Response to imatinib in patients who relapse after allogeneic stem cell transplantation for chronic myeloid leukemia

Haematopoietic stem cell transplantation after reduced intensity conditioning in children and adolescents with chronic myeloid leukaemia: A prospective multicentre trial of the I-BFM Study Group

This prospective multicentre trial evaluated the safety and the efficacy of a thiotepa/melphalan-based reduced intensity conditioning (RIC) haematopoietic stem cell transplantation (HSCT) in children and adolescents with chronic myeloid leukaemia (CML) in chronic phase (CP). Thirty-two patients were transplanted from matched siblings or matched unrelated donors. In 22 patients, HSCT was performed due to insufficient molecular response or loss of response to first- or second-generation tyrosine kinase inhibitor (TKI), with pretransplant BCR::ABL1 transcripts ranging between 0.001% and 33%. The protocol included a BCR::ABL1-guided intervention with TKI retreatment in the first year and donor lymphocyte infusions (DLI) in the second-year post-transplant. All patients engrafted. The 1-year transplant-related mortality was 3% (confidence interval [CI]: 0%-6%). After a median follow-up of 6.3 years, 5-year overall survival and event-free survival are 97% (CI: 93%-100%) and 91% (CI: 79%-100%) respectively. The current 5-year leukaemia-free survival with BCR::ABL1 <0.01% is 97% (CI: 88%-100%) and the current TKI- and DLI-free survival is 95% (CI: 85%-100%). The incidence of chronic graft-versus-host disease (GvHD) was 32%, being severe in four patients (13%). At last follow-up, 31 patients are GvHD-free and have stopped immunosuppression. RIC HSCT following pretreatment with TKI is feasible and effective in children and adolescents with CP-CML with an excellent disease-free and TKI-free survival.

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

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

The Role of Donor Lymphocyte Infusion (DLI) in Post-Hematopoietic Cell Transplant (HCT) Relapse for Chronic Myeloid Leukemia (CML) in the Tyrosine Kinase Inhibitor (TKI) Era

Treatment for relapse of chronic myeloid leukemia (CML) following hematopoietic cell transplantation (HCT) includes tyrosine kinase inhibitors (TKIs) with or without donor lymphocyte infusions (DLIs), but the most effective treatment strategy is unknown. This study was performed through the Center for International Blood and Marrow Transplant Research (CIBMTR) database. We retrospectively reviewed all patients reported to the CIBMTR registry from 2002 to 2014 who underwent HCT for CML and were alive 30 days postrelapse. A total of 215 HCT recipients relapsed and were analyzed in the following groups: (1) TKI alone (n = 128), (2) TKI with DLI (n = 48), and (3) DLI without TKI (n = 39). In multivariate analysis, disease status prior to HCT had a significant effect on overall survival (OS). Patients who received a DLI alone compared with a TKI with a DLI had inferior survival (hazard ratio, 2.28; 95% confidence interval, 1.23 to 4.24; P= .009). Those who received a TKI alone had similar survival compared with those who received a TKI with a DLI (P = .81). These data support that despite use of TKIs pretransplantation, TKI salvage therapy continues to provide significant survival following relapse in patients with CML following HCT. These data do not suggest that adding a DLI to a TKI adds an improvement in OS.

Cost Effectiveness of the Third-Generation Tyrosine Kinase Inhibitor (TKI) Ponatinib, vs. Second-Generation TKIs or Stem Cell Transplant, as Third-Line Treatment for Chronic-Phase Chronic Myeloid Leukemia

BACKGROUND AND OBJECTIVES

Third-line treatment options for patients with chronic-phase chronic myeloid leukemia include tyrosine kinase inhibitors and allogeneic hematopoietic stem cell transplantation (alloHSCT). The objective of this study was to develop a Markov model with a lifetime time horizon to assess the cost effectiveness of ponatinib for third-line chronic-phase chronic myeloid leukemia vs. second-generation tyrosine kinase inhibitors (dasatinib, nilotinib, bosutinib) or alloHSCT from the public healthcare system perspective in Germany, Sweden, and Canada.

METHODS

Clinical outcomes were derived from the literature, and from patient-level data (phase II PACE trial) for ponatinib. Resource use included drugs, alloHSCT, monitoring and follow-up, adverse events, and end-of-life care; costs were based on national tariffs. Quality-adjusted life-years (QALYs) were calculated using chronic myeloid leukemia health-state utilities from an international time-trade-off study. Costs and benefits were discounted at 3% per annum for Germany and Sweden, and 5% for Canada.

RESULTS

Ponatinib yielded more discounted QALYs than any second-generation tyrosine kinase inhibitor/alloHSCT in all three countries, mainly owing to better response rates and longer durations of response. Incremental cost-effectiveness ratios for ponatinib vs. second-generation tyrosine kinase inhibitors were US$21,543-37,755/QALY in Germany, $24,018-38,227/QALY in Sweden, and $43,001-58,515/QALY in Canada. Ponatinib was dominant over alloHSCT in Germany, while incremental cost-effectiveness ratios for ponatinib vs. alloHSCT in Sweden and Canada were $715/QALY and $31,534/QALY, respectively.

