Adult Low-Hypodiploid Acute Lymphoblastic Leukemia Emerges from Preleukemic TP53-Mutant Clonal Hematopoiesis

Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is a haematological malignancy characterized by the uncontrolled proliferation of immature lymphoid cells. Over past decades, significant progress has been made in understanding the biology of ALL, resulting in remarkable improvements in its diagnosis, treatment and monitoring. Since the advent of chemotherapy, ALL has been the platform to test for innovative approaches applicable to cancer in general. For example, the advent of omics medicine has led to a deeper understanding of the molecular and genetic features that underpin ALL. Innovations in genomic profiling techniques have identified specific genetic alterations and mutations that drive ALL, inspiring new therapies. Targeted agents, such as tyrosine kinase inhibitors and immunotherapies, have shown promising results in subgroups of patients while minimizing adverse effects. Furthermore, the development of chimeric antigen receptor T cell therapy represents a breakthrough in ALL treatment, resulting in remarkable responses and potential long-term remissions. Advances are not limited to treatment modalities alone. Measurable residual disease monitoring and ex vivo drug response profiling screening have provided earlier detection of disease relapse and identification of exceptional responders, enabling clinicians to adjust treatment strategies for individual patients. Decades of supportive and prophylactic care have improved the management of treatment-related complications, enhancing the quality of life for patients with ALL.

Acute Lymphoblastic Leukemia with Myeloid Mutations Is a High-Risk Disease Associated with Clonal Hematopoiesis

Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies.

SIGNIFICANCE

CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

"Myeloid" Mutations in ALL Are Not Uncommon: Implications for Etiology and Therapies

SUMMARY

In Blood Cancer Discovery, Saygin and colleagues report that somatic variants that are recurrent in myeloid malignancies can also occur with high frequency (16%) in adult acute lymphoblastic leukemia (ALL) where they correlate with older age, diagnosis following genotoxic therapy for a prior malignancy and worse outcome to chemotherapy. Mutations in these "myeloid" genes can precede ALL diagnosis and arise in hematopoietic stem or progenitor cells that clonally expand and differentiate into both lymphoblasts and nonmalignant myeloid cells, supporting a role for clonal hematopoiesis as premalignant state outside the context of myeloid malignancies and providing implications for both ALL etiology and therapeutic intervention. See related article by Saygin et al., p. 164 (4).

SOHO State of the Art Updates and Next Questions | Approach to Older Adults With Phildadelphia-Chromosome Negative Acute Lymphoblastic Leukemia

Philadelphia-chromosome-negative (Ph-neg) acute lymphoblastic leukemia (ALL) has historically been associated with poor outcomes in older patients due to adverse disease biology, as well as inferior tolerance of conventional chemotherapy. Fortunately, novel therapies, including inotuzumab ozogamicin, blinatumomab, and venetoclax, are now being incorporated into first-line therapy to improve efficacy and decrease toxicity of initial therapy. Inotuzumab ozogamicin, alone or in combination with low intensity chemotherapy, appears to be best suited for the induction phase of treatment due to efficacy in the setting of high tumor burden. In contrast, blinatumomab may be best suited for consolidation due to superior efficacy in setting of morphologic remission, with or without measurable residual disease (MRD). Venetoclax is being investigated in combination with chemotherapy and can be used for treatment of older adults with both B-cell and T-cell ALL. Ongoing trials incorporating inotuzumab, blinatumomab, and venetoclax demonstrate high rates of MRD-negative complete remissions with low early mortality. Long-term outcomes have been less favorable so far, with several trials reporting nonrelapse mortality during subsequent treatment. Unanswered questions remain regarding the optimal treatment of older adults with Ph-neg ALL, including central nervous system (CNS) prophylaxis, the most appropriate consolidation to minimize toxicity without compromising efficacy, and the role of transplant and cellular therapy. T-cell ALL remains an area of unmet need and effort is required to ensure that therapeutic advances benefit all populations equitably. In this manuscript, we review current data and ongoing trials regarding the treatment of older adults with Ph-neg ALL and define topics for further research.

Diagnostic work-up of hematological malignancies with underlying germline predisposition disorders (GPD)

Hematological malignancies with underlying germline predisposition disorders have been recognized by the World Health Organization 5th edition and International Consensus Classification (ICC) classification systems. The list of genes and the associated phenotypes are expanding and involve both pediatric and adult populations. While the clinical presentation and underlying molecular pathogenesis are relatively well described, the knowledge regarding the bone marrow morphologic features, the landscape of somatic aberrations associated with progression to hematological malignancies is limited. These pose challenges in the diagnosis of low-grade myelodysplastic syndrome (MDS) to hematopathologists which carries direct implication for various aspects of clinical management of the patient, donor selection for transplantation, and family members. Here in, we provide a focused review on the diagnostic work-up of hematological malignancies with underlying germline predisposition disorders with emphasis on the spectrum of hematological malignancies associated with each entity, and characteristic bone marrow morphologic, somatic cytogenetic and molecular alterations at the time of diagnosis of hematological malignancies. We also review the key clinical, morphologic, and molecular features, that should initiate screening for these entities.

Cytogenetics in the management of B-cell acute lymphoblastic leukemia: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Cytogenetic analysis is mandatory at initial assessment of B-cell acute lymphoblastic leukemia (B-ALL) due to its diagnostic and prognostic value. Results from chromosome banding analysis and complementary FISH are taken into account in therapeutic protocols and further completed by other techniques (RT-PCR, SNP-array, MLPA, NGS, OGM). Indeed, new genomic entities have been identified by NGS, mostly RNA sequencing, such as Ph-like ALL that can benefit from targeted therapy. Here, we have attempted to establish cytogenetic guidelines by reviewing the most recent published data including the novel 5th World Health Organization and International Consensus Classifications. We also focused on newly described cytogenomic entities and indicate alternative diagnostic tools such as NGS technology, as its importance is vastly increasing in the diagnostic setting.

Adult Low-Hypodiploid Acute Lymphoblastic Leukemia Evolves from TP53-Mutated Clonal Hematopoiesis

SUMMARY

Low-hypodiploid acute lymphoblastic leukemia (LH-ALL) in both children and adults is characterized by biallelic TP53 alterations in virtually all cases. However, in contrast to a common germline origin of the TP53 mutations in pediatric cases, those in adult cases are mostly somatic and are derived from age-related clonal hematopoiesis (ARCH), highlighting the role of TP53-mutant ARCH in the development not only of myeloid leukemogenesis but also of LH-ALL in aged populations. See related article by Kim et al., p. 134 (4).