High doses of transplanted CD34+ cells are associated with rapid T-cell engraftment and lessened risk of graft rejection, but not more graft-versus-host disease after nonmyeloablative conditioning and unrelated hematopoietic cell transplantation

The effect of increased collect pump rate on collection efficiency in hematopoietic progenitor cell collection by apheresis in allogeneic adult donors-A single center analysis

BACKGROUND

Optimizing CD34 recovery while minimizing harm to hematopoietic progenitor cell donors by apheresis (HPC(A) donors) is critical to the success of allogeneic hematopoietic cell transplantation. We examined the efficacy and safety of starting allogeneic HPC(A) donors at a collect pump rate (CPR) of 2 mL/min on the Spectra Optia regardless of the inlet flow rate and/or pre-apheresis white blood cell (WBC) count (high CPR group).

STUDY DESIGN AND METHODS

A single-center retrospective study was performed on allogeneic adult donors from 10/2020 to 12/2022. From 10/2020 to 6/19/2022, all donors had CPR of ~1 mL/min (historical group). High CPR group started 6/20/2022.

RESULTS

During the study period, 412 donors were in historical group versus 196 (32.2%) in high CPR group. Median CD34 collection efficiency (CE) was higher and more consistent in high CPR group (55.1% vs. 53% in historical group, p < .0001) and remained significant in multivariate analysis. Although product volume was higher in high CPR group, WBC, hematocrit, and platelet concentrations were significantly lower. No difference in engraftment outcomes in patients receiving products from two groups was observed. Moreover, no differences occurred in a significant peri-procedural adverse event or percent decrease in platelets (6.87% decrease in platelets per 100 × 106 CD34 cells collected versus 6.66% in historical group, p = .89). Furthermore, high CPR group had ~26 min less in collection time for every 100 × 106 CD34 cells collected, resulting in less positive fluid balances.

CONCLUSIONS

Starting allogeneic HPC(A) donor collection at a CPR of 2 mL/min is safe and effective.

Association between CD34+ and CD3+ T-cells in allogeneic grafts and acute graft-versus-host disease in children undergoing allogeneic hematopoietic stem cell transplantation: A single-center study

BACKGROUND

Acute graft-versus-host disease (aGVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). We examined the association between the composition of the cell subsets present in allogeneic grafts (allografts) and the occurrence and severity of aGVHD in pediatric patients.

METHODS

We retrospectively analyzed 80 consecutive pediatric patients undergoing allo-HSCT at our center.

RESULTS

Both univariate and multivariate analyses showed that the number of CD34⁺ and CD3⁺ T-cells in allografts were the two highest risk factors associated with II-IV aGVHD. Using receiver operating characteristic analysis, the cutoff levels of the allo-HSCT cell doses were used to divide the recipients into low-dose and high-dose groups. The 100-day cumulative incidence of II-IV aGVHD in the high-dose CD34⁺ and CD3⁺ T-cells group was significantly higher than that of the low-dose group (CD34⁺: 57% vs. 29%, p = 0.009; CD3⁺: 63% vs. 18%, p < 0.001). No other clinical factors or cell subsets correlated with aGVHD incidence.

CONCLUSIONS

Our analysis indicates that the CD34⁺ and CD3⁺ T-cell numbers in the allografts could be the risk factors for the development of severe aGVHD (level II-IV). Further studies should aim to optimize the critical number of CD34⁺ and CD3⁺ T-cells to reduce the risk of severe aGVHD occurrence in pediatric patients.

Endocrine sequelae of hematopoietic stem cell transplantation: Effects on mineral homeostasis and bone metabolism

Hematopoietic stem cell transplantation (HSCT) is an established therapeutic strategy for the treatment of malignant (leukemia and lymphoma) and non-malignant (thalassemia, anemia, and immunodeficiency) hematopoietic diseases. Thanks to the improvement in patient care and the development of more tolerable conditioning treatments, which has extended the applicability of therapy to the elderly, a growing number of patients have successfully benefited from HSCT therapy and, more importantly, HSCT transplant-related mortality has consistently reduced in recent years. However, concomitantly to long term patient survival, a growing incidence of late HSCT-related sequelae has been reported, being variably associated with negative effects on quality of life of patients and having a non-negligible impact on healthcare systems. The most predominantly observed HSCT-caused complications are chronic alterations of the endocrine system and metabolism, which endanger post-operative quality of life and increase morbidity and mortality of transplanted patients. Here, we specifically review the current knowledge on HSCT-derived side-effects on the perturbation of mineral metabolism; in particular, the homeostasis of calcium, focusing on current reports regarding osteoporosis and recurrent renal dysfunctions that have been observed in a percentage of HSC-transplanted patients. Possible secondary implications of conditioning treatments for HSCT on the physiology of the parathyroid glands and calcium homeostasis, alone or in association with HSCT-caused renal and bone defects, are critically discussed as well.

Can GCSF-stimulated donor lymphocyte infusions improve outcomes for relapsed disease following allogeneic hematopoietic cell transplantation? A systematic review and meta-analysis

Donor lymphocyte infusions (DLI) can produce graft-versus tumor effects to treat relapse after allogeneic hematopoietic cell transplantation, however, durable responses remain uncommon. A systematic review and meta-analysis are needed to clarify whether DLI collected after stimulation with granulocyte colony-stimulating factor (GCSF; G-DLI) can improve clinical outcomes. Sixteen studies (4 controlled) involving 585 patients were identified in a systematic search up to 17 September 2020. A meta-analysis demonstrated no significant difference in the risk of all-cause mortality (RR: 0.94, 95% CI 0.52-1.68, p = 0.82; n = 3 studies) or relapse-related mortality (RR: 0.72, 0.44-1.18, p = 0.19; n = 3 studies) between G-DLI and conventional DLI (C-DLI) groups. G-DLI products had similar mean CD3+ cells compared to C-DLI products, but median CD34+ cells/kg were increased. No improvement in disease progression, complete response rates, or risk of developing GVHD was observed with G-DLI, however, greater non-relapse mortality was observed compared to C-DLI. Alternative approaches to enhancing graft-versus-tumor effects are needed.

Establishment of Chimerism and Organ Transplant Tolerance in Laboratory Animals: Safety and Efficacy of Adaptation to Humans

The definition of immune tolerance to allogeneic tissue and organ transplants in laboratory animals and humans continues to be the acceptance of the donor graft, rejection of third-party grafts, and specific unresponsiveness of recipient immune cells to the donor alloantigens in the absence of immunosuppressive treatments. Actively acquired tolerance was achieved in mice more than 60 years ago by the establishment of mixed chimerism in neonatal mice. Once established, mixed chimerism was self-perpetuating and allowed for acceptance of tissue transplants in adults. Successful establishment of tolerance in humans has now been reported in several clinical trials based on the development of chimerism after combined transplantation of hematopoietic cells and an organ from the same donor. This review examines the mechanisms of organ graft acceptance after establishment of mixed chimerism (allo-tolerance) or complete chimerism (self-tolerance), and compares the development of graft versus host disease (GVHD) and graft versus tumor (GVT) activity in complete and mixed chimerism. GVHD, GVT activity, and complete chimerism are also discussed in the context of bone marrow transplantation to treat hematologic malignancies. The roles of transient versus persistent mixed chimerism in the induction and maintenance of tolerance and organ graft acceptance in animal models and clinical studies are compared. Key differences in the stability of mixed chimeras and tolerance induction in MHC matched and mismatched rodents, large laboratory animals, and humans are examined to provide insights into the safety and efficacy of translation of results of animal models to clinical trials.

Total nucleated cell dose in graft is a better prognostic factor for survival in pediatric patients transplanted with bone marrow compared to CD34+, CD3+, or total mononuclear cell count

BACKGROUND

Most studies investigating the impact of graft composition on transplant-related outcomes have focused on the effect of CD34+ cell dose and reported equivocal results. The aim of this study is to investigate the impact of doses of total nucleated cells (TNCs), total mononuclear cells (TMCs), CD3+, and CD34+ cells on the outcome of children receiving allogeneic hematopoietic stem cell transplantation (HSCT).

METHODS

Children and adolescents who underwent allogeneic HSCT for malignant hemato-oncological diseases or nonmalignant diseases in Cukurova University Faculty of Medicine, Pediatric Bone Marrow Transplantation Center between 2010 and 2020 were enrolled in the study.

