Allogeneic stem cell transplantation for chronic myeloid leukemia–status in 2007

Stem cell allografting for chronic Myeloid leukemia in the tyrosine kinase era - forgotten but not gone

Due to the remarkable success of tyrosine kinase inhibitors (TKI) in chronic myeloid leukemia (CML), allogeneic stem cell transplantation (alloSCT) is not first-line treatment for delivering durable, long-term survival. Consequently, alloSCT is reserved for patients with TKI-resistant or TKI-intolerant chronic phase CML (CP-CML) and advanced phase CML (AP-CML). Advances in transplant technology, such as high-resolution HLA typing, introduction of reduced intensity conditioning and increased alternative donor availability, coupled with improved supportive care, have significantly reduced transplant-related mortality and expanded the pool of transplant-eligible patients. Refinement of conditioning regimens, innovative use of post-transplant cellular and pharmacological therapies, and judicious post-transplant monitoring are important strategies for reducing risk of relapse. Given its potential to cure, alloSCT will invariably remain a key part of the treatment algorithm. This article reviews the data underpinning the role and outcomes of alloSCT and provides an update on current recommendations.

Is Imatinib Maintenance Required for Patients with Relapse Chronic Myeloid Leukemia Post-Transplantation Obtaining CMR? A Pilot Retrospective Investigation

Imatinib can induce complete molecular remission (CMR) in relapse chronic myelogenous leukemia (CML) after allogeneic hematopoietic stem cell transplantation, but it is indefinite whether imatinib is required to maintain CMR. We retrospectively reviewed 37 relapse CML post-transplants treated with imatinib (n = 20) or donor lymphocyte infusion (DLI) (n = 17). The rate of CMR was 85% and 76.47% (P = 0.509) and treatment-related mortality was 0% and 29.4% (P = 0.019), respectively, in imatinib and DLI groups. Fifteen patients obtaining CMR voluntarily ceased imatinib, and did not experience relapse. The 8-year overall survival (OS) after relapse was 85%±8% and 40.3±12.1% (P = 0.017), and disease-free survival (DFS) after relapse was 85%±8% and 40.3±12.1% (P = 0.011), respectively, in imatinib and DLI groups. Imatinib resulted in higher OS and DFS than that of DLI in relapse CML. Imatinib maintenance might not be required for patients with relapse CML post-transplants after they achieved full donor chimerism and CMR.

Allogeneic stem cell transplantation for chronic myeloid leukemia resistant to tyrosine kinase inhibitors

Allogeneic hematopoietic stem cell transplantation (HSCT) is well-established as a potentially curative treatment for patients who have chronic myeloid leukemia. The success of imatinib and other tyrosine kinase inhibitors (TKI) as initial therapy has changed the treatment paradigm for this disease. Allogeneic hematopoietic transplants are now reserved for patients whose disease does not respond optimally to TKI treatment. Patients whose disease does not have an optimal response to imatinib may respond to a second-generation TKI, dasatinib or nilotinib, and many achieve major or complete molecular and cytogenetic responses. The indication for allogeneic HSCT versus continued second-line therapy is not well-defined and is the subject of ongoing study. There has been continued progress in reducing the toxicity and risks of HSCT with development of reduced-intensity regimens; transplants can be routinely performed in patients up to the age of 75 years who are in fair general medical condition. Transplantation results from unrelated donors have improved, with survival rates similar that achieved with matched siblings. Results with haploidentical and cord blood transplants have markedly improved, and should be considered for patients lacking a matched donor. Allogeneic hematopoietic transplants have the best chance to be curative in patients with chronic phase that is under hematologic control with 80% disease-free survival; patients progressing to the accelerated phase or blast crisis have a much poorer prognosis. Thus, HSCT should be considered for patients with imatinib failure. Patients receiving second-line TKI therapy must be closely monitored and referred for transplantation if a complete cytogenetic response and major molecular response is not achieved. HSCT should be performed if feasible in patients without a continued response to TKI treatment.

Trends of hematopoietic stem cell transplantation in the Eastern Mediterranean region, 1984-2007

Hematopoietic stem cell transplantation (HSCT) activity was surveyed in the 9 countries in the World Health Organization Eastern Mediterranean region that reported transplantation activity. Between the years of 1984 and 2007, 7933 transplantations were performed. The number of HSCTs per year has continued to increase, with a plateau in allogeneic HSCT (allo-HSCT) between 2005 and 2007. Overall, a greater proportion of transplantations were allo-HSCT (n = 5761, 77%) compared with autologous HSCT (ASCT) (n = 2172, 23%). Of 5761 allo-HSCT, acute leukemia constituted the main indication (n = 2124, 37%). There was a significant proportion of allo-HSCT for bone marrow failures (n = 1001, 17%) and hemoglobinopathies (n = 885, 15%). The rate of unrelated donor transplantations remained low, with only 2 matched unrelated donor allo-HSCTs reported. One hundred umbilical cord blood transplantations were reported (0.017% of allo-HSCT). Peripheral blood stem cells were the main source of graft in allo-HSCT, and peripheral blood stem cells increasingly constitute the main source of hematopoietic stem cells overall. Reduced-intensity conditioning was utilized in 5.7% of allografts over the surveyed period. ASCT numbers continue to increase. There has been a shift in the indication for ASCT from acute leukemia to lymphoproliferative disorders (45%), followed by myeloma (26%). The survey reflects transplantation activity according to the unique health settings of this region. Notable differences in transplantation practices as reported to the European Group for Blood and Marrow Transplantation over recent years are highlighted.

