Allogeneic Stem Cell Transplantation for Patients with T315I BCR-ABL Mutated Chronic Myeloid Leukemia

The Contemporary Role of Hematopoietic Stem Cell Transplantation in the Management of Chronic Myeloid Leukemia: Is It the Same in All Settings?

Hematopoietic stem cell transplantation (HSCT) for chronic myeloid leukemia (CML) patients has transitioned from the standard of care to a treatment option limited to those with unsatisfactory tyrosine kinase inhibitor (TKI) responses and advanced disease stages. In recent years, the threshold for undergoing HSCT has increased. Most CML patients now have life expectancies comparable to the general population, and therefore, the goal of therapy is shifting toward achieving treatment-free remission (TFR). While TKI discontinuation trials in CML show potential for achieving TFR, relapse risk is high, affirming allogeneic HSCT as the sole curative treatment. HSCT should be incorporated into treatment algorithms from the time of diagnosis and, in some patients, evaluated as soon as possible. In this review, we will look at some of the recent advances in HSCT, as well as its indication in the era of aiming for TFR in the presence of TKIs in CML.

Chronic Myeloid Leukemia in Children and Adolescents

Acute leukemia is the most common malignancy in childhood, while chronic myeloid leukemia is rare, accounting for only 2% to 3% of all leukemia in childhood and 9% in adolescents, with an annual incidence of 1 and 2.2 cases per million in the two groups. The goal in Pediatrics is remission and cure with tyrosine kinase inhibitors (TKIs) and monitoring closely for long-term effects of TKI use.

The new generation tyrosine kinase inhibitor improves the survival of chronic myeloid leukemia patients after allogeneic stem cell transplantation

The introduction of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) treatment has dramatically improved the prognosis of CML patients and reduced the number of patients receiving allogeneic stem cell transplantation (allo-SCT). However, the impact of the newest-generation TKIs on the overall survival (OS) after allo-SCT has not been well described. To investigate the beneficial effects of TKIs on the prognosis after allo-SCT, we conducted a retrospective observational study using the Transplant Registry Unified Management Program database in Japan. We analyzed 1,188 patients (male/female: 738/450; median age: 44 years; range: 16-75) who underwent their first allo-SCT between January 2001 and December 2018. We divided the patients into two groups according to the TKI treatment used before allo-SCT: group 1 was treated with the 1^st generation TKI imatinib; group 2 was treated with the 2^nd generation TKIs nilotinib, dasatinib, or bosutinib and/or the 3^rd generation TKI ponatinib. We compared the post allo-SCT OS between the two groups. The 3-year OS rates (95%CI) of groups 1 and 2 were 59.3% (54.8-63.5%) and 65.8% (61.6-69.6%), respectively (p=0.017). Multivariate analysis confirmed that group 2 had superior OS after allo-SCT compared to group 1 (p=0.002). Other factors associated with superior prognosis were age ≤65, performance status (PS) 0/1, a 6/6 HLA-matched donor and chronic-phase (CP) disease status at allo-SCT. A subgroup analysis showed poor prognoses for patients who could not obtain a molecular response before allo-SCT and patients with positive T315I mutation in the BCR/ABL gene. In group 2, early allo-SCT was correlated with superior OS in patients with a blast-crisis disease status at allo-SCT (p=0.001). The cumulative incidence of non-relapse mortality rate significantly decreased in group 2 (p=0.0005). The post allo-SCT OS was improved both by pre- and post-management of allo-SCT and by the introduction of newer TKIs. This article is protected by copyright. All rights reserved.

The Clinical Significance of BCR-ABL1 Mutations in Patients With Philadelphia Chromosome-Positive Chronic Myeloid Leukemia Who Underwent Allogeneic Hematopoietic Cell Transplantation