RESULTS

A total of 212 patients receiving allogeneic HSCT (154 bone marrow transplantation; 58 peripheral blood stem cell transplantation) from matched related or unrelated donors were included in the study. Higher TNC doses associated with a superior 5-year event-free survival (EFS; 67.7% vs 44.7%) in the whole group (log-rank P = .027). Overall survival (OS) and EFS of bone marrow-transplanted patients differed significantly according to TNC doses (log-rank P = .041 and .027, respectively). Multivariant analysis for OS revealed a P value of .038 for TNC, Exp(B) = 1.939 (95% CI: [1.038, 3.621]). That for EFS revealed a P value of .025 for TNC, Exp(B) = 1.992 (95% CI: [1.088, 3.647]). There was no relationship between doses of CD34+ cells, CD3+ cells, TMC, TNC, and neutrophil or platelet engraftment.

CONCLUSION

Our data suggest that TNC dose is a better prognostic factor for pediatric allogeneic HSCT outcomes than doses of CD34+ cells, CD3+ cells, or TMC in patients transplanted with bone marrow. Future studies analyzing cell subsets and other components in TNC could elaborate the factor(s) accompanying this observed survival advantage.

Variable impact of graft CD3+ cell content on graft versus host disease in hematopoietic stem cell transplant recipients: Is the role of donor CD3+ cells overestimated?

Graft cellular composition is considered as a significant determinant of transplant outcome. Donor CD3⁺ cells were shown to have a significant association with the development of graft vs host disease (GvHD). The aim of this study was to investigate the impact of graft CD3⁺ cell content on transplant outcome, particularly in terms of GvHD and relapse. We retrospectively analysed the records of 515 allo-HCT recipients [median age: 37(15-71) years; male/female: 323/192]. The optimal threshold of infused CD3⁺ cell count for acute GvHD development was estimated to be 197.5 × 10⁶/kg (AUC: 0.572; 95 % CI: 0.513-0.631; p = 0.018) and 198.5 × 10⁶/kg (AUC: 0.6; 95 % CI: 0.520-0.679; p = 0.019) for the general population and reduced-intensity conditioning (RIC) subgroup, respectively. Acute GvHD was more frequent in low-CD3⁺ group in the whole study population, particularly in RIC transplants. The incidence of cytomegalovirus reactivation was higher in low-CD3⁺ group and neutrophil engraftment occured earlier in the same group of patients. Overall survival and non-relapse mortality were comparable between high and low-CD3⁺ groups. Age, ECOG performance status, hypogammaglobulinemia, chronic GvHD and post-transplant relapse were found to predict prognosis in multivariate analysis. By focusing mainly on donor T cells, the potential role of host immune cells in the early post-transplant milieu may have been underestimated. Drawing a more detailed profile of graft and host immune cells in the joint microenvironment may elucidate our way to a better understanding of GvHD pathogenesis. By this way a comprehensive pre-transplant risk assessment could be improved to generate more personalized approaches.

High Failure-Free Survival after Unrelated Donor Peripheral Blood Stem Cell Transplantation in Pediatric Severe Aplastic Anemia

The use of alternative donor peripheral blood stem cell transplantation (PBSCT) has increased in recent years. In this study, we analyzed the effect of stem cell source and HLA disparity on outcomes in pediatric patients with severe aplastic anemia (SAA). A total of 134 patients who underwent HSCT with nonmyeloablative conditioning between 2006 and 2020 were enrolled and classified into 3 groups: HLA-matched bone marrow transplantation (M-BMT; n = 24), HLA-matched PBSCT (M-PBSCT; n = 66), and HLA-mismatched PBSCT (MM-PBSCT; n = 44). Significantly higher stem cell doses were obtained for PBSCT than for BMT. A total of 13 patients experienced secondary graft failure (GF), with a cumulative incidence (CI) of 10.0%. HLA-mismatched PBSCT and a very severe degree of disease significantly decreased the incidence of secondary GF. The CI of grade II-IV acute graft-versus-host disease (GVHD) was significantly higher in PBSCT than in BMT, but the CI of grade III-IV acute GVHD and CI of chronic GVHD requiring systemic treatment did not increase in PBSCT. The estimated 5-year overall survival (OS), failure-free survival (FFS), and GVHD-free failure-free survival (GFFS) of the total cohort were 93.0%, 89.5%, and 77.5%, respectively. The most favorable FFS was observed in the MM-PBSCT group (97.6%; P = .03), whereas OS and GFFS were similar across the 3 groups. In multivariate analysis, HLA mismatch and short time from diagnosis to transplantation were associated with superior FFS. Unrelated donor PBSCT with low-intensity SAA conditioning showed favorable outcomes in terms of low rate of secondary GF, higher FFS, and manageable GVHD regardless of HLA compatibility. Our findings suggest the feasibility of PBSCT from unrelated donors, resulting in the possible expansion of the donor pool in transplantation for pediatric SAA. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

The effect of granulocyte colony-stimulating factor dose and administration interval after allogeneic hematopoietic cell transplantation on early engraftment of neutrophil and platelet

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is one of the treatments for hematologic malignancies. Numerous factors affect the HSCT outcome. The purpose of this study was to investigate the effect of post-HSCT administration of granulocyte colony-stimulating factor (post-G-CSF) on early neutrophil and platelet engraftment in allogeneic HSCT (allo-HSCT).

MATERIAL & METHODS

The study was performed on 76 patients diagnosed with AML and ALL. All patients underwent allo-HSCT at Taleghani stem cell transplantation center, Tehran, Iran, from February 2016 to December 2018. Chemotherapy regimens based on patients' conditions were selected between myeloablative and reduced-intensity regimens.

RESULTS

Statistical analysis revealed that the number of administered G-CSF units after HSCT was a time-dependent variable. Statistical analysis before day +11 reported that patients who received G-CSF <14 units had three times better early neutrophil engraftment than those with G-CSF ≥14 (CI 95%, AHR = 3.03, p:0.002). CD3+ cells count <318.5 × 10⁶ /kg was associated with fast platelet engraftment (CI 95%, AHR 2.28, p:0.01).

CONCLUSION

In this study, post-G-CSF stimulation was associated with early engraftment in a time- and dose-dependent manner. Administration of G-CSF beyond 14 units resulted in adverse effects on neutrophil early engraftment. It also appeared that with a reduction in CD3+ cell counts, the likelihood of GVHD decreases, and platelet engraftment occurs earlier. Further investigations in the future are required to determine the factors affecting the process of early engraftment.

Fractionated Infusion of Hematopoietic Progenitor Cells Does Not Improve Neutrophil Recovery or Survival in Allograft Recipients

Allogeneic hematopoietic cell transplantation (HCT) offers a potentially curative therapy in patients with hematologic malignancies; however, nonrelapse mortality (NRM) remains a concern. Strategies to improve neutrophil recovery and immune reconstitution are needed to decrease NRM. Murine models of allogeneic HCT suggest that fractionated hematopoietic progenitor cell (HPC) infusion may improve engraftment through improved access of HPCs to a viable hematopoietic niche. The primary objective of the present study was to determine the impact of fractionated infusion versus unfractionated (bulk) infusion of HPCs on the time to achieve neutrophil engraftment. Secondary objectives included the effect of fractionated versus bulk infusion of HPCs on platelet engraftment, immune reconstitution, the incidence of acute graft-versus-host disease (GVHD) grade II-IV, NRM, and overall survival (OS). In this randomized phase 2 study, patients with hematologic malignancies undergoing allogeneic HCT were randomized to receive HPC infusion as a bulk (bulk arm) or in fractions (fractionated arm): 4 × 106 CD34+ cells/kg recipient weight infused on day 0, with the remaining HPCs CD34+ cell-selected then infused in equally distributed aliquots on days 2, 4, and 6 post-HCT. Randomization was stratified by type of transplant, unmodified (i.e. T cell-replete graft) versus CD34+ cell-selected (T cell-depleted graft). Patients whose donor failed to collect at least 7 × 106 CD34+ cells/kg of recipient weight received bulk HPC infusions regardless of randomization, for safety. These patients continued the HCT process on study but were replaced until each arm reached the prespecified accrual target. Per protocol, these patients were not included in this modified intention-to-treat analysis. A total of 116 patients were enrolled. Donors of 42 patients failed to mobilize the minimum CD34+ cell dose (7 × 106 cells/kg recipient weight) and were excluded from the analysis. The 74 evaluable patients included 38 randomized to the bulk arm and 36 randomized to the fractionated arm. All patients engrafted. The median time to an absolute neutrophil count of ≥0.5 × 109/L was 11 days on both arms. The day +180 median CD4+ cell count was 179 cells/µL in the bulk arm and 111 cells/µL in the fractionated arm (P = .779). The cumulative incidence of grade II-IV acute GVHD on post-transplant day +100 was 32% in the bulk arm and 17% in the fractionated arm (P = .131). Two patients in the bulk arm, but none in the fractionated arm, experienced grade III-IV GVHD. The 4-year OS was 60% in the bulk arm and 62% in the fractionated arm (P = .414), whereas the 4-year cumulative incidences of NRM and relapse were similar in the 2 arms. Fractionated infusion of HPCs in allogeneic HCT recipients did not impact neutrophil or CD4+ cell recovery, NRM, relapse, or OS when compared with bulk HPC infusion. We also observed that with current mobilization techniques, it was unlikely that more than 60% of healthy donors would be able to collect >7 × 106 CD34+ cells/kg recipient weight for adult recipients. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

