Nonmyeloablative allogeneic stem cell transplantation for the treatment of chronic myeloid leukemia in first chronic phase

Indications and donor selections for allogeneic stem cell transplantation in children with hematologic malignancies

Allogeneic stem cell transplantation (SCT) is the only curative approach for many patients with advanced or high-risk leukemia. Advances in supportive care and management of graft-versus-host disease have resulted in improvements in outcomes of related and unrelated donor SCT, creating controversies as to which strategy might be the optimal therapy for individual patients. This article discusses the indications and donor selection strategies for SCT in patients with malignant hematologic disease.

Comparison of myeloablative and nonmyeloablative hematopoietic stem cell transplantation for treatment of chronic myeloid leukemia

This retrospective study compared outcomes for 81 chronic myeloid leukemia patients who underwent myeloablative or nonmyeloablative allogeneic hematopoietic stem cell transplantation (HSCT). Sixty-five patients received myeloablative HSCT, and 16 patients received fludarabine (Fd), low-dose busulfan (Bu), and antithymocyte globulin (ATG) in nonmyeloablative HSCT. We determined overall survival (OS) and disease-free survival (DFS), as well as the occurrence of acute and chronic graft-versus-host disease (GVHD). The incidences of acute GVHD of grades II to IV were 14.0% and 18.7% for the myeloablative and nonmyeloablative groups, respectively. The incidence of chronic GVHD was significantly higher in the nonmyeloablative group (80% versus 66%). Five-year OS and DFS rates were significantly higher in nonmyeloablative group (70% for both), compared with 56% and 54%, respectively, for the myeloablative group. A univariate analysis, however, revealed a strong but statistically insignificant trend for enhanced overall OS and DFS in the nonmyeloablative group (P = .1 and .07, respectively). A multivariate analysis with the factors of treatment, age, sex, acute and chronic GVHD, and disease status at the time of transplantation revealed that both OS and DFS were significantly higher in the nonmyeloablative group than in the myeloablative group. These findings suggest that nonmyeloablative Fd/Bu/ATG treatment is at least not inferior (and quite probably superior) in terms of patient outcome compared with standard myeloablative therapy. Further larger-scale randomized clinical trials are warranted to clarify the efficacy of this treatment regimen.

Allogeneic hematopoietic stem cell transplantation in the elderly

The development of reduced intensity or non-myeloablative conditioning (NST) in preparation for allogeneic stem cell transplantation (SCT) revolutionized the field and led to reconsideration of the dogma of upper age limit that was set up by the transplant centers as an eligibility parameter. Analysis of the literature data showed that NST regimens are associated with decreased transplant related mortality, and graft-versus-host disease, in comparison with standard myeloablative conditioning, in patients above the age of 50-55 years, or in younger patients with significant comorbidities. However we have to mention, that our considerations are based on the retrospective analysis of the literature data, and that well controlled prospective randomized studies are needed in order to definitely assess the role of NST. Comorbidity indices might be proved as the most important parameters for the choice of the most proper regimen for each patient in need and should be included in future trials.

Graft Versus Host Disease After Stem Cell Allotransplantation With Low-Dose Total Body Irradiation, Fludarabine, and Antithymocyte Globulin

BACKGROUND

We previously showed that antithymocyte globulin (ATG) given with total body irradiation (TBI) 200 cGy and fludarabine results in high rate of donor engraftment. Its influence on acute and chronic graft versus host disease (GVHD) and on graft versus tumor effect is less known.

METHODS

Sixty-five patients underwent nonmyeloablative stem cell transplant with ATG, TBI 200 cGy, and fludarabine. GVHD prophylaxis was mycophenolate mofetil and cyclosporine. Forty-two patients (pts) (65%) had match related donors, 18 (27%) match unrelated, 1 (1.5%) mismatch related, and 4 (6%) mismatch unrelated donors.

RESULTS

At a median follow-up of 862 days, 24 patients (37%) developed GVHD. The median age of the patients with and without GVHD was 56 years respectively. Acute GVHD grade II-IV developed in 19 pts (29%). Fatal GVHD of liver and/or gut occurred in nine pts (14%). Forty-one pts survived more than 100 days. Five pts (12%) had chronic GVHD, two had extensive, and three had limited involvement. Relapsed disease was observed in 22 pts (34%). Infections occurred in 15 pts (23%) and were fatal in 13 (20%).

CONCLUSIONS

The addition of ATG to TBI 200cGy and fludarabine resulted in a modest incidence of GVHD. The best transplant outcomes were observed in pts with lymphoid malignancies.

Chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) was the first neoplastic disease for which knowledge of the genotype led to a rationally designed therapy. As a result of its well known pathophysiology, straightforward diagnosis, well established prognostic factors, and treatment for the cause of disease, CML has been studied to an extent that far exceeds that expected from its frequency, and serves as a model disease for other cancers. Imatinib, an inhibitor of BCR-ABL tyrosine kinase, has revolutionised treatment of this disease, and is now recommended as standard treatment for chronic-phase CML. Interferon alfa is an acceptable alternative treatment in the early chronic phase for patients who do not tolerate imatinib. If imatinib treatment fails, allogeneic stem-cell transplantation, a dose increase of imatinib, or new drugs are recommended. Up to 87% of patients achieve complete cytogenetic remission, therefore we provide guidance for monitoring disease status. Many trials of new drugs and combination therapies that include imatinib are underway.

New myeloablative conditioning regimen with fludarabine and busulfan for allogeneic stem cell transplantation: comparison with BuCy2

A regimen of busulfan and cyclophosphamide (BuCy2) is regarded as the standard myeloablative regimen for SCT. This study evaluated the hypothesis that fludarabine can replace cyclophosphamide for myeloablative allogeneic SCT. Ninety-five patients underwent allogeneic SCT from HLA-identical donors, following BuCy2 (n=55) or busulfan+fludarabine (BF, n=40). The efficacy of fludarabine compared to cyclophosphamide was retrospectively evaluated. The BF group exhibited a shorter duration until engraftment (P=0.001), lower incidence of acute and chronic GVHD (P<0.001 and P=0.003, respectively), and non-relapse mortality (NRM) (P=0.039). Furthermore, the event-free survival and overall survival were significantly higher for the BF group compared to the BuCy2 group (P=0.004 and 0.002, respectively). After adjusting for age, the risk status of disease, GVHD prophylaxis and donor type, the BF regimen was found to be an independent favorable risk factor for event-free survival (hazard ratio (HR), 0.181; 95% confidence interval, 0.045-0.720; P=0.016) and overall survival (HR, 0.168; 0.035-0.807; P=0.026). The replacement of cyclophosphamide with fludarabine for myeloablative conditioning seems to be more effective in terms of short-term NRM, and GVHD compared to BuCy2 regimen in allogeneic transplantation.

