Clinical significance of minimal residual disease in childhood acute lymphoblastic leukemia after first relapse

Clinical characteristics and prognosis of pediatric patients with B cell acute lymphoblastic leukemia relapse

The aim of the present study was to investigate the clinical characteristics and prognosis of pediatric patients with B cell acute lymphoblastic leukemia (B-ALL) relapse. A total of 390 pediatric patients diagnosed as B-ALL and receiving regular chemotherapy in Jining First People's Hospital from August 2010 to May 2016 were selected. The clinical characteristics, therapeutic response and prognosis were compared between the two groups. There were significant differences in the comparisons of age, leukocyte count in the initial diagnosis and glucocorticoid sensitive test between B-cell ALL (B-ALL) relapse group and non-relapse group; the minimal residual disease (MRD) levels of pediatric patients in the two groups at 33 days and 12 weeks were significantly different. The 3-year event-free survival (EFS) rates of pediatric patients with early, medium and late B-ALL relapse were 12.5±7.8%, 33.1±9.8% and 63.6±6.1%, respectively, and the prognosis of late relapse was significantly better than that of early relapse (P<0.001). The 3-year EFS rates of pediatric patients with bone marrow relapse in standard risk group, intermediate risk group and high risk group were 29.1±6.9, 31.3±6.5 and 28.3±6.3%, respectively; there were no statistically significant differences (P=0.387, P>0.05). Pediatric patients with B-ALL relapse are characterized by higher onset age (≥10 years old), high leukocyte count and hormone insensitivity. Dynamic monitoring of MRD level in B-ALL pediatric patients can predict the relapse.

Genomic and transcriptional landscape of P2RY8-CRLF2-positive childhood acute lymphoblastic leukemia

Children with P2RY8-CRLF2-positive acute lymphoblastic leukemia have an increased relapse risk. Their mutational and transcriptional landscape, as well as the respective patterns at relapse remain largely elusive. We, therefore, performed an integrated analysis of whole-exome and RNA sequencing in 41 major clone fusion-positive cases including 19 matched diagnosis/relapse pairs. We detected a variety of frequently subclonal and highly instable JAK/STAT but also RTK/Ras pathway-activating mutations in 76% of cases at diagnosis and virtually all relapses. Unlike P2RY8-CRLF2 that was lost in 32% of relapses, all other genomic alterations affecting lymphoid development (58%) and cell cycle (39%) remained stable. Only IKZF1 alterations predominated in relapsing cases (P=0.001) and increased from initially 36 to 58% in matched cases. IKZF1's critical role is further corroborated by its specific transcriptional signature comprising stem cell features with signs of impaired lymphoid differentiation, enhanced focal adhesion, activated hypoxia pathway, deregulated cell cycle and increased drug resistance. Our findings support the notion that P2RY8-CRLF2 is dispensable for relapse development and instead highlight the prominent rank of IKZF1 for relapse development by mediating self-renewal and homing to the bone marrow niche. Consequently, reverting aberrant IKAROS signaling or its disparate programs emerges as an attractive potential treatment option in these leukemias.

Genetic alterations in glucocorticoid signaling pathway components are associated with adverse prognosis in children with relapsed ETV6/RUNX1-positive acute lymphoblastic leukemia

The ETV6/RUNX1 gene fusion defines the largest genetic subgroup of childhood ALL with overall rapid treatment response. However, up to 15% of cases relapse. Because an impaired glucocorticoid pathway is implicated in disease recurrence we studied the impact of genetic alterations by SNP array analysis in 31 relapsed cases. In 58% of samples, we found deletions in various glucocorticoid signaling pathway-associated genes, but only NR3C1 and ETV6 deletions prevailed in minimal residual disease poor responding and subsequently relapsing cases (p<0.05). To prove the necessity of a functional glucocorticoid receptor, we reconstituted wild-type NR3C1 expression in mutant, glucocorticoid-resistant REH cells and studied the glucocorticoid response in vitro and in a xenograft mouse model. While these results prove that glucocorticoid receptor defects are crucial for glucocorticoid resistance in an experimental setting, they do not address the essential clinical situation where glucocorticoid resistance at relapse is rather part of a global drug resistance.

