Long-term follow-up of 23 patients with Philadelphia chromosome-positive acute lymphoblastic leukemia treated with allogeneic bone marrow transplant in first complete remission

Clinical applications of BCR-ABL molecular testing in acute leukemia

Recent advances in molecular genetics impact the health care and outcome of patients with acute lymphoblastic leukemia (ALL). BCR-ABL, a common molecular defect in adult ALL, is a valuable tumor marker whose detection influences prognosis and clinical management decisions. Molecular methods such as fluorescence in situ hybridization (FISH), reverse-transcriptase polymerase chain reaction (rtPCR), and real-time quantitative rtPCR can be used to detect the chimeric BCR-ABL gene or its transcripts. These molecular assays improve our ability to measure residual disease and to estimate risk of relapse. On the horizon are gene expression profiles that will likely provide additional information beyond what is obtainable with current clinical and laboratory approaches.

A potential graft-versus-leukemia effect after allogeneic hematopoietic stem cell transplantation for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: results from the French Bone Marrow Transplantation Society

SUMMARY

Philadelphia chromosome (Ph) acute lymphoblastic leukemia-positive (ALL) is a subgroup of ALL with a poor prognosis. We sought to evaluate the results of allogeneic hematopoietic stem cell transplantation (HSCT) in this situation. From 1992 to 2000, 121 patients with Ph- positive ALL enrolled in one of the three main French prospective ALL chemotherapy trials and receiving allogeneic HSCT were reported to the registry of the French Society of Bone Marrow Transplantation (SFGM-TC). The median age was 35 years (range, 1-53). In all, 76 patients received HSCT in first complete remission and 45 in a more advanced disease stage. Minimal residual disease was evaluated just before the graft: 35 patients of the 52 patients in first remission had persistent BCR-ABL transcript detectable while 17 had no detectable minimal residual disease. Bone marrow and/or peripheral blood samples from 94 patients were submitted for reverse transcriptase polymerase chain reaction analysis at variable points after transplantation. Estimated 2-year survival and relapse rate for patients in CR1 were 50 and 37%, respectively, significantly better than for patients with more advanced disease (P=0.0001 and 0.01, respectively). There was no difference in survival or in relapse rates in terms of the donor used. Relapse was the most common cause of treatment failure. Hematological status at the time of transplant and the occurrence of acute graft-versus-host disease (GvHD) were the only two prognostic factors identified for relapse (P=0.02 and 0.02, respectively). Detection of BCR-ABL transcripts after transplantation had a predictive value on relapse occurrence. Finally, donor lymphocyte infusions were successfully used to treat some relapses. The graft-versus-leukemia effect of HSCT in Ph-positive ALL appears to be supported by (1) the lack of prognostic significance of pretransplant BCR-ABL transcript detection, (2) the efficacy of donor lymphocyte infusions in cases of relapse, and (3) the role of GvHD as protecting against relapse.

Bone marrow transplant in Ph+ ALL patients

Although the outcome for Philadelphia positive (Ph+) acute lymphoblastic leukemia (ALL) with conventional chemotherapy is poor, the outcome after a sibling-matched allogeneic bone marrow transplantation (BMT) seems to be significantly better. The surprising success of allogeneic BMT may be because of disease response to high-dose chemotherapy combined with a graft-versus-leukemia effect. However, less than 30% of patients have a matched related donor available, and some of them will be too old/not fit for conventional BMT. While young patients who do not have a matched related donor should be considered for matched unrelated donor (MUD) transplant, older patients may be treated with autologous stem cell transplantation (ASCT) or rarely considered for a low-intensity MUD transplant. The efficacy of autologous BMT compared with chemotherapy is still debatable, although the new tyrosine kinase inhibitor Imatinib may be used for pretransplant purging/post-transplant therapy, aiming to improve autologous and allogeneic BMT results. The advantage of low-intensity sib/MUD allograft compared with chemotherapy is not proven either and is currently under investigation. However, if shown to be curative, low-intensity allograft may significantly improve the outcome of older Ph+ ALL patients, who are not eligible for conventional allograft.