The incidence, clinical outcome, and protective factors of mixed chimerism following hematopoietic stem cell transplantation for severe aplastic anemia

OBJECTIVES

The aim of our study was to determine possible predictors and clinical course of mixed chimerism (MC) in aplastic anemia after transplantation.

METHODS

A total of 207 transplants were obtained from haploidentical donors (HID) using busulfan (Bu), cyclophosphamide (Cy), and anti-thymocyte globulin (ATG) regimens, and 69 transplants from matched related donors (MRD) and 29 transplants from unrelated donors (URD) using Cy/ATG regimens were obtained.

RESULTS

Incidences of MC were 1.93 ± 0.01%, 20.29 ± 0.01%, and 35.71 ± 0.01% in HID, MRD, and URD transplantation (p < .001). In multivariate analysis, incidence of MC was significantly higher in patients without adding Bu in conditioning (p < .001) and receiving a lower number of CD3 + cells in graft (p = .042). MC was associated with significantly lower II-IV aGvHD (3.70% vs. 27.7%, p = .007), but higher secondary graft rejection rates (14.8% vs. 0.4%, p < .001) and poorer overall survival (72.7 ± 8.9% vs. 89.6 ± 2.0%, p = .011) than those of donor chimerism cohort.

CONCLUSIONS

Mixed chimerism was an unsettling status even in non-malignancy. Haploidentical transplantation with more intense regimen by adding Bu to Cy and ATG was associated with reduced MC following HSCT for SAA. An intensified regimen should be explored in matched related or unrelated donors.

CD34+ cell dose effects on clinical outcomes after T-cell replete haploidentical allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia using peripheral blood stem cells. A study from the acute leukemia working Party of the European Society for blood and marrow transplantation (EBMT)

Previous observations have reported controversial conclusions regarding cell dose and survival endpoints after allogeneic hematopoietic stem cell transplantation (HSCT). We conducted a retrospective analysis on 414 adult patients (median age 54 years, range, 18-74 years) with acute myeloid leukemia (AML) in first and second complete remission. They received a T-cell replete allogeneic HSCT from haploidentical donors, using peripheral blood stem cells, between 2006-2018. Median number of infused CD34+ was 6.58 × 10⁶ /kg (range, 2.2-31.2 × 10⁶ /kg). Graft-vs-host disease (GVHD) prophylaxis was post-transplant cyclophosphamide in 293 patients and anti-lymphocyte serum in 121 patients. Conditioning was myeloablative in 179 patients and reduced-intensity in 235 patients. After a median follow-up of 23.3 months (range, 12.1-41.8 months), 2-year overall survival (OS) was 64.5% (95% CI 59.3%-69.7%) with leukemia-free survival (LFS) of 57.3% (95% CI 51.8%-62.7%) and non-relapse mortality (NRM) of 23.3% (95% CI 19%-27.7%). Grades III-IV acute GVHD day+100 incidence was 14.6% while extensive chronic GVHD was 14.4% at 2-years. Thirteen (3.2%) patients experienced graft failure. We found the optimal CD34+/kg threshold defining high (n = 334) vs low cell dose (n = 80) at 4.96 × 10⁶ . Recipients of >4.96 × 10⁶ /kg CD34+ cells experienced less NRM (Hazard ratio [HR] 0.48; 95% CI 0.30-0.76) and prolonged LFS (HR 0.63; 95% CI 0.43-0.91) and OS (HR 0.60; 95% CI 0.40-0.88) compared to those in the lower cell dose cohort. Larger cohort studies are needed to confirm these findings.

Feasibility and cost analysis of day 4 granulocyte colony-stimulating factor mobilized peripheral blood progenitor cell collection from HLA-matched sibling donors

BACKGROUND

Guidelines recommend treatment with 4-5 days of granulocyte colony-stimulating factor (G-CSF) for optimal donor peripheral blood progenitor cell (PBPC) mobilization followed by day 5 collection. Given that some autologous transplant recipients achieve adequate collection by day 4 and the possibility that some allogeneic donors may maximally mobilize PBPC before day 5, a feasibility study was performed evaluating day 4 allogeneic PBPC collection.

METHODS

HLA-matched sibling donors underwent collection on day 4 of G-CSF for peripheral blood (PB) CD34⁺ counts ≥0.04 × 10⁶/mL, otherwise they underwent collection on day 5. Those with inadequate collected CD34⁺ cells/kg recipient weight underwent repeat collection over 2 days. Transplant and PBPC characteristics and cost analysis were compared with a historical cohort collected on day 5 per our prior institutional algorithm.

RESULTS

Of the 101 patient/donor pairs, 50 (49.5%) had adequate PBPC collection on day 4, with a median PB CD34⁺ cell count of 0.06 × 10⁶/mL. Day 4 donors were more likely to develop bone pain and require analgesics. Median collected CD34⁺ count was significantly greater, whereas total nucleated, mononuclear and CD3⁺ cell counts were significantly lower, at time of transplant infusion for day 4 versus other collection cohorts. There were no significant differences in engraftment or graft-versus-host disease. Cost analysis revealed 6.7% direct cost savings for day 4 versus historical day 5 collection.

DISCUSSION

Day 4 PB CD34⁺ threshold of ≥0.04 × 10⁶/mL identified donors with high likelihood of adequate PBPC collection. Day 4 may be the optimal day of collection for healthy donors, without adverse effect on recipient transplant outcomes and with expected cost savings.

The importance of graft cell composition in outcome after allogeneic stem cell transplantation in patients with malignant disease

BACKGROUND

Graft-versus-host disease (GVHD) and relapse remain majobstacles ftreatment success in allogeneic hematopoietic stem cell transplantation (HSCT). In the present study, we evaluated the immune cell profile of the graft to outcome after HSCT.

STUDY DESIGN AND METHOD

Flow cytometry data of graft cell subsets [CD34⁺ , CD3⁺ , CD19⁺ , CD4⁺ , CD8⁺ , CD3-CD56⁺ CD16⁺ , CD4⁺ CD127^low CD25^high ] from G-CSF primed peripheral blood stem cell (PBSC) donors was collected retrospectively from 299 patients with hematological malignancies undergoing HSCT between 2006 and 2013. The association to overall survival, transplant-related mortality (TRM), GVHD and probability of relapse was analyzed. Patients outcome from HLA-identical sibling (Sib) (n = 97) and unrelated donors (URD) (n = 202) were analyzed separately as all URD patients received anti-thymocyte globulin (ATG).

RESULTS

Five-year overall survival was similar in the two cohorts (68% (Sib) vs 65% (URD)). The relapse incidence was significantly lower in the Sib cohort (24% vs 35%, P = 0.04). Multivariate analysis in the URD group revealed an association between a higher CD8⁺ dose and less relapse (HR, 0.94; 95%CI, 0.90-0.98; P = 0.006) as well as an association between higher CD34⁺ dose and both higher TRM (HR, 1.09; 95%CI, 1.02-1.20; P = 0.02) and relapse (HR, 1.09; 95%CI, 1.01-1.17; P = 0.025). The Sib analysis showed an association between a higher graft CD19⁺ dose and more severe acute GVHD (HR, 1,09; 95%CI, 1.03-1.15; P = 0.003) and TRM (HR, 1.09; 95%CI, 1.01-1.17; P = 0.036). In addition, a higher CD4⁺ graft content was associated to an increased risk for chronic GVHD (HR, 1.02; 95%CI 1.00-1.04; P = 0.06).

