Innovative approaches of targeted therapy for CML of childhood in combination with paediatric haematopoietic SCT

Priapism at Diagnosis of Pediatric Chronic Myeloid Leukemia: Data Derived from a Large Cohort of Children and Teenagers and a Narrative Review on Priapism Management

Pediatric chronic myeloid leukemia (CML) is a very rare malignancy (age-related incidence 0.1/100,000) typically presenting with leucocyte counts >100,000/µL. However, clinical signs of leukostasis are observed at diagnosis in only approximately 10% of all cases and among these, priapism is infrequent. Here, we analyze data from pediatric CML registries on the occurrence of priapism heralding diagnosis of CML in 16/491 (3.2%) boys (median age 13.5 years, range 4-18) with pediatric CML. In the cohort investigated, duration of priapism resulting in a diagnosis of CML was not reported in 5 patients, and in the remaining 11 patients, occurred as stuttering priapism over 3 months (n = 1), over 6 weeks (n = 1), over 1-2 weeks (n = 2), over several days (n = 2), or 24 h (n = 1), while the remaining 4 boys reported continuous erection lasting over 11-12 h. All patients exhibited splenomegaly and massive leukocytosis (median WBC 470,000/µL, range 236,700-899,000). Interventions to treat priapism were unknown in 5 patients, and in the remaining cohort, comprised intravenous fluids ± heparin (n = 2), penile puncture (n = 5) ± injection of sympathomimetics (n = 4) ± intracavernous shunt operation (n = 1) paralleled by leukocyte-reductive measures. Management without penile puncture by leukapheresis or exchange transfusion was performed in 3 boys. In total, 7 out 15 (47%) long-term survivors (median age 20 years, range 19-25) responded to a questionnaire. All had maintained full erectile function; however, 5/7 had presented with stuttering priapism while in the remaining 2 patients priapism had lasted <12 h until intervention. At its extreme, low-flow priapism lasting for longer than 24 h may result in partial or total impotence by erectile dysfunction. This physical disability can exert a large psychological impact on patients' lives. In a narrative review fashion, we analyzed the literature on priapism in boys with CML which is by categorization stuttering or persisting as mostly painful, ischemic (low-flow) priapism. Details on the pathophysiology are discussed on the background of the different blood rheology of hyperleukocytosis in acute and chronic leukemias. In addition to the data collected, instructive case vignettes demonstrate the diagnostic and treatment approaches and the outcome of boys presenting with priapism. An algorithm for management of priapism in a stepwise fashion is presented. All approaches must be performed in parallel with cytoreductive treatment of leukostasis in CML which comprises leukapheresis and exchange transfusions ± cytotoxic chemotherapy.

Definition, Epidemiology, Pathophysiology, and Essential Criteria for Diagnosis of Pediatric Chronic Myeloid Leukemia

Simple Summary

The low incidence (1:1,000,000) of chronic myeloid leukemia (CML) in the first two decades of life presents an obstacle to accumulation of pediatric experience and knowledge on this leukemia. Biological features of CML are shared but also differing between adult and pediatric patients. This review aims; (i) to define the disease based on an unified terminology, (ii) to list the diseases to be considered as a differential diagnosis in children, (iii) to outlines the morphological, histopathological and immuno-phenotypical findings of pediatric CML, (iv) to illustrate rare but classical complications resulting from high white cell and platelet counts at diagnosis, and (v) to recommend a uniform approach for the diagnostic procedures to be applied. Evidently, only a clear detailed picture of all relevant features can lay the basis for standardized treatment approaches.