How I treat chronic myeloid leukemia in the imatinib era

Although it is now generally accepted that imatinib is the best initial treatment for patients newly diagnosed with chronic myeloid leukemia (CML) in chronic phase, a number of questions remain unanswered. For example, (1) Is imatinib the best initial treatment for every chronic-phase patient? (2) At what dose should imatinib be started? (3) How should response to treatment be monitored? (4) For how long should the drug be continued in patients who have achieved and maintain a complete molecular response? (5) How does one handle a patient who achieves a 2-log but not a 3-log reduction in BCR-ABL transcripts? (6) How should response or failure be defined? (7) For the patient deemed to have failed imatinib, should one offer dasatinib or nilotinib? (8) For the patient who has failed imatinib but has a possible allogeneic transplant donor, should one offer dasatinib or nilotinib before recommending a transplantation? (9) Should the transplantation be myeloablative or reduced intensity conditioning? (10) How should one treat the patient who relapses after allografting? This paper will address these issues, many of which cannot yet be answered definitively.

Long-term follow-up of allogeneic bone marrow transplantation for patients with chronic phase chronic myeloid leukemia prepared with a regimen consisting of cyclophosphamide, cytarabine and single-dose total body irradiation conditioning

We evaluated long-term toxicities and outcomes in 96 patients with chronic phase chronic myeloid leukemia treated with a single bone marrow allograft regimen. Conditioning was cytosine arabinoside, cyclophosphamide (120 mg/kg) and single fraction total body irradiation (500 cGy). Median follow-up was 12.8 years (0.4-19.9 years). Graft failure occurred in one patient, nonfatal veno-occlusive disease in 13 patients (14%). Overall incidences of acute (a) and chronic (c) graft-vs-host disease (GVHD) were 77 and 63%. The 100-day and 1-year transplant-related mortality (TRM) were 1 and 9.2%, respectively, with no change through 5 years. Five- and 10-year event-free survival rates were 56 and 49%, overall survival (OS) rates 72 and 70%, respectively. Forty patients have relapsed: 8 cytogenetic (20%), 10 hematologic (25%) and 22 molecular (55%). Most have been salvaged with donor-leukocyte infusion, second transplants and/or imatinib therapy. Survival was worse for patients transplanted >2 years from diagnosis (10-year OS 56 vs 78%, P=0.01), for patients over 50 years old (10-year OS 44 vs 75%, P=0.05) and for patients without cGVHD (10-year OS 53 vs 86%, P<0.001). This regimen resulted in successful engraftment, low risk of TRM and long-term survival. In an era when imatinib is first line therapy, this regimen offers a potentially low-toxicity, highly successful alternative in the event of poor imatinib response.

Drug treatment is superior to allografting as first-line therapy in chronic myeloid leukemia

Early allogeneic hematopoietic stem cell transplantation (HSCT) has been proposed as primary treatment modality for patients with chronic myeloid leukemia (CML). This concept has been challenged by transplantation mortality and improved drug therapy. In a randomized study, primary HSCT and best available drug treatment (IFN based) were compared in newly diagnosed chronic phase CML patients. Assignment to treatment strategy was by genetic randomization according to availability of a matched related donor. Evaluation followed the intention-to-treat principle. Six hundred and twenty one patients with chronic phase CML were stratified for eligibility for HSCT. Three hundred and fifty four patients (62% male; median age, 40 years; range, 11-59 years) were eligible and randomized. One hundred and thirty five patients (38%) had a matched related donor, of whom 123 (91%) received a transplant within a median of 10 months (range, 2-106 months) from diagnosis. Two hundred and nineteen patients (62%) had no related donor and received best available drug treatment. With an observation time up to 11.2 years (median, 8.9 years), survival was superior for patients with drug treatment (P = .049), superiority being most pronounced in low-risk patients (P = .032). The general recommendation of HSCT as first-line treatment option in chronic phase CML can no longer be maintained. It should be replaced by a trial with modern drug treatment first.

Impact of imatinib therapy on the use of allogeneic haematopoietic progenitor cell transplantation for the treatment of chronic myeloid leukaemia

The discovery and approval of imatinib drastically changed the therapeutic algorithm for chronic myeloid leukaemia (CML). Imatinib is now considered the therapy of choice for patients with newly diagnosed CML, including those previously considered candidates for allogeneic haematopoietic cell transplantation (HCT). We compared numbers and types of allogeneic HCTs performed for CML in North America before and after the introduction of imatinib, and publication of the International Randomized Trial of Interferon and STI571 (IRIS) using transplants reported to the Center for International Blood and Marrow Transplant Research (CIBMTR). The number of HCTs for CML registered with the CIBMTR in 1998 was 617; 62% were performed in first chronic phase (CP1). Only 1% of patients had received imatinib prior to transplantation. In 2003, the number of HCTs reported was 223; 44% were performed in CP1 and 77% of patients received imatinib prior to transplantation. The introduction of imatinib therapy has had a profound impact on the use of allogeneic transplantation for CML, with a marked decrease in the number of transplants for CML and an accompanying decrease in the proportion done in CP1. Most patients now receive a trial of imatinib before proceeding to HCT.

Fludarabine vs cladribine plus busulfan and low-dose TBI as reduced intensity conditioning for allogeneic hematopoietic stem cell transplantation: a prospective randomized trial

Purine analogs are often used for conditioning preceding allogeneic hematopoietic stem cell transplantation (HCT). We prospectively tested fludarabine (Flu) 40 mg/m(2)/day x 5 days vs cladribine (Clad) 10 mg/m(2)/day x 5 days plus oral busulfan (1 mg/kg q6 h x 2 days) and total body irradiation 200 cGy in 32 recipients of matched sibling and unrelated donor (URD) HCT. Patients were similar in age (median 52 years), diagnosis, extensive pre-HCT therapy (56 vs 63%), and high-risk disease status (81 vs 93%). Neutrophil engraftment was prompt (median 11 vs 12 days), but early graft failure using Clad halted randomization. Platelet recovery was prompt (median Flu 18 vs Clad 24 days). Graft-versus-host disease (GVHD) after Flu vs Clad was similar; (acute grade II/IV 56 vs 69%, P=0.26; chronic 50 vs 31%, P=0.27). Nonrelapse mortality (Flu 25 vs Clad 38%, P=0.47) and progression-free survival at 3 years were similar as well. Multivariate analyses showed slightly, but not significantly lower relative risk (RR) of neutrophil engraftment with Clad (RR 0.6 (95% CI 0.2-1.3) P=0.16) and with URD RR 0.4 (0.2-1.0) P=0.04). Older patients with advanced hematologic malignancies achieve satisfactory outcomes using either of these reduced intensity conditioning regimens.

Reduced-intensity conditioning followed by T-cell depleted allogeneic stem cell transplantation for patients with chronic myeloid leukaemia and minimal residual disease at the time of transplant: high risk of molecular relapse

A pilot trial was initiated for chronic myeloid leukaemia patients, which employed imatinib for remission induction, followed by reduced-intensity conditioning and an in vivo T-cell depleted graft. Out of nine patients, six experienced a molecular relapse and one patient had a haematological relapse at a median interval of 5 months after transplantation. Five relapsing patients achieved a 2nd molecular remission after treatment with either donor lymphocyte infusions (n = 4) or imatinib (n = 1). Two of nine patients died due to infectious complications. The probability of survival 2 years after transplant was 74% (95% CI 42-100%).