CONCLUSION

These data indicate an importance of PBSC dongraft composition in patients with a hematological malignancy.

Impact of Day 14 Peripheral Blood Chimerism after Allogeneic Hematopoietic Stem Cell Bone Transplantation on the Treatment Outcome of Non-Malignant Disease

BACKGROUND

The impact of early peripheral blood chimerism on the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) is unclear. We aimed to determine whether day 14 peripheral blood chimerism after allo-HSCT predicts outcomes in patients with non-malignant diseases.

METHODS

Data from 56 patients who received allo-HSCT between April 2007 and March 2016 were retrospectively analyzed. Chimerism was evaluated using short-tandem repeat polymerase chain reaction, with mixed chimerism (MC) defined as greater than 1% recipient cells which was further categorized into low-level MC (> 1% and < 15% of recipient-derived cells) and high-level MC (≥ 15% of the recipient-derived cells).

RESULTS

Thirty-six patients showed complete donor chimerism (CC), 14 low-level MC, and 6 high-level MC at day 14 post-transplant. The estimated 5-year event-free survival (EFS) was higher in the CC or low-level MC groups than in the high-level MC group (86.1% vs. 71.4% vs. 33.3%; P = 0.001). In BM or peripheral blood stem cell (BM/PBSC) transplants, the 5-year EFS was higher in the CC or low-level MC group than in the high-level MC group (93.1% vs. 66.7% vs. 0%; P < 0.001). However, in cord blood transplants, the 5-year OS and EFS according to the day 14 peripheral blood chimerism did not reach statistical significance.

CONCLUSION

Although CC is not always necessary after allo-HSCT for non-malignant diseases, our data suggest that day 14 peripheral blood chimerism may predict outcomes in patients with non-malignant diseases who underwent BM/PBSC transplants.

Higher Donor Apheresis Blood Volumes Are Associated with Reduced Relapse Risk and Improved Survival in Reduced-Intensity Allogeneic Transplantations with Unrelated Donors

Allogeneic hematopoietic stem cell transplantation (HSCT) with reduced-intensity conditioning (RIC) offers a curative option for patients with hematologic malignancies who are unable to undergo myeloablative conditioning, but its success is limited by high rates of relapse. Several studies have suggested a role for T cell doses in peripheral blood stem cell grafts in RIC HSCT. Because T cell dose is typically not known until after the collection, and apheresis blood volume is easily modifiable, we hypothesized that higher donor apheresis blood volumes would improve transplantation outcomes through an effect on graft composition. Thus, we analyzed the relationships between apheresis volume, graft composition, and transplantation outcomes in 142 consecutive patients undergoing unrelated donor allogeneic RIC HSCT. We found that apheresis volume ≥15 L was associated with a significantly decreased risk of relapse (adjusted hazard ratio [aHR], .48; 95% confidence interval [CI], .28 to .84]; P = .01) and improved relapse-free survival (aHR, .56; 95% CI, .35 to .89; P = .02) and overall survival (aHR, .55; 95% CI, .34 to .91; P = .02). A high apheresis volume was not associated with increased rates of acute or chronic graft-versus-host disease. These results demonstrate that an apheresis volume of at least 15 L is independently predictive of improved transplantation outcomes after RIC allogeneic HSCT.

High CD3+ and CD34+ peripheral blood stem cell grafts content is associated with increased risk of graft-versus-host disease without beneficial effect on disease control after reduced-intensity conditioning allogeneic transplantation from matched unrelated donors for acute myeloid leukemia - an analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Inconsistent results have been reported regarding the influence of graft composition on the incidence of graft versus host disease (GVHD), disease control and survival after reduced-intensity conditioning (RIC) allogeneic peripheral blood stem cell transplantation (allo-PBSCT). These discrepancies may be at least in part explained by the differences in disease categories, disease status at transplant, donor type and conditioning. The current retrospective EBMT registry study aimed to analyze the impact of CD3+ and CD34+ cells dose on the outcome of RIC allo-PBSCT in patients with acute myelogenous leukemia (AML) in first complete remission, allografted from HLA-matched unrelated donors (10 of 10 match). We included 203 adults. In univariate analysis, patients transplanted with the highest CD3+ and CD34+ doses (above the third quartile cut-off point values, >347 x 10^6/kg and >8.25 x 10^6 /kg, respectively) had an increased incidence of grade III-IV acute (a) GVHD (20% vs. 6%, P = .003 and 18% vs. 7%, P = .02, respectively). There was no association between cellular composition of grafts and transplant-related mortality, AML relapse, incidence of chronic GVHD and survival. Neither engraftment itself nor the kinetics of engraftment were affected by the cell dose. In multivariate analysis, CD3+ and CD34+ doses were the only adverse predicting factors for grade III-IV aGVHD (HR = 3.6; 95%CI: 1.45-9.96, P = .006 and 2.65 (1.07-6.57), P = .04, respectively). These results suggest that careful assessing the CD3+ and CD34+ graft content and tailoring the cell dose infused may help in reducing severe acute GVHD risk without negative impact on the other transplantation outcomes.

Identification of cell morphology parameters from automatic hematology analyzers to predict the peripheral blood CD34-positive cell count after mobilization

Optimal timing of apheresis initiation is important for maximizing the hematopoietic stem cell (HSC) yield. This study aimed to identify useful parameters from automatic hematology analyzers for predicting the peripheral blood CD34+ cell count after mobilization. We prospectively enrolled 53 healthy donors and 72 patients, and evaluated 43 cell morphology parameters from Unicel DxH800 (Beckman Coulter, USA) and Advia 2120i (Siemens Healthcare Diagnostics, USA). The correlation of each parameter with the CD34+ cell count in pre-apheresis blood samples was analyzed. The delta neutrophil index (DNI) from Advia 2120i, standard deviation of volume of neutrophils and monocytes (SD-V-NE and SD-V-MO), standard deviation of conductivity of neutrophils and monocytes (SD-C-NE and SD-C-MO), mean conductivity of neutrophils and monocytes (MN-C-NE and MN-C-MO), and standard deviation of axial light loss of neutrophils and monocytes (SD-AL2-NE and SD-AL2-MO) from DxH800 showed significant correlations with the CD34+ cell count. SD-V-NE, SD-C-NE, and SD-C-MO showed good or fair area under the curve values for the prediction of the CD34+ cell count. SD-V-NE, SD-C-NE, and SD-C-MO from DxH800 will provide rapid, useful information for the initiation of apheresis after mobilization.

Factors affecting the CD34+ cell yields from the second donations of healthy donors: The steady-state lymphocyte count is a good predictive factor

BACKGROUND

A second allogeneic hematopoietic stem-cell transplantation and donor lymphocyte infusion using cells from the same donor is a therapeutic option in the case of stem-cell graft failure or disease relapse, but little is known about the factors associated with the CD34⁺ cell yields from second donations.

METHODS

One-hundred healthy donors who underwent a second mobilization treatment and peripheral blood stem-cell (PBSC) collection were studied. For both mobilization processes, 5 µg of granulocyte colony-stimulating factor per kg per day was administered. The blood counts of the donors were monitored during the processes.

RESULTS

The second donations from the same donors provided lower apheresis yields than did the initial collections. The number of CD34⁺ cells collected from normal donors after a second cycle of PBSC mobilization was associated with their steady-state lymphocyte counts and the intertransplantation interval. Female sex negatively affected the CD34⁺ cell yields. The cutoff value for the steady-state absolute lymphocyte count was 2.055 × 10⁹/L.

CONCLUSION

To harvest greater numbers of CD34⁺ cells from second collections, male donors and those with intervals of longer than 9 months between donations should be selected. The lymphocyte counts prior to the first donations may predict the content of CD34⁺ cells in the allografts prepared using the second donations.

