Successful treatment of Philadelphia chromosome-positive mixed phenotype acute leukemia by appropriate alternation of second-generation tyrosine kinase inhibitors according to BCR-ABL1 mutation status

Acute leukemia with KMT2A rearrangement: A master of disguise

Mixed-phenotype acute leukemia (MPAL) is a rare form of leukemia with ambiguous lineage, and there are challenges in accurately diagnosing this entity according to formal criteria. Here we report a case which was initially diagnosed as "AML" based on atypical peripheral blood flow cytometry that was subsequently determined to be B-ALL with KMT2A rearrangement based on marrow results. Although KMT2A rearrangements represent a defining genetic abnormality for acute leukemia of ambiguous lineage, this case did not meet the criteria for MPAL based on WHO 2022 criteria. This case highlights the diagnostic challenges of MPAL and the potential limitations of the current classification. We discuss the most appropriate workup and management of these patients and identify areas for future study.

Hypocellular Philadelphia chromosome-positive mixed-phenotype acute leukemia successfully treated with dasatinib: A case report

Both hypocellular leukemia and Philadelphia (Ph) chromosome-positive mixed-phenotype acute leukemia (MPAL) are rare subtypes of leukemia showing unfavorable outcomes and lacking established optimal management. Ph-positive leukemia most often presents with hypercellularity and hypoplasia is a rare condition. The present study reports an extremely rare case of hypocellular biclonal Ph-positive MPAL, which was diagnosed by biopsy and genetic analysis of bone marrow, and successfully treated with dasatinib and steroids. Briefly, a 77-year-old man presented with pancytopenia and flow cytometry of bone marrow could not be evaluated due to hypocellularity. The patient was finally diagnosed with hypocellular Ph-positive MPAL by genetic analysis and immunostaining of bone marrow biopsy. Although blood cells recovered with methylprednisolone pulse administration alone for concurrent optic neuritis, hematopoietic function rapidly normalized with dasatinib administered after definitive diagnosis of Ph-positive leukemia. Dasatinib and oral prednisolone were continued following methylprednisolone pulse administration and the patient achieved molecular complete remission (CR) on day 140 of treatment; molecular CR was maintained thereafter without any severe adverse events. In conclusion, the combination of dasatinib and a steroid may be one of the tolerable treatment options for elderly patients with hypocellular biclonal Ph-positive MPAL. Furthermore, genetic analysis and immunostaining of bone marrow biopsy can help with the diagnosis of leukemia with hypocellular bone marrow.

Efficacy and safety of low-dose imatinib in an elderly patient with mixed phenotype acute leukemia with t(9;22)(q34;q11.2);BCR-ABL1

Low-dose imatinib with monitoring of drug concentrations in blood may successfully control Philadelphia chromosome-positive mixed phenotype acute leukemia (Ph+MPAL), particularly in elderly patients with comorbidities.

Prognostic impact of Philadelphia chromosome in mixed phenotype acute leukemia (MPAL): A cancer registry analysis on real-world outcome

Mixed phenotype acute leukemia (MPAL) is thought to have poor outcome, and presence of the Philadelphia chromosome (Ph+) has been considered to be an adverse prognostic marker. However, most of these reports were in the pre-tyrosine kinase inhibitors (TKIs) era. Recent limited reports indicate improved outcomes for MPAL with the addition of TKIs. We examined the outcomes of 241 cases of MPAL according to the 2008 WHO classification from the Surveillance, Epidemiology, and End Results registry. The MLL+ patients had a median age of 6 years while other subtypes occurred mostly in adults and had comparable age. On multivariate analyses and after adjustment for age, year of diagnosis and chemotherapy status, Ph+ MPAL patients had reduced risk of death in comparison to Ph(-) MPAL patients (hazard ratio [HR] = 0.28, P = .002). So, MLL+ MPAL had the worst outcome with a 10-fold increased risk of death in comparison to Ph+ MPAL patients (HR = 10.2, P < .001). Importantly, the outcome of Ph+ MPAL was comparable to Ph+ acute lymphoblastic leukemia in a 1:1 matched case-control analysis. In conclusion, this is the largest registry study which examines the outcomes of MPAL subtypes. We confirm that MPAL is a heterogenous disease. Note, Ph+ MPAL nowadays has a better OS in comparison to other subtypes and is comparable to Ph+ ALL patients. This is most likely secondary to changes in practice and more utilization of TKIs. On the other hand, MLL rearrangement is associated with infantile MPAL and has a dismal prognosis.

Mixed phenotype acute leukemia: Biological profile, clinical characteristic and treatment outcomes: Report of the population-based study

OBJECTIVES

The aim of this population-based, retrospective study was to analyze biological and clinical features and treatment results in children diagnosed with MPAL in all Polish pediatric oncology centers between 2007 and 2018.

