Treatment of pediatric lymphoma in Japan: Current status and plans for the future

Integrated diagnosis based on transcriptome analysis in suspected pediatric sarcomas

Pediatric solid tumors are a heterogeneous group of neoplasms with over 100 subtypes. Clinical and histopathological diagnosis remains challenging due to the overlapping morphological and immunohistochemical findings and the presence of atypical cases. To evaluate the potential utility of including RNA-sequencing (RNA-seq) in the diagnostic process, we performed RNA-seq in 47 patients with suspected pediatric sarcomas. Histopathologists specialized in pediatric cancer re-evaluated pathological specimens to reach a consensus diagnosis; 42 patients were diagnosed with known subtypes of solid tumors whereas 5 patients were diagnosed with undifferentiated sarcoma. RNA-seq analysis confirmed and refined consensus diagnoses and further identified diagnostic genetic variants in four of the five patients with undifferentiated sarcoma. Genetic lesions were detected in 23 patients, including the novel SMARCA4-THOP1 fusion gene and 22 conventional or recently reported genetic events. Unsupervised clustering analysis of the RNA-seq data identified a distinct cluster defined by the overexpression of rhabdomyosarcoma-associated genes including MYOG and CHRNG. These findings suggest that RNA-seq-based genetic analysis may aid in the diagnosis of suspected pediatric sarcomas, which would be useful for the development of stratified treatment strategies.

T-cell lymphoblastic lymphoma and leukemia: different diseases from a common premalignant progenitor?

T-cell lymphoblastic lymphoma (T-LBL) and lymphoblastic leukemia (T-ALL) represent malignancies that arise from the transformation of immature precursor T cells. Similarities in T-LBL and T-ALL have raised the question whether these entities represent 1 disease or reflect 2 different diseases. The genetic profiles of T-ALL have been thoroughly investigated over the last 2 decades, whereas fairly little is known about genetic driver mutations in T-LBL. Nevertheless, the comparison of clinical, immunophenotypic, and molecular observations from independent T-LBL and T-ALL studies lent strength to the theory that T-LBL and T-ALL reflect different presentations of the same disease. Alternatively, T-LBL and T-ALL may simultaneously evolve from a common malignant precursor cell, each having their own specific pathogenic requirements or cellular dependencies that differ among stroma-embedded blasts in lymphoid tissues compared with solitary leukemia cells. This review aims to cluster recent findings with regard to clinical presentation, genetic predisposition, and the acquisition of additional mutations that may give rise to differences in gene expression signatures among T-LBL and T-ALL patients. Improved insight in T-LBL in relation to T-ALL may further help to apply confirmed T-ALL therapies to T-LBL patients.

Survival and long-term toxicities of pediatric Hodgkin lymphoma after combined modality treatment: a single institute experience

PURPOSE

To analyze the clinical outcomes and long-term toxicity of pediatric patients with Hodgkin lymphoma after combined-modality treatment (CMT) with involved-field or involved-nodal radiotherapy (RT).

MATERIALS AND METHODS

We retrospectively reviewed the records of 27 pediatric Hodgkin lymphoma patients who received CMT at a single institution between January 1990 and July 2017. Patients with stage I-III received a heterogeneous chemotherapy regimen depending on their risk group followed by 19.8-36 Gy RT, with the dose based on their response to the chemotherapy before RT. An optional 9-20 Gy boost was delivered to residual sites. The risk group was determined based on the initial stage, the presence of bulky disease, and any B symptoms. We evaluated overall survival, event-free survival, and long-term toxicities.

RESULTS

A total of 27 patients completed the CMT. At a median follow-up of 125 months (range, 9 to 337 months), the estimated 5-year event-free survival and overall survival were 88.9% and 96.3%, respectively. Late symptomatic cardiopulmonary toxicity was not observed, and only one patient was positive on a subclinical obstructive pulmonary function test. The incidence of hypothyroidism was 58.3% among 12 patients with an available thyroid function test. There was one papillary thyroid cancer diagnosed 7.2 years after treatment.

CONCLUSION

CMT for pediatric Hodgkin lymphoma with involved-field and involved-nodal RT achieved an excellent survival with only modest long-term toxicity. Smaller-field RT seemed to decrease long-term toxicities and had good local control.

The effect of graft-versus-host disease on outcomes after allogeneic stem cell transplantation for refractory lymphoblastic lymphoma in children and young adults

BACKGROUND

Patients with relapsed or refractory lymphoblastic lymphoma (LBL) have a poor prognosis. The efficacy of allogeneic blood stem cell transplantation for treatment of this disease remains unclear in terms of transplantation-related toxicity. Acute and chronic graft-versus-host diseases (GVHD) are both harmful to patients after allogeneic transplantation, but may have some positive effects through a substitute graft-versus-lymphoma effect.

