Reduced-intensity allogeneic stem cell transplantation in adults and children with malignant and nonmalignant diseases: end of the beginning and future challenges

Acute toxicity and outcome among pediatric allogeneic hematopoietic transplant patients conditioned with treosulfan-based regimens

Treosulfan-based regimens constitute a feasible and increasingly used, but still myeloablative, conditioning in pediatric allogeneic hematopoietic stem cell transplantation (HSCT). We retrospectively analyzed the acute toxicity and outcome of all consecutive (2004-2015) pediatric HSCT patients prepared for HSCT with treosulfan in a single-center setting. We included HSCTs performed for both nonmalignant (n = 23) and malignant diseases (n = 11). The controls were patients with nonmalignant diseases or hematological malignancies conditioned with cyclophosphamide (Cy)-total body irradiation (TBI)-based (39 patients) or busulfan-based regimens (11 patients). The major toxicities of the treosulfan-based regimens were limited to oral mucosa and skin. 50% of the patients needed IV morphine for severe mucositis compared to 31% in patients conditioned with Cy-TBI (P = 0.02). Other toxicities were rare. The disease-free survival (DFS) of patients transplanted for nonmalignant disorders was 88.9 ± 7.5% at 2 years. The event-free survival (EFS) at 2 years in this small cohort for those with a malignant disease and a treosulfan-based conditioning was 54.5 ± 1.5%. We conclude that a treosulfan-based conditioning regimen gives excellent DFS in pediatric HSCT performed for a nonmalignant disorder but with substantial mucosal toxicity. In a malignant disorder a treosulfan-based regimen looks promising but larger, preferably randomized, studies are needed to prove efficacy.

Umbilical Cord Blood Transplantation Corrects Very Early-Onset Inflammatory Bowel Disease in Chinese Patients With IL10RA-Associated Immune Deficiency

BACKGROUND

Hematopoietic stem cell transplantation is considered the only curative therapy for very early-onset inflammatory bowel disease with specific immune defects, such as interleukin-10 receptor deficiency. We performed reduced-intensity conditioning before umbilical cord blood transplantation in patients with interleukin-10 receptor-A deficiency.

METHODS

We enrolled 9 very early-onset inflammatory bowel disease patients with typical manifestations. We diagnosed the patients with interleukin-10 receptor-A deficiency by whole-exome sequencing. Umbilical cord blood transplantation was performed in all 9 patients. Eight patients received the reduced-intensity conditioning regimen, and 1 patient received the myeloablative conditioning regimen.

RESULTS

All 9 patients received transplantation between the ages of 6 months to 43 months (average, 16.8 months) with body weights ranging from 3 to 10.4 kg (average, 6.6 kg). The patients displayed complete chimerism at 2-8 weeks after transplantation; 6 patients achieved complete remission without evidence of graft-vs-host disease or infections; 1 patient died of chronic lung graft-vs-host disease at 6 months post-transplantation; and the other 2 patients died of sepsis post-transplantation because of unsuccessful engraftments. Severe malnutrition and growth retardation associated with interleukin-10 receptor-A deficiency were significantly improved post-transplantation.

CONCLUSIONS

We recommend umbilical cord blood transplantation as a potential treatment for very early-onset inflammatory bowel disease with a defined monogenic immunodeficiency, and we suggest that reduced-intensity conditioning chemotherapy is more suitable than myeloablative conditioning for patients with severe malnutrition and bowel disease. We have demonstrated success with reduced-intensity conditioning for interleukin-10 receptor-A deficiency in pediatric patients with severe clinical conditions. 10.1093/ibd/izy028_video1izy028.video15786489183001.