CONCLUSIONS

Ponatinib may improve outcomes (mainly because of higher response rates and longer response durations) at an acceptable cost level compared with other third-line treatment options for chronic-phase chronic myeloid leukemia in Germany, Sweden, and Canada; however, the lack of an indirect comparison is a limitation of our study.

Chronic Myeloid Leukemia Relapsing 25 Years after Allogenic Stem Cell Transplantation

Chronic myeloid leukemia (CML) is a myeloproliferative disorder in which neoplastic cells exhibit the Philadelphia chromosome and the related oncoprotein BCR-ABL1. Allogeneic stem cell transplantation (allo-SCT) was considered the first-line treatment for CML, before the introduction of tyrosine kinase inhibitors (TKIs). However, patients are at risk for relapse years after transplantation. We present a patient who relapsed 25 years after allo-SCT for chronic phase CML. Polymerase chain reaction (PCR) detected gradually evaluated levels of BCR-ABL1 transcripts, eventually leading to the diagnosis of relapsed disease. Additional mutational analyses did not reveal mutations in the BCR-ABL1 gene, or other cooperating mutations. The patient was successfully treated with imatinib 400 mg daily, leading to new molecular remission. The case presentation emphasizes the need for long-term follow-up of such patients and the potential benefit of initiating TKI treatment with early signs of relapse.

Canadian chronic myeloid leukemia outcomes post-transplant in the tyrosine kinase inhibitor era

The majority of patients with TKI failure respond to HCT. However, the relapse risk remains high. This study has evaluated transplant outcomes in 223 CML patients with TKI failure due to resistance (n = 132) or intolerance (n = 29), as well as those that were TKI naïve/responding with advanced disease (n = 35) or with chronic phase (CP, n = 27). We studied outcomes according to post-transplant BCR-ABL transcript level within 3 months. With respect to transplant outcomes according to the post-transplant BCR/ABLtranscript level within 3 months, the group failing to achieve a 1.3 log reduction (n = 14, 12.4%) showed the highest relapse rate of 78.6% at 5 years, compared to 26.2% and 24.1% in the groups achieving 1.3-4.0 log reduction (n = 45, 39.8%), and ≥4.1 log reduction (n = 54, 47.8%) respectively (p < 0.001). Multivariate analysis confirmed that the group failing to achieve a 1.3 log reduction had a 2.3-fold higher risk of death and 6.6 times higher risk of relapse. Poor overall survival after HCT was associated with advanced disease at diagnosis, but not disease status prior to HCT. Of 61 patients who relapsed after HCT, 47 were treated with post-transplant TKI therapy; those receiving TKI after loss of MR2 or MMR showed higher rates of response and survival compared to those receiving TKI after hematologic relapse (p < 0.001). QPCR log reduction level within 3 months post transplantation is prognostic in this population.

Ponatinib for Treating Chronic Myeloid Leukaemia: An Evidence Review Group Perspective of a NICE Single Technology Appraisal

As part of its single technology appraisal process, the National Institute for Health and Care Excellence (NICE) invited the company that manufactures ponatinib (Inclusig^®; Incyte Corporation) to submit evidence for the clinical and cost effectiveness for previously treated chronic myeloid leukaemia (CML) and Philadelphia-chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL). This paper focusses on the three phases of CML: the chronic phase (CP), the accelerated phase (AP) and the blast crisis phase (BP). The School of Health and Related Research Technology Appraisal Group at the University of Sheffield was commissioned to act as the independent Evidence Review Group (ERG). This article presents the critical review of the company's submission by the ERG and the outcome of the NICE guidance. Clinical evidence for ponatinib was derived from a phase II, industry-sponsored, single-arm, open-label, multicentre, non-comparative study. Despite the limited evidence and potential for biases, this study demonstrated that ponatinib was likely to be an effective treatment (in terms of major cytogenetic response and major haematological response) with an acceptable safety profile for patients with CML. Given the absence of any head-to-head studies comparing ponatinib with other relevant comparators, the company undertook a matching-adjusted indirect comparison (MAIC) of ponatinib with bosutinib. The approach was only used for patients with CP-CML because comprehensive data were not available for the AP- or BP-CML groups to allow the matching technique to be used. Despite the uncertainty about the MAIC approach, ponatinib was considered likely to offer advantages over bosutinib in the third-line setting, particularly for complete cytogenetic response. The company developed two health economic models to assess the cost effectiveness of ponatinib for the treatment of patients in CP-CML or in advanced CML (AP- or BP-CML, which were modelled separately). The company did not adequately explore the uncertainty in the survivor functions. As a result, the ERG believed the uncertainty in the decision problem was underestimated. Exploratory analyses undertaken by the ERG produced the following results for ponatinib. In CP-CML, from £18,246 to £27,667 per quality-adjusted life-year (QALY) gained compared with best supportive care (BSC), from £19,680 to £37,381 per QALY gained compared with bosutinib and from £18,279 per QALY gained to dominated compared with allogeneic stem cell transplant (allo-SCT). In AP-CML, the cost per QALY gained for ponatinib ranged from £7123 to £17,625 compared with BSC, and from dominating to £61,896 per QALY gained compared with allo-SCT. In BP-CML, the cost effectiveness of ponatinib ranged from £5033 per QALY gained to dominated compared with allo-SCT, although it was likely to be at the more favourable end of this range, and dominant in all scenarios compared with BSC. The NICE appraisal committee concluded that ponatinib is a cost-effective use of NHS resources in the considered population, subject to the company providing the agreed discount in the Patient Access Scheme.

