Intensive treatment and stem cell transplantation in chronic myelogenous leukemia: long-term follow-up

Tolerability-adapted imatinib 800 mg/d versus 400 mg/d versus 400 mg/d plus interferon-α in newly diagnosed chronic myeloid leukemia

PURPOSE

Treatment of chronic-phase (CP) chronic myeloid leukemia (CML) with imatinib 400 mg/d can be unsatisfactory. Optimization of treatment is warranted.

PATIENTS AND METHODS

In all, 1,014 newly diagnosed CP-CML patients were randomly assigned to imatinib 800 mg/d (n = 338), imatinib 400 mg/d (n = 325), or imatinib 400 mg/d plus interferon alfa (IFN-α; n = 351). Dose adaptation to avoid higher-grade toxicity was recommended. First primary end point was major molecular remission (MMR) at 12 months.

RESULTS

A higher rate of MMR at 12 months occurred with tolerability-adapted imatinib 800 mg/d than with imatinib 400 mg/d (59% [95% CI, 53% to 65%] v 44% [95% CI, 37% to 50%]; P < .001) or imatinib 400 mg/d plus IFN-α (59% v 46% [95% CI, 40% to 52%]; P = .002). Median dose in the 800-mg/d arm was 628 mg/d with a maximum dose of 737 mg/d during months 4 to 6 and a maintenance dose of 600 mg/d. All three treatment approaches were well tolerated with similar grade 3 and 4 adverse events. Independent of treatment approach, MMR at 12 months showed better progression-free survival (99% v 94%; P = .0023) and overall survival (99% v 93%; P = .0011) at 3 years when compared with > 1% on the international scale or no MMR but showed no difference in 0.1% to < 1% on the international scale, which closely correlates with complete cytogenetic remission.

CONCLUSION

Treatment of early-phase CML with imatinib can be optimized. Early high-dose therapy followed by rapid adaptation to good tolerability increases the rate of MMR at 12 months. Achievement of MMR by month 12 is directly associated with improved survival.

Chronic myelogenous leukemia: treatment and monitoring

BACKGROUND

The treatment options for bcr-abl positive chronic myelogenous leukemia (CML) include chemotherapy, immune therapy, allogeneic stem cell transplantation, and molecular therapy. The tyrosine kinase inhibitor imatinib was approved for the treatment of CML in 2002. Data from clinical trials allow a comparison of treatment options.

METHODS

The literature on the treatment and monitoring of CML was selectively reviewed. A total of 94 original articles were analyzed, along with the recommendations of an international expert committee and the medical societies. This review is current as of November 2009.

RESULTS

In a clinical phase 3 trial of imatinib treatment for patients in the chronic phase of CML, the rates of progression-free and overall survival at 6 years were 93% and 88%, respectively. Thus, imatinib is clearly superior to interferon-alpha, hydroxyurea, and busulfan with respect to survival. Allogeneic stem-cell transplantation is only a fall back option because of transplantation-associated mortality. One in four patients in the chronic phase of CML has an inadequate cytogenetic response to imatinib and therefore requires a change of treatment. Most imatinib-resistant patients in the chronic phase of CML go into remission again after switching to one of the new tyrosine kinase inhibitors, dasatinib and nilotinib.

CONCLUSION

Imatinib is now the standard initial first-line treatment for CML in the chronic phase. Regular hematologic and cytogenetic monitoring during treatment is indispensable so that patients with an inadequate response can be identified.

Current status of therapy for chronic myeloid leukemia: a review of drug development

Chronic myeloid leukemia (CML) has led the way for developing rational drug development in cancer. Most cases of CML diagnosed and treated in chronic phase are extremely well controlled with imatinib monotherapy, and primary resistance is very uncommon. Even though the treatment failure rate is low, the emergence of drug resistance and the lack of eradication of the hematopoietic stem cell clone has prompted a wave of drugs to address one or both these problems. Several clinical trials (Phase I and II) of dasatinib or nilotinib in the treatment of imatinib-resistant or -intolerant Ph chromosome-positive leukemia have already reported a remarkable rate of hematologic response greater than 90% for chronic-phase patients. These drugs minimize the risk of acquired drug resistance that is particularly seen within the first 24-36 months of therapy, and can prevent early failure in these patients, Furthermore, rational, noncross-resistant combinations that include a T315I inhibitor and drugs that can eradicate the hematopoietic stem cell clone may extend the coverage to virtually all patients with bcr-abl. Here we review the 6-year impact of the 'magic pill', Gleevec, (Glivec), including the emerging problems with its treatment, the efficacy data of dasatinib and nilotinib and the very promising data of the newer generation of drugs for CML.