Hematopoietic stem cell transplantation for sickle cell disease: state of the science

Sickle cell disease (SCD) is an inherited disorder secondary to a point mutation at the sixth position of the beta chain of human hemoglobin resulting in the replacement of valine for glutamic acid. This recessive genetic abnormality precipitates the polymerization of the deoxygenated form of hemoglobin S inducing a major distortion of red blood cells (S-RBC), which decreases S-RBC deformability leading to chronic hemolysis and vaso-occlusion. These processes can result in severe complications including chronic pain, end-organ dysfunction, stroke, and early mortality. The only proven curative therapy for patients with SCD is myeloablative conditioning and allogeneic stem cell transplantation from HLA-matched sibling donors. In this review, we discuss the most recent advances in allogeneic stem cell transplantation in patients with SCD including more novel approaches such as reduced toxicity conditioning and the use of alternative allogeneic donors, including matched unrelated donors (MUDs), unrelated cord blood donors (UCBT), and familial haploidentical (FHI) donors. The results to date are very encouraging regarding allogeneic stem cell transplantation for patients with SCD including high survival rates and enabling a greater number of patients suffering from this chronic and debilitating condition to receive curative allogeneic stem cell therapies. However, we still have several areas to investigate and barriers to overcome to successfully cure the majority of patients with severe SCD through allogeneic stem cell therapies.

Reduced toxicity, myeloablative conditioning with BU, fludarabine, alemtuzumab and SCT from sibling donors in children with sickle cell disease

BU and CY (BU/CY; 200 mg/kg) before HLA-matched sibling allo-SCT in children with sickle cell disease (SCD) is associated with ~85% EFS but is limited by the acute and late effects of BU/CY myeloablative conditioning. Alternatives include reduced toxicity but more immunosuppressive conditioning. We investigated in a prospective single institutional study, the safety and efficacy of a reduced-toxicity conditioning (RTC) regimen of BU 12.8-16 mg/kg, fludarabine 180 mg/m(2), alemtuzumab 54 mg/m(2) (BFA) before HLA-matched sibling donor transplantation in pediatric recipients with symptomatic SCD. Eighteen patients, median age 8.9 years (2.3-20.2), M/F 15/3, 15 sibling BM and 3 sibling cord blood (CB) were transplanted. Mean whole blood and erythroid donor chimerism was 91% and 88%, at days +100 and +365, respectively. Probability of grade II-IV acute GVHD was 17%. Two-year EFS and OS were both 100%. Neurological, pulmonary and cardiovascular function were stable or improved at 2 years. BFA RTC and HLA-matched sibling BM and CB allo-SCT in pediatric recipients result in excellent EFS, long-term donor chimerism, low incidence of GVHD and stable/improved organ function.

Impact of cyclosporine levels on the development of acute graft versus host disease after reduced intensity conditioning allogeneic stem cell transplantation

We analyze the impact of cyclosporine (CsA) levels in the development of acute graft-versus-host disease (aGVHD) after reduced intensity conditioning allogeneic hematopoietic transplantation (allo-RIC). We retrospectively evaluated 156 consecutive patients who underwent HLA-identical sibling allo-RIC at our institution. CsA median blood levels in the 1st, 2nd, 3rd and 4th weeks after allo-RIC were 134 (range: 10–444), 219 (54–656), 253 (53–910) and 224 (30–699) ng/mL; 60%, 16%, 11% and 17% of the patients had median CsA blood levels below 150 ng/mL during these weeks. 53 patients developed grade 2–4 aGVHD for a cumulative incidence of 45% (95% CI 34–50%) at a median of 42 days. Low CsA levels on the 3rd week and sex-mismatch were associated with the development of GVHD. Risk factors for 1-year NRM and OS were advanced disease status (HR: 2.2, P = 0.02) and development of grade 2–4 aGVHD (HR: 2.5, P < 0.01), while there was a trend for higher NRM in patients with a low median CsA concentration on the 3rd week (P = 0.06). These results emphasize the relevance of sustaining adequate levels of blood CsA by close monitoring and dose adjustments, particularly when engraftment becomes evident. CsA adequate management will impact on long-term outcomes in the allo-RIC setting.

Fludarabine-based reduced-intensity conditioning regimen for hematopoietic stem cell transplantation in primary hemophagocytic lymphohistiocytosis

OBJECTIVE

Primary hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition that clinically characterized by fever, hepatosplenomegaly, and cytopenia. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment option for patients diagnosed with primary HLH.

METHODS

In this prospective study, we analyzed the outcome of 10 pediatric patients with primary HLH who had received HSCT, using reduced-intensity conditioning (RIC) regimen from 2007 to 2012. The median age at transplantation was 22.6 months (range: 6-60). All of the patients received the same RIC regimen based on the use of fludarabine in combination with melphalan and horse antithymocyte globulin (ATG). Cyclosporine and methylprednisolone were used as graft-vs.-host disease (GvHD) prophylaxis.