Immunological effects of nilotinib prophylaxis after allogeneic stem cell transplantation in patients with advanced chronic myeloid leukemia or philadelphia chromosome-positive acute lymphoblastic leukemia

Allogeneic stem cell transplantation remains the standard treatment for resistant advanced chronic myeloid leukemia and Philadelphia chromosome–positive acute lymphoblastic leukemia. Relapse is the major cause of treatment failure in both diseases. Post-allo-SCT administration of TKIs could potentially reduce relapse rates, but concerns regarding their effect on immune reconstitution have been raised. We aimed to assess immune functions of 12 advanced CML and Ph+ ALL patients who received post-allo-SCT nilotinib. Lymphocyte subpopulations and their functional activities including T-cell response to mitogens, NK cytotoxic activity and thymic function, determined by quantification of the T cell receptor (TCR) excision circles (TREC) and TCR repertoire, were evaluated at several time points, including pre-nilotib-post-allo-SCT, and up to 365 days on nilotinib treatment. NK cells were the first to recover post allo-SCT. Concomitant to nilotinib administration, total lymphocyte counts and subpopulations gradually increased. CD8 T cells were rapidly reconstituted and continued to increase until day 180 post SCT, while CD4 T cells counts were low until 180−270 days post nilotinib treatment. T-cell response to mitogenic stimulation was not inhibited by nilotinib administration. Thymic activity, measured by TREC copies and surface membrane expression of 24 different TCR Vβ families, was evident in all patients at the end of follow-up after allo-SCT and nilotinib treatment. Finally, nilotinib did not inhibit NK cytotoxic activity. In conclusion, administration of nilotinib post allo-SCT, in attempt to reduce relapse rates or progression of Ph+ ALL and CML, did not jeopardize immune reconstitution or function following transplantation.

New drugs and allogeneic hematopoietic stem cell transplantation for hematological malignancies: do they have a role in bridging, consolidating or conditioning transplantation treatment?

INTRODUCTION

Novel targeted therapies and monoclonal antibodies can be combined with allogeneic stem cell transplantation (allo-SCT) at different time-points: 1) before the transplant to reduce tumour burden, 2) as part of the conditioning in place of or in addition to conventional agents 3) after the transplant to allow long-term disease control. Areas covered: This review focuses on the current integration of new drugs with allo-SCT for the treatment of major hematological malignancies for which allo-SCT has been a widely-adopted therapy. Expert opinion: After having been used as single agent salvage treatments in relapsed patients after allo-SCT or in combination with donor lymphocyte infusions, many new drugs have also been safely employed before allo-SCT as a bridge to transplantation or after it as planned consolidation/maintenance. This era of new drugs has opened new important opportunities to 'smartly' combine 'targeted drugs and cell therapies' in new treatment paradigms that may lead to higher cure rates or longer disease control in patients with hematological malignancies.

Allogeneic stem cell transplantation in chronic myeloid leukemia patients: Single center experience

Chronic myeloid leukemia (CML) is a myeloproliferative disease which leads the unregulated growth of myeloid cells in the bone marrow. It is characterized by the presence of Philadelphia chromosome. Reciprocal translocation of the ABL gene from chromosome 9 to 22 t (9; 22) (q34; q11.2) generate a fusion gene (BCR-ABL). BCR-ABL protein had constitutive tyrosine kinase activity that is a primary cause of chronic phase of CML. Tyrosine kinase inhibitors (TKIs) are now considered standard therapy for patients with CML. Even though, successful treatment with the TKIs, allogeneic stem cell transplantation (ASCT) is still an important option for the treatment of CML, especially for patients who are resistant or intolerant to at least one second generation TKI or for patients with blastic phase. Today, we know that there is no evidence for increased transplant-related toxicity and negative impact of survival with pre-transplant TKIs. However, there are some controversies about timing of ASCT, the optimal conditioning regimens and donor source. Another important issue is that BCR-ABL signaling is not necessary for survival of CML stem cell and TKIs were not effective on these cells. So, ASCT may play a role to eliminate CML stem cells. In this article, we review the diagnosis, management and treatment of CML. Later, we present our center’s outcomes of ASCT for patients with CML and then, we discuss the place of ASCT in CML treatment in the TKIs era.

Management of advanced-phase chronic myeloid leukemia

The management of chronic myeloid leukemia (CML) in accelerated or blast phase (advanced phase) remains a significant challenge despite the introduction of very effective tyrosine kinase inhibitors (TKIs). The biology of advanced-phase CML is complex and engages several pathways that are not optimally targeted by TKIs. Allogeneic stem cell transplantation remains the only potentially curative therapy, but the effectiveness of this conventional approach is limited. New strategies are required to improve the outlook for these patients.