Reduced-Intensity Stem Cell Transplantation

The recognition that the immune system can play a major role in the control and cure of transplantable disorders led to the development of reduced-intensity allogeneic transplantation. The notion is that a compromise can be made between the intensity of conditioning and the fostering of graft-versus-host disease/ graft-versus-leukemia (GVHD/GVL), allowing the use of less intense conditioning with concomitantly less intense immediate toxicity. Reduced-intensity conditioning regimens have allowed the application of transplantation to older patients and to patients with underlying medical problems that preclude full-dose transplantation. Clearly, in some settings in which dose intensity is important, reduced-intensity regimens are less useful. However, for diseases that are either indolent, highly susceptible to GVL, or under good control before entering transplantation, this approach appears to have substantial benefits. Although the therapy appears to be valuable, concerns about delayed immune reconstitution and GVHD remain.

Long-term follow-up of allogeneic HSCT for CML reveals significant improvement in the outcome over the last decade

Allogeneic hematopoetic stem cell transplantation (HSCT) is still the only curative therapeutic option for chronic myelogenous leukemia (CML). To examine the development of allogeneic HSCT at our center over the past two decades (decade 1: 1984-1994; decade 2: 1995-2005), all CML patients transplanted in first chronic phase (n = 234) were analyzed with respect to patient characteristics, overall survival, transplant-related mortality (TRM), and relapse incidence. The median follow up time was 54 months (range 1-218). The incidence of acute graft vs host disease (GvHD) degrees II-IV and extensive chronic GvHD were not different between the two decades (p = 0.894 and p = 0.422, respectively). There was also no difference in the relapse incidence (23 vs 26%, p = 0.869). One-year TRM and overall survival were improved in the later decade (33 vs 18%, p = 0.011 and 62 vs 73% at 5 years, p = 0.063, respectively). The major reason for improved outcome in decade 2 was the improved management of acute GvHD and infections in the early phase after transplantation (p = 0.026). In conclusion, the past decade has seen significant improvement in the performance of allogeneic HSCT for CML.

Early allogeneic stem cell transplantation for chronic myelogenous leukemia in the imatinib era: A preliminary assessment

We have examined the role of early allogeneic hematopoietic stem cell transplantation in patients with chronic phase chronic myelogenous leukemia (CML) who enter a complete cytogenetic remission with imatinib mesylate. Three kinds of data were used to examine the effect of the outcome of current BCR-ABL inhibitor treatment compared to early allogeneic stem cell transplantation: (1) the life expectancy of the general population of the United States as a function of age, (2) the life expectancy of CML patients as a function of the age of patients treated with imatinib mesylate (imatinib) who achieve a complete cytogenetic remission, and (3) the life expectancy of patients with CML treated with matched-related or matched-unrelated stem cell transplantation as a function of age, derived from data provided by the Center for International Blood and Marrow Transplant Research (CIBMTR). We also considered separately the transplant results of the Fred Hutchinson Cancer Research Center (FHCRC), which are substantially better than the "average" outcome from the CIBMTR. We have calculated the projected life expectancy from the age at which patients with CML enter complete cytogenetic remission with imatinib and that of those who receive allogeneic stem cell transplantation. The outcome with imatinib therapy of newly diagnosed patients with CML has been documented for only 4 and 1/2 years, whereas transplant data were available for up to 25 years. Thus, in order to compare life expectancy and 10-year survival probability, it was necessary to extrapolate the imatinib data. A basis for extrapolation is offered and conservative estimates have been used for comparison. Our best estimate is that patients receiving imatinib who have a complete cytogenetic remission have a higher projected probability of 10-year survival than patients who are transplanted, based on results provided by the CIBMTR, and have about the same probability compared to the data from the Fred Hutchinson Cancer Center for patients in the 30- to 60-year-old range. The mathematical approach used here permits reexamining the analysis using future data on BCR-ABL inhibitor therapy or allogeneic stem cell transplantation therapy or both.

Clinical outcomes and direct hospital costs of reduced-intensity allogeneic transplantation in chronic myeloid leukemia

A reduced-intensity conditioning allogeneic stem cell transplantation was given to 19 patients (aged 15-59 years) in the first chronic phase and one patient in the accelerated phase with chronic myeloid leukemia (CML) after a regimen consisting of fludarabine (Flu), busulfan (Bu) and ATG Fresenius. The median follow-up was 27 months. Until day +100, no transplant-related mortality was recorded. The incidence of acute and chronic graft-versus-host disease (GvHD) was 55 and 75%, respectively. Two patients (10%) died from GvHD. Fourteen (70%) patients achieved molecular remission. Additional post-transplant intervention (donor lymphocyte infusion, imatinib) was necessary, however, in 10 patients (50% of the patients; non-achievement of stable molecular remission or later relapses). The total direct cost of the transplantation treatment for all of the patients came to 1,572,880 euro. If the patients had been treated with imatinib and followed-up with the same time period as they were following a transplantation, the direct cost of the imatinib treatment would have been 2,005,117 euro. The transplantation treatment appears to be less expensive after approximately 2 years of follow-up. Flu+Bu+ATG is a low-toxicity regimen for patients with CML. However, a close follow-up is necessary and about 50% of the patients require further therapeutic intervention.

Role of Allogeneic Stem Cell Transplantation for Adult Chronic Myeloid Leukemia in the Imatinib Era

Due to superior survival in the short to medium term, the first-generation ABL kinase inhibitor imatinib mesylate has generally supplanted all other therapies as the initial treatment of choice in chronic phase chronic myeloid leukemia. The role of allogeneic stem cell transplantation (alloSCT) has shifted from a preferred first-line therapy to a possible second- or third-line therapy. However, despite generally excellent responses to imatinib, some patients respond poorly or lose response, and the risk-benefit equation in these cases may rapidly shift in favor of the alloSCT option. These patients need to be identified as soon as possible so that the alloSCT option can be applied while they are still in controlled chronic phase. Monitoring of imatinib response in patients who have suitable donors and are potentially eligible for alloSCT needs to be frequent, sensitive, and accurate. Clear criteria for switching from imatinib therapy to the alloSCT option should be established for each patient according to the specific risk profile of the transplant. The potential efficacy and safety of clinical trials combining reduced intensity alloSCT with ABL kinase inhibitor therapy warrants further consideration.

Stem cell transplantation with reduced-intensity conditioning regimens: a review of ten years experience with new transplant concepts and new therapeutic agents

The realization in the 1990s that allogeneic stem cell transplants (SCT) have a potentially curative graft-versus-leukemia (GVL) effect in addition to the antileukemic action of myeloablative conditioning regimens was a major stimulus for the development of reduced-intensity conditioning (RIC) regimens, aimed primarily at securing engraftment to provide the GVL effect, while minimizing regimen-related toxicity. It is now over 10 years since RIC regimens were heralded as a new direction in the field of SCT. Over the last decade much has been learned about the ways in which the conditioning regimen can be tailored to provide adequate immunosuppression, and modulated to deliver a chosen degree of antimalignant treatment. The huge literature of clinical data with RIC transplantation now permits us to more clearly define the success and limitations of the approach. This review examines the origins of RIC SCT, explores the degree to which the initial expectations and purpose of the approach have been realized, and outlines some ways forward for the field.

