Pediatric Precursor B-Cell Lymphoblastic Malignancies: From Extramedullary to Medullary Involvement

Mutational and transcriptional landscape of pediatric B-cell precursor lymphoblastic lymphoma

ABSTRACT

Pediatric B-cell precursor (BCP) lymphoblastic malignancies are neoplasms with manifestation either in the bone marrow or blood (BCP acute lymphoblastic leukemia [BCP-ALL]) or are less common in extramedullary tissue (BCP lymphoblastic lymphoma [BCP-LBL]). Although both presentations are similar in morphology and immunophenotype, molecular studies have been virtually restricted to BCP-ALL so far. The lack of molecular studies on BCP-LBL is due to its rarity and restriction on small, mostly formalin-fixed paraffin-embedded (FFPE) tissues. Here, to our knowledge, we present the first comprehensive mutational and transcriptional analysis of what we consider the largest BCP-LBL cohort described to date (n = 97). Whole-exome sequencing indicated a mutational spectrum of BCP-LBL, strikingly similar to that found in BCP-ALL. However, epigenetic modifiers were more frequently mutated in BCP-LBL, whereas BCP-ALL was more frequently affected by mutation in genes involved in B-cell development. Integrating copy number alterations, somatic mutations, and gene expression by RNA sequencing revealed that virtually all molecular subtypes originally defined in BCP-ALL are present in BCP-LBL, with only 7% of lymphomas that were not assigned to a subtype. Similar to BCP-ALL, the most frequent subtypes of BCP-LBL were high hyperdiploidy and ETV6::RUNX1. Tyrosine kinase/cytokine receptor rearrangements were detected in 7% of BCP-LBL. These results indicate that genetic subtypes can be identified in BCP-LBL using next-generation sequencing, even in FFPE tissue, and may be relevant to guide treatment.

18 F-FDG-PET/CT imaging in diagnostic workup of pediatric precursor B-cell lymphoblastic lymphoma

18 F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT) imaging is currently not used in standard diagnostics for B-cell precursor lymphoblastic lymphoma (BCP-LBL), and it is unknown whether PET/CT imaging would lead to agreement between detection of lesions with the gold standard imaging methods. Therefore, we performed a retrospective cohort study in which we included 32 pediatric BCP-LBL patients and determined localizations by reviewing local imaging reports. There was a disagreement between protocol-based imaging and PET/CT in 59% of the patients, and the discrepancies mostly comprise of additional lesions detected with PET/CT, typically in lymph node and bone or the absence of bone marrow involvement with PET/CT. If PET/CT was leading in determining definite stage of disease, this would lead to a different stage and therapy branch in 31% and 28% of the patients, respectively.

Precursor B-cell Lymphoblastic Lymphoma in Children: Hacettepe Experience

The purpose of the study was to review the clinical and pathologic characteristics and treatment results of children with precursor B-cell lymphoblastic lymphoma. Of 530 children diagnosed with non-Hodgkin lymphomas between 2000 and 2021, 39 (7.4%) were identified as having precursor B-cell lymphoblastic lymphoma. Clinical characteristics, pathologic, radiologic, laboratory data, treatments, responses, and overall outcomes were recorded from hospital files and analyzed. The median age of 39 patients (males/females, 23/16) was 8.3 years (range 1.3 to 16.1). The most common sites of involvement were the lymph nodes. At a median follow-up of 55.8 months, 14 patients (35%) had a recurrence of disease (11 stage IV, 3 stage III); 4 were in complete remission with salvage therapies, 9 died of progressive disease and one died due to febrile neutropenia. Five-year event-free survival and overall survival rates were 65.4% and 78.3% for all cases, respectively. Survival rates were higher in patients with a complete remission at the end of induction therapies. The survival rates were lower in our study compared with other studies, which could be explained by the high relapse rate and higher incidence of advanced-stage disease due to bone marrow involvement. We demonstrated a prognostic impact of treatment response at the end of the induction phase. Cases with a disease relapse have poor prognosis.

How I approach B-lymphoblastic lymphoma in children

There are limited data pertaining to the prognostic features and optimal therapeutic approach for the 20%-25% of children with lymphoblastic lymphoma (LLy) who have the B-lymphoblastic subtype. Outcomes are favorable following treatment modeled after acute lymphoblastic leukemia (ALL) regimens, but prognosis is dismal after relapse, and there are no established features for predicting therapy response. Ongoing US and international trials will include the largest cohort of uniformly treated patients with B-LLy to date, providing an opportunity to define clinical and molecular predictors of relapse and to establish a standard of care for treatment to improve outcomes for this rare pediatric cancer.

Diagnosis and management of lymphoblastic lymphoma in children, adolescents and young adults

Lymphoblastic lymphoma (LBL) is the second most common type of non-Hodgkin Lymphoma (NHL) in children, adolescents, and young adults (CAYA), accounting for 25-35% of all cases. T-lymphoblastic lymphoma (T-LBL) comprises 70-80% of cases, while precursor B-lymphoblastic lymphoma (pB-LBL) makes up the remaining 20-25% of cases. Event-free and overall survival (EFS and OS) for paediatric LBL patients both exceed 80% with current therapies. Treatment regimens, especially in T-LBL with large mediastinal tumours, are complex with significant toxicity and long-term complications. Though prognosis overall is good for T-LBL and pB-LBL with upfront therapy, outcomes for patients with relapsed or refractory (r/r) disease remain dismal. Here, we review new understanding about the pathogenesis and biology of LBL, recent clinical results and future directions for therapy, and remaining obstacles to improve outcomes while reducing toxicity.