The role of stem cell transplantation for chronic myelogenous leukemia in the 21st century

The introduction of tyrosine kinase inhibitors (TKIs), a treatment of chronic myelogenous leukemia (CML), has largely replaced curative strategies based on allogeneic stem cell transplantation (SCT). Nevertheless, SCT still remains an option for accelerated/blastic-phase and selected chronic-phase CML. Transplant outcomes can be optimized by peritransplant TKIs, conditioning regimen, BCR-ABL monitoring, and relapse management. Controversies exist in transplant timing, pediatric CML, alternative donors, and economics. SCT continues to serve as a platform of "operational cure" for CML with TKIs and immunotherapies.

Donor Lymphocyte Infusions for Chronic Myeloid Leukemia Relapsing after Allogeneic Stem Cell Transplantation: May We Predict Graft-versus-Leukemia Without Graft-versus-Host Disease?

Donor lymphocyte infusions (DLI) are an effective treatment for relapsed chronic myeloid leukemia (CML) after allogeneic stem cell transplantation (alloSCT). Leukemia resistance and secondary graft-versus-host disease (GVHD) are major obstacles to success with DLI. The aim of this study was to identify pre-DLI factors associated with prolonged survival in remission without secondary GVHD. We retrospectively analyzed 500 patients treated with DLI for CML relapse (16% molecular, 30% cytogenetic, and 54% hematological) after alloSCT. The overall probabilities of failure- and secondary GVHD-free survival (FGFS) were 29% and 27% at 5 and 10 years after DLI, respectively. The type of relapse was the major factor influencing FGFS (40% for molecular and/or cytogenetic relapse and 20% for hematological relapse at 5 years, P < .001). Chronic GVHD before DLI and an interval <1 year between alloSCT and first DLI were independently associated with inferior FGFS in patients with molecular and/or cytogenetic relapse. Consequently, FGFS was 13%, 35%, to 56% at 5 years in patients with 2, 1, and 0 adverse features, respectively. In patients with hematological relapse, independent adverse prognostic factors for FGFS were initial dose of CD3(+) cells ≥ 50 × 10(6)/kg, donor-recipient sex mismatch, and chronic GVHD before DLI. FGFS was 0%, 17%, 33%, to 37% in patients with 3, 2, 1, and 0 adverse features, respectively. The probability of survival in remission without secondary GVHD was highest (>50% at 5 years) when DLI were given beyond 1 year from alloSCT for molecular and/or cytogenetic CML relapse that was not preceded by chronic GVHD.

Phase 1/2 study of nilotinib prophylaxis after allogeneic stem cell transplantation in patients with advanced chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia

BACKGROUND

Allogeneic stem cell transplantation (SCT) remains the standard treatment for advanced chronic myeloid leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL). Relapsed disease is the major cause of treatment failure, especially when SCT is given in the setting of advanced disease. Tyrosine kinase inhibitors can be given after transplantation prophylactically or after the detection of minimal residual disease (MRD) to reduce the relapse risk.

METHODS

Posttransplant nilotinib was started after the achievement of sustained engraftment and the resolution of transplant-related toxicities. Nilotinib was continued until progression or unacceptable toxicity.

RESULTS

Twenty-two patients with advanced CML (n = 15) or Ph(+) ALL (n = 7) underwent SCT with human leukocyte antigen-matched siblings (n = 11), unrelated donors (n = 7), or alternative donors (n = 4). Sixteen patients were given prophylactic nilotinib maintenance, which was started at a median of 38 days after transplantation. Six patients stopped the treatment because of toxicities (mostly gastrointestinal and hepatic). After nilotinib maintenance, 11 patients achieved (n = 9) or maintained (n = 2) a complete molecular response (CMR), and only 1 of them later relapsed. Four of the 5 patients not achieving CMR relapsed. At a median follow-up of 46 months, 9 patients were alive, and 13 had died. The 2-year overall and progression-free survival rates were 55% (95% confidence interval [CI], 34%-75%) and 45% (95% CI, 25%-66%), respectively. Among the 16 nilotinib recipients, the rates were 69% (95% CI, 46%-92%) and 56% (95% CI, 32%-81%), respectively. The 2-year nonrelapse mortality and relapse rates for all patients were 32% (95% CI, 17%-58%) and 23% (95% CI, 11%-49%), respectively.

CONCLUSIONS

Nilotinib is relatively safe and effective prophylactic therapy for the prevention of relapse after SCT. It may control MRD and convert patients to CMR, which is associated with prolonged survival. These observations merit further study in larger scale studies.

