Incorporating measurable ('minimal') residual disease-directed treatment strategies to optimize outcomes in adults with acute myeloid leukemia

Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia in Adolescents and Young Adults

Adolescents and young adults (AYAs) with Philadelphia chromosome-negative acute lymphoblastic leukemia (ALL) represent a unique patient population with a disproportionate survival disadvantage compared with younger children. Substantial progress has been made as we began to understand and address the multifaceted drivers behind this outcome disparity. New insights into the biology of B-cell ALL have uncovered distinct genetic characteristics more commonly found in AYAs that affect prognosis. Dramatic improvements in survival have been achieved with the use of pediatric-inspired protocols in the front-line setting, as well as antibody-based and chimeric antigen receptor T-cell therapies in the relapsed and refractory setting. Guided by the incorporation of minimal residual disease testing to inform clinical decision making, these represent major paradigm shifts in management. Efforts to design clinical trials geared toward AYAs and to enroll AYAs in available clinical trials will ensure ongoing progress. Holistic care of AYAs with ALL further involves recognition of psychosocial issues arising as a consequence of their diagnosis and the delivery of age-appropriate supportive care.

Early (Day 15 Post Diagnosis) Peripheral Blood Assessment of Measurable Residual Disease in Flow Cytometry is a Strong Predictor of Outcome in Childhood B-Lineage Lymphoblastic Leukemia

BACKGROUND

In children with acute lymphoblastic leukemia (ALL) low levels of minimal residual disease (MRD) after induction, essentially assessed in the bone marrow, have been shown to be of good prognosis. However, only few studies have tested the peripheral blood for MRD.

METHODS

Here, we report the impact on survival of peripheral blood (PB) MRD assessment by multiparameter flow cytometry (MFC) at early time points of treatment in 125 B-ALL children, compared to Day 35 molecular bone marrow (BM) MRD. Patients were sampled for MFC one week postdiagnosis after a pre-phase of corticotherapy (Day 8), then after one week of chemotherapy (Day 15). The study enrolled 67 boys and 58 girls with a median follow-up of 52 months. Over the duration of the study, 20 patients relapsed and eight died. MFC was performed based on the leukemia-associated immunophenotype at diagnosis, using panels of 10 antibodies.

RESULTS

Although, PB MFC-MRD had no prognostic impact at Day 8, Day 15 MRD negativity was associated with a significantly better 4 years DFS (91.6 ± 3% vs. 67.6 ± 9% P = 0.0013). Furthermore, while MFC and molecular data were concordant in most cases, patients with detectable PB MRD on Day 15, yet negative in BM on Day 35 had a significantly lower DFS (P < 0.0001).

CONCLUSION

This study demonstrates that the less invasive procedure of MFC-MRD assessment in PB can be informative for childhood ALL patients at the early point of Day 15 of the treatment schedule. © 2019 International Clinical Cytometry Society.

Tissue "Hypoxia" and the Maintenance of Leukemia Stem Cells

The relationship of the homing of normal hematopoietic stem cells (HSC) in the bone marrow to specific environmental conditions, referred to as the stem cell niche (SCN), has been intensively studied over the last three decades. These conditions include the action of a number of molecular and cellular players, as well as critical levels of nutrients, oxygen and glucose in particular, involved in energy production. These factors are likely to act also in leukemias, due to the strict analogy between the hierarchical structure of normal hematopoietic cell populations and that of leukemia cell populations. This led to propose that leukemic growth is fostered by cells endowed with stem cell properties, the leukemia stem cells (LSC), a concept readily extended to comprise the cancer stem cells (CSC) of solid tumors. Two alternative routes have been proposed for CSC generation, that is, the oncogenic staminalization (acquisition of self-renewal) of a normal progenitor cell (the "CSC in normal progenitor cell" model) and the oncogenic transformation of a normal (self-renewing) stem cell (the "CSC in normal stem cell" model). The latter mechanism, in the hematological context, makes LSC derive from HSC, suggesting that LSC share SCN homing with HSC. This chapter is focused on the availability of oxygen and glucose in the regulation of LSC maintenance within the SCN. In this respect, the most critical aspect in view of the outcome of therapy is the long-term maintenance of the LSC subset capable to sustain minimal residual disease and the related risk of relapse of disease.

State of the Art Update and Next Questions: Acute Myeloid Leukemia

As our general understanding regarding the complex nature of acute myeloid leukemia (AML) is expanding, so is our ability to translate this biological data into clinically relevant information. The use of whole genome and whole exome sequencing has begun to shed light on the importance of a variety of somatic mutations that are frequently identified in AML. In turn, this has allowed the field to incorporate mutational data into prognostic classifications which can guide treatment decisions. Furthermore, minimal residual disease (MRD) monitoring in AML is more commonplace as the prognostic relevance of MRD at various time points during treat is becoming clear. Many novel treatments have recently been approved, or are expected to gain approval in the near future, and this is opening the door to a more personalized approach to the management of AML.