Despite Inhibition of Hematopoietic Progenitor Cell Growth In Vitro, the Tyrosine Kinase Inhibitor Imatinib Does Not Impair Engraftment of Human CD133+Cells into NOD/SCIDβ2mNullMice

There is potential interest for combining allogeneic hematopoietic cell transplantation (HCT), and particularly allogeneic HCT with a nonmyeloablative regimen, to the tyrosine kinase inhibitor imatinib (Glivec; Novartis, Basel, Switzerland, http://www.novartis.com) in order to maximize anti-leukemic activity against Philadelphia chromosome-positive leukemias. However, because imatinib inhibits c-kit, the stem cell factor receptor, it could interfere with bone marrow engraftment. In this study, we examined the impact of imatinib on normal progenitor cell function. Imatinib decreased the colony-forming capacity of mobilized peripheral blood human CD133(+) cells but not that of long-term culture-initiating cells. Imatinib also decreased the proliferation of cytokine-stimulated CD133(+) cells but did not induce apoptosis of these cells. Expression of very late antigen (VLA)-4, VLA-5, and CXCR4 of CD133(+) cells was not modified by imatinib, but imatinib decreased the ability of CD133(+) cells to migrate. Finally, imatinib did not decrease engraftment of CD133(+) cells into irradiated nonobese diabetic/severe combined immunodeficient/beta2m(null) mice conditioned with 3 or 1 Gy total body irradiation. In summary, our results suggest that, despite inhibition of hematopoietic progenitor cell growth in vitro, imatinib does not interfere with hematopoietic stem cell engraftment.

Chronic myeloid leukemia: diagnosis and treatment

Chronic myeloid leukemia (CML) has become a model in research and management among malignant disorders. Since the discovery of the presence of a unique and constant chromosomal abnormality slightly more than 40 years ago, substantial progress has been made in the understanding of the biology of the disease. This progress has translated into significant improvement in the longterm prognosis of patients with this disease. This change came first with the use of stem cell transplantation and interferon alfa, but recently it has opened the era of molecularly targeted therapies. Imatinib, a potent and selective tyrosine kinase inhibitor, may be the best example of our attempts to identify molecular abnormalities and develop drugs directed specifically at them. Furthermore, the understanding of at least some of the mechanisms of resistance to imatinib has led to rapid development of new agents that may overcome this resistance. The outlook today for patients with CML is much brighter than just a few years ago. It is our hope that this fascinating journey in CML can be replicated in other malignancies. In this article, we review our current understanding of this disease.

Reduced-intensity conditioning followed by unrelated umbilical cord blood transplantation for advanced hematologic malignancies: rapid engraftment in bone marrow

Reduced-intensity (RI) conditioning followed by cord blood transplantation (CBT) is a new treatment modality, but failure to engraft is a major concern. We describe 12 patients with advanced hematologic malignancies who underwent RI conditioning and CBT with a conditioning regimen consisting of 200 mg/m(2) fludarabine (Flu), 50 mg/kg cyclophosphamide (CY), and 3 Gy total body irradiation (TBI). Cyclosporin A and/or methotrexate were used for graft-versus-host disease prophylaxis. Cord blood grafts were not mismatched for more than 2 serologically defined HLA alleles but were later found by high-resolution DNA typing to be mismatched for 2 to 4 alleles in most cases. Short tandem repeat analysis of bone marrow cells at day 14 showed complete donor chimerism in 6 of the patients and mixed chimerism in 5, indicating rapid engraftment in the bone marrow, whereas the remaining patient experienced graft rejection. Neutrophil recovery was achieved at a median of day 17 (range, days 11-24) in 10 of the 11 patients with marrow chimerism at day 14. Of these 10 patients, however, transplantation-related mortality within 100 days occurred in 4 patients who showed failed platelet recovery and a lack of durable engraftment. Overall survival and disease-free survival rates were 41.7% and 33.3%, respectively. These results show that CB mismatched at 2 to 4 HLA alleles and transplanted with the Flu/CY/3 Gy TBI regimen is able to engraft in the bone marrow as early as day 14.

The Role of Alemtuzumab in Nonmyeloablative Hematopoietic Transplantation

Nonmyeloablative stem cell transplants provide a viable therapeutic option for older patients or patients with comorbid conditions, who were previously deemed to be ineligible for transplantation. Despite improvements in clinical outcomes, graft-versus-host disease (GVHD) remains a significant and potentially lethal complication. One approach by which GVHD has been managed is through introduction of new agents, such as alemtuzumab, into the conditioning regimen. Alemtuzumab is a humanized monoclonal antibody that targets the CD52 antigen, which is highly expressed on both B and T lymphocytes. By depleting T cells in both the donor and the recipient, alemtuzumab has been shown to prevent development of both acute and chronic GVHD, without inhibiting the benefits associated with the graft-versus-leukemia effect. Clinical trials have shown that alemtuzumab is able to decrease the incidence of acute and chronic GVHD without impairing engraftment. Furthermore, in chronic lymphocytic leukemia therapy, alemtuzumab has been shown to purge malignant cells from the host to allow for harvesting for the purpose of autologous transplantation. Despite results showing that alemtuzumab can play an important role in managing GVHD, little information is available regarding a standardized dosing schedule. Greater insight into alemtuzumab's pharmacokinetic activity would assist in developing a schedule that can optimize alemtuzumab-mediated T-cell depletion to prevent GVHD, while retaining sufficient host T-cell activity to encourage the graft-versus-leukemia effect and prevent relapse.

The early referral for reduced-intensity stem cell transplantation in patients with Ph1 (+) chronic myelogenous leukemia in chronic phase in the imatinib era: results of the Latin American Cooperative Oncohematology Group (LACOHG) prospective, multicenter study

Using a reduced-intensity stem cell transplantation (RIST) schedule, 24 patients with Philadelphia (Ph1) (+) chronic myelogenous leukemia (CML) in first chronic phase (CP) were prospectively allografted in four Latin American countries: México, Brazil, Colombia and Venezuela, using HLA-identical siblings as donors. The median age of the patients was 41 years (range 10-71 years); there were eight females. Patients received a median of 4.4 x 10(6)/kg CD34 cells. The median time to achieve above 0.5 x 10(9)/l granulocytes was 12 days, range 0-41 days, and the median time to achieve above 20 x 10(9)/l platelets was also 12 days, range 0-45 days. In all, 22 patients are alive 81-830 (median 497) days after RIST. The 830-day probability of survival is 92%, and the median survival has not been reached, being beyond 830 days. A total of 11 patients (46%) developed acute graft-versus-host disease (GVHD), and seven of 23 (30%) developed chronic GVHD. Two patients died 43 and 210 days after RIST, one as a result of sepsis and the other of chronic GVHD. The 100-day mortality was 4.4%, and transplant-related mortality was 8%. RIST for patients with CML in CP appears to be an adequate therapeutic option.