Clinical and biological predictors of outcome following relapse of CML post-allo-SCT

While there are now fewer allogeneic stem cell transplants (allo-SCT) performed for chronic myeloid leukemia (CML), leukemic relapse post-transplant remains a persistent problem. To better define clinical and biological parameters determining post-relapse outcome, we studied 59 patients with CML relapsing after HLA-identical sibling allo-SCT between 1993 and 2008. Eighteen (30.5%) were transplanted in advanced phase and 41(69.5%) in chronic phase. With a median follow up from relapse of 7.9 years, 5-year post-relapse survival (PRS) was 62%. Multivariate analysis found disease status at transplant, time to diagnosis of relapse from transplant, and pre- transplant TKI use as significant factors associated with PRS. Analysis of BCR-ABL transcript expression in the hematopoietic progenitor compartment was performed in 36 patients (22 relapsed, 8 non-relapsed, and 6 TKI alone controls). Patients with BCR-ABL expression in their early hematopoietic stem cell compartment (HSC: Lineage⁻CD34⁺CD38-CD90⁺) had worse survival irrespective of the disease status. We conclude disease status remains the strongest clinical prognostic factor for PRS in CML following allo-SCT. The persistence of BCR-ABL expression in the progenitor cell compartment in some patients after SCT emphasizes the need to target CML-leukemia stem cells.

Patients with Philadelphia-positive leukemia with BCR-ABL kinase mutations before allogeneic transplantation predominantly relapse with the same mutation

Despite the successes of tyrosine kinase inhibitors (TKIs) in improving outcomes in patients with chronic myeloid leukemia (CML) and Philadelphia-positive acute lymphoblastic leukemia (Ph + ALL), allogeneic hematopoietic stem cell transplantation (HSCT) continues to be an important and potentially curative option for selected patients with either disease. After HSCT, TKIs are increasingly being used to treat or prevent disease relapse, and practice patterns suggest that these TKIs are often chosen empirically without regard to pre-HSCT mutation status. We investigated whether ABL kinase domain mutations persist after transplantation and, thus, whether pre-HSCT mutation status should inform the selection of post-HSCT TKIs in these patients. We retrospectively analyzed adults who underwent allogeneic HSCT for CML and Ph + ALL at our institution between 2000 and 2010, and we identified subjects who had detectable BCR-ABL transcripts by polymerase chain reaction (PCR), as well as available RNA for Sanger sequencing of the ABL kinase domain, in both the pre- and post-HSCT settings. In total, 95 CML and 20 Ph + ALL patients with positive PCR transcripts were identified, of which 10 (10.5%) and 4 (20.0%), respectively, were found to have pre-HSCT ABL kinase mutations known to confer TKI resistance. In 9 (64.2%) of these 14 patients, the same kinase mutation was also detectable at an average time of 191 days after HSCT. Seven (50.0%) of the 14 harboring mutations had relapsed/refractory disease by last follow-up, of which, in retrospect, 6 had received a predictably ineffective TKI within the first 100 days after transplantation based on our mutation analysis. These data support the idea that pre-existing mutations in the ABL kinase domain, frequently associated with resistance to TKIs and prevalent in a transplantation population, are persistently detectable in the majority of patients after transplantation. We propose that such resistance patterns should be considered when selecting TKIs in the post-HSCT setting, including clinical trials of post-HSCT TKI prophylaxis.

Chronic myeloid leukemia-transplantation in the tyrosine kinase era

Allogeneic hematopoietic stem cell transplantation (HSCT) revolutionized the outlook for many patients with chronic myeloid leukemia (CML) in the 1980s. The introduction of the tyrosine kinase inhibitors (TKIs) nearly 15 years ago displaced HSCT as the first-line treatment for most CML patients. However, in the twenty-first century HSCT remains a viable treatment option for many patients with CML. This review focuses on the role of HSCT for CML in the TKI era, paying particular attention to patient selection and transplant outcome.

Early administration of donor lymphocyte infusions upon molecular relapse after allogeneic hematopoietic stem cell transplantation for chronic myeloid leukemia: a study by the Chronic Malignancies Working Party of the EBMT

Patients with chronic myeloid leukemia relapsing after allogeneic hematopoietic stem cell transplantation may be treated by tyrosine kinase inhibitors and/or by donor lymphocyte infusions. The best strategies and timing of administration of lymphocytes are unclear. We analyzed 155 patients who relapsed after allogeneic stem cell transplantation with disease detectable only by molecular methods and who subsequently received lymphocytes. Transplants were performed in first chronic phase (n=125) or in advanced disease (n=29) from identical siblings (n=84) or unrelated donors (n=71) between 1986 and 2003. They received lymphocytes either during molecular relapse (n=85) or upon progression to more advanced disease (1993 to 2004). The median interval from relapse to lymphocyte infusion was 210 (0-1673) days. The median follow up after it was 46 (3-135) months. Overall survival was 76±4% at five years after lymphocyte infusions (89±8% with sibling donors and 63±13% with unrelated donors (P=0.003)). Survival was 69±14% when lymphocytes were given within six months of the detection of molecular relapse and 81±10% (P=0.061) when given later; 81±11% if given at molecular relapse versus 71±12% (P=0.26) with more advanced disease. In multivariate analysis survival was worse if the donor was unrelated (HR 2.54 (95% CI: 1.15-5.53), P=0.021) and better with lymphocyte infusions beyond six months from molecular relapse (HR 0.4 (95%CI: 0.19-0.84), P=0.018). These data confirm the remarkable efficacy of lymphocyte infusions for this disease. There appears to be no advantage from administering it early upon detection of molecular relapse in patients who received allogeneic stem cell transplantation for chronic myeloid leukemia.