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.

Gene expression analysis identifies a genetic signature potentially associated with response to α-IFN in chronic phase CML patients

Microarray-based gene expression analysis was performed on diagnostic chronic phase CML patient samples prior to interferon treatment. Fifteen patient samples corresponding to six cytogenetic responders and nine non-responders were included. Genes differentially expressed between responder and non-responder patients were listed and a subsequent leave-one-out cross validation (LOOV) procedure showed that the top 20 genes allowed the highest prediction accuracy. The relevant genes were quantified by real-time PCR that supported the microarray results. We conclude that it might be possible to use gene expression analysis to predict future response to interferon in CML diagnostic samples.

Optimal initial therapy for patients with newly diagnosed chronic myeloid leukemia in chronic phase

PURPOSE OF REVIEW

Imatinib mesylate, a tyrosine kinase inhibitor, has revolutionized the therapy of newly diagnosed patients with chronic myeloid leukemia. Prior to imatinib, treatment algorithms for chronic myeloid leukemia patients recommended stem cell transplantation for patients less than 50 years old who had a donor and could undergo stem cell transplantation. Other than stem cell transplantation, interferon was the only drug that could induce cytogenetic remissions in minority of patients.

RECENT FINDINGS

After 5 years of follow-up, the rate of relapse with imatinib therapy continues to decrease, and the numbers of patients achieving a complete molecular response continue to increase. In addition, with a longer follow up, imatinib continues to be safe and easily tolerated. Recent studies have shown a survival benefit with imatinib. The use of imatinib before stem cell transplant did not have an effect on mortality or morbidity posttransplant.

SUMMARY

Currently, imatinib is considered first line therapy in all patients with early chronic phase chronic myeloid leukemia with stem cell transplant reserved for patients who have disease resistant to imatinib therapy. Our aim is to review current recommendations for initial therapy of patients with early chronic phasechronic myeloid leukemia, current areas of controversy and future directions.

Treatment of chronic myeloid leukemia in the imatinib era

BACKGROUND

There is paucity of data from developing countries on the efficacy and safety of imatinib mesylate in chronic myeloid leukemia (CML). The primary objective of this study was to document complete and partial cytogenetic responses to imatinib in all phases of CML. Secondary objectives included evaluations of complete hematologic response, safety, time to progression, and survival.

METHODS

Two hundred seventy-five patients in all phases of CML who received treatment with imatinib from January 2001 to December 2005 were included in the study. All patients had on bone marrow or BCR-ABL positive in peripheral blood by polymerase chain reaction.

RESULTS

After a median follow-up of 18 months, major cytogenetic responses (Ph <35%) in chronic phase (CP), accelerated phase (AP), and blastic phase (BP) were documented in 61%, 57%, and 28% of patients, respectively. A complete cytogenetic response was observed in 39.4%, 35.7%, and 14.3% of patients in CP, AP, and BP, respectively; and a complete hematologic response was observed in 90%, 86%, and 30%, respectively. The median time to progression at 18 months was 91% in CP and 68% in AP. The overall survivals in CP, AP, and BP at 18 months was 92%, 74%, and 38%, respectively.

CONCLUSIONS

Impressive hematologic, cytogenetic, and molecular responses to imatinib were observed, similar to the responses reported in patients from Western countries. Patients had good compliance, toxicity was limited, and overall quality of life was improved markedly. The results indicated that the biology of CML is not different in patients from developing countries.

