Peripheral blood cells chimerism after unrelated cord blood transplantation in children: kinetics, predictive factors and impact on post-transplant outcome

Clinical Outcomes after One-day or Two-day Intervals in Conditioning Regimens for allo-HCT

One-day or two-day intervals are generally inserted into scheduled conditioning regimens for allogeneic hematopoietic cell transplantation, primarily due to various social circumstances, such as unexpected natural adversities, abrupt deterioration of patient health, and delays in graft source arrival. We compared the clinical outcomes of patients with interrupted conditioning with those with ordinarily scheduled conditioning. We analyzed 83 patients (children and adolescents) with oncologic disease who underwent myeloablative conditioning with total body irradiation. Overall and event-free survival were similar between the groups ( P =0.955, P =0.908, respectively). Non-relapse mortality and relapse rates were similar between the groups ( P =0.923, P =0.946, respectively). The engraftment rate was not affected by interruption ( P =1.000). In contrast, the incidence of chronic graft-versus-host disease (GVHD) was higher in the interrupted group compared with the scheduled group, although there was no statistical significance (42% vs. 19%, P =0.063). Conditioning interruption was identified to be an independent risk factor for chronic GVHD by multivariate analysis (odds ratio: 3.72; 95% CI: 1.04 to 13.3; P =0.043). In conclusion, apart from the incidence of chronic GVHD, clinical outcomes were not affected by one-day or two-day intervals during conditioning.

Primary graft failure, but not relapse, may be identified by early chimerism following double cord unit transplantation

Primary graft failure may be identified by early chimerism analysis after DUCBT with RIC.

Chimerism does not appear to be useful in predicting relapse.

Umbilical cord blood transplantation (UCBT) has increased access to potentially curative therapy for patients with life-threatening disorders of the bone marrow and immune system. The introduction of reduced intensity conditioning (RIC) regimens and double umbilical cord unit infusions (DUCBT) has broadened the applicability of UCBT to more frail or larger recipients. The kinetics of chimerism after RIC DUCBT and their clinical utility are poorly understood. The RIC CBT trial reported here sought to prospectively evaluate the role of lineage-specific chimerism after DUCBT in adult patients with hematologic malignancies in the United Kingdom. Fifty-eight patients with a median age of 52 years were recruited, with overall and progression-free survivals of 59% (95% confidence interval [CI], 45%-71%) and 52% (95% CI, 39%-64%), respectively, at 2 years. Nonrelapse mortality was 4% (95% CI, 1%-13%) at day 100, and the relapse rate was 31% (95% CI, 21%-45%) at 1 year. Peripheral blood lineage-specific chimerism was feasible from day 7 after transplant onward. Five patterns of chimerism were observed including (1) complete single unit dominance (39 patients), (2) sustained donor-donor mixed chimerism (3 patients), (3) sustained donor-recipient mixed chimerism (5 patients), (4) dominance reversion (1 patient), and (5) primary graft failure (4 patients). The RIC CBT trial enabled adult patients with high-risk hematologic malignancies to safely access UCBT in the United Kingdom and provided novel insights into the kinetics of donor and recipient chimerism after RIC DUCBT that are clinically relevant. This trial was registered at https://www.clinicaltrialsregister.eu/ctr-search/trial/2004-003845-41/GB as #NCT00959231 and EudraCT 2004-003845-41.

Donor-Host Lineage-Specific Chimerism Monitoring and Analysis in Pediatric Patients Following Allogeneic Stem Cell Transplantation: Influence of Pretransplantation Variables and Correlation with Post-Transplantation Outcomes