The evolution of treatment strategies for patients with chronic myeloid leukemia relapsing after allogeneic bone marrow transplant: can tyrosine kinase inhibitors replace donor lymphocyte infusions?

The optimal treatment for chronic myeloid leukemia (CML) relapsing following allogeneic bone marrow transplant (alloBMT) is unknown. We performed a single-center retrospective analysis of 71 consecutive patients undergoing alloBMT for CML from 1995 to 2008. A multi-state model was used to quantify cumulative incidences of complete molecular response (CMR) and death following alloBMT. The primary analysis was comparison of three treatment interventions (tyrosine kinase inhibitor: TKI, donor lymphocyte infusion: DLI, and TKI + DLI) for relapsed disease post-alloBMT. Forty-five (63%) patients relapsed post-alloBMT (molecular relapse: n = 16, cytogenetic relapse: n = 20, hematologic relapse: n = 2, advanced phase relapse: n = 7) and 40 patients underwent one of three treatments: TKI-only (n = 13), DLI-only (n = 11) or TKI + DLI (n = 16). Although not statistically significant, the TKI-only group had the highest cumulative incidence of CMR and lowest cumulative incidence of death compared to DLI and TKI + DLI. These data support the finding that TKI therapy is active in the post-alloBMT setting.

A comparison of long-term outcomes of donor lymphocyte infusions and tyrosine kinase inhibitors in patients with relapsed CML after allogeneic hematopoietic cell transplantation

BACKGROUND

Donor lymphocyte infusion (DLI) and tyrosine kinase inhibitors (TKIs) are the 2 standard treatment options in chronic myeloid leukemia (CML) that relapses after hematopoietic cell transplantation (HCT), but reports comparing long-term outcomes of these modalities are rare.

PATIENTS AND METHODS

A total of 46 patients were treated with either DLI (n = 28) or TKIs (n = 18) during a first relapse of CML after HCT between 1993 and 2012. The stage of relapse was the chronic phase in 37 patients and the advanced phase in 9 patients. All patients had myeloablative conditioning without T-cell depletion during HCT. The median interval between HCT and treatment for relapse was 34 (range, 2-197) months.

RESULTS

At a median follow-up of 146 and 70 months, respectively, 32% of the DLI group and 33% of the TKI group had died. Six (21%) patients initially treated with DLI received TKIs during a second relapse. In multivariable analyses, DLI was associated with inferior overall survival (OS) (hazard ratio [HR], 37.4; 95% confidence interval [CI], 2.2-625.4; P = .01), shorter failure-free survival (FFS) (HR, 21.15; 95% CI, 1.8-251; P = .02), higher cumulative incidence of failure (CIF) (HR, 19.5; 95% CI, 1.6-236.5; P = .02), and increased incidence of treatment-induced graft vs. host disease (GVHD) (68% vs. 6%; P = .001).

CONCLUSION

TKIs appear better than DLI in chronic-phase relapses after myeloablative non-T-cell-depleted HCT. Outcomes were poor in advanced-phase relapses irrespective of treatment modality.

Allogeneic stem cell transplantation for chronic myeloid leukemia

In recent years new, more potent tyrosine-kinase inhibitors have been introduced to accompany imatinib for the treatment of chronic myeloid leukemia. Most patients in chronic phase obtain an optimal response to these oral agents with minimal toxicity. Allogeneic stem cell transplantation is therefore indicated only in a minority of patients who do not achieve an adequate response to first, second or third generation agents. Patients in accelerated phase have a lower chance of achieving an optimal response on these drugs. For patients in blast phase, transplantation remains the only therapy with curative potential, although now it is increasingly used in combination with tyrosine-kinase inhibitors. In this review we address the role of allogeneic stem cell transplantation in the treatment of this disease and how patients should be transplanted.

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

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

Chronic myelogenous leukemia: role of stem cell transplant in the imatinib era

In the pre-tyrosine kinase (TKI) era, allogeneic stem cell transplant (allo-SCT) was the front-line treatment of choice for young patients with chronic myelogenous leukemia (CML). Today, imatinib is well established as front-line therapy for CML, with excellent long-term outcomes. This has changed the role of allo-SCT and the number of patients undergoing allo-SCT has declined dramatically. Allo-SCT is currently recommended for patients in accelerated/blast phase disease, those who have failed a second-generation TKI and those with TKI-resistant mutations such as T315I. The role of allo-SCT in the management of CML will require continual reappraisal as medical therapies continue to evolve.

Controversies in the treatment of CML in children and adolescents: TKIs versus BMT?

