αß T Cell-Depleted Haploidentical Hematopoietic Stem Cell Transplantation without Antithymocyte Globulin in Children with Chemorefractory Acute Myelogenous Leukemia.

We evaluated the outcome of αß T cell-depleted haploidentical hematopoietic stem cell transplantation (HSCT) in a cohort of children with chemorefractory acute myelogenous leukemia (AML). Twenty-two patients with either primary refractory (n = 10) or relapsed refractory (n = 12) AML in active disease status received a transplant from haploidentical donors. The preparative regimen included cytoreduction with fludarabine and cytarabine and subsequent myeloablative conditioning with treosulfan and thiotepa. Antithymocyte globulin was substituted with tocilizumab in all patients and also with abatacept in 10 patients. Grafts were peripheral blood stem cells engineered by αß T cell and CD19 depletion. Post-transplantation prophylactic therapy included infusion of donor lymphocytes, composed of a CD45RA-depleted fraction with or without a hypomethylating agent. Complete remission was achieved in 21 patients (95%). The cumulative incidence of grade II-IV acute graft-versus-host disease (GVHD) was 18%, and the cumulative incidence of chronic GVHD was 23%. At 2 years, transplantation-related mortality was 9%, relapse rate was 42%, event-free survival was 49%, and overall survival was 53%. Our data suggest that αß T cell-depleted haploidentical HSCT provides a reasonable chance of long-term survival in a cohort of children with chemorefractory AML and creates a solid basis for further improvement.

Midline Low-Grade Gliomas of Early Childhood: Focus on Targeted Therapies.

PURPOSE: Midline low-grade gliomas (mLGGs) of early childhood have a poorer prognosis compared with tumors of other localizations and in older patients. LGGs are associated with aberrant activation of RAS-RAF-MEK pathway, and pharmacological inhibition of the pathway has therapeutic promise. The aim of this study was clinical and molecular characterization of infantile mLGGs, with emphasis on the efficacy of targeted kinase inhibition. PATIENTS AND METHODS: This study enrolled 40 patients with mLGG age <3 years. The majority of the patients (30/40) received first-line chemotherapy (CT) as per International Society of Paediatric Oncology LGG 2004 guidelines. In all patients, molecular genetic investigation of tumor tissue by polymerase chain reaction and RNA sequencing was performed. The median follow-up was 3.5 years. RESULTS: First-line CT failed in 24 of 30 recipients. The identified molecular profiles included KIAA1549::BRAF fusions in 26 patients, BRAF V600E in six patients, FGFR1::TACC1 fusions in two patients, and rare fusion transcripts in four patients. At disease progression, targeted therapy (TT) was initiated in 27 patients (22 patients received trametinib) on the basis of molecular findings. TT was administered for a median of 16 months, with partial response achieved in 12 of 26 (46%) patients in which response was evaluated. Severe adverse events were detected only on trametinib monotherapy: acute damage of GI or urinary mucosa complicated by hemorrhage and development of transfusion-dependent anemia in four patients and grade 3 skin toxicity in three patients. CONCLUSION: mLGGs of early childhood are often aggressive tumors, resistant to CT, and frequently require alternative treatment. The majority of patients harbor druggable molecular targets and respond to molecular TT.

EWSR1-TFCP2 in an adolescent represents an extremely rare and aggressive form of intraosseous spindle cell rhabdomyosarcomas.

The WHO Classification of Tumors of Soft Tissue and Bone subdivides rhabdomyosarcomas (RMS) into alveolar, embryonal, pleomorphic, and spindle cell RMS. Advances in molecular genetic diagnostics have made it possible to identify new RMS subgroups within traditional morphological entities. One of these subgroups comprises rare tumors characterized by epithelioid and spindle cell morphology, highly aggressive clinical course with pronounced tendency to intraosseous growth, and the presence of pathognomonic recurring genetic aberrations- chimeric genes/transcripts EWSR1::TFCP2, FUS::TFCP2, or MEIS1::NCOA2. Starting from 2018, only 26 reported cases of RMS have been assigned to this subgroup. The rarity of such tumors hampers their correct diagnostics for both anatomic pathologists and molecular oncologists. Here we describe a clinical case of intraosseous spindle cell RMS expressing EWSR1::TFCP2 fusion gene, encountered for the first time in our practice, in a 16-year-old female patient presenting with mandibular lesion. The diagnostic process took considerable time and involved RNA sequencing; a high-throughput method of molecular genetic research. The tumor was extremely aggressive, showing resistance to polychemotherapy, radiation therapy, and crizotinib targeted therapy, with the fatal outcome.

GATA1 mutation analysis and molecular landscape characterization in acute myeloid leukemia with trisomy 21 in pediatric patients.

INTRODUCTION: Accurate detection of GATA1 mutation is highly significant in patients with acute myeloid leukemia (AML) and trisomy 21 as it allows optimization of clinical protocol. This study was aimed at (a) enhanced search for GATA1 mutations; and (b) characterization of molecular landscapes for such conditions. METHODS: The DNA samples from 44 patients with newly diagnosed de novo AML with trisomy 21 were examined by fragment analysis and Sanger sequencing of the GATA1 exon 2, complemented by targeted high-throughput sequencing (HTS). RESULTS: Acquired GATA1 mutations were identified in 43 cases (98%). Additional mutations in the genes of JAK/STAT signaling, cohesin complex, and RAS pathway activation were revealed by HTS in 48%, 36%, and 16% of the cases, respectively. CONCLUSIONS: The GATA1 mutations were reliably determined by fragment analysis and/or Sanger sequencing in a single PCR amplicon manner. For patients with extremely low blast counts and/or rare variants, the rapid screening with simple molecular approaches must be complemented with HTS. The JAK/STAT and RAS pathway-activating mutations may represent an extra option of targeted therapy with kinase inhibitors.