Imatinib mesylate (STI571) in preparation for allogeneic hematopoietic stem cell transplantation and donor lymphocyte infusions in patients with Philadelphia-positive acute leukemias

Chronic myeloid leukemia in blast crisis (BC) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL) are associated with extremely poor outcome. Allogeneic transplantation during BC or active leukemia is most often unsuccessful due to high-rates of both treatment-related complications and relapse. Long-term results are significantly better if a second chronic phase or remission can be achieved prior to transplantation. Similarly, DLI given for the treatment of post-transplant relapse is more successful when given during a second remission. In this study we report our results with a previously unreported approach consisting of short-term treatment with imatinib mesylate (formerly, STI571) to induce or maintain remission, followed by allogeneic transplantation or DLI and the impact on transplantation/DLI outcome. Sixteen patients were treated either in preparation for transplantation (n = 12), for DLI (n = 1), or for both (n = 3). Ten had CML in BC; seven myeloid and three lymphoid BC. Six patients had Ph(+) ALL. The donors were matched unrelated (n = 9), matched siblings (n = 5) or haplo-identical (n = 2). Eleven of 15 patients given imatinib pre-transplant were transplanted in complete hematologic response. Engraftment and GVHD rates were not different from expected. Seven patients had grade II-III hepatic toxicity after transplantation. After a median follow-up of 10 months (range, 3-16 months) six remain alive, two after further therapy. The 1-year survival rate was 25%. Four patients were given imatinib prior to DLI, all had complete response. Two remain in remission >6 months from relapse. In conclusion, treatment with imatinib allows transplantation in a more favorable status or maintaining remission with low toxicity until transplantation is feasible. Pre-transplant imatinib seems safe and not associated with excess post-transplant complications. Imatinib may have substantial activity in combination with DLI. Further study of a larger group of patients is required to assess the impact on long-term outcome and the role of post-transplant imatinib in controlling residual disease.

Risk factors for adults with Philadelphia-chromosome-positive acute lymphoblastic leukaemia in remission treated with allogeneic bone marrow transplantation: the potential of real-time quantitative reverse-transcription polymerase chain reaction

The aim of this study was to evaluate the outcomes for Philadelphia-chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL) patients in remission treated with allogeneic bone marrow transplantation (BMT). Twenty-three adults were entered onto this study. The 2-year probabilities of relapse and disease-free survival (DFS) were 39.4 +/- 11.6% and 43.5 +/- 10.3% respectively. The presence of chronic graft-versus-host disease (GVHD) was found to be an independent predictive factor affecting lower relapse and DFS. To monitor the BCR-ABL transcript, we also analysed 48 bone marrow samples of eight patients using real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR). The kinetics of the BCR-ABL transcript correlated well with the patients' clinical course. In six patients who were in continuous remission after BMT, a rapid decrease in BCR-ABL copy number to the PCR-negative status was observed after the development of chronic GVHD. Meanwhile, routine bone marrow examination of two patients showed PCR positivity with a 3 or 4-log increase of BCR-ABL copy number and subsequent haematological relapse, which occurred 2 and 4 months later respectively. Although our data should be interpreted cautiously, the presence of chronic GVHD may reduce the risk of relapse in Ph+ ALL. Real-time quantitative RT-PCR appears to be a useful test for BCR-ABL transcript monitoring.

Therapy with imatinib mesylate (Glivec) preceding allogeneic stem cell transplantation (SCT) in relapsed or refractory Philadelphia-positive acute lymphoblastic leukemia (Ph+ALL)

Imatinib has pronounced antileukemic activity in Ph+ALL, although responses are usually short. To determine whether imatinib may facilitate allogeneic SCT in relapsed or refractory Ph+ALL, we evaluated 46 consecutive, not previously transplanted patients who were enrolled in phase II studies of imatinib. Of 30 patients eligible for SCT, 22 (73%) were actually transplanted. Ten patients were in complete hematologic remission (CHR) (n = 5) or had a complete marrow response (CMR) (n = 5) at the time of SCT, 12 patients had again relapsed or were refractory. After SCT, 18 patients were in complete remission, one patient was refractory, three patients died prior to response assessment. Seven patients (32%) are in ongoing complete remission with a median follow-up of 9.4 (range 1.7-23.8) months. Seven patients (32%) relapsed a median of 5.2 months after SCT. Transplant-related mortality (TRM) was 36%. Probability of disease-free survival (DFS) is 25.5 +/- 9.8% overall and 51.4 +/- 17.7% when SCT was performed in CHR or CMR, compared with 8.3 +/- 8% for SCT during overt leukemia (P = 0.06). In conclusion, imatinib is a well-tolerated salvage therapy prior to allogeneic SCT in patients with Ph+ALL, but requires that SCT be performed within a few weeks of starting treatment to avoid resistance. Disease status at time of transplantation is an important determinant of DFS and TRM.