The global standard therapy for chronic myeloid leukemia (CML) is tyrosine kinase inhibitors (TKIs). One of the causes of therapeutic resistance to some TKIs corresponds to point mutations in the BCR-ABL1 fusion gene. Allogeneic hematopoietic cell transplantation (HCT) is a treatment option for high-risk CML, including TKI resistance. Although BCR-ABL1 point mutations comprise a major factor in the assessment of the indications for HCT, there is limited evidence for their significance in relation to transplant outcomes. This study aimed to evaluate the profiles and transplant outcomes of BCR-ABL1 mutations in allografted patients with CML. The retrospective study used a nationwide registry data including adult patients with CML who underwent their first HCT between 2006 and 2016. The inclusion criterion was the evaluation of the status of the BCR-ABL1 mutation before HCT. The cohort included 315 patients with a median age of 44 years (range 16-70 years). Point mutations were detected in 152 patients, of which 101 (66%) harbored T315I mutations and 51 harbored mutations other than T315I (non-T315I). With a median follow-up period of 38 months (range 2-114 months), overall survival (OS) at 3 years was worse in the mutation group than in the no-mutation group (53% versus 71%; P = .002), which was validated by multivariate analysis (hazard ratio [HR] = 1.50; 95% confidence interval [CI], 1.0-2.2; P = .038); this difference was remarkable in the chronic phase of CML. OS in the non-T315I group was significantly worse than that in the no-mutation group (HR = 1.69; 95% CI, 1.0-2.8; P = .035). The nationwide study has successfully evaluated the BCR-ABL1 mutational profile and its outcomes in patients with CML who received HCT. The mortality risk was significantly higher in patients with the BCR-ABL1 mutation than in patients without the mutation. These findings would be useful to understand the clinical significance of various BCR-ABL1 mutations in CML and provide insight into the on mid need for treatment strategies for cases of CML with BCR-ABL1 mutations.

Precision diagnostics: Integration of tissue pathology and genomics in cancer

Traditionally, cancer diagnosis and management has been reactionary in that symptoms lead to investigations, then a diagnosis is followed by clinical management. This process is heavily dependent on tissue diagnosis mainly by histopathology and to a lesser extent, cytopathology. However, in recent times there has been a shift towards precision medicine to enable prevention, prediction and personalisation in healthcare. The core of precision medicine is optimising therapeutic benefit for patients, by using genomic and molecular profiling, analogously termed precision pathology. This review explores (1) the evolution of pathology from a para-clinical discipline to a mainstream medical field integral to oncology tumour boards; (2) its critical role in preventative, diagnostic, therapeutic and follow-up cancer care; (3) the future of tissue pathology in the era of precision oncology; and (4) how pathologists may evolve to future-proof their profession.

Tyrosine Kinase Inhibitors and Beyond for Chronic Myeloid Leukemia in Children

Chronic myeloid leukemia (CML) is rare in children but presents a unique challenge as recent drug innovations have turned CML into a chronic disease with implications for treatment into adulthood. With the approval of newer-generation tyrosine kinase inhibitors (TKIs) in addition to imatinib, providers have more options for the treatment of chronic-phase CML (CML-CP) in children. The second-generation TKIs approved for use in children, nilotinib and dasatinib, have higher response rates than first-generation imatinib; however, overall survival rates appear to be the same. Even more options may soon become available with ongoing investigations into the use of bosutinib and ponatinib and other new agents in children. Possible long-term side effects of TKIs, including growth failure, should be carefully acknowledged by the treating provider. Although these known associations may not preclude treatment, providers should be aware of them to guide their management of pediatric patients with CML being treated long term with TKI therapy. Treatment-free remission is a desired goal for pediatric patients and providers alike, but current recommendations are for attempts at achieving this to be restricted to clinical study settings.

Ponatinib therapy in recurrent Philadelphia chromosome-positive central nervous system leukemia with T315I mutation after Allo-HSCT

Central nervous system leukemia (CNSL) relapse is relatively common among Philadelphia chromosome-positive (Ph+) leukemia patients who undergo allogeneic hematopoietic stem cell transplantation (allo-HSCT). The prognosis of patients is dismal for those with a BCR-ABL T315I mutation, which is resistant to TKIs including second-generation drugs. We assessed ponatinib for nine patients with recurrent Ph+ CNSL and a T315I mutation after allo-HSCT, including five patients with Ph+ acute lymphoblastic leukemia and four with chronic myelogenous leukemia. Five patients experienced isolated CNSL relapse, and four experienced CNSL with hematologic relapse. All patients received ponatinib combined with intrathecal chemotherapy, and four patients with hematologic relapse received systemic chemotherapy and/or donor lymphocyte infusion. All patients achieved a deep molecular response and central nervous system remission (CNSR) at a median time of 1.5 (range: 0.7-3) months after ponatinib treatment. Two patients experienced a second CNSL relapse due to ponatinib reduction, but they achieved CNSR again after an increase to the standard dosage. Six patients developed graft versus host disease. By April 1, 2019, eight patients were alive, and one died of pneumonia. The median time of survival after the first CNSL relapse posttransplantation was 18 (range: 11.2-48.5) months. Our data from a small number of samples suggests that ponatinib is effective for recurrent Ph+ CNSL patients with a BCR-ABL T315I mutation after allo-HSCT and warrants broader clinical evaluation.

