Is there a role for allogeneic transplantation in 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.

Hematopoietic Stem Cells and Regeneration

Hematopoietic stem cell (HSC) regeneration is the remarkable process by which extremely rare, normally inactive cells of the bone marrow can replace an entire organ if called to do so by injury or harnessed by transplantation. HSC research is arguably the first quantitative single-cell science and the foundation of adult stem cell biology. Bone marrow transplant is the oldest and most refined technique of regenerative medicine. Here we review the intertwined history of the discovery of HSCs and bone marrow transplant, the molecular and cellular mechanisms of HSC self-renewal, and the use of HSCs and their derivatives for cell therapy.

Oncogenic kinase fusions: an evolving arena with innovative clinical opportunities

Cancer biology relies on intrinsic and extrinsic deregulated pathways, involving a plethora of intra-cellular and extra-cellular components. Tyrosine kinases are frequently deregulated genes, whose aberrant expression is often caused by major cytogenetic events (e.g. chromosomal translocations). The resulting tyrosine kinase fusions (TKFs) prompt the activation of oncogenic pathways, determining the biological and clinical features of the associated tumors. First reported half a century ago, oncogenic TKFs are now found in a large series of hematologic and solid tumors. The molecular basis of TKFs has been thoroughly investigated and tailored therapies against recurrent TKFs have recently been developed. This review illustrates the biology of oncogenic TKFs and their role in solid as well as hematological malignancies. We also address the therapeutic implications of TKFs and the many open issues concerning their clinical impact.

The role of hematopoietic stem cell transplantation in chronic myeloid leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) is currently recommended as 2nd or 3rd line therapy for patients with chronic myeloid leukemia (CML) in first chronic phase or as salvage for patients with very advanced disease. As a consequence, numbers of HSCT in chronic phase have dropped significantly since the introduction of tyrosine kinase inhibitors (TKI), numbers of transplants in advanced disease to a lesser extent. These current recommendations consider primarily disease risk, defined as failure of TKI therapy; they might need to be adapted. We propose a more balanced appraisal of HSCT for individual patients which should include disease risk, transplant risk, and macroeconomic aspects. HSCT should be integrated into the treatment algorithms from diagnosis and be considered very early at first TKI failure for patients with high disease but low transplant risk. For patients with very advanced disease and high transplant risk in contrast, HSCT might only be recommended in a restricted research setting.

Hematopoietic stem cell transplantation-50 years of evolution and future perspectives

Hematopoietic stem cell transplantation is a highly specialized and unique medical procedure. Autologous transplantation allows the administration of high-dose chemotherapy without prolonged bone marrow aplasia. In allogeneic transplantation, donor-derived stem cells provide alloimmunity that enables a graft-versus-tumor effect to eradicate residual disease and prevent relapse. The first allogeneic transplantation was performed by E. Donnall Thomas in 1957. Since then the field has evolved and expanded worldwide. New indications beside acute leukemia and aplastic anemia have been constantly explored and now include congenital disorders of the hematopoietic system, metabolic disorders, and autoimmune disease. The use of matched unrelated donors, umbilical cord blood units, and partially matched related donors has dramatically extended the availability of allogeneic transplantation. Transplant-related mortality has decreased due to improved supportive care, including better strategies to prevent severe infections and with the incorporation of reduced-intensity conditioning protocols that lowered the toxicity and allowed for transplantation in older patients. However, disease relapse and graft-versus-host disease remain the two major causes of mortality with unsatisfactory progress. Intense research aiming to improve adoptive immunotherapy and increase graft-versus-leukemia response while decreasing graft-versus-host response might bring the next breakthrough in allogeneic transplantation. Strategies of graft manipulation, tumor-associated antigen vaccinations, monoclonal antibodies, and adoptive cellular immunotherapy have already proved clinically efficient. In the following years, allogeneic transplantation is likely to become more complex, more individualized, and more efficient.