RESULTS

Hematopoietic engraftment occurred in all patients. At the present time, 8 patients with a median follow-up of 39 months are still alive and all of them are disease free. Acute and chronic GvHD developed in 6 and 2 patients, retrospectively. Two patients died of sepsis and chronic GvHD during the study.

CONCLUSION

Because of pretransplant infections caused by underlying immunodeficiency in patients with primary HLH, the use of less toxic regimen with RIC seems to be highly effective in this regard. Recipients of RIC transplant, with either full or mixed chimerism, had a long-term survival rate with no manifestation of primary HLH symptoms.

Successful allogeneic hematopoietic cell engraftment after a minimal conditioning regimen in children with relapsed or refractory solid tumors

Children with relapsed or refractory solid tumors face dismal prognoses, and novel therapies are desperately needed. Allogeneic hematopoietic cell transplantation (HCT) offers potential for cell-based therapy, but the toxicity of myeloablation limits this approach in heavily pretreated patients. We sought to determine the feasibility of HCT in a cohort of 24 children with incurable solid tumors using human leukocyte antigen-matched sibling or unrelated donors and a minimal conditioning regimen. Before stem cell infusion, all patients received 3 daily doses of 30 mg/m(2) fludarabine followed by 2 Gy of total body irradiation. Hematopoietic cell recovery was rapid and reliable. Median time to neutrophil engraftment was 13.5 days for sibling donors and 12 days for unrelated donors. Donor lymphocyte infusions were used safely in 4 patients, all of whom had either improved chimerism or apparent tumor response. Graft-versus-host disease was comparable across donor sources and did not affect survival. Relapse remains a substantial barrier, although objective graft-versus-tumor effect was observed in several patients. Four patients with detectable disease before HCT achieved a complete response for at least 30 days after HCT, and two remain long-term survivors. Three patients were in complete response before HCT and remained in remission for 3, 6, and 74 months after HCT. Early disease response was associated with improved survival. Allogeneic HCT using this conditioning regimen offers a potential platform for novel immunotherapies.

Allogeneic cellular and autologous stem cell therapy for sickle cell disease: 'whom, when and how'

Sickle cell disease (SCD) is an autosomal recessive inherited hematological disorder characterized by chronic hemolysis and vaso-occlusion, resulting in multiorgan dysfunction and premature death. The only known curative therapy for patients with severe SCD is myeloablative conditioning and allo-SCT from HLA-matched sibling donors. In this state of the art review, we discuss current and future considerations including patient selection/eligibility, intensity of conditioning regimens, allogeneic graft sources, graft manipulation, mixed donor chimerism, organ function and stability and autologous gene correction stem cell strategies. Recent novel approaches to promote mixed donor chimerism have included the use of matched unrelated adult donors, umbilical cord blood donors, haploidentical familial donors and the utilization of nonmyeloablative, such as reduced intensity and reduced toxicity conditioning regimens. Future strategies will include gene therapy and autologous gene correction stem cell designs. Prospects are bright for novel stem and cellular approaches for patients with severe SCD, and we are currently at the end of the beginning for utilizing cellular therapeutics for the curative treatment of this chronic and debilitating condition.

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

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

Comparison of reduced intensity and myeloablative conditioning regimens for stem cell transplantation in patients with malignancies: a meta-analysis

OBJECTIVE

The reduced intensity conditioning (RIC) stem cell transplantation is widely employed for the treatment of many hematologic malignancies, but the survival effectiveness is still unclear. This study conducted an updated meta-analysis to determine whether any significant difference could be found by using RIC vs. myeloablative conditioning (MAC) regimen for transplantation in patients with malignancies.

METHODS

We electronically searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and relevant articles (1987.01-2009.12). Comparative studies were carried out on clinical therapeutic effect of RIC and MAC on the survival outcomes and the transplantation-related complications.