Stem cell transplantation in patients with chronic myelogenous leukemia: when should it be used?

Hematopoietic stem cell transplantation has been a cornerstone of therapy for chronic myelogenous leukemia (CML) for more than 15 years and is still a standard treatment option for patients with CML. The advent of imatinib mesylate, an inhibitor of the molecular defect driving CML, the BCR-ABL tyrosine kinase, has rewritten treatment algorithms for this disease and has shifted focus away from allografting. Despite advances in stem cell transplantation, such as broader availability with the use of modified conditioning regimens, use of allografting has diminished. Also, the nearly universal patient exposure to imatinib or other kinase inhibitors before transplantation may affect the biology of the disease that is currently being treated with an allograft and ultimately may affect outcomes. Exceedingly high rates of meaningful and stable response with longer follow-up continue to drive enthusiasm for imatinib use, and understanding of resistance mechanisms has driven rapid investigation of second-generation tyrosine kinase inhibitors to address imatinib failure and suboptimal response. In most patients, imatinib reduces CML to a minimal residual disease state in which options to further deepen remission, such as immunotherapy, are sought; monitoring techniques and interpretation of response advance in parallel to meet demands; and uncertainty remains as a new natural history of CML is defined in an era of kinase inhibitor therapy. This review summarizes the state of transplant and nontransplant therapy for CML and discusses the decision making for patients with an aim to optimize the use of our best therapies for CML in an era of uncertainty.

Staging of chronic myeloid leukemia in the imatinib era

BACKGROUND

Several staging classification systems, all of which were designed in the preimatinib era, are used for chronic myeloid leukemia (CML). The World Health Organization (WHO) recently proposed a new classification system that has not been validated clinically. The authors investigated the significance of the WHO classification system and compared it with the classification systems used to date in imatinib trials ("standard definition") to determine its impact in establishing the outcome of patients after therapy with imatinib.

METHODS

In total, 809 patients who received imatinib for CML were classified into chronic phase (CP), accelerated phase (AP), and blast phase (BP) based on standard definitions and then were reclassified according to the new WHO classification system. Their outcomes with imatinib therapy were compared, and the value of individual components of these classification systems was determined.

RESULTS

With the WHO classification, 78 patients (10%) were reclassified: 45 patients (6%) were reclassified from CP to AP, 14 patients (2%) were reclassified from AP to CP, and 19 patients (2%) were reclassified from AP to BP. The rates of complete cytogenetic response for patients in CP, AP, and BP according to the standard definition were 72%, 45%, and 8%, respectively. After these patients were reclassified according to WHO criteria, the response rates were 77% (P = 0.07), 39% (P = 0.28), and 11% (P = 0.61), respectively. The 3-year survival rates were 91%, 65%, and 10%, respectively, according to the standard classification and 95% (P = 0.05), 63% (P = 0.76), and 16% (P = 0.18), respectively, according to the WHO classification. Patients who had a blast percentage of 20-29%, which is considered CML-BP according to the WHO classification, had a significantly better response rate (21% vs. 8%; P = 0.11) and 3-year survival rate (42% vs. 10%; P = 0.0001) compared with patients who had blasts > or = 30%.

CONCLUSIONS

Different classification systems had an impact on the outcome of patients, and some prognostic features had different prognostic implications in the imatinib era. The authors believe that a new, uniform staging system for CML is warranted, and they propose such a system.

Increased intensity of acute graft-versus-host disease after reduced-intensity bone marrow transplantation compared to conventional transplantation from an HLA-matched sibling in children

Eight children underwent reduced-intensity stem cell transplantation (RIST) from an HLA-matched sibling. They received a fludarabine-melphalan based preparative regimen. Stem cell source was bone marrow, and GVHD prophylaxis consisted of cyclosporine A alone. Acute GVHD grade II-IV and grade III-IV were observed in four (50%) and three (37.5%), respectively, out of these eight patients. This incidence was significantly higher than that after conventional bone marrow transplantation, without severe tissue damage, in the same setting of stem cell source and GVHD prophylaxis. Although the number of patients is small, our results suggest that incidence of acute GVHD after RIST for children is significant. It should be remembered that RIST for children does not seem to be an easy transplant procedure from the viewpoint of acute GVHD, although RIST is less toxic.

Outcomes with Myeloid Malignancies

Reduced-intensity conditioning (RIC) regimens were initially introduced to provide allogeneic stem cell transplantation (HCT), a potentially curative procedure for myeloid malignancies, for patients who were not considered eligible for conventional myeloablative HCT either because of advanced age or excessive comorbidities. A variety of RIC regimens have been studied. The exact definition of RIC remains arbitrary and generally depends upon the perceived toxicity of a given regimen rather than the actual dose of chemotherapy or radiotherapy administered. In several published series, RIC regimens have demonstrated a reduction in non-relapse mortality (NRM), thereby accomplishing the initial goal of expanding the patient population eligible for this potentially curative procedure. Most retrospective studies performed to date have shown a decrease in NRM and an increase in relapse-related mortality with the use of RIC as opposed to conventional myeloablative HCT in myeloid malignancies. This appears to be particularly true for patients who are in relapse at the time of HCT. In contrast, patients who are in remission at time of HCT appear to have a reduction in NRM without a subsequent increase in relapse-related mortality. There is interest in applying RIC to younger patients and to patients with fewer comorbidities as they may have a reduction in NRM without a concomitant increase in relapse. Prospective multicenter studies are needed to define the optimal conditioning regimen, which is likely dependent upon a variety of disease-specific and patient-specific factors.

Managing the Patient with Chronic Myeloid Leukemia Through and After Allogeneic Stem Cell Transplantation

Although the only curative therapy for chronic myeloid leukemia remains allogeneic stem cell transplantation (allo-SCT), early to mid-term results of imatinib in newly diagnosed patients are sufficiently impressive to have displaced allo-SCT to second- or third-line treatment. Patients now arrive at a decision for transplantation in a variety of disease situations: failing to achieve certain hematological, cytogenetic and molecular milestones by some pre-determined timepoint, having lost a previous best response or by progression to advanced phase. The decision, therefore, is not simply whether to transplant or not, but also how to transplant. Evolving transplant technology requires that the individual circumstances of each patient should be considered when recommending the procedure. Attempts to improve the safety of transplant are generally associated with a reduction in long-term disease control and patient monitoring, and management is life-long. The treatment of recurrent disease is no longer straightforward, with the choices being donor lymphocytes or tyrosine kinase inhibitors alone or in combination. This section will review the evidence supporting some of these decisions and highlight current controversies.