The impact of donor-host chimerism in post-hematopoietic stem cell transplantation (HSCT) outcomes is poorly understood. We were interested in studying whether pre-HSCT variables influenced lineage-specific donor-host chimerism and how lineage-specific chimerism impacts post-HSCT outcomes. Our main objective was to study pre-HSCT variables as predictors of lineage-specific donor-host chimerism patterns and to better characterize the relationship between post-HSCT lineage-specific chimerism and adverse outcomes, including graft failure and disease relapse. We conducted a retrospective data analysis of all patients who underwent allogeneic HSCT at the Pediatric Transplantation and Cellular Therapy service at Memorial Sloan Kettering Cancer Center between January 2010 and June 2015 and had at least 2 measurements of split-lineage chimerism. The trend of lineage-specific donor-host chimerism post-HSCT and the impact of age, disease, graft type, and pretransplantation conditioning regimen on chimerism at 3 months and 12 months post-HSCT were studied. The Wilcoxon signed-rank test, Mann-Whitney-Wilcoxon test, and Cox proportional hazard models were used for statistical analyses. A total of 137 patients were included (median age, 11.3 years). Most patients had a hematologic malignancy (n = 95), and fewer had a nonmalignant disorder (n = 27) or primary immune deficiency (n = 15). Myeloablative conditioning regimens (n = 126) followed by T cell-depleted (TCD) peripheral blood stem cell or bone marrow grafts (n = 101) were most commonly used. Mixed chimerism (MC) of total peripheral blood leukocytes (PBLs) did not predict loss of donor chimerism in all lineages and when stable was not associated with graft failure or rejection in this analyses. Split chimerism with complete donor chimerism (CC) of myeloid, B, and natural killer cells, but not T cells, occurred early post-HSCT, but full donor T cell chimerism was achieved at 12 months post-HSCT by most patients. MC within the T cell lineage was the major contributor to PBL MC, with lower median donor T cell chimerism at 3 months than at 12 months (91%) post-HSCT (51% versus 91%; P < .0001). Predictors of MC at 3 and 12 months were (1) age <3 years (P = .01 for PBLs and P = .003 for myeloid lineage); (2) nonmalignant disorder (P = .007 for PBLs); and (3) the use of reduced-intensity conditioning regimens. TCD grafts produced lower donor T cell chimerism at 3 months post-HSCT compared with unmodified grafts (P < .0001), where T cell lineage CC was achieved early post-HSCT. The donor T cell chimerism was similar at 12 months in the 2 types of grafts. Umbilical cord blood grafts had CC in all lineages at all time points post-HSCT. Loss of donor B cell chimerism was associated with increased risk of relapse in hematologic malignancies (hazard ratio, 1.33; P = .05). Age, underlying disease, conditioning regimen, and graft manipulation can impact post-HSCT donor-host chimerism and be predictors for early MC. MC in total PBLs and T cells was not related to graft failure or disease relapse. Whole-blood PBL chimerism analysis is not sufficient to assess the significance of post-HSCT donor-host status; rather, lineage-specific chimerism, particularly for myeloid, T, and B cells, should be analyzed to guide interventions and inform outcomes.

Early phase mixed chimerism in bone marrow does not affect long-term outcomes of myeloablative single-unit cord blood transplantation for adult patients with hematological malignancies

Coexisting hematopoiesis from donor and recipient origin, called a mixed chimerism status, can occur in patients after myeloablative allogeneic hematopoietic stem cell transplantation. However, its impact on the outcomes of cord blood transplantation (CBT) has yet to be clarified. We retrospectively analyzed 150 adult patients who received myeloablative single-unit CBT for hematological malignancies in our institute. At the median time of first bone marrow analysis of 41 days after CBT, mixed chimerism was observed in 16 of the 150 patients. Among patients with mixed chimerism, 4 patients relapsed. The remaining 12 patients were alive and in remission at a median follow-up of 50 months. Bone marrow-mixed chimerism did not have a significant impact on the incidences of disease-free survival, relapse, or transplant-related mortality after CBT. These data show that early phase mixed chimerism did not have a significant impact on long-term outcomes after myeloablative single-unit CBT for hematological malignancies.

Peripheral blood late mixed chimerism in leucocyte subpopulations following allogeneic stem cell transplantation for childhood malignancies: does it matter?

The impact of persistent mixed chimerism (MC) after haematopoietic stem cell transplantation (HSCT) remains unclarified. We investigated the incidence of MC in peripheral blood beyond day +50 after HSCT and its impact on rejection, chronic graft-versus-host disease (c-GvHD) and relapse in 161 children receiving allogeneic HSCT for haematological malignancies. The 1-year incidence of late MC was 26%. Spontaneous conversion to complete donor chimerism (CC) occurred in 43% of patients as compared to 62% after donor lymphocyte infusions. No graft rejection occurred. The 1-year incidence of c-GvHD was 20 ± 7% for MC, and 18 ± 4% for CC patients (P = 0·734). The 3-year cumulative incidence of relapse (CIR) according to chimerism status at days +50 and +100 was 22 ± 4% for CC patients vs. 22 ± 8% for MC patients (day +50; P = 0·935) and 21 ± 4% vs. 20 ± 7% (day +100; P = 0·907). Three-year CIRs in patients with persistent MC and patients with CC/limited MC were comparable (8 ± 7% vs. 19 ± 4%; P = 0·960). HSCT for acute leukaemia or myelodysplastic syndrome as secondary malignancies (hazard ratio (HR) 4·7; P = 0·008), for AML (HR 3·0; P = 0·02) and from mismatched donors (HR 3·1; P = 0·03) were independent factors associated with relapse. Our data suggest that late MC neither protects from c-GvHD nor does it reliably predict impending disease relapse.