CDK4/CDK6 inhibition as a novel strategy to suppress the growth and survival of BCR-ABL1T315I+ clones in TKI-resistant CML

Purpose

Ponatinib is the only approved tyrosine kinase inhibitor (TKI) suppressing BCR-ABL1^T315I-mutated cells in chronic myeloid leukemia (CML). However, due to side effects and resistance, BCR-ABL1^T315I-mutated CML remains a clinical challenge. Hydroxyurea (HU) has been used for cytoreduction in CML for decades. We found that HU suppresses or even eliminates BCR-ABL1^T315I+ sub-clones in heavily pretreated CML patients. Based on this observation, we investigated the effects of HU on TKI-resistant CML cells in vitro.

Methods

Viability, apoptosis and proliferation of drug-exposed primary CML cells and BCR-ABL1+ cell lines were examined by flow cytometry and ³H-thymidine-uptake. Expression of drug targets was analyzed by qPCR and Western blotting.

Findings

HU was more effective in inhibiting the proliferation of leukemic cells harboring BCR-ABL1^T315I or T315I-including compound-mutations compared to cells expressing wildtype BCR-ABL1. Moreover, HU synergized with ponatinib and ABL001 in inducing growth inhibition in CML cells. Furthermore, HU blocked cell cycle progression in leukemic cells, which was accompanied by decreased expression of CDK4 and CDK6. Palbociclib, a more specific CDK4/CDK6-inhibitor, was also found to suppress proliferation in primary CML cells and to synergize with ponatinib in producing growth inhibition in BCR-ABL1^T315I+ cells, suggesting that suppression of CDK4/CDK6 may be a promising concept to overcome BCR-ABL1^T315I-associated TKI resistance.

Interpretation

HU and the CDK4/CDK6-blocker palbociclib inhibit growth of CML clones expressing BCR-ABL1^T315I or complex T315I-including compound-mutations. Clinical studies are required to confirm single drug effects and the efficacy of `ponatinib+HU´ and ´ponatinib+palbociclib´ combinations in advanced CML.

Funding

This project was supported by the Austrian Science Funds (FWF) projects F4701-B20, F4704-B20 and P30625.

How I treat chronic myeloid leukemia in children and adolescents

Evidence-based recommendations have been established for treatment of chronic myeloid leukemia (CML) in adults treated with tyrosine kinase inhibitors (TKIs), but the rarity of this leukemia in children and adolescents makes it challenging to develop similar recommendations in pediatrics. In addition to imatinib, which was approved for pediatric CML in 2003, the second-generation TKIs dasatinib and nilotinib were recently approved for use in children, expanding the therapeutic options and pushing allogeneic stem cell transplantation to a third-line treatment of most pediatric cases. Yet, without sufficient data on efficacy and safety specific to pediatric patients, the selection of a TKI continues to rely on clinical experience in adults. Here, we present 4 case scenarios highlighting common yet challenging issues encountered in the treatment of pediatric CML (suboptimal response, poor treatment adherence, growth retardation, and presentation in advanced phases). Limited experience with very young children, the transition of teenagers to adult medicine, and the goal of achieving treatment-free remission for this rare leukemia are additional significant obstacles that require further clinical investigation through international collaboration.

We do still transplant CML, don't we?

The remarkable clinical activity of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) has transformed patient outcome. Consequently, allogeneic stem cell transplantation (allo-SCT) is no longer the only treatment modality with the ability to deliver long-term survival. In contrast to the central position it held in the treatment algorithm 20 years ago, allografting is now largely reserved for patients with either chronic-phase disease resistant to TKI therapy or advanced-phase disease. Over the same period, progress in transplant technology, principally the introduction of reduced intensity conditioning regimens coupled with increased donor availability, has extended transplant options in patients with CML whose outcome can be predicted to be poor if they are treated with TKIs alone. Consequently, transplantation is still a vitally important, potentially curative therapeutic modality in selected patients with either chronic- or advanced-phase CML. The major causes of transplant failure in patients allografted for CML are transplant toxicity and disease relapse. A greater understanding of the distinct contributions made by various factors such as patient fitness, patient-donor HLA disparity, conditioning regimen intensity, and transplant toxicity increasingly permits personalized transplant decision making. At the same time, advances in the design of conditioning regimens coupled with the use of adjunctive posttransplant cellular and pharmacologic therapies provide opportunities for reducing the risk of disease relapse. The role of SCT in the management of CML will grow in the future because of an increase in disease prevalence and because of continued improvements in transplant outcome.