Minimal residual disease analysis by eight-color flow cytometry in relapsed childhood acute lymphoblastic leukemia

Multiparametric flow cytometry is an alternative approach to the polymerase chain reaction method for evaluating minimal residual disease in treatment protocols for primary acute lymphoblastic leukemia. Given considerable differences between primary and relapsed acute lymphoblastic leukemia treatment regimens, flow cytometric assessment of minimal residual disease in relapsed leukemia requires an independent comprehensive investigation. In the present study we addressed evaluation of minimal residual disease by flow cytometry in the clinical trial for childhood relapsed acute lymphoblastic leukemia using eight-color flow cytometry. The major challenge of the study was to reliably identify low amounts of residual leukemic cells against the complex background of regeneration, characteristic of follow-up samples during relapse treatment. In a prospective study of 263 follow-up bone marrow samples from 122 patients with B-cell precursor acute lymphoblastic leukemia, we tested various B-cell markers, adapted the antibody panel to the treatment protocol, and evaluated its performance by a blinded parallel comparison with the polymerase chain reaction data. The resulting eight-color single-tube panel showed a consistently high overall concordance (P<0.001) and, under optimal conditions, sensitivity similar to that of the reference polymerase chain reaction method. Overall, evaluation of minimal residual disease by flow cytometry can be successfully integrated into the clinical management of relapsed childhood acute lymphoblastic leukemia either as complementary to the polymerase chain reaction or as an independent risk stratification tool. ALL-REZ BFM 2002 clinical trial information: NCT00114348.

High-risk pediatric acute lymphoblastic leukemia: to transplant or not to transplant?

Because survival with both chemotherapy and allogeneic hematopoietic stem cell transplantation (HSCT) approaches to high-risk pediatric acute lymphoblastic leukemia (ALL) generally improves through the years, regular comparisons of outcomes with either approach for a given indication are needed to decide when HSCT is indicated. Improvements in risk classification are allowing clinicians to identify patients at high risk for relapse early in their course of therapy. Whether patients defined as high risk by new methods will benefit from HSCT requires careful testing. Standardization and improvement of transplant approaches has led to equivalent survival outcomes with matched sibling and well-matched unrelated donors; however, survival using mismatched and haploidentical donors is generally worse. Trials comparing chemotherapy and HSCT must obtain sufficient data about therapy and stratify the analysis to assess the outcomes of best-chemotherapy with best-HSCT approaches.

Allogeneic hematopoietic SCT in children with ALL: current concepts of ongoing prospective SCT trials

The definition of indications for allogeneic SCT in children with high-risk (HR) ALL in the first remission or after the first or subsequent relapse depends on biological features, response to treatment and survival after chemotherapy alone. As the results of frontline and relapse protocols are improving over time, there is a strong need for prospective SCT trials, ensuring a well-standardized procedure regarding all relevant components that are potentially responsible for heterogeneity in post-SCT outcome. Therefore, in 2003, the ALL-BFM and the ALL-REZ BFM Study Group initiated a prospective, international, multicenter trial (ALL-SCT-BFM 2003). This trial will now be extended to a larger consortium, trial ALL-SCT-BFM-international (ALL-SCT-BFMi). Strict rules define HLA-typing, donor selection, conditioning regimen, GvHD prophylaxis and therapy as well as standards of supportive care to reduce treatment-related mortality and establish an early GVL effect. Moreover, comprehensive and closely reviewed documentation and serious adverse event reporting shall ensure high study quality. Case-by-case discussions of any fatal or critical course during annual meetings will improve the culture of failure management and lead to modifications of guidelines of supportive care. Finally, the results of these prospective trials will determine the current potential of the different SCT procedures in HR or relapsed childhood ALL.