Prognostic Role of Postinduction Minimal Residual Disease and Myeloid Sarcoma Type Extramedullary Involvement in Pediatric RUNX1-RUNX1T1 (+) Acute Myeloid Leukemia

Extramedullary infiltration in pediatric acute myeloid leukemia: Results from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) initiative

BACKGROUND

The outcome of extramedullary infiltration (EMI) in pediatric acute myeloid leukemia (AML) is controversial, and little is known about the implications of stem cell transplantation (SCT) and gemtuzumab ozogamicin (GO) treatment on patients with EMI.

METHODS

We retrieved the clinical data of 713 pediatric patients with AML from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) dataset, and analyzed the clinical and prognostic characteristics of patients with EMI at diagnosis and relapse.

RESULTS

A total of 123 patients were identified to have EMI at diagnosis and 64 presented with EMI at relapse. The presence of EMI was associated with age ≤2 years, M5 morphology, abnormal karyotype, and KMT2A rearrangements. Hyperleukocytosis and complex karyotype were more prevalent in patients with EMI at relapse. Additionally, patients with EMI at diagnosis had a reduced incidence of FLT3 ITD-/NPM1+, whereas those with EMI at relapse displayed a lower frequency of FLT3 ITD+. Patients with EMI at diagnosis exhibited a lower complete remission (CR) rate at the end of Induction Course 1 and higher relapse incidence. Importantly, EMI at diagnosis independently predicted both shorter event-free survival (EFS) and overall survival (OS). Regarding relapse patients, the occurrence of EMI at relapse showed no impact on OS. However, relapse patients with myeloid sarcoma (MS)/no central nervous system (CNS) exhibited poorer OS compared to those with CNS/no MS. Furthermore, regarding patients with EMI at diagnosis, SCT failed to improve the survival, whereas GO treatment potentially enhanced OS.

CONCLUSION

EMI at diagnosis is an independent adverse prognostic risk factor for pediatric AML, and GO treatment potentially improves survival for patients with EMI at diagnosis.

Myeloid sarcoma: An overview

Myeloid Sarcoma (MS) is a high grade, hematological malignancy defined as an extramedullary tumor mass of myeloid blasts with or without maturation that effaces tissue architecture. It is a highly heterogenous condition that represents a variety of myeloid neoplasms. This heterogeneity of MS, together with its rarity, have greatly hampered our understanding of the condition. Diagnosis requires tumor biopsy, which should be accompanied by bone marrow evaluation for medullary disease. It is presently recommended that MS be treated similar to AML. Additionally, ablative radiotherapy and novel targeted therapies may also be beneficial. Genetic profiling has identified recurrent genetic abnormalities including gene mutations associated with MS, supporting its etiology similar to AML. However, the mechanisms by which MS homes to specific organs is unclear. This review provides an overview of pathogenesis, pathological and genetic findings, treatment, and prognosis. Improving the management and outcomes of MS patients requires a better understanding of its pathogenesis and its response to various therapeutic approaches.

Pediatric Myeloid Sarcoma, More than Just a Chloroma: A Review of Clinical Presentations, Significance, and Biology

Myeloid sarcomas (MS), commonly referred to as chloromas, are extramedullary tumors of acute myeloid leukemia (AML) with varying incidence and influence on outcomes. Pediatric MS has both a higher incidence and unique clinical presentation, cytogenetic profile, and set of risk factors compared to adult patients. Optimal treatment remains undefined, yet allogeneic hematopoietic stem cell transplantation (allo-HSCT) and epigenetic reprogramming in children are potential therapies. Importantly, the biology of MS development is poorly understood; however, cell-cell interactions, epigenetic dysregulation, cytokine signaling, and angiogenesis all appear to play key roles. This review describes pediatric-specific MS literature and the current state of knowledge about the biological determinants that drive MS development. While the significance of MS remains controversial, the pediatric experience provides an opportunity to investigate mechanisms of disease development to improve patient outcomes. This brings the hope of better understanding MS as a distinct disease entity deserving directed therapeutic approaches.

Extramedullary Infiltration in Pediatric Acute Myeloid Leukemia on Surveillance Magnetic Resonance Imaging and its Relationship With Established Risk Factors

PURPOSE

Extramedullary infiltration (EMI) is a rare condition defined by the accumulation of myeloid tumor cells beyond the bone marrow. The clinical significance is still controversial. This study was aimed to evaluate the incidence, characteristics, and prognostic significance of EMI on complete magnetic resonance imaging (MRI) investigation in newly diagnosed pediatric acute myeloid leukemia (AML) patients who are asymptomatic without clinical evidence to suspect EMI.

MATERIALS AND METHODS

Retrospective clinical and radiologic review of 121 patients with MRI examination at the time of initial diagnosis of AML without any clinical evidence suggestive of EMI was performed. Patients were divided into 2 groups according to the presence or absence of EMI, and the relationship between EMI and established risk factors was analyzed. Initial white blood cell count, the occurrence of an event (including relapse, death, and primary refractory disease), survival status, and detailed information on cytogenetic/molecular status was performed by a thorough review of electronic medical records system. All patients underwent full imaging evaluation with the contrast-enhanced whole body and some regional MRI at the time of initial diagnosis.