Abstract

Depending on the analytical tool applied, the hallmarks of chronic myeloid leukemia (CML) are the Philadelphia Chromosome and the resulting mRNA fusion transcript BCR-ABL1. With an incidence of 1 per 1 million of children this malignancy is very rare in the first 20 years of life. This article aims to; (i) define the disease based on the WHO nomenclature, the appropriate ICD 11 code and to unify the terminology, (ii) delineate features of epidemiology, etiology, and pathophysiology that are shared, but also differing between adult and pediatric patients with CML, (iii) give a short summary on the diseases to be considered as a differential diagnosis of pediatric CML, (iv) to describe the morphological, histopathological and immunophenotypical findings of CML in pediatric patients, (v) illustrate rare but classical complications resulting from rheological problems observed at diagnosis, (vi) list essential and desirable diagnostic criteria, which hopefully in the future will help to unify the attempts when approaching this rare pediatric malignancy.

Horn of plenty: Value of the international registry for pediatric chronic myeloid leukemia

Chronic myeloid leukemia (CML) in minors is a rare disease which can be effectively treated by tyrosine kinase inhibitors (TKIs) since the year 2000. A majority of pediatricians will encounter one or two CML patients in the course of their careers and will typically have to rely on written information along with their own intuition to provide care. Knowledge of response to TKIs and of age-specific side effects has an impact on the design of pediatric CML trials in many ways aiming to contribute toward greater predictability of clinical improvements. Information from a registry on a rare disease like CML offers the enormous benefit of enabling treating physicians to interact and share their collective experience. The International Registry on Pediatric CML (IR-PCML) was founded at Poitiers/France almost 10 years ago. Since then, the number of collaboration centers and in parallel of registered patients continuously increased (> 550 patients as of December 2019). Ideally, from a given treatment center in a country data are transferred to a national coordinator who interacts with the IR-PCML. In the sense of quality assurance, the registry can offer dissemination of knowledge on state-of-the-art diagnostics (including reference appraisal), optimal treatment approaches, and follow-up procedures within a network that is exerting its strength via participation. With continuous growth during the recent years, very rare subgroups of patients could be identified (e.g., CML diagnosed at age < 3 years, children presenting with specific problems at diagnosis or during course of treatment) which had not been described before. Publications coming from the IR-PCML disseminated this useful information derived from patients who robustly participate and share information about their disease, among themselves and with their caregivers and clinicians. Patient input driving the collection of data on this rare leukemia is the basis for the considerable success of bringing new therapeutics into clinical use.

Profile of Pediatric Chronic Myeloid Leukemia in the Era of Imatinib: A Study from South India

Introduction: Chronic myeloid leukemia (CML), a chronic hematologic malignancy, is rare in pediatric patients. Studies of the tyrosine kinase inhibitor imatinib are required so that uniform guidelines may focus on disease therapy and follow-up for children. We analyzed the clinicohematologic features of the disease, treatment response to imatinib, follow-up measures, and the impact of the disease on the patients and their family. Materials and Methods: All pediatric patients diagnosed with CML and treated and followed-up were studied regarding demographics, clinical features at presentation, and diagnostic profile, including laboratory parameters, peripheral blood smear test, fluorescent in situ hybridization and karyotyping, and reverse-transcriptase polymerase chain reaction for the BCR-ABL fusion gene. Treatment modalities, adverse reactions, remedial measures, assessment at every follow-up visit, patient’s education, parents’ socioeconomic status, and economic and psychological stresses were also evaluated. Results: Six patients were administered upfront therapy with a standard dose of imatinib. Hematological and biochemical parameters were monitored after the drug administration. We assessed the treatment response using molecular detection of the BCR-ABL transcripts. All patients who complied with drug therapy showed a complete molecular response and minimal toxic symptoms. However, parents found it difficult to cope socially and economically. Conclusion: Imatinib mesylate is effective and has a good molecular response, minimal toxicity, and good patient compliance. However, due to its cost, families reacquire financial debt, and the disease creates uncertainty about the child’s future, thereby necessitating psychosocioeconomic support for parents. Changes in the policies of cancer support groups are urgently needed to provide lifelong, lifesaving drugs free of cost.

Cure of relapsing nephrosis by an allogeneic marrow graft for chronic myelogenous leukemia

BACKGROUND

Minimal-change nephrotic syndrome has recently been attributed to an immature, dysfunctional T-cell population.