The consensus on indications, conditioning regimen, and donor selection of allogeneic hematopoietic cell transplantation for hematological diseases in China-recommendations from the Chinese Society of Hematology

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is widely used to treat malignant hematological neoplasms and non-malignant hematological disorders. Approximately, 5000 allo-HSCT procedures are performed in China annually. Substantial progress has been made in haploidentical HSCT (HID-HSCT), pre-transplantation risk stratification, and donor selection in allo-HSCT, especially after the establishment of the "Beijing Protocol" HID-HSCT system. Transplant indications for selected subgroups in low-risk leukemia or severe aplastic anemia (SAA) differ from those in the Western world. These unique systems developed by Chinese doctors may inspire the refining of global clinical practice. We reviewed the efficacy of allo-HSCT practice from available Chinese studies on behalf of the HSCT workgroup of the Chinese Society of Hematology, Chinese Medical Association and compared these studies to the consensus or guideline outside China. We summarized the consensus on routine practices of all-HSCT in China and focused on the recommendations of indications, conditioning regimen, and donor selection.

A review of hematopoietic cell transplantation in China: data and trends during 2008-2016

Hematopoietic cell transplantation (HCT) activity in China was surveyed to assess its current status. A record number of HCTs (21 884: 16 631 allogeneic (76%) and 5253 autologous (24%)) were reported by 76 centers in China between 1 January 2008 and 30 June 2016. HCT trends included continued growth in transplant activity, a continued rapid increase in haploidentical donors (HID), and slower growth for unrelated donors, matched-related donors (MRD) and cord blood transplantation (CBT). The proportion of HID HCT among allogeneic HCTs increased from 29.6% (313/1062) in 2008 to 48.8% (1939/3975) in 2015, even 51.7% (1157/2237) in the first half of 2016. During this time frame, the proportion of MRD HCTs among allogeneic HCTs decreased from 48.1% (511/1062) to 33.0% (332/3975). The proportion of unrelated donor HCTs among allogeneic HCTs decreased from 20.4 (216/1062) to 13.6% (540/3975). The proportion of CBTs among allogeneic HCTs was increased from 2.1% (22/1062) to 4.2% (184/3975). HCTs have been increasing continuously for all indications except chronic myelogenous leukemia. Severe aplastic anemia is a common HCT indication among non-malignant diseases in China. The number of cases of allogeneic HCT for this disorder has increased annually, from 59 (5.6%) in 2008 to 569 (14.3%) in 2015, even 334 (14.9%) in the first half year in 2016. This survey clearly shows recent trends for HCTs in China.

Allogeneic stem cell transplantation in chronic myeloid leukemia patients: Single center experience

Chronic myeloid leukemia (CML) is a myeloproliferative disease which leads the unregulated growth of myeloid cells in the bone marrow. It is characterized by the presence of Philadelphia chromosome. Reciprocal translocation of the ABL gene from chromosome 9 to 22 t (9; 22) (q34; q11.2) generate a fusion gene (BCR-ABL). BCR-ABL protein had constitutive tyrosine kinase activity that is a primary cause of chronic phase of CML. Tyrosine kinase inhibitors (TKIs) are now considered standard therapy for patients with CML. Even though, successful treatment with the TKIs, allogeneic stem cell transplantation (ASCT) is still an important option for the treatment of CML, especially for patients who are resistant or intolerant to at least one second generation TKI or for patients with blastic phase. Today, we know that there is no evidence for increased transplant-related toxicity and negative impact of survival with pre-transplant TKIs. However, there are some controversies about timing of ASCT, the optimal conditioning regimens and donor source. Another important issue is that BCR-ABL signaling is not necessary for survival of CML stem cell and TKIs were not effective on these cells. So, ASCT may play a role to eliminate CML stem cells. In this article, we review the diagnosis, management and treatment of CML. Later, we present our center’s outcomes of ASCT for patients with CML and then, we discuss the place of ASCT in CML treatment in the TKIs era.