Infused total nucleated cell dose is a better predictor of transplant outcomes than CD34+ cell number in reduced-intensity mobilized peripheral blood allogeneic hematopoietic cell transplantation

Mobilized peripheral blood is the most common graft source for allogeneic hematopoietic stem cell transplantation following reduced-intensity conditioning. In assessing the effect of donor cell dose and graft composition on major transplant outcomes in the reduced-intensity setting, prior studies focused primarily on CD34(+)cell dose and reported conflicting results, especially in relation to survival end-points. While the impact of total nucleated cell dose has been less frequently evaluated, available studies suggest higher total nucleated cell dose is associated with improved survival outcomes in the reduced-intensity setting. In order to further explore the relationship between CD34(+)cell dose and total nucleated cell dose on reduced-intensity transplant outcomes, we analyzed the effect of donor graft dose and composition on outcomes of 705 patients with hematologic malignancies who underwent reduced-intensity peripheral blood stem cell transplantation at the Dana Farber Cancer Institute from 2000 to 2010. By multivariable analysis we found that higher total nucleated cell dose (top quartile; ≥10.8 × 10(10)cells) was associated with improved overall survival [HR 0.69 (0.54-0.88),P=0.0028] and progression-free survival [HR 0.68 (0.54-0.85),P=0.0006]. Higher total nucleated cell dose was independently associated with decreased relapse [HR 0.66 (0.51-0.85),P=0.0012] and increased incidence of chronic graft-versus-host disease [HR 1.4 (1.12-1.77),P=0.0032]. In contrast, higher doses of CD34(+)cells (top quartile; ≥10.9 × 10(6)/kg) had no significant effect on graft-versus-host disease or survival outcomes. These data suggest total nucleated cell dose is a more relevant prognostic variable for reduced-intensity transplant outcomes than the more commonly studied CD34(+)cell dose.

HLA haploidentical peripheral blood stem cell transplantation using reduced dose of posttransplantation cyclophosphamide for poor-prognosis or refractory leukemia and myelodysplastic syndrome

Nonmyeloablative, human leukocyte antigen (HLA) haploidentical, T-cell-replete bone marrow transplantation followed by high-dose posttransplantation cyclophosphamide (PT/Cy) has recently been developed. This transplantation milieu has resulted in favorable outcomes with low transplantation-related mortality, owing to a low incidence of graft-versus-host disease (GVHD), without increased infectious complications. However, the high relapse rate remains a major concern. We therefore performed a prospective pilot study of HLA haploidentical peripheral blood stem cell transplantation (PBSCT) with intensified conditioning, followed by two lower doses of PT/Cy. A total of 20 patients with refractory or poor-prognosis myelodysplastic syndrome (MDS) and leukemia were enrolled in the study. A trend toward a lower incidence of grade III-IV acute GVHD at day 100 in the group receiving 25 mg/kg × 2 doses of PT/Cy, compared with the group receiving 25 mg/kg of PT/Cy (9.1% vs. 33%, p = 0.20), was noted. However, the cumulative incidence of chronic GVHD was low, at 10% irrespective of PT/Cy dose. The number of infused CD34(+) cells significantly correlated with the grade of acute GVHD (p = 0.004). In addition, the occurrence of BK virus hemorrhagic cystitis was significantly more common in the double-dose PT/Cy group (25% vs. 0%, p = 0.043), especially when combined with busulfan. The probability of overall survival at 1 year in the double-dose group tended to be better compared with that in the single-dose group (64% vs. 44%, respectively; p = 0.20). In conclusion, HLA haploidentical, T-cell-replete PBSCT with 25 mg/kg × 2 doses of PT/Cy might be a feasible option for treating high-risk leukemia and MDS.

Complications of Reduced Intensity Conditioning HSCT for XIAP Deficiency (Alloimmune Cytopenias and HLH) Successfully Managed With Donor Lymphocyte Infusion

X-linked inhibitor of apoptosis protein deficiency is a rare illness and although stem cell transplant is curative, full intensity conditioning is associated with high mortality rates. We describe a child with unusual complications associated with residual host lymphocytes following reduced intensity stem cell transplant. Recipient derived, donor directed, antigranulocyte antibodies led to life-threatening and prolonged neutropenia and residual recipient lymphocytes reestablished hemophagocytic lymphohistiocytosis after withdrawal of immune suppression despite high levels of whole blood chimerism. Hemophagocytic lymphohistiocytosis was abolished following specific improvement in donor T-cell chimerism after donor lymphocyte infusions, and alloimmune cytopenias were no longer evident.

Reduced-intensity conditioned allogeneic SCT in adults with AML

AML is currently the most common indication for reduced-intensity conditioned (RIC) allo-SCT. Reduced-intensity regimens allow a potent GVL response to occur with minimized treatment-related toxicity in patients of older age or with comorbidities that preclude the use of myeloablative conditioning. Whether RIC SCT is appropriate for younger and more standard risk patients is not well defined and the field is changing rapidly; a prospective randomized trial of myeloablative vs RIC (BMT-CTN 0901) was recently closed when early results indicated better outcomes for myeloablative regimens. However, detailed results are not available, and all patients in that study were eligible for myeloablative conditioning. RIC transplants will likely remain the standard of care as many patients with AML are not eligible for myeloablative conditioning. Recent publication of mature results from retrospective and prospective cohorts provide contemporary efficacy and toxicity data for these attenuated regimens. In addition, recent studies explore the use of alternative donors, introduce regimens that attempt to reduce toxicity without reducing intensity, and identify predictive factors that pave the way to personalized approaches. These studies paint a picture of the future of RIC transplants. Here we review the current status of RIC allogeneic SCT in AML.

Conditioning regimens for hematopoietic cell transplantation: one size does not fit all

An essential component of allogeneic and autologous hematopoietic cell transplantation (HCT) is the conditioning regimen administered before the hematopoietic cell infusion. Early regimens relied on dose intensity, assuming that high-dose chemoradiotherapy would eliminate malignant disease and reinfusion of the graft would then restore hematopoiesis. However, as the contribution of graft-versus-tumor effects to the success of allogeneic HCT was recognized over time, in an effort to exploit these, many investigators lowered the dose of radiation and chemotherapeutic agents in the preparative regimen. This resulted in a major paradigm shift, and consequently, the pool of eligible patients underwent a remarkable expansion. In this article, we provide a review of the definition of high-dose, reduced-intensity, and nonmyeloablative conditioning regimens, the most commonly used agents and combinations, and the evolution of some early regimens. We also provide a brief review of the toxicities associated with these regimens.

Advances in stem cell mobilization

Use of granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood hematopoietic progenitor cells (HPCs) has largely replaced bone marrow (BM) as a source of stem cells for both autologous and allogeneic cell transplantation. With G-CSF alone, up to 35% of patients are unable to mobilize sufficient numbers of CD34 cells/kg to ensure successful and consistent multi-lineage engraftment and sustained hematopoietic recovery. To this end, research is ongoing to identify new agents or combinations which will lead to the most effective and efficient stem cell mobilization strategies, especially in those patients who are at risk for mobilization failure. We describe both established agents and novel strategies at various stages of development. The latter include but are not limited to drugs that target the SDF-1/CXCR4 axis, S1P agonists, VCAM/VLA-4 inhibitors, parathyroid hormone, proteosome inhibitors, Groβ, and agents that stabilize HIF. While none of the novel agents have yet gained an established role in HPC mobilization in clinical practice, many early studies exploring these new pathways show promising results and warrant further investigation.

Pre-transplant prognostic factors of long-term survival after allogeneic peripheral blood stem cell transplantation with matched related/unrelated donors

Mobilized peripheral blood has become the predominant stem cell source for allogeneic hematopoietic cell transplantation. In this retrospective single center study of 442 patients with hematologic malignancies, we analyzed prognostic factors for long-term survival after peripheral blood stem cell transplantation from HLA-matched related or unrelated donors. To account for disease/status heterogeneity, patients were risk-stratified according to the Disease Risk Index. Five-year overall survival was similar after transplants with matched related and unrelated donors (45% and 46%, respectively; P=0.49). Because donor age ≥60 years impacted outcome during model building, we further considered 3 groups of donors: matched unrelated (aged <60 years by definition), matched related aged <60 years and matched related aged ≥60 years. In multivariate analysis, the donor type/age group and the graft CD34(+) and CD3(+) cell doses impacted long-term survival. Compared with matched unrelated donor transplant, transplant from matched related donor <60 years resulted in similar long-term survival (P=0.67) while transplant from matched related donor ≥60 years was associated with higher risks for late mortality (hazard ratio (HR) 4.41; P=0.006) and treatment failure (HR: 6.33; P=0.009). Lower mortality risks were observed after transplant with CD34(+) cell dose more than 4.5×10(6)/kg (HR: 0.56; P=0.002) and CD3(+) cell dose more than 3×10(8)/kg (HR: 0.61; P=0.01). The Disease Risk Index failed to predict survival. We built an "adapted Disease Risk Index" by modifying risks for myeloproliferative neoplasms and multiple myeloma that improved stratification ability for progression-free survival (P=0.04) but not for overall survival (P=0.82).