CASE-DIAGNOSIS/TREATMENT

A woman, now 23 years old, developed nephrotic syndrome when she was 6 years old. Despite treatment with steroids and immunosuppressants such as cyclosporine, mizoribine, mycophenolate mofetil, and tacrolimus, the patient relapsed 14 times. At the age of 19 years, she developed chronic myelogenous leukemia, against which imatinib achieved cytogenetic remission. The patient received an allogeneic bone marrow graft transplantation from an unrelated marrow bank donor, with an uncomplicated recovery and molecular genetic remission. Immunosuppressants were withdrawn within 6 months. The patient is now without drug treatment. Complete remission of nephrotic syndrome has also been maintained for over 4 years without any drug administration.

CONCLUSIONS

The patient's course supports suggestions that immunological dysfunction in nephrosis is associated with abnormality of immature, relatively unclassified T cells (CD34(+)) representing hematopoietic stem cells, as opposed to mature T cells (CD34(-)).

Imatinib has adverse effect on growth in children with chronic myeloid leukemia

BACKGROUND

Long-term adverse effects of Imatinib in children with chronic myeloid leukemia (CML) are uncertain. The aim was to study the effect of imatinib on growth in children with CML.

PROCEDURE

Children ≤13 years of age at diagnosis were enrolled retrospectively, from 2004 to 2011, from a single center in India. Patients who received imatinib for >1 year were included for growth assessment. Height standard deviation scores (SDS) were derived from WHO-AnthroPlus, a global growth monitoring tool.

RESULTS

Thirty-four children received imatinib. Twenty children fulfilled the criteria for assessment of growth. Median age was 10 years (range: 2-13). Of 20 children, 13 were prepubertal at commencement of imatinib. The mean duration of imatinib in 20 children was 61.3 ± 16.2 months (range: 31-83). No patient was treated with a second-generation tyrosine kinase inhibitor or a stem cell transplant. Highly significant reduction in height SDS's was observed (P = 0.002 at 5th year). Children who started imatinib therapy after the onset of puberty were immune to this adverse effect (P = 0.448 and 0.003 at 5th year of treatment for pubertal and prepubertal children, respectively). The 5-year survival probability of 33 children who received imatinib in chronic phase was 80% with a median survival time of 60 months (mean: 70.2; 95% CI: 60-80.5).

CONCLUSIONS

Growth retardation is a significant adverse effect of imatinib in children with CML. The failure to gain appropriate height was most discernible when imatinib was initiated in the prepubertal period. Etiology and remedial measures need to be investigated.

Chronic myeloid leukemia (CML) in children: classical and newer therapeutic approaches

Chronic myeloid leukemia (CML) represents a rare myeloproliferative disease among children where allogeneic stem cell transplantation (SCT) remains the curative gold standard. However, the impressive early cytogenetic and molecular responses achieved by tyrosine kinase inhibitors [TKIs (imatinib, nilotinib, and dasatinib)] as first-line or even sole treatment in adults, has led to their increasing use also among children. Due to limited data regarding long-term results of TKIs and especially those of second generation in pediatric cohorts, we would like to add clinical information in this rare series of patients by reporting on four children with CML over a 10-year period, focusing on TKIs, dose escalations and clinical responses.

Management of chronic myeloid leukemia in childhood

Childhood chronic myelogenous leukemia (CML) is a rare malignancy, and experience with optimal treatment is very limited. Traditionally, allogeneic hematopoietic stem cell transplantation was considered the only curative treatment. Imatinib, a small-molecule inhibitor of the BCR-ABL tyrosine kinase (TKI), has been proven highly successful in adults with CML, resulting in prolonged molecular response with limited drug toxicity. This drug is now included as front-line therapy for CML in pediatrics as well, though valid concerns about serious late sequelae remain unresolved. Specific pediatric treatment guidelines have not yet been formulated, and most algorithms are derived from experience in adult CML. This overview attempts to summarize pediatric studies on issues such as dose, duration, adverse effects, and steering criteria for TKI treatment, adapting guidelines developed in adult medicine to pediatrics. Most importantly, pediatric patients with CML receiving TKI treatment should be enrolled into formal trials.