Chronic myeloid leukemia (CML) is a relatively rare hematopoietic malignancy in the pediatric and adolescent population. This makes it difficult to perform clinic trials that can define the best therapeutic option when considering the impact of tyrosine kinase inhibitors (TKIs) versus the established approach of allogeneic hematopoietic cell transplantation (HCT). With the relatively low toxicity of TKIs, there are little data regarding when HCT or long-term TKI therapy is a better option. There are even less data regarding the duration of TKI treatment in the pediatric CML in chronic phase (CML-CP) patients who may receive over 60 years of therapy. As children and adolescent are treated for longer times with TKIs, it has become clear that toxicities may make long-term TKI therapy less attractive compared to allogeneic HCT. HCT has the long-term complications of growth failure, infertility, chronic graft-versus-host disease (GVHD), metabolic syndrome, and secondary malignancies, whereas prolonged TKIs may cause growth failure, hepatic, and cardiac complications. Moreover, HCT is a potentially curative intervention, whereas TKI is not curative, requiring prolonged exposure. In this article, we discuss the relative merit of the 2 therapeutic approaches and recommend that all children and adolescents with CML-CP should initially be treated with imatinib and maintained with TKI therapy indefinitely if there is a good response. We recommend that allogeneic HCT with an HLA-identical sibling donor or closely matched unrelated donor be considered for patients with treatment failure or recurrence after receiving salvage second-generation TKI treatment. We also conclude that randomized international trials are urgently needed to evaluate the best therapies for pediatric CML.

Allogeneic immunotherapy to optimize the graft-versus-tumor effect: concepts and controversies

Allogeneic stem cell transplantation (SCT) can be considered the most successful method of adoptive immunotherapy of cancer. It is successful in part because of the potent graft-versus-tumor (GVT) effects of the donor graft, which are independent of the conditioning regimen. This potent GVT reaction can be harnessed in some cases to treat patients who relapse after allogeneic SCT with the use of donor leukocyte infusions (DLIs). This has led to the rapid development of reduced-intensity conditioning (RIC) regimens for allogeneic SCT, an approach that relies primarily on GVT activity. However, the effects of GVT have clear disease specificity and remain associated with significant GVHD. Optimization of GVT induction will require a better understanding of the important target antigens and effector cells, as well as the development of methods that enhance GVT reactivity without excessive GVHD. The appropriate clinical setting and timing for GVT induction need to be defined more clearly, but ultimately, the immunologic control of cancer through allogeneic adoptive immunotherapy represents one of the most potent and promising therapeutic strategies for patients with hematologic malignancies.

Long-term prognostic significance of early molecular response to imatinib in newly diagnosed chronic myeloid leukemia: an analysis from the International Randomized Study of Interferon and STI571 (IRIS)

This study examines the prognostic significance of early molecular response using an expanded dataset in chronic myeloid leukemia patients enrolled in the International Randomized Study of Interferon and STI571 (IRIS). Serial molecular studies demonstrate decreases in BCR-ABL transcripts over time. Analyses of event-free survival (EFS) and time to progression to accelerated phase/blast crisis (AP/BC) at 7 years were based on molecular responses using the international scale (IS) at 6-, 12-, and 18-month landmarks. Patients with BCR-ABL transcripts > 10% at 6 months and > 1% at 12 months had inferior EFS and higher rate of progression to AP/BC compared with all other molecular response groups. Conversely, patients who achieved major molecular response [MMR: BCR-ABL (IS) ≤ 0.1%] by 18 months enjoyed remarkably durable responses, with no progression to AP/BC and 95% EFS at 7 years. The probability of loss of complete cytogenetic response by 7 years was only 3% for patients in MMR at 18 months versus 26% for patients with complete cytogenetic response but not MMR (P < .001). This study shows a strong association between the degree to which BCR-ABL transcript numbers are reduced by therapy and long-term clinical outcome, supporting the use of time-dependent molecular measures to determine optimal response to therapy. This study is registered at www.clinicaltrials.gov as NCT00006343.

CML in pregnancy and childhood

With the improved survivals offered by the tyrosine kinase inhibitors has come the necessity to address issues relating to quality of life and one such area is that of fertility and parenting. Animal data suggest that imatinib at standard dosages is unlikely to impair fertility in either adult males or females but human data remain limited. Children born to men who are actively taking imatinib at the time of conception appear healthy and current advice is not to discontinue treatment. In contrast the data relating to children born to women exposed to imatinib during pregnancy are less encouraging. Although numbers are small there has been a disturbing cluster of rare congenital malformations such that imatinib cannot be safely recommended, particularly during the period of organogenesis. The appropriate management of children with CML has also been radically changed by the advent of imatinib. The features of the disease at presentation, the natural history and the response to therapy seem to be identical in children to that seen in adults. Now that imatinib has been in clinical use for almost ten years without severe long-term side effects, most physicians are now comfortable advising a trial of imatinib prior to consideration of transplant. Data relating to the efficacy and safety of second generation tyrosine kinase inhibitors in childhood is entirely absent and transplant remains the first choice for patients failing imatinib and perhaps also for young patients with sub-optimal responses.

Targeted agents for chronic myelogenous leukemia: will that be the end of allogeneic bone marrow transplantation for that disease?