Allogeneic hematopoietic cell transplantation following nonmyeloablative conditioning as treatment for hematologic malignancies and inherited blood disorders

Allogeneic hematopoietic cell transplantation (HCT) after myeloablative conditioning regimens has been an effective treatment for many patients with hematologic malignancies or inherited blood disorders. Unfortunately, such regimens have been associated with significant toxicity, limiting their use to otherwise healthy, relatively young patients. In an attempt to extend treatment by allogeneic HCT to older patients and those with comorbid conditions, several groups of investigators have developed reduced-intensity or truly nonmyeloablative conditioning regimens, lacking such toxicity. Analogous to conventional regimens, reduced-intensity regimens both eliminated host-versus-graft (rejection) reactions and produced major anti-tumor effects. In contrast, nonmyeloablative regimens have relied on optimizing both pre-and posttransplant immunosuppression to overcome host-versus-graft reactions, while anti-tumor responses have depended mainly on immune-mediated graft-versus-tumor effects. In this review, we define reduced-intensity and truly nonmyeloablative regimens, describe the preclinical development and clinical application of a very low intensity nonmyeloablative regimen, and review results with reduced-intensity regimens in patients with hematologic malignancies or inherited blood disorders.

Allogeneic hematopoietic cell transplantation as consolidation immunotherapy of cancer after autologous transplantation

Autologous and allogeneic hematopoietic cell transplantations (HCT) after high-dose conditioning are curative for many patients with hematologic malignancies. The major limitation of autologous HCT is disease recurrence, while the problem with allogeneic HCT is the restriction to relatively young and otherwise medically fit patients because of complications from high-dose therapy coupled with those from graft-versus-host disease (GVHD). The well-described benefits of graft-versus-tumor (GVT) effects have stimulated the development of conditioning regimens with attenuated doses of chemoradiotherapy that may provide both a degree of cytoreduction before allografting (reduced intensity) and facilitate allogeneic cell engraftment through immuno- suppression (nonmyeloablative). Both reduced-intensity and nonmyeloablative approaches seek to exploit GVT activity of donor cells to eradicate cancer. Because of intrinsic or acquired insensitivity of some malignancies to standard dose chemotherapy and the limitations of GVT effects in eradicating large tumor burdens, high-dose autologous HCT has been used before reduced-intensity and nonmyeloablative allogeneic HCT. This approach appears to improve response rates for malignancies such as multiple myeloma and lymphoma, while avoiding morbidity and mortality of high-dose allogeneic HCT. This review details the rationale, benefits and limitations of this approach.

Current status of hematopoietic stem cell transplantation after nonmyeloablative conditioning

PURPOSE OF REVIEW

Allogeneic hematopoietic stem cell transplantation was originally developed as a form of rescue from high-dose chemoradiotherapy, which is given both to eradicate malignancy and provide sufficient immunosuppression for allogeneic engraftment. However, it was observed that allogeneic immunocompetent cells transplanted with the stem cells, or arising from them, mediated therapeutic antitumor effects independent of the action of the high-dose therapy. This was termed a graft-versus-tumor effect. This has prompted the recent development of nonmyeloablative conditioning regimens for allogeneic hematopoietic stem cell transplantation that have opened the way to include elderly patients and those with comorbid conditions.

RECENT FINDINGS

Recent retrospective studies comparing hematopoietic stem cell transplantation after myeloablative or nonmyeloablative regimens suggested that the use of nonmyeloablative conditioning might be associated with lower transplant-related toxicity, lower nonrelapse mortality, and at least similar intermediate-term progression-free survival.

SUMMARY

Hematopoietic stem cell transplantation after nonmyeloablative conditioning might become the procedure of choice also for younger patients. Phase 3 studies are needed to determine outcomes for different diseases and age groups.

Reduced-intensity allogeneic stem cell transplantation in adults and children with malignant and nonmalignant diseases: end of the beginning and future challenges

During the last 10 years, multiple studies using reduced-intensity (RI) conditioning followed by allogeneic stem cell transplantation (AlloSCT) have been reported in adult and, less so, pediatric recipients. RI AlloSCT allegedly eradicates malignant cells through a graft-versus-leukemia/graft-versus-tumor effect provided by alloreactive donor T lymphocytes, natural killer cells, or both. Various studies have clearly demonstrated a graft-versus-leukemia/graft-versus-tumor effect in hematologic malignancies and solid tumors. Acute short-term toxicity, including infection and organ decompensation after myeloablative conditioning therapy, can result in a significant incidence of early transplant-related mortality. More importantly, long-term late effects-including growth retardation, infertility, and secondary malignancies-are major complications after myeloablative conditioning therapy, especially in vulnerable children, who are more susceptible to these complications. Recent results comparing RI conditioning with myeloablative conditioning followed by HLA-matched sibling AlloSCT have demonstrated a significant reduction in use of blood products, risk of infections, transplant-related mortality, length of hospitalization, and feasibility of conditioning therapy in outpatient settings. Despite the success of RI AlloSCT, large prospective randomized multicenter studies are necessary to define the appropriate patient population, optimal conditioning regimens and pretransplantation immunosuppression, role of donor lymphocyte infusions, duration of hospitalization, overall survival, cost-benefit ratio, and differences in long-term effects to evaluate the role of RI AlloSCT more fully. We review the recent experience of RI AlloSCT in adults and children with both malignant and nonmalignant diseases and discuss the challenges for the future.

Survival after reduced-intensity conditioning is not inferior to standard high-dose conditioning before allogeneic haematopoietic cell transplantation in acute leukaemias

To assess the role of allogeneic stem cell transplantation (SCT) after reduced-intensity conditioning (RIC) in acute leukaemias, we retrospectively compared 25 patients with acute lymphoblastic leukaemia or acute myelogenous leukaemia after RIC to a historical group of 50 matched controls after high-dose conditioning. Engraftment, acute GvHD and severe infections were comparable in both groups. During the observation period, 1/25 patients (4%) after RIC and 14/50 (28%) after standard SCT died due to transplant-related causes; cumulative nonrelapse mortality (NRM) was 4% after RIC and 24% after standard SCT (P=0.029). In total, 15/25 patients (60%) relapsed after RIC and 20/50 (40%) after standard SCT; probability of disease-free survival (DFS) at 3 years was 43% after RIC and 49% after standard SCT (NS). Overall survival (OS) was 40% after RIC and 37% after standard SCT (NS). Stage of disease, cytogenetic risk profile, acute and chronic GvHD, chimerism status at day 90 and severe infections after transplantation were risk factors with significant impact on DFS and/or OS. In retrospective analysis, patients with acute leukaemias who receive RIC because of contraindications against standard SCT have a comparable outcome to standard SCT, but the higher relapse rate warrants further studies.