Distinct impact of imatinib on growth at prepubertal and pubertal ages of children with chronic myeloid leukemia

OBJECTIVE

To determine the extent of growth impairment resulting from imatinib treatment in children with chronic myeloid leukemia (CML).

STUDY DESIGN

Clinical records of 48 chronic-phase CML children administered imatinib as the first-line therapy between 2001 and 2006 were analyzed retrospectively. Cumulative change in height was assessed using the height height-SDS and converted height data from age- and sex-adjusted Japanese norms.

RESULTS

A decrease in height-SDS was observed in 72.9% of children, with a median maximum reduction in height-SDS of 0.61 during imatinib treatment. Median follow-up time was 34 months (range, 10-88 months). Growth impairment was seen predominantly in children who started imatinib at a prepubertal age compared with those who started at pubertal age. Growth velocity tended to recuperate in prepubertal children with growth impairment, as they reached pubertal age, suggesting that imatinib had little impact on growth during puberty.

CONCLUSIONS

Growth impairment was a major adverse effect of long-term imatinib treatment in children with CML. We report the distinct inhibitory effect of imatinib on growth in prepubertal and pubertal children with CML. We should be aware of growth deceleration in children, especially in young children given imatinib before puberty and subjected to prolonged exposure.

Successful bone marrow transplantation in a pediatric patient with chronic myeloid leukemia from a HLA-identical sibling selected by preimplantation HLA testing

We report successful bone marrow transplantation in an 11-year-old male with chronic myeloid leukemia from his HLA-identical sibling selected by preimplantation HLA testing. Because collection of cord blood failed, the transplantation was performed when the donor reached the age of 19 months, and sufficient bone marrow could be harvested safely. The patient was BCR/ABL negative at the time of transplantation after complete molecular response to imatinib. Currently, 16 months post-transplantation he is well and in complete molecular remission. This report describes preimplantation HLA-genotyping to deliver a matched sibling donor for successful transplantation of a malignant disorder.

Targeted therapy in pediatric and adolescent oncology

Cancers in children and adolescents are fortunately infrequent. Overall, cure rates are good, approximately 80%, although this varies by histology and stage. Targeted therapies aim to improve efficacy and decrease toxicity by more specifically affecting malignant cells or their supporting stroma. Cancers of early life are often of different histology than those seen in adults. Sometimes, the same pathway is affected, even if the histology is different. Toxicities may also be different, particularly in younger children. These factors render drug development in young people challenging. This article reviews some successes and challenges to that development, including brief discussions of imatinib, lestaurtinib, antiangiogenesis, and anti-GD2 therapies.

The treatment of pediatric chronic myelogenous leukemia in the imatinib era

Childhood chronic myelogenous leukemia (CML) is a rare hematologic disease, with limited literature on the methods of treatment. Previously, allogeneic hematopoietic stem cell transplantation (HSCT) was considered the only curative treatment for this disease. Treatment with imatinib, a selective inhibitor of the BCR-ABL tyrosine kinase (TKI), has resulted in prolonged molecular response with limited drug toxicity. Imatinib is now implemented in the primary treatment regimen for children, but the paucity of evidence on its ability to result in permanent cure and the potential complications that may arise from long-term treatment with TKIs have prevented imatinib from superseding HSCT as the primary means of curative treatment in children. The results of allogeneic HSCT in children with CML are similar to those observed in adults; HSCT-related complications such as transplant-related mortality and graft-versus-host disease remain significant challenges. An overall consensus has been formed with regards to the need for HSCT in patients with imatinib resistance or those with advanced-phase disease. However, issues such as when to undertake HSCT in chronic-phase CML patients or how best to treat patients who have relapsed after HSCT are still controversial. The imatinib era calls for a reevaluation of the role of HSCT in the treatment of CML. Specific guidelines for the treatment of pediatric CML have not yet been formulated, underscoring the importance of prospective studies on issues such as duration of imatinib treatment, optimal timing of HSCT and the type of conditioning utilized, possible treatment pre- and post-HSCT, and the role of second-generation TKIs.