Rapid donor T-cell engraftment increases the risk of chronic graft-versus-host disease following salvage allogeneic peripheral blood hematopoietic cell transplantation for bone marrow failure syndromes

The risk of graft-rejection after allogeneic hematopoietic cell transplantation using conventional cyclophosphamide-based conditioning is increased in patients with bone marrow failure syndromes (BMFS) who are heavily transfused and often HLA-alloimmunized. Fifty-six patients with BMFS underwent fludarabine-based reduced-intensity conditioning and allogeneic peripheral blood progenitor cell (PBPC) transplantation at a single institution. The conditioning regimen consisted of intravenous cyclophosphamide, fludarabine, and equine antithymocyte globulin. Graft-versus-host disease (GVHD) prophylaxis included cyclosporine A alone or in combination with either mycophenolate mofetil or methotrexate. To reduce the risk of graft-rejection/failure, unmanipulated G-CSF mobilized PBPCs obtained from an HLA-identical or single HLA-antigen mismatched relative were transplanted rather than donor bone marrow. Despite a high prevalence of pretransplant HLA-alloimmunization (41%) and a heavy prior transfusion burden, graft-failure did not occur with all patients having sustained donor lympho-hematopoietic engraftment. The cumulative incidence of grade II-IV acute-GVHD and chronic-GVHD was 51.8% and 72%, respectively; with 87.1% surviving at a median follow-up of 4.5 years. A multivariate analysis showed pretransplant alloimmunization and rapid donor T-cell engraftment (≥95% donor by day 30) were both significantly (P < 0.05) associated with the development of chronic-GVHD (adjusted HR 2.13 and 2.99, respectively). These data show fludarabine-based PBPC transplantation overcomes the risk of graft-failure in patients with BMFS, although rapid donor T-cell engraftment associated with this approach appears to increase the risk of chronic-GVHD. (Clinicaltrials.gov identifier: NCT00003838).

Biologic markers of chronic GVHD

Biologic markers of chronic GVHD may provide insight into the pathogenesis of the syndrome, identify molecular targets for novel interventions, and facilitate advances in clinical management. Despite extensive work performed to date largely focused on prediction and diagnosis of the syndrome, little synthesis of findings and validation of promising candidate markers in independent populations has been performed. Studies suggest that risk for subsequent chronic GVHD development may be associated with donor-recipient genetic polymorphism, deficiency in regulatory immune cell populations (NK, Treg, DC2), and variation in inflammatory and immunoregulatory mediators post-HCT (increased TNFα, IL-10 and BAFF, and decreased TGFβ and IL-15). Established chronic GVHD is associated with alteration in immune cell populations (increased CD3(+) T cells, Th17, CD4(+) and CD8(+) effector memory cells, monocytes, CD86 expression, BAFF/B cell ratio, and deficiency of Treg, NK cells, and naïve CD8(+) T cells). Inflammatory and immunomodulatory factors (TNFα, IL-6, IL-1β, IL-8, sIL-2R, and IL-1Ra, BAFF, anti-dsDNA, sIL-2Rα, and sCD13) are also perturbed. Little is known about biologic markers of chronic GVHD phenotype and severity, response to therapy, and prognosis.

Risk factors for invasive fungal disease after allogeneic hematopoietic stem cell transplantation: a single center experience

Invasive fungal disease (IFD) is a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HCT). We performed a retrospective review of 271 adults with a hematologic malignancy undergoing allogeneic HCT to determine the incidence of and risk factors for IFD and to examine the impact of IFD on nonrelapse mortality and overall survival. We defined IFD using standard criteria and selected proven and probable cases for analysis. Diagnoses in the study group included acute leukemia (42%), non-Hodgkin lymphoma (24%), myelodysplastic syndrome (15%), chronic lymphocytic leukemia (5%), and other hematologic disorders (14%). Conditioning included reduced-intensity (64%) and myeloablative (36%) regimens. Donor sources were HLA-matched sibling (60%), matched unrelated (20%), haploidentical (12%), and cord blood (8%). A total of 51 episodes of IFD were observed in 42 subjects (15%). Aspergillus spp (47%) was the most frequent causative organism, followed by Candida spp (43%). The majority of IFD cases (67%) were reported after day +100 post-HCT. In multivariate analysis, haploidentical donor transplantation (hazard ratio [HR], 3.82; 95% confidence interval [CI], 1.49-9.77; P = .005) and grade II-IV acute graft-versus-host disease (HR, 2.55; 95% CI, 1.07-6.10; P = .03) were risk factors for the development of IFD. Conversely, higher infused CD34(+) cell dose was associated with a lower risk of IFD (HR, 0.80; 95% CI, 0.68-0.94; P = .006, per 1 × 10(6) cells/kg increase in CD34(+) cell infusion). IFD-related mortality was 33.3%. Nonrelapse mortality was significantly higher in patients who developed IFD compared with those without IFD (P < .001, log-rank test). Patients with IFD had lower overall survival (5.8 months versus 76.1 months; P < .001, log-rank test). Further studies exploring strategies to increase the infused cell dose and determine adequate prophylaxis, especially against aspergillus, beyond day +100 are needed.

Promising role of reduced-toxicity hematopoietic stem cell transplantation (PART-I)

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potential curative option for many patients with hematological malignancies (HM). However, the high rate of transplantation-related mortality (TRM) restricted the use of standard myeloablative HSCT to a minority of young and fit patients. Over the past few years, it has become evident that the alloreactivity of the immunocompetent donor cells mediated anti-malignancy effects independent of the action of high dose chemoradiotherapy. The use of reduced intensity conditioning (RIC) regimens has allowed a graft-versus-malignancy (GvM) effect to be exploited in patients who were previously ineligible for HSCT on the grounds of age and comorbidity. Retrospective analysis showed that RIC has been associated with lower TRM but a higher relapse rate leading to similar intermediate term overall and progression-free survivals when compared to standard myeloablative HSCT. However, the long term antitumor effect of this approach is less well established. Prospective studies are ongoing to define which patients might most benefit from reduced toxicity stem cell transplant (RT-SCT) and which transplant protocols are suitable for the different types of HM. The advent of RT-SCT permits the delivery of a potentially curative GvM effect to the majority of patients with HM whose outcome with conventional chemotherapy would be dismal. Remaining challenges include development of effective strategies to reduce relapse rates by augmenting GvM effects without increasing toxicity.

Extensive chronic GVHD is associated with donor blood CD34+ cell count after G-CSF mobilization in non-myeloablative allogeneic PBSC transplantation

The correlation between the incidence of GVHD and the number of infused CD34(+) cells remains controversial for PBSC transplantation after a reduced-intensity-conditioning (RIC) regimen. We evaluated 99 patients transplanted with an HLA-identical sibling after the same RIC (2-Gy-TBI/fludarabine). Donor and recipient characteristics, donor's blood G-CSF-mobilized CD34(+) cell count, and number of infused CD34(+) and CD3(+) cells were analyzed as risk factors for acute and chronic GVHD There was a trend for an increased incidence of extensive chronic GVHD in the quartile of patients receiving more than 10 × 10(6) CD34(+) cells/kg (P = 0.05). Interestingly, the number of donor's blood CD34(+) cells at day 5 of G-CSF mobilization was closely associated with the incidence of extensive chronic GVHD, that is, 48% (95% CI: 28-68) at 24-months in the quartile of patients whose donors had the highest CD34(+) cell counts versus 24.3% (95% CI: 14-34) in the other patients (P = 0.007). In multivariate analysis, the only factor correlating with extensive chronic GVHD (cGVHD) was the donor's blood CD34(+) cell count after G-CSF (HR 2.49; 95% CI: 1.16-5.35, P = 0.019). This study shows that the incidence of cGVHD is more strongly associated with the donor's ability to mobilize CD34(+) cells than with the number of infused CD34(+) cells.