Chimerism analysis in clinical practice and its relevance for the detection of graft rejection and malignant relapse in pediatric hematopoietic stem cell transplant patients

Chimerism and clinical outcome data from 244 hematopoietic stem cell transplants in 218 children were retrospectively analyzed to assess their relevance for the detection of graft rejection and malignant relapse. Patients transplanted for a non-malignant disease had significantly higher proportions of residual recipient T cells in peripheral blood at one, three, and six months compared with patients transplanted for malignant disease. Recipient T-cell levels were below 50% at one month after transplantation in most patients (129 of 152 transplants). Graft rejection occurred more frequently in the group of patients with high levels of recipient cells at one month (10 graft rejections in the 23 patients with recipient T cells >50% at one month as compared to seven graft rejections occurred in 129 patients with recipient T cells <50% (p < 0.001). Multilineage chimerism data in 87 children with leukemia at one, three, and six months after transplantation were not correlated with subsequent relapse of malignant disease. In conclusion, early analysis of lineage-specific chimerism in peripheral blood can be used to identify patients who are at high risk of graft rejection. However, the efficacy of early chimerism analysis for predicting leukemia relapse was limited.

National Institutes of Health Consensus Development Project on Criteria for Clinical Trials in Chronic Graft-versus-Host Disease: III. The 2014 Biomarker Working Group Report

Biology-based markers to confirm or aid in the diagnosis or prognosis of chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation or monitor its progression are critically needed to facilitate evaluation of new therapies. Biomarkers have been defined as any characteristic that is objectively measured and evaluated as an indicator of a normal biological or pathogenic process, or of a pharmacologic response to a therapeutic intervention. Applications of biomarkers in chronic GVHD clinical trials or patient management include the following: (1) diagnosis and assessment of chronic GVHD disease activity, including distinguishing irreversible damage from continued disease activity; (2) prognostic risk to develop chronic GVHD; and (3) prediction of response to therapy. Sample collection for chronic GVHD biomarkers studies should be well documented following established quality control guidelines for sample acquisition, processing, preservation, and testing, at intervals that are both calendar and event driven. The consistent therapeutic treatment of subjects and standardized documentation needed to support biomarker studies are most likely to be provided in prospective clinical trials. To date, no chronic GVHD biomarkers have been qualified for use in clinical applications. Since our previous chronic GVHD Biomarkers Working Group report in 2005, an increasing number of chronic GVHD candidate biomarkers are available for further investigation. This paper provides a 4-part framework for biomarker investigations: identification, verification, qualification, and application with terminology based on Food and Drug Administration and European Medicines Agency guidelines.

Complete donor T cell chimerism predicts lower relapse incidence after standard double umbilical cord blood reduced-intensity conditioning regimen allogeneic transplantation in adults

Double umbilical cord blood (dUCB) allogeneic transplantation after a low-dose total body irradiation, cyclophosphamide, and fludarabine (TCF)-based reduced-intensity conditioning regimen (RIC) is increasingly used in adults lacking a suitable related or unrelated donor. Currently, there are little data regarding the long-term outcome of CD3(+) T cell chimerism (TCC) in this particular setting. Thirty-six adults with various hematological diseases who received dUCB allogeneic transplants conditioned with TCF were included in this retrospective study. Peripheral blood CD3(+) TCC was considered until day +100 after transplantation to determine the impact of full versus mixed chimerism on long-term outcomes. Twenty-nine and 7 patients were documented with full and mixed CD3(+) TCC, respectively, within the first 100 days after transplantation. With a median follow-up of 36 months, 3 year-overall survival (OS), disease-free survival (DFS), and cumulative incidence of relapse (CIR) were 61%, (95% confidence interval [CI], 43% to 75%); 50% (95% CI, 32.5% to 66%), and 28% (95% CI, 16% to 44%), respectively. In univariate analysis, a full CD3(+) TCC was associated with a better 3-year DFS: 59% (95% CI, 39% to 75.5%) versus 14% (95% CI, 7% to 46%); hazard ratio (HR), .24 (.09 to .65); P = .005 and a lower CIR: 24% (95% CI, 21.5% to 57%) versus 78% (95% CI, 52% to 99%); HR, .18 (.05 to .50); P = .004. In multivariate analysis, a full CD3(+) TCC remained associated with a lower CIR (HR, .17 [.028 to .99]; P = .049). CD3(+) TCC has no impact on graft-versus-host disease and nonrelapse mortality in this study. In conclusion, here, full CD3(+) TCC was independently associated with a lower risk of relapse in adults receiving a dUCB TCF RIC allogeneic transplantation. This highlights the need to develop immunotherapy approaches allowing for early conversion to full chimerism after this type of transplantation.