Late mortality and relapse following BuCy2 and HLA-identical sibling marrow transplantation for chronic myelogenous leukemia

Female Sex Is Associated with Improved Long-Term Survival Following Allogeneic Hematopoietic Stem Cell Transplantation

Life expectancy for long-term survivors of allogeneic hematopoietic stem cell transplantation (alloHSCT), defined as those living ≥5 years post-transplantation, is significantly lower compared with that of the age-matched general population despite a relatively low primary disease relapse rate at >2 years post-transplantation. Among several factors, patient sex is increasingly recognized as a prognostic indicator of long-term survival. We examined the influence of patient sex and donor-recipient sex matching on overall survival (OS) in a landmark analysis of long-term survivors. Using our institutional database supplemented with individual patient record review, we retrospectively investigated the relative influence of recipient sex and donor-recipient sex matching on outcomes of long-term survivors of alloHSCT between 1994 and 2014. Over this 20-year period, 247 met inclusion criteria for analysis; males and females had similar demographic and treatment characteristics. However, significantly more deaths after the 5-year landmark occurred in male recipients. Interestingly, donor sex did not have a significant impact on OS in multivariate analysis, and differences in OS of donor-recipient sex pairs was driven by recipient sex. In addition to recipient sex, only chronic graft-versus-host disease (cGVHD) retained significance as a covariate with an impact on OS in multivariate analysis. Men experienced slightly higher, but statistically nonsignificant, rates and increased severity of cGVHD, and had higher cGVHD-related mortality compared with females. In this long-term survival analysis of adult alloHSCT recipients, one of the only to include follow-up to 15 years, our results show that women survive significantly longer than men irrespective of their age at transplantation. This outcome is independent of other common pretransplantation prognostic indicators, such as donor sex or performance status at transplantation. The inferior survival in males is consistent with survival outcomes described in the transplantation literature. Increasing evidence suggests a biological basis for long-term sex-determined outcomes, possibly owing to differing rates or severity of cGVHD or sustained alloimmune tolerance in females. Larger studies are warranted to validate these retrospective clinical results.

Myeloablative vs reduced-intensity conditioning allogeneic hematopoietic cell transplantation for chronic myeloid leukemia

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment of chronic myeloid leukemia (CML). Optimal conditioning intensity for allo-HCT for CML in the era of tyrosine kinase inhibitors (TKIs) is unknown. Using the Center for International Blood and Marrow Transplant Research database, we sought to determine whether reduced-intensity/nonmyeloablative conditioning (RIC) allo-HCT and myeloablative conditioning (MAC) result in similar outcomes in CML patients. We evaluated 1395 CML allo-HCT recipients between the ages of 18 and 60 years. The disease status at transplant was divided into the following categories: chronic phase 1, chronic phase 2 or greater, and accelerated phase. Patients in blast phase at transplant and alternative donor transplants were excluded. The primary outcome was overall survival (OS) after allo-HCT. MAC (n = 1204) and RIC allo-HCT recipients (n = 191) from 2007 to 2014 were included. Patient, disease, and transplantation characteristics were similar, with a few exceptions. Multivariable analysis showed no significant difference in OS between MAC and RIC groups. In addition, leukemia-free survival and nonrelapse mortality did not differ significantly between the 2 groups. Compared with MAC, the RIC group had a higher risk of early relapse after allo-HCT (hazard ratio [HR], 1.85; P = .001). The cumulative incidence of chronic graft-versus-host disease (cGVHD) was lower with RIC than with MAC (HR, 0.77; P = .02). RIC provides similar survival and lower cGVHD compared with MAC and therefore may be a reasonable alternative to MAC for CML patients in the TKI era.

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.

Outcomes of Allogeneic Hematopoietic Cell Transplantation in Children and Young Adults with Chronic Myeloid Leukemia: A CIBMTR Cohort Analysis