Nonmyeloablative stem cell transplantation and cell therapy for malignant and non-malignant diseases

The conditioning prior to allogeneic stem cell transplantation was originally designed as a myeloablative conditioning, designed to eliminate malignant or genetically abnormal cells and then use the transplant procedure for rescue of the patients or to replace missing bone marrow products. However, allografts can induce effective graft vs. malignancy effects and can also eliminate undesirable hematopoietic stem cells in patients with genetic disorders and autoimmune diseases, thus documenting that alloreactive effects mediated by donor lymphocytes post-grafting can play a major role in eliminating hematopoietic cell of host origin, as well as provide effective immunotherapy for the treatment of disease recurrence. The efficacy of donor lymphocyte infusion (DLI) could be improved by activation with rIL-2 or by donor immunization. The cumulative experience over the years suggesting that alloreactive donor lymphocytes were most effective in eliminating tumor cells of host origin resulted in an attempt to reduce the intensity of the conditioning in preparation for the transplant procedure used for the treatment of hematological and other malignancies as well as life-threatening non-malignant disorders for which allogeneic stem cell transplantation may be indicated. Our working hypothesis proposed that the myeloablative conditioning which is hazardous and may be associated with early and late side effects, may not be required for treatment of patients with any indication for allogeneic stem cell transplantation. Instead, nonmyeloablative conditioning based on the use of reduced intensive preparatory regimen, also known as nonmyeloablative stem cell transplantation, may be sufficient for engraftment of donor stem cells while avoiding procedure-related toxicity and mortality, followed by elimination of undesirable cells of host origin by post-transplant effects mediated by alloreactive donor lymphocytes infused along with donor stem cells or administered subsequently as DLI. Improvement of the immediate outcome of stem cell transplantation using NST due to a significant decrease in transplant related mortality has broadened the spectrum of patients eligible for allogeneic stem cell transplantation, including elderly patients and other patients with less than optimal performance status. Likewise, the safer use of stem cell transplantation prompted expanding the scope of potential indications for allogeneic stem cell transplantation, such as metastatic solid tumors and autoimmune disorders, which now are slowly becoming much more acceptable. Current strategies focus on the need to improve the capacity of donor lymphocytes to eliminate undesirable malignant and non-malignant hematopoietic cells of host origin, replacing abnormal or malignant stem cells or their products with normal hematopoietic stem cells of donor origin, while minimizing procedure-related toxicity and mortality and improving the quality of life by reducing the incidence and severity of hazardous acute and chronic GVHD.

Reduced-intensity allogeneic hematopoietic stem cell transplantation for acute leukemias: ‘what is the best recipe?’

Reduced-intensity stem cell transplantation (RIST) has been shown to be a safe and useful alternative transplant method for patients including elderly and medically unfit patients. RIST conditioning regimens vary widely in the intensity of myeloablation, immunoablation, and antileukemia effects, and thus optimal regimen for each disease entity is yet to be determined. Most reports on RIST to date are small, single-institution experiences or retrospective studies with heterogeneous patient populations and primary diseases, complicating any direct comparison between studies. In acute myeloid leukemia (AML), moderate-intensity regimens may be effective, achieving 30-70% 1-year disease-free survival in various series, but minimal-intensity regimens are associated with high relapse rates. In acute lymphoblastic leukemia (ALL), not even moderate-intensity regimens are effective and most patients with advanced ALL relapse post transplant. Thus, the risk/benefit ratios of graft-versus-host disease/graft-versus-leukemia effect differ among diseases. Larger, prospective, multi-center clinical trials are needed to determine the best use of RIST in hematologic malignancies.

Control of advanced and refractory acute myelogenous leukaemia with sirolimus-based non-myeloablative allogeneic stem cell transplantation

Non-myeloablative conditioning has extended the use of allogeneic haematopoietic transplant to many previously ineligible patients. We added the immunosuppressive and antitumour agent sirolimus (rapamycin) to an established transplant regimen of fludarabine 25 mg/m(2) days -7 through -3 and cyclophosphamide 1000 mg/m(2) days -7 and -6, with tacrolimus and methotrexate immunoprophyllaxis. A total of 23 patients with acute myelogenous leukaemia (AML) were treated, with a median age of 59 years (range: 28-72) at transplant. Only seven patients in total were in complete remission prior to transplantation. Nine patients were in chemotherapy-refractory progression and seven were primarily refractory to induction therapy. Six patients received matched sibling, 11 unrelated donor, 1-5/6 matched and five haploidentical (haplo - three of six or four of six matched) transplants. The haplo-recipients also received antithymocyte globulin, all patients engrafted. Only two, both recipients of haploidentical cells, have died from transplant-related causes. Twelve of 23 patients survived at 198-1162-d post-transplant (median 578). Four of 12 survivors relapsed at 83, 88, 243 and 508 d and three were in remission after chemotherapy and donor lymphocyte infusion. Although follow up is short, this data suggests that non-myeloablative haematopoietic cell transplantation with sirolimus (rapamycin)-based immunosuppression may provide disease control over several years in some patients with advanced and poor prognosis AML.

Chronic myeloid leukemia: a model for oncology

Leukemias have traditionally served as model systems for research on neoplasia because of the easy availability of cell material from blood and marrow for diagnosis, monitoring and studies on pathophysiology. Beyond these more technical aspects, chronic myeloid leukemia (CML) became the first neoplasia in which the elucidation of the genotype led to a rationally designed therapy of the phenotype. Targeting of the pathogenetically relevant BCR-ABL tyrosine kinase with the selective kinase inhibitor imatinib has induced remissions with almost complete disappearance of any signs and symptoms of CML. This therapeutic success has triggered an intensive search for target structures in other cancers and has led to the development of numerous inhibitors of potential targets, which are being studied in preclinical and clinical trials worldwide. This review deals with some of the recent developments that have evolved since our last review in this journal in 2000 (Hehlmann R, Hochhaus A, Berger U, Reiter A (2000) Current trends in the management of chronic myelogenous leukemia.

Reduced-Intensity Conditioning Allogeneic Blood Stem Cell Transplantation with Fludarabine and Oral Busulfan with or without Pharmacokinetically Targeted Busulfan Dosing in Patients with Myeloid Leukemia Ineligible for Conventional Conditioning

We prospectively compared outcomes after a fludarabine (Flu) plus oral busulfan (Bu)-containing reduced-intensity conditioning regimen (150 mg/m2 Flu and 10 mg/kg oral Bu), with (n = 32; Flu- T Bu group) or without (n = 30; Flu-Bu group) therapeutic dose monitoring and dose adjustment of Bu. All patients received peripheral blood stem cells from a genoidentical sibling, and study cohorts had similar patient characteristics. Dose adjustments of Bu were required in 20 (63%) patients in the Flu- T Bu group (median final dose, 8.89 mg/kg; range, 6.3-13.34 mg/kg). Donor T-cell and granulocyte engraftments were similar, and early conditioning-related toxicities were mild and similar in both study groups. With a median follow-up of 45 months (51 months in the 37 survivors), posttransplantation outcomes did not differ between cohorts. The strongest predictor of 2-year overall survival and leukemia-free survival was the presence of chronic graft-versus-host disease (77% versus 34% for overall survival and 74% versus 34% for leukemia-free survival; P < .001 for both outcomes). In conclusion, therapeutic dose monitoring of oral Bu in a reduced-intensity conditioning setting does not seem to affect outcome, although further studies may identify very-high-risk patients who benefit from this strategy.

