Post-relapse therapy remains critical for survival in children with acute myeloid leukemia (AML). We evaluated survival, response and prognostic variables following relapse in independent cooperative group studies conducted by COG and the population-based AML-BFM study group. BFM included 197 patients who relapsed after closure of the last I-BFM relapse trial until 2017, while COG included 852 patients who relapsed on the last Phase 3 trials (AAML0531, AAML1031). Overall survival at 5 years (OS) was 42 ± 4% (BFM) and 35 ± 2% (COG). Initial high-risk features (BFM 32 ± 6%, COG 26 ± 4%) and short time to relapse (BFM 29 ± 4%, COG 25 ± 2%) predicted diminished survival. In the BFM dataset, there was no difference in OS for patients who had a complete remission with full hematopoietic recovery (CR) following post-relapse re-induction compared to those with partial neutrophil and platelet recovery (CRp and CRi) only (52 ± 7% vs. 63 ± 10%, p = 0.39). Among 90 patients alive at last follow-up, 87 had received a post-relapse hematopoietic stem cell transplant (HSCT). OS for patients with post-relapse HSCT was 54 ± 4%. In conclusion, initial high-risk features and early relapse remain prognostic. Response assessment with full hematopoietic recovery following initial relapse therapy does not predict survival. These data indicate the need for post-relapse risk stratification in future studies of relapse therapies.

Successful management of relapse is critical to improve outcomes of children with acute myeloid leukemia (AML). We evaluated response, survival and prognostic factors after a second relapse of AML. Among 1222 pediatric patients of the population-based AML-Berlin–Frankfurt–Munster (BFM) study group (2004 until 2017), 73 patients met the quality parameters for inclusion in this study. Central review of source documentation warranted the accuracy of reported data. Treatment approaches included palliation in 17 patients (23%), intensive therapy with curative intent (n = 46, 63%) and other regimens (n = 10). Twenty-five patients (35%) received hematopoietic stem cell transplantation (HSCT), 21 of whom (88%) had a prior HSCT. Survival was poor, with a five-year probability of overall survival (pOS) of 15 ± 4% and 31 ± 9% following HSCT (n = 25). Early second relapse (within one year after first relapse) was associated with dismal outcome (pOS 2 ± 2%, n = 44 vs. 33 ± 9%, n = 29; p < 0.0001). A third complete remission (CR) is required for survival: 31% (n = 14) of patients with intensive treatment achieved a third CR with a pOS of 36 ± 13%, while 28 patients (62%) were non-responders (pOS 7 ± 5%). In conclusion, survival is poor but possible, particularly after a late second relapse and an intensive chemotherapy followed by HSCT. This analysis provides a baseline for future treatment planning.

BACKGROUND: A risk-adapted approach incorporating genetic data, complemented by response evaluation may help to identify patients with high-risk disease (HR) who could benefit from hematopoietic stem cell transplantation (HSCT) at initial disease. Several international study groups currently recommend HSCT in pediatric HR AML. However, the impact of a risk-adapted treatment strategy is unknown. Here, we present results of our first treatment period with a risk-adapted indication for HSCT in the AML-BFM study group. PATIENTS AND METHOD: From 2012 until 2017 a total of 324 children &lt;18 years of the AML-BFM registry 2012 (hereafter named R12; Germany, Austria and Czech Republic) with de novo AML were included. Down syndrome or secondary leukemia, FAB M3, an accompanying disease or pre-treatment &gt;14 days were excluded. Patients or guardians provided written informed consent. Treatment guidelines were recommended but were not obligatory: Chemotherapy followed the best arm of study AML-BFM 2004, but patients were stratified according to new genetic and response-adapted (≥10% leukemic blasts after induction 1 or ≥5% after induction 2) risk criteria with the indication of HSCT in HR patients. We used AML-BFM 2004 (hereafter called S04) as historical comparison. The analysis was performed following the Declaration of Helsinki. Five-year estimates of overall survival (pOS) and event-free survival (pEFS) were calculated using SPSS (version 25). EFS is defined as the time from diagnosis to the first event (relapse, death, failure to achieve remission or secondary malignancy) or until last follow-up. Data were frozen on May 1st, 2019. RESULTS: We sought to systematically decipher the impact of a risk-adapted approach in pediatric AML. The total cohort showed a pEFS of 58±5% and pOS of 78±3% (vs S04 52±2%, p=0.014 and 70±2%, p=0.059) and significantly increased rates of HSCT (S04 vs R12: p&lt;0.001). Importantly, the SR group did not change between periods. The increase in survival was rather explained by improvements in patients with genetically defined HR AML resulting in a survival similar to IR AML (pEFS IR vs HR: p=0.684; pOS: p=0.861). Next, we compared outcome of a previously well-defined subgroup with rare very high-risk criteria (VHR). The risk-adapted therapy resulted in a significantly higher pEFS (S04 vs R12: 33±5% vs 48±11; p=0.017) and higher rates of HSCT (37% vs 78%, p&lt;0.001). Nevertheless, salvage treatment was equally efficient in both periods, resulting in a pOS of 56±6% vs 72±7% (p=0.202). To evaluate the effects of inclusion of response to mere genotype-driven stratification we reanalyzed all R12 patients retrospectively according to their genetic risk only (see table 1). Response-guided re-stratification led to major shifts of patients to higher risk groups. Importantly, despite the fact that the registry made only recommendations according to the new risk stratification, compliance with guidelines including HSCT indication was very high (n=319; 98%). Discrepancies were as follows: SR have been treated with a higher intensity (i.e. more chemotherapy and/or HSCT; n=2); HR AML treated as IR (n=2), IR AML received HR treatment including HSCT (n=2). Seventy-five percent of HR AML have been transplanted. Discrepancies