METHODS

To investigate the effect of GVHD on the survival of patients with refractory LBL, we retrospectively studied the outcomes of 213 patients with LBL who underwent first allogeneic stem cell transplantation before the age of 18 years, between 1990 and 2015 in Japan.

RESULTS

The five-year overall survival (OS) and event-free survival rates after stem cell transplantation were 50.3% (95% confidence interval [CI], 43.2-56.9) and 47.8% (95% CI, 40.8-54.4), respectively. In univariate landmark analyses, the probability of OS was significantly better in patients with aGVHD than in those without (P = 0.002, five-year OS 58.1% vs 39.0%). The probability of OS was also better in patients with cGVHD than in those without (P = 0.036, five-year OS 72.2% vs 54.7%). Multivariate analysis demonstrated that only aGVHD was associated with better OS (hazard ratio, 0.63; 95% CI, 0.42-0.94, P = 0.024). Progression and recurrence statuses at SCT were associated with poor prognosis. The patients with grade II aGVHD showed the best prognosis (five-year OS: 65.6%).

CONCLUSION

Our results suggest that the occurrence of aGVHD may be associated with better outcomes in patients with relapsed/refractory LBL who undergo allogeneic transplantation.

The lysine methyltransferase SMYD2 is required for normal lymphocyte development and survival of hematopoietic leukemias

The 5 membered SET and MYND Domain-containing lysine methyltransferase (SMYD) family plays pivotal roles in development and proliferation. Initially characterized within the cardiovascular system, one such member, SMYD2, has been implicated as an oncogene in leukemias deriving from flawed hematopoietic stem cell (HSC) differentiation. We show here that conditional SMYD2 loss disrupts hematopoiesis at and downstream of the HSC via both apoptotic loss and transcriptional deregulation of HSC proliferation and disruption of Wnt-β-Catenin signaling. Yet previously documented SMYD2 cell cycle targets were unscathed. Turning our analysis to human leukemias, we observed that SMYD2 is highly expressed in CML, MLLr-B-ALL, AML, T-ALL and B-ALL leukemias and its levels in B-ALL correlate with poor survival. SMYD2 knockdown results in apoptotic death and loss of anchorage-independent transformation of each of these hematopoietic leukemias. These data provide an underlying mechanism by which SMYD2 acts during normal hematopoiesis and as a proto-oncogene in leukemia.

Treatment and biology of pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. In the past ALL was intractable but now the survival probability is as high as 80-90%. Improved supportive care, treatment stratification based on relapse risk, biological features of leukemic cells, and optimization of treatment regimens by nationwide and international collaboration have contributed to this dramatic improvement. While including traditional risk factors (e.g. age and leukocyte count at diagnosis), the treatment has been modified based on biological characteristics (aneuploidy and translocation) and treatment response (assessed by minimal residual disease). Treatment for pediatric ALL typically consists of induction therapy with steroids, vincristine, and asparaginase with or without anthracycline, followed by multi-agent consolidation including high-dose methotrexate and re-induction therapy. After consolidation, less intensive maintenance therapy is required for 1-2 years to maintain event-free survival. Recently, using advanced genomic analysis technology, novel sentinel genomic alterations that may provide more precise stratification or therapeutic targets, were identified. Moreover, in the last decade germline variations have been recognized as similarly important contributors to understanding the etiology and sensitivity of ALL to treatment. A more individualized approach based on genomic features (somatic and germline) and treatment response, the introduction of newly developed agents such as molecular targeted drugs or immunotherapy, and social support including long-term follow up are required for further improvement.

Pediatric follicular lymphoma in Japan

Follicular lymphoma (FL) is quite rare in children. There have been only two major reports on pediatric FL. The present retrospective study on pediatric FL in Japan, including FL with diffuse large B cell lymphoma (DLBCL), analyzed data from 1991 to 2014. Twenty-two patients with pediatric FL were analyzed. Sixteen patients were boys and six were girls. Median age of onset was 9 years (range 4-17 years). In 11 patients, DLBCL co-existed with FL. The initial lesions involved cervical lesions in 16 patients, and the abdomen in six. With regard to stage of disease at diagnosis, 17 patients were at stage I or II, four were at stage III, and one was at stage IV. Chemotherapy was administered in 18 patients, and only resection was performed in four patients. Mature B lymphoma regimens were selected for 17 patients who received chemotherapy. Although two patients relapsed, all patients are currently alive and disease free. The median follow-up period was 54.5 months (range 6-126 months). Patients having FL with DLBCL were younger compared with those having FL, and this disease was more frequently observed in female patients. Our data revealed that FL in Japanese children is a tumor with good prognosis, as in reports from the United States and Europe.