Stem cell transplantation in adult ALL patients

Less than 40% of adult acute lymphocytic leukaemia (ALL) patients will still be alive at 5 years post-diagnosis. Ways to improve patients' outcome, using high-dose therapy followed by autologous/allogeneic stem cell transplantation (SCT) in first complete remission (CR1) rather than consolidation/maintenance chemotherapy, have been investigated. However, prospective studies are small and results are inconclusive. The largest prospective trial ever being performed in adult ALL patients, the ongoing UKALL 12/ECOG 2993 trial, is assigning all patients who have a sibling donor to receive allogeneic SCT (alloSCT) in CR1, whereas all other patients are randomized to continue chemotherapy versus autologous SCT. An interim analysis of this trial seems to support an alloSCT in first CR in adult ALL patients (reflected by a significantly reduced relapse rate with an improved disease-free survival). However, less than 30% of the patients have a matched sibling donor, the majority of the patients are over 40 years old, which makes them less suitable for conventional allograft, and even in those who have a matched sibling donor and are young and fit enough to receive it the treatment-related mortality (TRM) is about 20%. Strategies for expanding donor availability, meanwhile, to reduce the TRM, remain challenges. Data regarding the efficacy of reduced-intensity regimens in ALL patients are still scanty. Another way of improving patient outcome is to select patients for allograft more carefully. There are enough data to suggest now that children who achieved a clinical remission but failed to obtain a molecular/immunological remission are more prone to relapse. Similar data have recently been published for adult ALL. However, data are still limited, and the significance of minimal residual disease (MRD) has never been studied prospectively in adult ALL patients. A reasonable approach is to assign all patients with a matched related donor who has failed to achieve a molecular/immunological remission to receive a conventional alloSCT, whereas all others might be randomized to receive alloSCT versus chemotherapy/autologousSCT. However, patients with Ph(+) ALL who have a donor should receive an alloSCT in CR1, regardless of their MRD results. It appears that alloSCT provides the best chance for cure. However, by improving our ability to select those who have the highest risk for relapse, unnecessary toxicity/mortality might be prevented and the general outcome might improve.

Molecular measurement of minimal residual disease in Philadelphia-positive acute lymphoblastic leukaemia

The Philadelphia chromosome (Ph) is found in approximately 5-25% of acute lymphoblastic leukaemia (ALL) cases and is the harbinger of a poor outcome. Polymerase chain reaction (PCR) assays can detect leukaemia-specific genetic lesions down to a sensitivity approaching one leukaemia cell in a background of a million normal cells. In Ph(+) ALL, the unique BCR-ABL translocation is thus a specific target for the detection of minimal residual disease (MRD). After chemotherapy or transplantation the detection of residual BCR-ABL transcripts is associated with a high risk of subsequent relapse. With the advent of novel therapeutics that target the structure and function of BCR-ABL, the detection of MRD may allow for targeted therapy that could abort a potential relapse.

Detection of minimal residual disease

A high percentage of patients with leukemia, lymphoma, and solid tumors achieve a complete clinical remission after initial treatment, but the majority of these patients will finally relapse from residual tumor cells detectable in clinical remission only by the most sensitive methods. The in vitro amplification of tumor-specific DNA or RNA sequences by polymerase chain reaction (PCR) allows identification of a few neoplastic cells in 10(4) to 10(6) normal cells. Depending on the underlying malignant disease and therapeutic treatment, the presence of residual tumor cells in an individual patient may herald relapse, but a long-term stable situation or slowly vanishing tumor cells are also possible. Molecular monitoring of residual leukemia and lymphoma cells by quantitative PCR techniques has provided important information about the effectiveness of treatment and the risk of recurrent disease as shown by minimal residual disease (MRD) analysis in patients with various malignant diseases. Such diseases include childhood acute lymphoblastic leukemia, after induction therapy; acute promyelocytic leukemia, during and after chemotherapy; and chronic myelogenous leukemia, during treatment with alpha-interferon and after allogeneic bone marrow transplantation. Evaluation of the predictive value of the detection of MRD has to take into account its evolution and course, the pathogenesis, biology, and natural course of the underlying malignant disease, the molecular genetic lesion, and finally, the type of treatment. Quantification of minimal residual cells by the recently developed real-time quantitative PCR technique will surely have a major impact on our therapeutic strategies for patients with leukemia, lymphomas, and solid tumors. Based on quantitative PCR data, the terms molecular remission and molecular relapse have to be exactly defined and validated in prospective clinical trials to assess the biological and clinical significance of MRD in various types of malignancies.