are explainable by early relapses or death before HSCT. To validate the response-guided re-stratification more specifically, we performed a subgroup analysis of HR AML: The survival was similar in re-stratified IR patients and genetic HR patients with poor response (p=0.656) but was higher in genetic HR patients with good response (p=0.01), indicating an effective selection of re-stratified patients with IR. CONCLUSION: This analysis indicates the benefit of risk-adapted indications for HSCT in pediatric AML: After a long period with a stable pEFS (Rasche et al. Leukemia 2018) the current cohort now demonstrates a significant improvement. The efficacy of the risk-adapted approach is reflected by remarkable survival rates for patients with HR AML. At the same time, it seems not to impair the ongoing improvement of salvage therapy. However, for patients with poorly responding IR AML the outcome is dismal despite HSCT and they require alternative treatment approaches. Further studies are also needed to detect genetically defined HR patients who may not need HSCT, but also to develop efficient re-stratification approaches to enhance the survival in SR patients. Table 1. Disclosures Reinhardt: Novartis: Other: Participation in Advisory Boards; Roche: Research Funding; CSL Behring: Research Funding; Jazz: Other: Participation in Advisory Boards, Research Funding.

BACKGROUND: Children with high risk acute myeloid leukemia (AML) still experience consistently high rates of relapse. Survival after first relapse increased from 21% between 1987 and 1997 up to 39% in recent studies. However, since 2009, there have been no publications on subsequent large pediatric AML relapse trials. As the indications for HSCT during first-line treatment have been extended since then, the current survival of these patients at relapse remains unclear. Herein, we report outcome results from the BFM and COG study group, which represents the largest available dataset analyzed for post-relapse survival. PATIENTS AND METHODS: Pediatric patients with first relapse of AML (no Down syndrome, secondary leukemia or FAB M3) have been analyzed from two large study groups with patients from the United States, Canada, Australia, New Zealand, Germany, Austria, Czech Republic and Switzerland. Out of 1222 patients in the BFM cohort (AML-BFM study 2004, registry 2012 and study 2012), 350 experienced at least one relapse and 197 of those had a first relapse after closure of the last I-BFM relapse trial (04/2009 through 2017). Within the Children's Oncology Group (COG) Phase 3 trials (AAML0531 and AAML1031, n=2119) 852 pediatric patients suffered a relapse. Five-year probability of overall survival (pOS) and event-free survival (pEFS) were calculated according to Kaplan-Meier. EFS was calculated for the BFM cohort as time from relapse to the next event (second relapse, death, failure to achieve a second remission or secondary malignancy) or until last follow-up, while OS reflects the time from relapse until death or last follow-up. The Cox proportional hazards model was used for multivariate analysis of outcomes. Living patients were censored at last follow-up with a median follow-up after relapse of 4·2 years (BFM) and 4·8 years (COG). Data have been frozen at 03/27/2020 (BFM) and 03/31/2020 (COG). RESULTS: In the 197 patients with relapse after closure of the last BFM relapse trial (04/2009 through 2017) the pOS at 5 years was 42±4% (BFM). The 5-year pOS in patients relapsing after COG trials 2006-2018 was 35±2% (n=852). Patients experiencing a relapse between 2014 to 2017 had a pOS of 49±6% (BFM, n=78) and 40±3% (COG, n=333). Risk classification at initial diagnosis and a short time from diagnosis to relapse predicted a diminished survival probability in both cohorts (see Table 1). However, the absence of full hematopoietic regeneration of the bone marrow after re-induction did not predict survival: Within the BFM dataset, a subgroup analysis in all patients receiving DNX-FLA (n=156) have been performed. Initial characteristics are comparable to the total cohort. Among these patients 147 were evaluable for response (7 excluded due to early death before evaluation, 2 for insufficient data). Eighty-nine (57%) achieved a CR (n=69) or CRp (n=20) and 52 (33%) no response. Overall survival was superior for patients with a CR/CRp (54±6% (CR/CRp) vs. 32±7% (No CR/CRp); p=0·0064), but long-term survival was still possible even with a poor re-induction response. Patients with a CRp had a comparable survival to those with a CR after a second re-induction (pOS 60±11% (CRp) vs. pOS 52±7% (CR); p=0·57). Patients with &gt;5% leukemic blasts (n=32) had the lowest survival (pOS 27±9%). The 5-year pEFS for this cohort was 29±4% (pEFS 50±6% (CR) vs. pEFS 50±11% (CRp)). The analysis of post-relapse treatment showed that the vast majority of patients who survive had a HSCT following relapse. By landmark analysis, survival was significantly higher in patients with subsequent HSCT compared to that of non-transplanted patients (BFM: pOS 53±4%, n=154 vs. pOS 5±5%, n=21; p(Mantel-Byar)=0·0002). CONCLUSION: This is the largest report to date on post relapse survival in children with AML. Our analysis confirmed previously described risk factors for poor survival while also highlighting new findings contrary to established standards. Strikingly, the absence of full hematopoietic regeneration of the bone marrow after re-induction did not predict survival at first relapse, thereby questioning the current value of the established International Working Group Criteria published by Cheson et al for response-evaluation in pediatric AML. As the international pediatric AML community embarks on collaborative efforts to evaluate new therapies in children with relapsed AML, a comprehensive review of post relapse survival is critical. Disclosures Bourquin: Servier: Other: Travel Support. Reinhardt:Novartis: Membership on an entity's Board of Directors or advisory committees; CLS Behring: Research Funding; bluebird bio: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding.