RESULTS

The median age at diagnosis was 10.77 years (range, 0.37 to 18.83 y). Based on the risk stratification system of AML, 36, 45, and 40 patients are classified as low-risk, intermediate-risk, and high-risk groups, respectively. MRI at the time of the initial diagnosis of AML revealed 35 of 121 patients (28.9%) with EMI. The most common site of EMI was a skull, followed by the lower extremity bone and meninges of the brain. The median age at diagnosis was significantly younger in patients with EMI (7.87 vs. 11.08 y, P=0.0212). Low incidence of FLT3/ITD mutation, low incidence of AML-ETO gene rearrangement, and the larger extent and more severe degree of bone marrow involvement was related with EMI. However, there was no significant prognostic difference in event-free survival and overall survival regardless of the presence of EMI in the overall patient population and each risk group. The location of EMI occurrence was also not related to prognosis.

CONCLUSIONS

Even if EMI symptoms are not evident, surveillance MRI scans at the initial diagnosis of pediatric AML patients are very helpful in detecting a significant number of EMIs. Younger age, some molecular features, and more severe bone marrow involvement of AML patients were related with EMI. However, there was no significant prognostic difference between patients with or without EMI regardless of risk group. Further prospective investigation is necessary to validate the prognostic effect of EMI in a larger group of patients with different risk groups.

Characteristics of RAS pathway mutations in juvenile myelomonocytic leukaemia: a single-institution study from Korea

Juvenile myelomonocytic leukaemia (JMML), a rare clonal haematopoietic disorder of childhood, is characterised as a myelodysplastic/myeloproliferative neoplasm. Despite ground-breaking genetic discoveries, JMML remains difficult to diagnose given its diverse clinical features and disease course. A total of 24 patients with JMML were diagnosed and treated at a single institution, and their genetic profiles and association with clinical and laboratory characteristics were analysed. In all, 22 of the patients received allogeneic haematopoietic stem cell transplantation after myeloablative conditioning, mostly from a haploidentical family donor. RAS pathway mutations were identified in 88% of patients: PTPN11 [nine (38%)], NRAS [nine (38%)], KRAS [two (8%)], NF1 [five (21%)] and CBL [one (4%)]. Secondary mutations were found in 25% of patients: SETBP1, JAK3, ASXL1, GATA2, KIT, KDM6A, and BCOR. Six patients showed cytogenetic abnormalities, including three with monosomy 7. The estimated 5-year event-free survival (EFS) and overall survival (± standard error) of the entire cohort were 58·9 (10·9)% and 73·5 (10·8)% respectively. NRAS (+) patients had a higher 5-year EFS than NRAS (-) patients [72·9 (16·5)% vs. 52·5 (13·1)%, P = 0·127]. NRAS (+) patients had a better 5-year EFS than PTPN11 (+) patients [41·7 (17·3)%, P = 0·071]. Our study revealed the genetic characteristics of Korean JMML patients with RAS pathway and secondary mutations.

Post-transplant leukemia relapse in organs: biology. and behavior in 585 reports

Resistance of extramedullary leukemia growth post-transplant prevents cure. Review of its behavior detailed in 585 published cases should lead to better treatment. Leukemic tumors were found up to 13 years after transplant, most in sites inaccessible to physical exam. In 83%, marrow was not in morphologic relapse; next relapse was most often extramedullary. Induction protocols alone produced few durable responses in acute leukemias and fatal marrow aplasia in 17 %. Overall, 120 patients survived over 2 years, 43 relapse-free up to 18 years, the majority after combined tumor-directed and systemic therapy. Overall median survival was 9 months. This review highlights how results can improve: by defining extent of leukemia involvement with scans before transplant, and emergently when leukemic tumor is found after, ablating tumor directly to abort metastasis, and determining dosing of systemic chemotherapy that protects, without ablating, donor marrow. Monitoring total body remission with body scans should increase transplant cures.

Allogeneic hematopoietic stem cell transplantation can improve the prognosis of high-risk pediatric t(8;21) acute myeloid leukemia in first remission based on MRD-guided treatment

Background

Pediatric acute myeloid leukemia (AML) with t(8;21) (q22;q22) is classified as a low-risk group. However, relapse is still the main factor affecting survival. We aimed to investigate the effect of allogeneic hematopoietic stem cell transplantation (allo-HSCT) on reducing recurrence and improving the survival of high-risk pediatric t(8;21) AML based on minimal residual disease (MRD)-guided treatment, and to further explore the prognostic factors to guide risk stratification treatment and identify who will benefit from allo-HSCT.

Methods

Overall, 129 newly diagnosed pediatric t(8;21) AML patients were included in this study. Patients were divided into high-risk and low-risk group according to RUNX1-RUNX1T1 transcript levels after 2 cycles of consolidation chemotherapy. High-risk patients were divided into HSCT group and chemotherapy group according to their treatment choices. The characteristics and outcomes of 125 patients were analyzed.

Results

For high-risk patients, allo-HSCT could improve 5-year relapse-free survival (RFS) rate compared to chemotherapy (87.4% vs. 61.9%; P = 0.026). Five-year overall survival (OS) rate in high-risk HSCT group had a trend for better than that in high-risk chemotherapy group (82.8% vs. 71.4%; P = 0.260). The 5-year RFS rate of patients with a c-KIT mutation in high-risk HSCT group had a trend for better than that of patients with a c-KIT mutation in high-risk chemotherapy group (82.9% vs. 75%; P = 0.400). Extramedullary infiltration (EI) at diagnosis was associated with a high cumulative incidence of relapse for high-risk patients (50% vs. 18.4%; P = 0.004); allo-HSCT can improve the RFS (P = 0.009).

Conclusions

allo-HSCT can improve the prognosis of high-risk pediatric t(8;21) AML based on MRD-guided treatment. Patients with a c-KIT mutation may benefit from allo-HSCT. EI is an independent prognostic factor for high-risk patients and allo-HSCT can improve the prognosis.