk of cardiovascular side effects and can inhibit tumor uptake of 131I-MIBG, reducing tumor radiation. Our primary aim was to establish the maximum tolerated dose (MTD) of no-carrier-added MIBG with autologous hematopoietic stem cell (AHSC) support. Methods: Eligible patients were age 1-30 years with resistant neuroblastoma, MIBG avid tumors, and cryopreserved AHSC. The nca-MIBG therapeutic dose was escalated in 3 mCi/kg increments from 12-21 mCi/kg using a 3+3 design. The administered dose was limited by gamma image-derived pretreatment organ dosimetry and normal tissue tolerance estimates of Emami (1991). AHSC were infused 14 days post therapy. Response and toxicity were evaluated day 60. Dose limiting toxicity (DLT) was failure to engraft or grade 3 or 4 non-hematologic toxicity except grade 3 pre-defined exclusions. Re...

9516 Background: Over the past 2 decades, radiolabeled metaiodobenzylguanidine (mIBG) has proven to be a highly sensitive and specific marker for the detection of primary and metastatic neuroblasto...

9532 Background: TrkB acts as an oncogenic kinase in a subset of human NB. Lestaurtinib, a multi-kinase inhibitor with potent activity against Trk kinases, has demonstrated anti-tumor activity in p...

9518 Background: In NB, most patients (pts) who relapse eventually die. Prognostic factors are used to stratify treatment at diagnosis, but typically not at the time of relapse. Our goals were to d...

10022 Background: ZA, a bisphosphonate, delays progression of bone metastases in adult malignancies. Bone metastases occur in 60% of children with advanced NB. A xenograft mouse model demonstrated ZA with low dose chemotherapy delayed progression of NB bone lesions prompting a phase I trial of ZA. Methods: Three dose levels of intravenous ZA (2, 3, or 4 mg/m2) administered every 28 days were evaluated with continuous daily oral CTX (25 mg/m2/day) in patients with recurrent/refractory NB and bone metastases. The primary objective was to determine a recommended dose of ZA for future trials. PKs with the first dose of ZA and serial serum IL-6 levels (stimulator of osteoclast activity) were evaluated. Results: 21 patients (14 male), median age 7.9 years (0.8–26.6 years), were enrolled at ZA dose levels 2 mg/m2 (n=4), 3 mg/m2 (n=3), and 4 mg/m2 (n=13). Seventy-five cycles were administered with median of 1 cycle per patient (range 1–18). Two DLT (Gr 3 hypophosphatemia) occurred at 4 mg/m2 ZA. Other Gr 3 or 4 toxicities included hypocalcemia (n = 2), elevated transaminases (n = 2), neutropenia (n = 2), anemia (n = 1), lymphopenia (n = 1), and hypokalemia (n = 1). A fracture related to osteosclerosis occurred after 18 cycles. There were no renal or dental complications. There was 1 complete response, 9 stable disease median 4.5 cycles (range 3–18), and 10 progressions (central review pending). At 4 mg/m2, mean serum IL-6 levels decreased from 3.9 pg/mL (95% CI: 2.8–5.2 pg/mL) (n = 11) to 2.9 pg/mL (95% CI: 1.8–4.4 pg/mL) after cycle 1 (n = 8). ZA PK were similar to adults. Conclusions: ZA with low dose CTX is well tolerated with evidence of clinical benefit in children with recurrent/refractory NB. The recommended ZA dose for future study is 4 mg/m2 every 28 days. No significant financial relationships to disclose.