Chronic myeloid leukemia (CML) in children and young adults is uncommon. Young patients have long life expectancies and low morbidity with hematopoietic cell transplantation (HCT). Prolonged tyrosine kinase inhibitor (TKI) use may cause significant morbidity. In addition, indication for HCT in patients in the first chronic phase is not established. We hence retrospectively evaluated outcomes in 449 CML patients with early disease receiving myeloablative HCT reported to the CIBMTR. We analyzed various factors affecting outcome, specifically the effect of age and pre-HCT TKI in pediatric patients (age < 18 years, n = 177) and young adults (age 18 to 29 years, n = 272) with the goal of identifying prognostic factors. Post-HCT probability rates of 5-year overall survival (OS) and leukemia-free survival (LFS) were 75% and 59%, respectively. Rates of OS and LFS were 76% and 57% in <18-year and 74% and 60% in 18- to 29-year group, respectively, by univariate analysis (P = .1 and = .6). Five-year rates of OS for HLA matched sibling donor (MSD) and bone marrow (BM) stem cell source were 83% and 80%, respectively. In multivariate analysis there was no effect of age (<18 versus 18 to 29) or pre-HCT TKI therapy on OS, LFS, transplant related mortality, or relapse. Favorable factors for OS were MSD (P < .001) and recent HCT (2003 to 2010; P = .04). LFS was superior with MSD (P < .001), BM as graft source (P = .001), and performance scores > 90 (P = .03) compared with unrelated or mismatched peripheral blood stem cells donors and recipients with lower performance scores. Older age was associated with increased incidence of chronic graft-versus-host disease (P = .0002). In the current era, HCT outcomes are similar in young patients and children with early CML, and best outcomes are achieved with BM grafts and MSD.

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.

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.

Challenges for allogeneic hematopoietic stem cell transplantation in chronic myeloid leukemia in the era of tyrosine kinase inhibitors

Following the introduction of the tyrosine kinase inhibitor (TKI) imatinib in the treatment of chronic myeloid leukemia (CML) patients, the allogeneic hematopoietic stem cell transplantation (HSCT) scene in CML has changed dramatically. The number of patients receiving HSCT in first chronic phase (CP) has declined rapidly, as allogeneic HSCT in CP is now performed in these patients only in case of failure or intolerance of TKIs. Second, those CML patients who undergo allogeneic HSCT represent a selection of high-risk patients due to more advanced disease with high rates of accelerated or blast phase (being associated with an increased relapse risk), advanced age and relevant co-morbidities. Efforts at meeting these special challenges are being developed: treatment with TKIs aims to improve the pre-transplant remission status before HSCT. Dose-reduced conditioning protocols were introduced to decrease transplant-related mortality in patients with co-morbidities or older age. In the post-transplant period, TKIs may be administered for prophylaxis and for treatment of post-transplant relapse. Still, the outcome of patients in advanced CML phases remains guarded, and requires an improvement in current transplant strategies.

Relapse and late mortality in 5-year survivors of myeloablative allogeneic hematopoietic cell transplantation for chronic myeloid leukemia in first chronic phase

PURPOSE Allogeneic hematopoietic cell transplantation (HCT) is curative therapy for chronic myeloid leukemia (CML), but its long-term outcomes are not well described. We studied the long-term outcomes of CML patients in first chronic phase who receive an allogeneic HCT. PATIENTS AND METHODS Our study included 2,444 patients who received myeloablative HCT for CML in first chronic phase between 1978 and 1998 and survived in continuous complete remission for at least 5 years (median follow-up, 11 years; range, 5 to 25 years). Donor sources were human leukocyte antigen-matched siblings in 1,692 patients, unrelated donors in 639 patients, and other related donors in 113 patients. RESULTS Overall survival rates at 15 years were 88% (95% CI, 86% to 90%) for sibling HCT and 87% (95% CI, 83% to 90%) for unrelated donor HCT. Corresponding cumulative incidences of relapse were 8% (95% CI, 7% to 10%) and 2% (95% CI, 1% to 4%), respectively. The latest relapse was reported 18 years post-HCT. In multivariable analyses, history of chronic graft-versus-host disease increased risks of late overall mortality and nonrelapse mortality but reduced risks of relapse. In comparison with age-, race-, and sex-adjusted normal populations, the mortality of HCT recipients was significantly higher until 14 years post-HCT; thereafter, mortality rates were similar to those of the general population (relative mortality ratio at 15 years, 2.3; 95% CI, 0 to 4.9). CONCLUSION Recipients of allogeneic HCT for CML in first chronic phase who remain in remission for at least 5 years have favorable subsequent long-term survival, and their mortality rates eventually approach those of the general population.

Incidence and reasons for late failure after allogeneic haematopoietic cell transplantation following BuCy2 in acute myeloid leukaemia

The long-term follow-up is presented for 317 patients with acute myeloid leukaemia who underwent human leucocyte antigen-identical sibling marrow transplants between 1984 and 1995 following preparation with busulfan 16 mg/kg and cyclophosphamide 120 mg/kg. Among the 142 (45%) who were alive and leukaemia-free 3 years following transplantation, the leukaemia-free survival at 15 years was 72.8%. The cumulative incidence of late (>3 years beyond transplant) non-relapse mortality at 15 years was 12.9% and of late relapse was 16.5%. None of the variables considered (including age, disease stage, and graft-versus-host disease) were predictive of late failure.