Clinical implications of chimerism after allogeneic hematopoietic stem cell transplantation in children with non-malignant diseases

Background

The effects of chimerism on outcomes following allogeneic hematopoietic stem cell transplantation (HSCT) are unclear and may differ between diseases. We retrospectively evaluated the association between chimerism and transplant outcomes in children with nonmalignant diseases.

Methods

Chimerism was evaluated using short-tandem repeat polymerase chain reaction (STR-PCR) in 48 patients, with mixed chimerism (MC) defined as greater than 1% recipient cells.

Results

The only variable exerting a significant influence on patients' chimerism status was the number of infused CD34+ cells. MC was detected in 23 transplants (9 showing transient MC; 10 with sustained low levels [≤30%] of autologous cells; and 4 with high-level MC [>30%]). The degree of STR-PCR at 28 days after HSCT was significantly higher in patients with high-level MC than those with transient or low-level MC. All patients with transient or low-level MC successfully maintained engraftment and showed a clinical response to HSCT, whereas 2 of the 4 patients with high-level MC experienced graft failure. The incidences of grades II-IV acute and chronic graft-versus-host disease (GVHD) were significantly higher in patients with complete donor chimerism (CC) than MC. We observed no significant survival differences between CC and MC groups. However, the survival rate was lower in patients with high MC than those with low-level or transient MC (P=0.03).

Conclusion

In non-malignant diseases, MC may indicate a tolerant state with a decreased incidence of GVHD. However, high-level MC may signify an increased risk of graft failure and a lower survival rate.

T cell-depleted unrelated donor stem cell transplantation provides favorable disease-free survival for adults with hematologic malignancies

We report a prospective phase II clinical trial in 35 adult patients (median age 40.5 years) with hematologic malignancies who received T cell-depleted, hematopoietic stem cell transplants from HLA-compatible, unrelated donors. The cytoreductive regimen consisted of hyperfractionated total-body irradiation, thiotepa, and fludarabine. The preferred graft source was granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSC). PBSC were CD34(+) selected, followed by sheep erythrocyte rosetting to deplete residual T cells. Anti-thymocyte globulin provided graft rejection prophylaxis. No additional graft-versus-host disease (GVHD) prophylaxis was planned. Estimated disease-free survival at 4 years is 56.8% for the entire group and 75% in patients with standard-risk disease. The cumulative incidence of relapse is 6%. Acute GVHD grade II-III developed in 9% and chronic GVHD in 29% of patients. Fatal infections occurred in 5 of 35 (14%) patients. There was 1 late graft failure. This study demonstrates durable engraftment with a low overall incidence of GVHD. Its curative potential is reflected in the remarkably low relapse rate at 4 years.

Post-transplant immune reconstitution after unrelated allogeneic stem cell transplant in patients with acute myeloid leukemia

We evaluated immune recovery in 67 patients with acute myeloid leukemia (AML) with a median age of 40 years (4-69) following allo-SCT after reduced (n = 35) or myeloablative (n = 32) conditioning. The following lymphocyte populations were determined on days +30, +90, +180, +270, and +365 by flow associated cell sorting: CD3+, CD3+CD4+, CD3+CD8+, CD3+CD4+/CD3+CD8+ ratio, CD3-CD56+, and CD19+ cells. Peripheral blast count >5% was related to lower number of CD3+CD4+ (day +30) and NK cells (day +180; p = 0.02). Intensity of conditioning did not have any significant impact on the kinetics of immune recovery. Patients with normal CD3+CD4+/CD3+CD8+ ratio (day +30) and NK cell count (day +90; p <0.05) experienced better survival than those with decreased parameters. Post-transplant sepsis/severe infections impaired CD3+CD8+ (day +90; p = 0.015) and CD19+ (day +90; p = 0.02) recovery. Relapse in patients following allo-SCT showed an association with decreased numbers of CD19+ (day +270) and NK cells (day +365). Acute GvHD (II-IV) was accompanied by reduced CD19+ and CD3+CD4+ cells. Thus, the evaluation of post-transplant immune reconstitution in patients with AML might improve risk stratification concerning either relapse or TRM and remains to be further explored.

Higher CD34(+) and CD3(+) cell doses in the graft promote long-term survival, and have no impact on the incidence of severe acute or chronic graft-versus-host disease after in vivo T cell-depleted unrelated donor hematopoietic stem cell transplantation in children

The aim of our study was to compare the results of unrelated donor (UD) peripheral blood stem cell transplantation versus UD bone marrow transplantation and to analyze the impact of infused CD34(+) and CD3(+) cell doses on survival and incidence of severe graft-versus-host disease (GVHD) in 187 children who underwent UD hematopoietic cell transplantation with the use of in vivo T cell depletion (antithymocyte globulin or CAMPATH-1H). HLA typing was performed at the "high-resolution" level. Patients receiving > or =10 x 10(6) CD34(+) cells/kg and > or =4 x 10(8) CD3(+) cells/kg had better overall and disease-free survival. Multivariate analysis has shown that both infused CD34(+) cell dose <10 x 10(6)/kg and CD3(+) cell dose <4 x 10(8)/kg were independent risk factors for mortality (relative risk [RR] 1.8 and 1.71, P = .009 and .016, respectively). Regarding disease-free survival, multivariate analysis has revealed another independent risk factor for poor outcome apart from the 2 earlier-mentioned cell doses, which was the use of donors mismatched at 2 HLA antigens or 3 HLA allele/antigens (RR 2.5, P = .004). In age groups 0-10 years and 10-20 years, CD34(+) cell doses higher than the age-adjusted median dose clearly favored survival. Higher infused doses of CD34(+) and CD3(+) cells did not result in an increased rate of severe GVHD. The use of mismatched donors was the only independent risk factor for the incidence of severe acute GVHD (RR 2.2, P = .046). The report demonstrates for the first time in a pediatric cohort, that higher doses of transplanted CD34(+) and CD3(+) cells lead to an improved survival without an increased risk of severe GVHD. The study findings may be limited to the population of patients receiving in vivo T cell depletion, which is now broadly used in unrelated donor setting in Europe.

Chronic graft-versus-host disease (GVHD) in children

Five-year survival rates for childhood cancer now exceed 80% and with the significant progress made by the transplant community in developing less toxic conditioning regimens and in the treatment of posttransplant complications, allo-hematopoietic stem cell transplantation (HSCT) contributes significantly to that population of long-term survivors. In this context, the acute and long-term toxicities of chronic graft-versus-host disease (cGVHD) have an ever-increasing effect on organ function, quality of life, and survival; patients and families who initially felt great relief to be cured from the primary disease, now face the challenge of a chronic debilitating illness for which preventative and treatment strategies are suboptimal. Hence, the development of novel strategies that reduce and or control cGVHD, preserve graft-versus-tumor effects, facilitate engraftment and immune reconstitution, and enhance survival after allo-HSCT represents one of the most significant challenges facing physician-scientists and patients.

Recent advances in quantitative chimerism analysis

Quantitative chimerism analysis is a diagnostic tool used to monitor engraftment kinetics after allogeneic stem cell transplantation. It reflects the proportion of recipient and donor genotypes and is based on the identification of genetic markers characteristic to a given transplant pair. Currently, PCR amplification of short tandem repeats and single-nucleotide polymorphism-specific quantitative real-time PCR are the most widely used techniques for this purpose. In this review, we will address advances as well as technology-specific imperfections, of both techniques that have emerged over the recent years. We will discuss new principles that may simplify assay design, and improve its robustness and reliability. A better chimerism assay could then guide clinical interventions and may, eventually, improve the outcome of allogeneic stem cell transplantation.

The number of infused CD34+ cells does not influence the incidence of GVHD or the outcome of allogeneic PBSC transplantation, using reduced-intensity conditioning and antithymocyte globulin

The influence of graft composition on the outcome of reduced-intensity (RIC) allogeneic PBSC transplantation (allo-PBSC) remains controversial. In this study, we analyzed the impact of CD34+ cell dose on the incidence of GVHD, and on the outcome after allo-PBSC, in 103 patients with hematological malignancies, using a uniform RIC regimen. The following variables were included in statistical analysis: (1) number of C34+ cells, (2) high-risk vs low-risk disease status, (3) matched related vs matched unrelated donor, (4) female donor to male recipient vs any other combination, (5) age of recipient (above vs below the median). Univariate and multivariate analysis did not reveal any association between CD34+ cell dose and acute grade-2 to grade-4, cGVHD, non-relapse mortality (NRM), relapse rate (RR) and OS. High-risk disease status was the only variable independently associated with increased NRM (P=0.001), increased RR (P=0.012) and decreased OS (P<0.001). The same results were obtained when analysis was restricted to a subgroup of 55 patients with myeloid neoplasms. The influence of graft composition on the outcome of RIC allo-PBSC should be further investigated via well-controlled randomized prospective studies.