METHODS

Among 2893 children and adolescents diagnosed and treated for acute leukemia, 39 (1.35%) patients fulfilled the WHO criteria of MPAL. The T/myeloid phenotype was most prevalent.

RESULTS

Cytogenetics findings were seen in 2 (5.1%), while chromosomal abnormalities were found in 14 (35.9%) patients. Thirty-two patients achieved CR-1, including 23 (92.0%) treated with ALL-directed chemotherapy and 9 (64.3%) treated with AML-type induction regimens. Within these patients, 4 (12.5%) died due to treatment-related complications and 11 (34.4%) relapsed. Nineteen (63.3%) patients underwent allo-HSCT in CR-1 and 14 (73.7%) of them have been in CR-1. In total, 17 (43.6%) patients remain in CR-1 for 1-12 years, including 14 (58.3%) with T/myeloid MPAL. The 5-year pOS and pEFS were 51.8% and 44.2%, respectively. The overall survival for ALL-directed therapy was significantly better than the one for AML-type chemotherapy (P = .001). It was also better for patients who underwent HSCT in CR-1 (P = .001).

CONCLUSIONS

The prognosis of MPAL is unsatisfactory, but initial treatment with ALL-directed chemotherapy consolidated with allo-HSCT improves the outcomes in MPAL.

PDGFRB mutation and tyrosine kinase inhibitor resistance in Ph-like acute lymphoblastic leukemia

Philadelphia chromosome (Ph)-like acute lymphoblastic leukemia (ALL) comprises ∼10% to 15% of childhood ALL cases, many of which respond exquisitely to tyrosine kinase inhibitors (TKIs), for example, imatinib in PDGFRB-rearranged ALL. However, some cases developed drug resistance to TKIs and the mechanisms are poorly understood. In this study, we identified a novel PDGFRB fusion gene, namely AGGF1-PDGFRB, and functionally characterized its oncogenic potential in vitro. Further genomic profiling of longitudinally collected samples during treatment revealed the emergence of a mutation, PDGFRBC843G , which directly conferred resistance to all generations of ABL TKIs, including imatinib, dasatinib, nilotinib, and ponatinib. PDGFRB-mutant leukemia cells are highly sensitive to multitarget kinase inhibitor CHZ868, suggesting potential therapeutic options for some patients resistant to ABL TKIs. In summary, we describe a complex clonal evolution pattern in Ph-like ALL and identified a novel PDGFRB point mutation that drives leukemia relapse after ABL TKI treatment.

Therapy for children and adults with mixed phenotype acute leukemia: a systematic review and meta-analysis

The rarity of mixed-phenotype acute leukemia (MPAL) has resulted in diffuse literature consisting of small case series, thus precluding a consensus treatment approach. We conducted a meta-analysis and systematic review to investigate the association of treatment type (acute lymphoblastic leukemia [ALL], acute myeloid leukemia [AML], or "hybrid" regimens), disease response, and survival. We searched seven databases from inception through June 2017 without age or language restriction. Included studies reported sufficient treatment detail for de novo MPAL classified according to the well-established European Group for Immunological Characterization of Acute Leukemias (EGIL) or World Health Organization (WHO2008) criteria. Meta-analyses and multivariable analyses of a patient-level compiled case series were performed for the endpoints of complete remission (CR) and overall survival (OS). We identified 97 reports from 33 countries meeting criteria, resulting in 1,499 unique patients with data, of whom 1,351 had sufficient detail for quantitative analysis of the study endpoints. Using either definition of MPAL, meta-analyses revealed that AML induction was less likely to achieve a CR as compared to ALL regimens, (WHO2008 odds ratio [OR] = 0.33, 95% confidence interval [95% CI] 0.18-0.58; EGIL, OR = 0.18, 95% CI 0.08-0.40). Multivariable analysis of the patient-level data supported poorer efficacy for AML induction (versus ALL: OR = 0.45 95% CI 0.27-0.77). Meta-analyses similarly found better OS for those beginning with ALL versus AML therapy (WHO2008 OR = 0.45, 95% CI 0.26-0.77; EGIL, OR = 0.43, 95% CI 0.24-0.78), but multivariable analysis of patient-level data showed only those starting with hybrid therapy fared worse (hazard ratio [HR] = 2.11, 95% CI 1.30-3.43). MPAL definition did not impact trends within each endpoint and were similarly predictive of outcome. Using either definition of MPAL, ALL-therapy is associated with higher initial remission rates for MPAL and is at least equivalent to more intensive AML therapy for long-term survival. Prospective trials are needed to establish a uniform approach to this heterogeneous disease.