Successful mobilization of Ph-negative blood stem cells with intensive chemotherapy + G-CSF in patients with chronic myelogenous leukemia in first chronic phase

The aim of the study was to investigate the feasibility of mobilizing Philadelphia chromosome negative (Ph-) blood stem cells (BSC) with intensive chemotherapy and lenograstim (G-CSF) in patients with CML in first chronic phase (CP1). During 1994-1999 12 centers included 37 patients <56 years. All patients received 6 months' IFN, stopping at median 36 (1-290) days prior to the mobilization chemotherapy. All received one cycle of daunorubicin 50 mg/m2 and 1 hour infusion on days 1-3, and cytarabine (ara-C) 200 mg/m2 24 hours' i.v. infusion on days 1-7 (DA) followed by G-CSF 526 microg s.c. once daily from day 8 after the start of chemotherapy. Leukaphereses were initiated when the number of CD 34+ cells was >5/microl blood. Patients mobilizing poorly could receive a 4-day cycle of chemotherapy with mitoxantrone 12 mg/m2/day and 1 hour i.v infusion, etoposide 100 mg/m2/day and 1 hour i.v. infusion and ara-C 1 g/m2/twice a day with 2 hours' i.v infusion (MEA) or a second DA, followed by G-CSF 526 microg s.c once daily from day 8 after the start of chemotherapy. Twenty-seven patients received one cycle of chemotherapy and G-CSF, whereas 10 were mobilized twice. Twenty-three patients (62%) were successfully (MNC >3.5 x 10(8)/kg, CFU-GM >1.0 x 10(4)/kg, CD34+ cells >2.0 x 10(6)/kg and no Ph+ cells in the apheresis product) [n = 16] or partially successfully (as defined above but 1-34% Ph+ cells in the apheresis product) [n = 7] mobilized. There was no mortality during the mobilization procedure. Twenty-one/23 patients subsequently underwent auto-SCT. The time with PMN <0.5 x 10(9)/l was 10 (range 7-49) and with platelets <20 x 10(9)/l was also 10 (2-173) days. There was no transplant related mortality. The estimated 5-year overall survival after auto-SCT was 68% (95% CI 47 - 90%), with a median follow-up time of 5.2 years.We conclude that in a significant proportion of patients with CML in CP 1, intensive chemotherapy combined with G-CSF mobilizes Ph- BSC sufficient for use in auto-SCT.

Imatinib activity in vitro in tumor cells from patients with chronic myeloid leukemia in chronic phase and blast crisis

The aims of this study were to evaluate the feasibility of using the non-clonogenic fluorometric microculture cytotoxicity assay in drug sensitivity testing of tumor cells from patients with chronic myeloid leukemia. In nine samples (six chronic phase, three blast crisis), the drug sensitivities in tumor cells from blood versus from bone marrow and fresh tumor cells versus cryopreserved were compared. In 26 samples obtained in chronic phase (pretreatment), in six samples from patients in blast crisis and in the K 562 cell line, the activity of imatinib alone and in combination with cytarabine, vincristine, daunorubicin, interferon, arsenic trioxide and homoharringtonine was evaluated. All chronic myeloid leukemia chronic phase samples were sensitive to imatinib, with a mean IC50 at 10.3 mumol/l. The chronic myeloid leukemia samples from blast crisis (n=6) were significantly more sensitive to imatinib than the samples from chronic phase (n=26) (P<0.05), with an IC50 mean at 0.4 mumol/l. In blast crisis samples, significant positive interaction effects were observed between imatinib and all other tested drugs except for interferon. In chronic phase samples, interferon, daunorubicin and arsenic trioxide were the drugs with the highest frequency of positive interactions with imatinib (P<0.05). We conclude that the fluorometric microculture cytotoxicity assay may be a useful method for drug sensitivity testing in chronic myeloid leukemia patient samples from both chronic phase and blast crisis, and that testing primary tumor cells may have advantages over cell line studies. Imatinib shows a higher in vitro activity and more positive drug interactions in cells from blast crisis than chronic phase chronic myeloid leukemia patients. Combinations between imatinib and interferon, daunorubicin and arsenic trioxide may be interesting for future clinical trials in patients with chronic myeloid leukemia chronic phase.