Use of a T cell-specific monoclonal antibody, T10B9, in a novel allogeneic stem cell transplantation protocol for hematologic malignancy high-risk patients

To reduce the toxicity of traditional conditioning regimens for allogeneic stem cell transplantation (allo-SCT), we used single-agent chemotherapy conditioning with either busulfan (total cumulative dose, 16 mg/kg) or melphalan (200 to 240 mg/m 2 ), followed by the anti-T cell-specific monoclonal antibody T10B9 (MEDI-500) daily for 3 days. T cell-replete SCT was performed from HLA-identical sibling donors. Acute graft-versus-host disease (aGVHD) prophylaxis consisted of 7 additional days of T10B9 and delayed onset of cyclosporine (ie, on day +4 or +5). Twenty-six high-risk hematologic malignancy patients were entered onto this study. All 24 patients who survived longer than 8 days engrafted, although 1 patient experienced late graft failure. Deaths occurred in 21 of 26 patients because of infection (n = 7), progression/recurrence of primary disease (n = 6), aGVHD (n = 4), regimen-related toxicity (n = 1), and other causes (n = 3). Five of these patients are enjoying disease-free survival with a median survival of 1193 days after allo-SCT. The conditioning regimen induced modulation of surface expression of CD3 (but not CD4 or CD8) and was associated with decreasing tumor necrosis factor-alpha (but not interleukin-6) serum levels. In conclusion, single-agent chemotherapy conditioning with T10B9 produced durable engraftment and long-term survival in some patients who would not have qualified for a traditional allo-SCT.

Personalized medical treatment strategies for patients with chronic myeloid leukemia

Management of patients with chronic myeloid leukemia has become increasingly difficult over the last few years since there are a variety of treatment options available. The ultimate challenge is to decide the most appropriate treatment strategy for an individual patient. To facilitate this, assessment of an individual patient's disease in terms of status, tempo and response to initial treatment needs to be determined. This review article discusses the current treatment options in the management of chronic myeloid leukemia, the factors that influence management decisions and suggests how treatment for the individual patient may be tailored whilst involving the patient in the decision-making process.

Kinetics of engraftment following allogeneic hematopoietic cell transplantation with reduced-intensity or nonmyeloablative conditioning

Nonmyeloablative or reduced-intensity conditioning regimens have been used to condition elderly or ill patients with hematological malignancies for allogeneic hematopoietic cell transplantation (HCT). Initial mixed donor/host chimerism (i.e. the coexistence of hematopoietic cells of host and donor origin) has been observed in most patients after such transplants. Here, we describe both factors affecting engraftment kinetics in patients given a nonmyeloablative or a reduced-intensity conditioning, and associations between peripheral blood cell subset chimerism levels and HCT outcomes.

Targeting the silent minority: emerging immunotherapeutic strategies for eradication of malignant stem cells in chronic myeloid leukaemia

Standard allogeneic stem cell transplantation (alloSCT) has provided a cure for chronic myeloid leukaemia (CML) over the last 25 years, but is only an option for a minority of patients. It was hoped that the introduction of imatinib mesylate (IM), a specific tyrosine kinase inhibitor that targets the Bcr-Abl oncogene product, would provide long-term remission or even cure for those patients without a donor, but studies have shown that IM does not eliminate leukaemic stem cells in CML patients. To overcome this problem of molecular persistence, research is underway to combine reduced intensity stem cell transplant or non-donor-dependent immunotherapies with IM with the aim of increasing cure rate, reducing toxicity and improving quality of life. The alternative approach is to combine IM or second-generation agents with other novel drugs that interrupt key signalling pathways activated by Bcr-Abl. This article will focus on the latest immunotherapy and molecularly targeted therapeutic options in CML and how they may be combined to improve the outcome for CML patients in the future.

HLA-matched unrelated donor hematopoietic cell transplantation after nonmyeloablative conditioning for patients with chronic myeloid leukemia

We evaluated 10/10 HLA antigen-matched unrelated hematopoietic cell transplantation (HCT) after nonmyeloablative conditioning with fludarabine 3 x 30 mg/m2 and 2 Gy of total body irradiation as treatment for patients with chronic myeloid leukemia who were ineligible for conventional HCT. Data from 21 consecutive patients in first chronic phase (CP1; n = 12), accelerated phase (AP; n = 5), second CP (CP2; n = 3), and blast crisis (n = 1) were analyzed. Stem cell sources were bone marrow (n = 4) or granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells (G-PBMCs; n = 17). The patient who underwent transplantation in blast crisis died on day 21 (too early to be evaluated for engraftment) from progressive disease. Sustained engraftment was achieved in 5 of 12 patients who underwent transplantation in CP1, 4 of 5 patients who underwent transplantation in AP, and 2 of 3 patients who underwent transplantation in CP2, whereas 9 patients rejected their grafts between 28 and 400 days after HCT. Specifically, 1 of 4 marrow recipients and 10 of 17 G-PBMC recipients achieved sustained engraftment. Graft rejections were nonfatal in all cases and were followed by autologous reconstitution with persistence or recurrence of chronic myeloid leukemia. Seven of 11 patients with sustained engraftment--including all 5 patients in CP1, 2 of 4 patients in AP, and neither of the 2 patients in CP2--were alive in complete cytogenetic remissions 118 to 1205 days (median, 867 days) after HCT. Two of the remaining 4 patients died of nonrelapse causes in complete (n = 1) or major (n = 1) cytogenetic remissions, and 2 died of progressive disease. Further efforts are directed at reducing the risk of graft rejection by exclusive use of G-PBMC and increasing the degree of pretransplantation immunosuppression.

Hematopoietic cell transplantation from HLA-identical sibling donors after low-dose radiation-based conditioning for treatment of CML

A total of 24 patients (median age 58; range, 27-71 years) with chronic myeloid leukemia (CML) in first chronic (CP1) (n=14), second chronic (n=4), or accelerated phase (n=6) who were not candidates for conventional hematopoietic cell transplantation (HCT), received nonmyeloablative HCT from HLA-matched siblings a median of 28.5 (range, 11-271) months after diagnosis. They were conditioned with 2 Gy total body irradiation (TBI) alone (n=8) or combined with fludarabine, 90 mg/m(2) (n=16). Postgrafting immunosuppression included cyclosporine and mycophenolate mofetil. All patients initially engrafted. However, 4 of 8 patients not given fludarabine experienced nonfatal rejection while all others had sustained engraftment. With a median follow-up of 36 (range, 4-49) months, 13 of 24 patients (54%) were alive and in complete remission. There were five (21%) deaths from nonrelapse mortality, one (4%) during the first 100 days after transplant. The proportions of grade II, III, and IV acute GVHD were 38, 4, and 8%, respectively. The 2-year estimate of chronic GVHD was 32%. The 2-year survival estimates for patients in CP1 (n=14) and beyond CP1 (n=10) were 70 and 56%, respectively. This study shows encouraging remission rates for patients with CML not eligible for conventional allografting.