Mixed-phenotype acute leukemia: suboptimal treatment when the 2008/2016 WHO classification is used

Background

Different criteria have been used to diagnose mixed-phenotype acute leukemia (MPAL), which has impacted the number of individuals diagnosed with this pathology. Better outcomes have been reported when using acute lymphoblastic leukemia (ALL)-type chemotherapy in the treatment of MPAL.

Methods

We compared the outcome of 4 groups of patients with MPAL. Group 1 included patients diagnosed using the 2008/2016 World Health Organization (WHO) classification; group 2 included patients diagnosed using the European Group for the Immunological Characterization of Leukemias (EGIL) criteria; group 3 included patients diagnosed using either the EGIL or the 2008/2016 WHO criteria; and group 4 was comprised of patients diagnosed with MPAL using the EGIL classification only.

Results

We found a significantly worse disease-free survival (groups 1-4) and overall survival (OS) (groups 2 and 3) when comparing MPAL patients to other acute leukemia (AL) patients. A significantly better OS was obtained in patients (groups 2-4) treated with ALL-type chemotherapy compared to acute myeloid leukemia (AML)-type regimens.

Conclusion

In light of these results, and because a trend (P=0.06) was found with regard to a better OS in group 4 when compared to other AL patients, an argument can be made that the 2008/2016 WHO classification is underpowered to diagnose all MPAL cases, potentially resulting in the suboptimal treatment of some individuals with AL.

The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia

The World Health Organization (WHO) classification of tumors of the hematopoietic and lymphoid tissues was last updated in 2008. Since then, there have been numerous advances in the identification of unique biomarkers associated with some myeloid neoplasms and acute leukemias, largely derived from gene expression analysis and next-generation sequencing that can significantly improve the diagnostic criteria as well as the prognostic relevance of entities currently included in the WHO classification and that also suggest new entities that should be added. Therefore, there is a clear need for a revision to the current classification. The revisions to the categories of myeloid neoplasms and acute leukemia will be published in a monograph in 2016 and reflect a consensus of opinion of hematopathologists, hematologists, oncologists, and geneticists. The 2016 edition represents a revision of the prior classification rather than an entirely new classification and attempts to incorporate new clinical, prognostic, morphologic, immunophenotypic, and genetic data that have emerged since the last edition. The major changes in the classification and their rationale are presented here.

Two Elderly Patients with Philadelphia Chromosome Positive Mixed Phenotype Acute Leukemia Who Were Successfully Treated with Dasatinib and Prednisolone

Philadelphia chromosome positive (Ph+) mixed phenotype acute leukemia (MPAL) is a rare type of acute leukemia having both myeloid and lymphoid features for which no optimal treatment has yet been established. We herein describe two elderly Ph+MPAL patients who achieved molecular remission without any serious adverse events by treatment with dasatinib and prednisolone. Although dasatinib induction therapy combined with prednisolone is known to be a highly effective treatment for Ph+ acute lymphoblastic leukemia, its efficacy for Ph+MPAL has not been shown. The clinical courses of the present cases suggest that combination therapy with dasatinib and prednisolone is a safe and effective therapeutic modality in elderly Ph+MPAL patients.

Induction of heme oxygenase-1 by Na+-H+ exchanger 1 protein plays a crucial role in imatinib-resistant chronic myeloid leukemia cells

Resistance toward imatinib (IM) and other BCR/ABL tyrosine kinase inhibitors remains troublesome in the treatment of advanced stage chronic myeloid leukemia (CML). The aim of this study was to estimate the reversal effects of down-regulation of Na(+)/H(+) exchanger 1 (NHE1) on the chemoresistance of BCR-ABL-positive leukemia patients' cells and cell lines. After treatment with the specific NHE1 inhibitor cariporide to decrease intracellular pH (pHi), the heme oxygenase-1 (HO-1) levels of the K562R cell line and cells from IM-insensitive CML patients decreased. HO-1, as a Bcr/Abl-dependent survival molecule in CML cells, is important for the resistance to tyrosine kinase inhibitors in patients with newly diagnosed CML or IM-resistant CML. Silencing PKC-β and Nrf-2 or treatment with inhibitors of p38 pathways obviously blocked NHE1-induced HO-1 expression. Furthermore, treatment with HO-1 or p38 inhibitor plus IM increased the apoptosis of the K562R cell line and IM-insensitive CML patients' cells. Inhibiting HO-1 enhanced the activation of caspase-3 and poly(ADP-ribose) polymerase-1. Hence, the results support the anti-apoptotic role of HO-1 induced by NHE1 in the K562R cell line and IM-insensitive CML patients and provide a mechanism by which inducing HO-1 expression via the PKC-β/p38-MAPK pathway may promote tumor resistance to oxidative stress.