BACKGROUND: Children with acute myeloid leukemia (AML) still experience high rates of relapse. Facing increasing survival after first relapse, it appears critically important to examine the consequences of a second relapse in more detail. However, there is no population-based data available in pediatric AML and no reliable statement about general survival, patients' characteristics or treatment approaches can be made. Herein, we report current survival results following second relapse from the BFM study group, which represents to our knowledge the largest available dataset for this subgroup of patients. PATIENTS AND METHODS: Between 2004 and 2017, 1222 pediatric patients (age less than 18 years at initial AML diagnosis) with AML (no secondary leukemia, no Down syndrome, no acute promyelocytic leukemia) were registered in the population-based AML-BFM registry and trials in Germany, Austria, Czech Republic and Switzerland providing a longitudinal data collection with treatment, response rates, survival and disease characteristics. Central review of source documentation confirmed accuracy and consistency of all reported data. Only patients with a documented date of first and second complete remission (CR1 and CR2) and a diagnosed second relapse until the age of 21 are included. Statistical analyses were performed with SAS version 9.4 (SAS Institute). All living patients were censored at the time of last follow-up, but no patient later than 03/27/2020. The median follow-up after diagnosis of second relapse was 6,5 years. RESULTS: In all registered patients, 7% (83 out of 1222) met the strict criteria for a second relapse. For further analyses patients with a date of second relapse diagnosis after 12/31/2017 (n=6), two patients with isolated CNS relapse, who did not receive systemic chemotherapy, one patient with an underlying syndrome and one patient with insufficient data have been excluded. The median age at second relapse was 9,2 years. Sixty percent (n=44) of the patients, who experienced a second relapse, did so within a year after first relapse diagnosis. Eighty percent (n=58) and 7% (n=5) had one or two previous HSCTs, respectively. Eighty-nine percent (n=65) received an anthracycline-containing re-induction (DNX-FLA) followed by FLA or another intensive treatment regimen before at first relapse. In contrast to the standardized treatment approaches in first relapse, patients with second relapse received a wide range of therapy. Forty-six patients (63%) have been treated with an intensive cytotoxic treatment (Table 1). Seventeen patients (23%) got palliation only. Among the 25 patients (35%) who proceeded to HSCT, 21 patients (88%) had a prior HSCT. Survival after second relapse was very poor with a 5-year pOS of 15±4% (see Figure 1A) and a considerable cumulative incidence of early deaths (until day 56 after diagnosis: CI ED 19±5%). Prognosis did not improve over time with consistent overall survival rates until 2017 (see Figure 1B). Causes of death include disease progression (n= 51, 70% of all patients), a combined SCT-related and disease-related cause (n=3, 5%) and SCT-related complications (n=4, 4%) or treatment-associated toxicity (n=5, 7%). The 5-year pOS was 2±2% for patients with an early second relapse vs. 33±9% for those experiencing a second relapse more than a year after the first. (p&lt;0.0001; Figure 1C). The timing of a first relapse and age did not show any influence on overall survival. The best response achieved in the respective bone marrow sample after up to two cycles with cytotoxic treatment have been categorized. Out of 45 patients with conclusive data 31.1% (n=14) achieved a third CR with a pOS of 36±13%, while 62.2% of the patients showed a nonresponse to the treatment (n=28, pOS 7±5%) or no evidence of leukemia, but also no peripheral regeneration (6.7%, n=3, pOS 0±0%). CONCLUSION: These data provide new insights into treatment strategies, prognostic factors and outcome of children with second relapse in pediatric AML. As expected, survival is poor, but nonetheless possible in this increasingly relevant subgroup of patients. These data may serve as foundation for urgently needed international clinical trials for relapsed and refractory AML in children. Disclosures Bourquin: Servier: Other: Travel Support. Reinhardt:CLS Behring: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; bluebird bio: Membership on an entity's Board of Directors or advisory committees.