Long-term outcomes of HLA-matched sibling compared with mismatched related and unrelated donor hematopoietic stem cell transplantation for chronic phase chronic myelogenous leukemia: a single institution experience in China

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only curative therapy for chronic myelogenous leukemia (CML). In this study, the long-term outcomes of HLA-matched sibling donor (MSD) with mismatched related donor (MRD) and unrelated donor (URD) transplantation for CML in the first chronic phase (CML-CP1) using different graft vs. host disease (GVHD) prophylaxis regimens according to donor source and the degree of HLA matching were compared. The data of 91 patients with CML-CP1 were analyzed with respect to GVHD, overall survival (OS), and transplant-related mortality (TRM). The incidence of grade II-IV acute GVHD was 25.5% in the MSD and 40.5% in the MRD/URD group (P = 0.133). The 1-year cumulative incidence of chronic GVHD was not different between the MSD and the MRD/URD groups, while extensive chronic GVHD was different between the two groups (31.9% vs. 10.8%, P = 0.023). The 5-year cumulative relapse rate was not different between the MSD and the MRD/URD groups, while TRM was different between the two groups (6.6% vs. 26.3%, P = 0.010). The 5-year cumulative OS was 90.9%, 71.5%, and 85.4% in the MSD, the MRD/URD, and the HLA allele-matched URD transplantation, respectively (MSD vs. MRD/URD, P = 0.013; MSD vs. HLA allele-matched URD, P = 0.437). In conclusion, survival in HLA allele-matched URD is equivalent to MSD, but in MRD and mismatched URD is inferior to MSD in patients with CML-CP1 undergoing allo-HSCT using different GVHD prophylaxis regimens according to donor source and degree of HLA matching. Patients undergoing MRD/URD transplantation have an equal quality of life as patients undergoing MSD transplantation.

Critical molecular pathways in cancer stem cells of chronic myeloid leukemia

Inhibition of BCR-ABL with kinase inhibitors in the treatment of Philadelphia-positive (Ph(+)) chronic myeloid leukemia (CML) is highly effective in controlling but not curing the disease. This is largely due to the inability of these kinase inhibitors to kill leukemia stem cells (LSCs) responsible for disease relapse. This stem cell resistance is not associated with the BCR-ABL kinase domain mutations resistant to kinase inhibitors. Development of curative therapies for CML requires the identification of crucial molecular pathways responsible for the survival and self-renewal of LSCs. In this review, we will discuss our current understanding of these crucial molecular pathways in LSCs and the available therapeutic strategies for targeting these stem cells in CML.

Whither the bone marrow transplant?

Bone marrow transplantation (BMT) has become an accepted and important medical intervention which has become a routine part of medical practice. Its utility has, however, been questioned recently in a number of diseases in which its role has been clearly established on the basis that there are better non-transplant therapeutic options. The suspicion that these moves to eradicate BMT as an option may not stem from purely scientific reasons has prompted the preparation of these personal reflections. I will focus this discussion only on two diseases in which BMT has been shown to be useful: chronic myelogenous leukemia (CML) and multiple myeloma (MM).

The use of imatinib mesylate as a lifesaving treatment of chronic myeloid leukemia relapse after bone marrow transplantation

We describe the response of imatinib as lifesaving treatment of chronic myeloid leukemia (CML) relapse in seven patients who underwent allogeneic bone marrow transplantation (alloBMT) at our institution over a period of 4 years. Retrospective analysis of their medical records revealed that a mean age at transplant was 45.2 years. The median time to diagnosis was 7.4 years after transplant. At relapse, four, two, and one patients were classified as having hematologic, major molecular, and cytogenetic relapse, respectively. At imatinib initiation, five had CML in a chronic phase, while one patient was diagnosed as having accelerated phase and blast crisis. All these patients could be evaluated for the therapeutic efficacy. At a mean of follow-up of 1.9 years of therapy, all evaluable patients achieved major molecular response without compromising safety. Consistent with available data, our results indicate that imatinib is safe and effective treatment option for patients with relapse after BMT.

Tyrosine kinase inhibitors and allogeneic hematopoietic cell transplantation for chronic myeloid leukemia: targeting both therapeutic modalities

BACKGROUND

Due to its curative potential, allogenic hematopoietic transplantation (HCT) was a mainstay of treatment for chronic myeloid leukemia (CML), but the advent of tyrosine kinase inhibitors (TKIs) has markedly altered the use of allogeneic HCT.

METHODS

The authors reviewed their experiences as well as the published data regarding the impact of TKIs on the natural history of CML and thus on the application and timing of TKIs in the management of CML.

RESULTS

Most patients with CML respond well to TKIs given as up-front therapy. Available retrospective data suggest that allogenic HCT is safe after TKI therapy. Work is ongoing regarding salvage of postallogeneic HCT failures using TKIs with and without donor lymphocyte infusion.

CONCLUSIONS

While allogeneic HCT therapy remains useful, the timing of its application in CML has changed, and it is now considered as second- or third-line therapy.