The effect of the composition of unrelated donor bone marrow and peripheral blood progenitor cell grafts on transplantation outcomes

To test the hypothesis that the outcome of hematopoietic stem cell (HSC) grafts is at least partially determined by the cellular composition of the graft, the National Marrow Donor Program (NMDP) analyzed the correlation of cellular phenotypes of unrelated grafts with graft outcome. Samples from 94 bone marrow (BM) and 181 peripheral blood progenitor cell (PBPC) grafts for transplantations at 40 U.S. transplant centers between 2003 and 2005 were analyzed at a single immunophenotyping reference laboratory. Samples were shipped from transplant centers upon receipt of graft. Graft cellular composition included analysis of leukocyte total cell numbers, and subsets of myeloid [CD34(+), CD34(+) CD38(-)], lymphoid [CD3(+), CD3(+) CD4(+), CD3(+) CD8(+)], and activated lymphoid cells [CD3(+) CD25(+), CD3(+) CD69(+), CD3(+) HLA-DR(+)] coexpressing CD3(+). There was substantial variability in the cellular composition of BM and PBPC grafts before and after graft processing by red blood cell (RBC) removal or plasma depletion in preparation for transplant. With BM grafts, cellular composition was not associated with hematopoietic recovery, graft-versus-host disease (GVHD), or survival. With PBPC grafts, survival rates were higher with CD34(+)>5 x 10(6)/kg, 59% compared to 34% with CD34(+)< or =5 x 10(6)/kg at 1 year. Platelet recovery was higher with PBPC containing CD3(+) CD8(+) >8 x 10(7)/kg. Neutrophil recovery or GVHD could not be predicted by any cellular subsets of PBPC grafts. Although survival was superior with PBPC grafts containing >5 x 10(6) CD34(+)/kg, an optimal graft mix of myeloid, lymphoid, and activated lymphoid subsets was not identified.

Donor, recipient, and transplant characteristics as risk factors after unrelated donor PBSC transplantation: beneficial effects of higher CD34+ cell dose

We report outcomes of 932 recipients of unrelated donor peripheral blood stem cell hematopoietic cell transplantation (URD-PBSC HCT) for acute myeloid leukemia, acute lymphoblastic leukemia, chronic myelogenous leukemia, and myelodysplastic syndrome enrolled on a prospective National Marrow Donor Program trial from 1999 through 2003. Preparative regimens included myeloablative (MA; N = 611), reduced-intensity (RI; N = 160), and nonmyeloablative (NMA; N = 161). For MA recipients, CD34(+) counts greater than 3.8 x 10(6)/kg improved neutrophil and platelet engraftment, whereas improved overall survival (OS) and reduced transplant-related mortality (TRM) were seen for all preparative regimens when CD34(+) cell doses exceeded 4.5 x 10(6)/kg. Higher infused doses of CD34(+) cell dose did not result in increased rates of either acute or chronic graft-versus-host disease (GVHD). Three-year OS and disease-free survival (DFS) of recipients of MA, RI, and NMA approaches were similar (33%, 35%, and 32% OS; 33%, 30%, and 29% DFS, respectively). In summary, recipients of URD-PBSC HCT receiving preparative regimens differing in intensity experienced similar survival. Higher CD34(+) cell doses resulted in more rapid engraftment, less TRM, and better 3-year OS (39% versus 25%, MA, P = .004; 38% versus 21% RI/NMA, P = .004) but did not increase the risk of GVHD. This trial was registered at www.clinicaltrials.gov as #NCT00785525.

What is the role for donor natural killer cells after nonmyeloablative conditioning?

We investigated the impacts of the tempo of early (days 14, 28, and 42) donor T cell and natural killer (NK) cell engraftment, missing recipient killer cell immunoglobulin-like receptor (KIR) ligands, and numbers of donor inhibitory and activating KIR genes on hematopoietic cell transplantation (HCT) outcomes in 282 patients with hematologic malignancies given nonmyeloablative conditioning. Modeling chimerism levels as a continuous linear variable, we found that high early donor T cell chimerism was significantly associated with acute graft-versus-host disease (aGVHD) (P = .01), whereas high donor NK cell chimerism levels had no such association (P = .38). Conversely, high donor NK cell chimerism levels were significantly associated with low relapse risk (P = .0009), whereas no significant association was seen with high donor T cell chimerism (P = .10). The qualitative associations between donor T cell and NK cell chimerism levels and GVHD and relapse did not change after adjustment for the presence of recipient KIR ligands or numbers of donor inhibitory or activating KIR genes. Our data indicate that prompt engraftment of donor NK cells correlated with lessened risks of relapse, but not with GVHD, whereas the converse was true for T cells.

Use of the haematopoietic progenitor cell parameter in optimizing timing of peripheral blood stem cell harvest

BACKGROUND AND OBJECTIVES

Timing of peripheral blood stem cell (PBSC) harvest is typically based on quantification of peripheral blood (PB) CD34+ cells. CD34 enumeration is expensive, requires expertise and takes a minimum of 1-2 h to perform. The Sysmex XE2100 is an automated haematology analyser that can rapidly and inexpensively identify haematopoietic progenitor cell (HPC) populations in PB. The aim of this study was to examine if HPC can be used to optimize timing of PBSC harvest.

MATERIALS AND METHODS

White blood cell (WBC), HPC and CD34 counts were determined in a total of 60 mobilized donors. Data were analysed to examine the utility of WBC and HPC counts in predicting preharvest CD34+ counts.

RESULTS

In adults presenting for autologous collection, a PB HPC threshold of > 30/microl predicts a preharvest CD34+ count of > 20/microl with sensitivity of 86% and positive predictive value (PPV) of 100%. Among paediatric patients with a diagnosis of neuroblastoma, an HPC threshold of > 16/microl yielded sensitivity and PPV of 100%, while in children with other diagnoses, an HPC cut-off of > 44/microl yielded sensitivity and PPV of 67% and 100%, respectively. Eighty per cent of adequately mobilized allogeneic donors were identified using an HPC threshold > 15/microl, with a PPV of 100%. PB WBC can also aid in predicting CD34 counts in most patient groups, albeit with lower sensitivity than HPC.

CONCLUSION

By virtue of being a sensitive and accurate predictor of preharvest CD34+ counts, our data support the use of the HPC parameter in optimizing the timing of PBSC harvest.

Nonmyeloablative allografting for newly diagnosed multiple myeloma: the experience of the Gruppo Italiano Trapianti di Midollo

Despite recent advances, allografting remains the only potential cure for myeloma. From July 1999 to June 2005, 100 newly diagnosed patients younger than 65 years were enrolled in a prospective multicenter study. First-line treatment included vincristin, adriamycin, and dexamethasone (VAD)-based induction chemotherapy, a cytoreductive autograft (melphalan 200 mg/m(2)) followed by a single dose of nonmyeloablative total body irradiation and allografting from an human leukocyte antigen (HLA)-identical sibling. Primary end points were the overall survival (OS) and event-free survival (EFS) from diagnosis. After a median follow-up of 5 years, OS was not reached, and EFS was 37 months. Incidences of acute and chronic graft-versus-host disease (GVHD) were 38% and 50%, respectively. Complete remission (CR) was achieved in 53% of patients. Profound cytoreduction (CR or very good partial remission) before allografting was associated with achievement of posttransplantation CR (hazard ratio [HR] 2.20, P = .03) and longer EFS (HR 0.33, P < .01). Conversely, development of chronic GVHD was not correlated with CR or response duration. This tandem transplantation approach allows prolonged survival and long-term disease control in patients with reduced tumor burden at the time of allografting. We are currently investigating the role of "new drugs" in intensifying pretransplantation cytoreduction and posttransplantation graft-versus-myeloma effects to further improve clinical outcomes. (http://ClinicalTrials.gov; NCT-00702247.).