Clinical characteristics and treatment outcome of pediatric patients with chronic myeloid leukemia

As chronic myeloid leukemia is rare in children, most data on imatinib mesylate therapy is derived from adult studies. We retrospectively evaluated pediatric (<14 years) patients with Ph+ chronic myeloid leukemia treated with imatinib mesylate, from January 2003 through June 2008. Of the 12 chronic myeloid leukemia patients (2% of all leukemias) 11 were in chronic phase while one had myeloid blast crisis. Six subsequently underwent stem cell transplantation. Five patients had grade 3-4 arthralgia requiring therapy alteration. None achieved complete molecular remission (MR) with imatinib mesylate alone. In contrast 3/6 patients post stem cell transplantation have undetectable BCR-ABL. Three patients relapsed to chronic phase (1 imatinib mesylate; 2 stem cell transplantation). Relapse free survival is 65.6% at four years and all are alive. Imatinib mesylate is effective therapy for children with chronic myeloid leukemia. However, cure probably requires stem cell transplantation. Acute toxicity of imatinib mesylate is tolerable, but long-term effects on growing children are unknown. Pediatric patients with chronic myeloid leukemia should undergo stem cell transplantation when appropriate related donors are available.

Megakaryocytic blast crisis at presentation in a pediatric patient with chronic myeloid leukemia

Patients with chronic myeloid leukemia (CML) infrequently present in blast crisis (BC). While most BC are of myeloid origin, megakaryocytic BC is rare, especially at the time of CML diagnosis. We describe the first pediatric patient presenting with megakaryocytic leukemia and having BCR-ABL1 translocation as the single chromosomal abnormality. Clinical features were more suggestive of CML in megakaryocytic blast crisis than Philadelphia chromosome positive de novo AML. The patient was treated with AML-directed chemotherapy and imatinib mesylate followed by umbilical cord blood stem cell transplantation. The patient was in complete molecular response 16 months after stem cell transplantation.

CML in pregnancy and childhood

With the improved survivals offered by the tyrosine kinase inhibitors has come the necessity to address issues relating to quality of life and one such area is that of fertility and parenting. Animal data suggest that imatinib at standard dosages is unlikely to impair fertility in either adult males or females but human data remain limited. Children born to men who are actively taking imatinib at the time of conception appear healthy and current advice is not to discontinue treatment. In contrast the data relating to children born to women exposed to imatinib during pregnancy are less encouraging. Although numbers are small there has been a disturbing cluster of rare congenital malformations such that imatinib cannot be safely recommended, particularly during the period of organogenesis. The appropriate management of children with CML has also been radically changed by the advent of imatinib. The features of the disease at presentation, the natural history and the response to therapy seem to be identical in children to that seen in adults. Now that imatinib has been in clinical use for almost ten years without severe long-term side effects, most physicians are now comfortable advising a trial of imatinib prior to consideration of transplant. Data relating to the efficacy and safety of second generation tyrosine kinase inhibitors in childhood is entirely absent and transplant remains the first choice for patients failing imatinib and perhaps also for young patients with sub-optimal responses.

Treatment of pediatric chronic myeloid leukemia in the year 2010: use of tyrosine kinase inhibitors and stem-cell transplantation