Although the drug imatinib has been accepted as the treatment of choice for chronic myelogenous leukemia (CML) in chronic phase (CP) throughout the Western world, allogeneic stem cell transplantation (allo-SCT) continues to remain a widely practiced first-line treatment in countries with limited health care budgets. The rationale is not scientific, but largely economically based. We analyzed a cohort of 46 CML patients who participated in a graft-versus-host disease (GVHD) prophylaxis clinical trial and underwent related HLA-matched allogeneic peripheral blood stem cell transplantation. The median time of follow-up in surviving patients was 43 months (range: 4-89 months). Risk stratification of the population was done by European Blood and Marrow Transplant (EBMT) criteria. The estimated probabilities of overall survival (OS) and leukemia-free survival (LFS) at 3 years in low EBMT risk score (0-2) patients were both 91%, respectively. We conclude that in countries with restricted access to imatinib, allo-SCT should be considered early on as front-line therapy. Continued research support for bone marrow transplantation will be needed to make a global impact on this disease.

Optimizing reduced-intensity conditioning regimens for myeloproliferative neoplasms

The myeloproliferative neoplasms (MPNs) are a group of clonal disorders that arise from a pluripotent hematopoietic stem cell and are characterized by excess cellular proliferation. These disorders tend to be chronic in nature and can terminate over time into a bone marrow failure syndrome characterized by marrow fibrosis or transform into a leukemic phase. MPNs are predominantly diseases of the elderly and this is one reason why until very recently the standard treatment was supportive care. The only curative modality for these disorders is allogeneic hematopoietic cell transplantation. The introduction of reduced-intensity conditioning regimens now allows this life-saving therapy to be offered to elderly patients who were previously considered ineligible for high-dose conditioning owing to age or comorbidity. In this review, we will summarize the current strategies and future directions regarding the use of reduced-intensity conditioning regimens in the treatment of MPNs.

Allogeneic stem cell transplantation with alemtuzumab-based conditioning for patients with advanced chronic myelogenous leukemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the treatment of choice for patients with chronic myelogenous leukemia (CML) who have failed or are intolerant to tyrosine kinase inhibitors (TKI). Myeloablative conditioning regimens have been associated with high treatment-related mortality (TRM) rate in such patients, and reduced-intensity conditioning (RIC) regimens are often preferred but have high rates of disease recurrence and graft-versus-host-disease (GVHD). We report our experience with nine CML patients (four chronic phase and five with accelerated phase or blast crisis) who failed TKI and underwent allo-HSCT using an alemtuzumab-based RIC regimen. The conditioning regimen was well tolerated and induced engraftment in all patients, and complete cytogenetic remission (CCyR) in eight of nine. Four patients, all with a history of accelerated phase or blast crisis, died. Four of the five remaining patients had a cytogenetic relapse a median of 10 months after transplantation. Donor lymphocyte infusion (DLI), TKI or both induced a CCyR in all cases. With a median follow-up of 47 months, five patients, including all those transplanted in first or second chronic phase, are alive and in remission. Allo-HSCT with an alemtuzumab-based conditioning regimen induces remission in patients with CML that have failed TKI therapy and has a low incidence of GVHD. Disease recurrence is frequent but responds to DLI. In some cases, restoration of susceptibility to TKI was observed. Outcomes may improve with the routine administration of post-transplant TKI.

Old and new cancers after hematopoietic-cell transplantation

Relapse of primary disease and occurrence of new cancers can cause significant morbidity and mortality in recipients of autologous and allogeneic hematopoietic-cell transplantation (HCT). Treatment options for relapse are generally limited and can include disease-specific chemotherapy or targeted therapy. Additional relapse-directed therapies that are available for allogeneic HCT recipients include withdrawal of immunosuppression and donor lymphocyte infusion. Selected patients can be offered a second transplant procedure. Newer strategies to eliminate minimal residual disease and, in allogeneic HCT recipients, to augment the graft-versus-tumor effect are needed for patients who are at high risk for relapse after HCT. Second cancers after HCT include post-transplant lymphoproliferative disorder, hematologic malignancies and new solid cancers. The incidence of second solid cancers continues to rise without a plateau with increasing follow up of HCT survivors. Secondary myelodysplastic syndrome and acute leukemia are almost exclusively seen in autologous HCT recipients while post-transplant lymphoproliferative disorders complicate recipients of allogeneic HCT. Appropriate screening evaluations should be performed in HCT survivors to facilitate early detection and treatment of second cancers.

Posttransplantation imatinib as a strategy to postpone the requirement for immunotherapy in patients undergoing reduced-intensity allografts for chronic myeloid leukemia

Disease relapse is a major cause of treatment failure after reduced-intensity allografts and while donor lymphocyte infusions (DLIs) can be effective salvage therapy they are associated with severe graft-versus-host disease (GVHD) when administered early after transplantation. We have therefore examined whether imatinib mesylate can delay relapse and postpone the requirement for DLI in 22 patients with chronic myeloid leukemia (CML) allografted using a reduced-intensity regimen. Imatinib was commenced on day + 35 and continued until 1 year after transplantation. Posttransplantation imatinib was well tolerated and abolished the risk of relapse during this period. Twenty-one patients completed 11 months of imatinib therapy, 15 of whom subsequently relapsed and received DLI. Ten patients to date have achieved molecular remission after DLI. Adjunctive targeted therapy allows the kinetics of disease relapse after a reduced-intensity allograft to be manipulated and represents a novel strategy by which outcome may be improved in patients who undergo transplantation for CML and other leukemias.