Acute lymphoblastic leukemia

This is a comprehensive overview on the most recent developments in diagnosis and treatment of acute lymphoblastic leukemia (ALL). Dr. Dieter Hoelzer and colleagues give an overview of current chemotherapy approaches, prognostic factors, risk stratification, and new treatment options such as tyrosine kinase inhibitors and monoclonal antibodies. Furthermore the role of minimal residual disease (MRD) for individual treatment decisions in prospective clinical studies in adult ALL is reviewed. Drs. Ching-Hon Pui and Mary Relling discuss late treatment sequelae in childhood ALL. The relation between the risk of second cancer and treatment schedule, pharmacogenetics, and gene expression profile studies is described. Also pathogenesis, risk factors, and management of other complications such as endocrinopathy, bone demineralization, obesity, and avascular necrosis of bone is reviewed. Dr. Fred Appelbaum addresses long-term results, late sequelae and quality of life in ALL patients after stem cell transplantation. New options for reduction of relapse risk, e.g., by intensified conditioning regimens or donor lymphocyte infusions, for reduction of mortality and new approaches such as nonmyeloablative transplantation in ALL are discussed. Drs. Jacques van Dongen and Tomasz Szczepanski demonstrate the prognostic value of MRD detection via flow cytometry or PCR analysis in childhood ALL. They discuss the relation between MRD results and type of treatment protocol, timing of the follow-up samples, and the applied technique and underline the importance of standardization and quality control. They also review MRD-based risk group definition and clinical consequences.

Unrelated marrow transplantation for adult patients with poor-risk acute lymphoblastic leukemia: strong graft-versus-leukemia effect and risk factors determining outcome

Between 1988 and 1999, 127 patients with poor-risk acute lymphoblastic leukemia (ALL) received a matched unrelated donor transplant using marrow procured by National Marrow Donor Program (NMDP) collection centers and sent out to 46 transplant centers worldwide. Poor risk was defined by the presence of the translocations t(9;22) (n = 97), or t(4;11) (n = 25), or t(1;19) (n = 5). Sixty-four patients underwent transplantation in first remission (CR1), 16 in CR2 or CR3, and 47 patients had relapsed ALL or primary induction failure (PIF). Overall survival at 2 years from transplant was 40% for patients in CR1, 17% in CR2/3, and 5% in PIF or relapse. Treatment-related mortality (TRM) and relapse mortality, estimated as competing risk factors, were 54% and 6%, respectively, in CR1, 75% and 8% in CR2/3, and 64% and 31% in PIF or relapse. Currently 23 CR1 patients are alive and free of disease with a median follow-up of 24 months (range, 3-97). Multivariable analysis showed that CR1, shorter interval from diagnosis to transplantation, DRB1 match, negative cytomegalovirus (CMV) serology (patient and donor), and presence of the Philadelphia chromosome, t(9;22), were independently associated with better disease-free survival (DFS). Transplantation in CR and presence of t(9;22) were associated with lower risk of relapse. Shorter interval from diagnosis to transplantation, DRB1-match, negative CMV, higher marrow cell dose, and Karnofsky score of 90 or higher were associated with less TRM. These results indicate that, despite a relatively high TRM, the low relapse rate resulted in a 37% +/- 13% DFS for CR1 patients, comparing favorably to results obtained with chemotherapy alone and matching results following HLA-identical sibling transplantation.

Philadelphia chromosome-positive acute lymphocytic leukemia

On a molecular and cellular level, Ph+ ALL seems to be a heterogeneous disease. Unfortunately, the unifying theme of Ph positivity is the poor outcome associated with its presence. Further characterization of molecular subtypes of Ph+ ALL may in the future distinguish those few patients with a potentially good outcome from the majority who face inevitable relapse. Also, novel targeted biologic therapy especially in combination with aggressive, early chemotherapy, may soon be able to temper the disease. Most patients who obtain a remission would be best served by transplantation during remission. For those without a donor, following the disease by PCR-based techniques may detect early relapse. For relapsed patients without the option of transplantation, investigative studies are appropriate.

Allogeneic stem cell transplantation for acute lymphocytic leukemia in adults

Acute lymphocytic leukemia remains a difficult disease to treat in adults. Allogeneic bone marrow transplantation can cure some patients with ALL, but GVHD transplant-related mortality and disease relapse remain problematic. Immunotherapeutic approaches aimed at eliminating minimal residual disease and enhancing the GVL effect may decrease relapse rates and improve overall survival. Because of the rarity of this disease in adults, every new patient should be entered in well-designed, peer-reviewed, investigational trial.

Management of adult acute lymphoblastic leukemia: moving toward a risk-adapted approach

The vast majority of adults with acute lymphoblastic leukemia (ALL) now achieve remission with current intensive chemotherapy regimens. Nevertheless, most adults with ALL will eventually relapse and die of their disease. Specific clinical and molecular-cytogenetic prognostic factors have been identified that are beginning to provide insights for the development of risk-adapted management strategies that appear to improve survival for several high-risk patient groups, including those with mature B-cell ALL and B-lineage ALL patients with a Philadelphia chromosome. We review standard and some recently described prognostic factors in adult ALL, describe current therapy based on a risk-adapted approach, and look toward the future with a brief discussion of novel, targeted treatments that could be incorporated into postremission strategies to improve survival for adults with ALL.