Allogeneic hematopoietic stem cell transplantation (allo-SCT) remains the only proven cure for chronic myeloid leukemia (CML), a rare malignancy in childhood. With the excellent results induced by the tyrosine kinase inhibitor (TKI) imatinib in adults in the last decade, the appropriate management of children with CML has also changed radically, and only a minority are now transplanted as a front-line treatment. Data on pediatric experiences with imatinib in CML from controlled trials remain very limited, but this review of available data describes the role of imatinib in children with CML, addressing: 1) the starting dose; 2) pharmacokinetics in childhood; 3) possible adverse effects, with a focus on the still-growing skeleton; 4) early monitoring of treatment efficacy in an attempt to avoid failure; 5) the timing of allo-SCT in children; and 6) treatment of CML relapse after allo-SCT. Because the characteristics of CML in children seem to overlap extensively with what is described in adult internal medicine, most answers and pediatric algorithms are adapted from the treatment of CML in adults. Today in 2010, allo-SCT in children should be postponed until CML becomes refractory to imatinib. The approach for young patients with suboptimal responses is unclear because data on the efficacy and safety of second-generation TKIs in childhood are almost entirely missing. Other than being included in a formal trial on second-generation TKIs, allo-SCT for patients failing imatinib remains the first choice.

Initial treatment for patients with CML

For adult patients who present with chronic myeloid leukemia (CML) in chronic phase it is now generally agreed that initial treatment should start with the tyrosine kinase inhibitor (TKI) imatinib at 400 mg daily. Five years after starting imatinib about 60% of these patients will be in complete cytogenetic response (CCyR), still taking imatinib; an appreciable proportion of these will have achieved a major molecular response, defined as a 3-log reduction in the level of BCR-ABL1 transcripts in their blood. The patients in CCyR seem to have a very low risk of relapse to chronic phase or of progression to advanced phase. Other patients may be resistant to imatinib or may experience significant side effects that require change of therapy. The best method of monitoring responding patients is to enumerate Philadelphia chromosome–positive marrow metaphases at 3-month intervals until CCyR and to perform RQ-PCR for BCR-ABL1 transcripts at 3-month intervals after starting imatinib. The recommendations for defining “failure” and “sub-optimal response” proposed by the European LeukemiaNet in 2006 have proved to be a major contribution to assessing responses in individual patients and are now being updated. Patients who fail imatinib may respond to second-generation TKIs, but allogeneic stem cell transplantation still plays an important role for eligible patients who fare badly with TKIs. Patients who present in advanced phases of CML should be treated initially with TKI alone or with TKI in conjunction with cytotoxic drugs, but their overall prognosis is likely to be much inferior to that of those presenting in early chronic phase.

Correlation of BCR/ABL transcript variants with patients' characteristics in childhood chronic myeloid leukaemia

BACKGROUND AND OBJECTIVE

The characteristic chromosomal translocation t(9;22)(q34;q11) in chronic myeloid leukaemia (CML) mainly results in the two different BCR/ABL fusion transcripts b2a2 or b3a2. Both transcript variants can occur simultaneously due to alternative splicing of the b3a2 transcript. Conflicting results have been reported on the influence of the transcripts on haematological findings at diagnosis and the course of the disease in adults while data concerning these topics on childhood CML are still missing. This paper reports on a correlation of BCR/ABL transcript variants with patients' characteristics in childhood CML.

DESIGN AND METHODS

Transcript types were determined in 146 paediatric patients with CML enrolled in trial CML-paed-I. Fifty-five patients (38%) expressed b2a2, 53 patients (36%) b3a2 and 38 patients (26%) both transcripts, respectively. These findings were correlated with patients' characteristics (sex, age, WBC, Hb, platelet count, hepatosplenomegaly, etc.) assessed at diagnosis.

RESULTS

While the co-expression of both transcripts was evenly distributed among genders [b2a2 + b3a2: 22 females (28%), 16 males (24%)] a highly significant difference (P = 0.007) was found concerning the expression of the b2a2 transcript [34 male (51%) vs. 21 female (27%)] and vice versa of the b3a2 transcript [17 male (25%) vs. 36 female (45%)]. High platelet counts and the combination of high platelet counts in conjunction with pronounced leukocytosis were observed more often in patients expressing the b3a2 transcript.

CONCLUSIONS

These findings demonstrate that in children like in adults specific BCR/ABL transcript types present at diagnosis are associated with distinct haematological alterations (e.g. a high platelet count with the transcript b3a2). However, the sex-dependent skewed distribution of the BCR/ABL transcript types observed so far in this paediatric cohort only deserves further investigation.