RESULTS

We obtained 1776 records, and 29 studies totaling 6235 patients have been assessed. Compared with MAC regimen, the RIC regimen had a higher overall survival (OS) at one-yr and no difference at two-yr later after transplantation. RIC regimen had significantly lower rates of disease-free survival (DFS) after two-yr follow-up, lower incidences of ≥ II degree acute graft-versus-host disease (aGVHD), and lower TRM [OR, 0.61, 95% CI (0.53, 0.69)], but with a higher relapse rate [OR, 1.88(1.41, 2.51)]. No significant difference was found in rates of cytomegalovirus (CMV) infection and chronic GVHD between the regimens.

CONCLUSIONS

This meta-analysis confirmed that compared with MAC condition regimen, the RIC regimen had a consistently equivalent or even better rate in OS, but with lower DFS at longer follow-up.

A pilot study of reduced toxicity conditioning with BU, fludarabine and alemtuzumab before the allogeneic hematopoietic SCT in children and adolescents

We report the results of a pilot study of a BU-fludarabine-alemtuzumab (BFA)-reduced toxicity conditioning (RTC) followed by allogeneic hematopoietic SCT (AlloHSCT) in 12 children and adolescents (<21 years) with malignant and non-malignant diseases. Stem cell sources were: two unrelated cord blood, one unrelated BM, two related and seven unrelated PBSC. Positive CD34 selection was performed in five unrelated PBSC grafts. RCT was carried out with BFA, and GVHD prophylaxis was FK506 and mycophenolate mofetil. The median time for neutrophil and platelet engraftment was 16 and 31 days, respectively. The P of developing ≥ grade II, ≥ grade III aGVHD and cGVHD was 41.6, 25 and 9%, respectively. Only 1 out of 12 developed ≥ grade III toxicity. There was one primary and no secondary graft failure. Mixed donor chimerism on day 100 and 1 year was median 99 and 96%, respectively; ≥ 90% of recipients achieved ≥ 80% donor chimerism. The 3-year overall survival (OS) in all patients was 91.7 ± 8% (100% for malignant vs. 80% for non-malignant diseases, ns). In all, 11 (91%) patients remain alive at median 2.8 (0.3-6.8) years. RTC followed by AlloHSCT, based on BFA conditioning, is feasible and tolerable in children and adolescents, and results in prompt achievement of durable mixed donor chimerism and excellent OS.

CML in pregnancy and childhood

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

Incidence of Viral and fungal infections following busulfan-based reduced-intensity versus myeloablative conditioning in pediatric allogeneic stem cell transplantation recipients

Reductions in the duration and nadir of neutropenia have translated into a significant decrease in bacteremia in adult recipients of allogeneic stem cell transplantation (allo-SCT) with reduced-intensity conditioning (RIC) during the first 30 days after transplantation. It remains to be determined whether RIC allo-SCT also will result in a decrease in systemic viral infections (SVIs) and invasive fungal infections (IFIs), which are more dependent on alterations in cellular immunity. We compared the incidence of SVIs and IFIs in children receiving busulfan-based RIC allo-SCT and in children receiving myeloablative conditioning (MAC) allo-SCT for various malignant and nonmalignant diseases. Allo-SCT recipients at risk for cytomegalovirus (CMV) received ganciclovir/foscarnet, and most of the patients received antifungal prophylaxis with liposomal amphotericin B until day +100. Eighty-six patients (median age, 7.5 years; 70% with malignant disease, 30% with nonmalignant disease; 80% average risk, 20% poor risk) were evaluated. The probability of developing grade II-IV acute graft-versus-host disease (aGVHD) was 29.1% (95% confidence interval [CI]=16.7%-41.6%) in RIC allo-SCT versus 40.3% (95% CI=23.9%-56.6%) in MAC allo-SCT (P=.23), and that of chronic GVHD (cGVHD) was 28.9% (95% CI=14.7%-43.0%) in RIC allo-SCT versus 28.4% (95% CI=10.5%-46.3%) in MAC allo-SCT (P=.73). The overall probability of developing an SVI was 58%, and that of developing an IFI was 15%. These probabilities did not differ significantly by conditioning intensity. In a multivariate Cox regression model, the following were identified as independent risk factors for invasive fungal infection: older age (hazard ratio [HR]=1.3; 95% CI=1.1-1.6; P=< .01), poor risk status (HR=6.5; 95% CI =1.1-37.4; P=.03), and CMV-positive recipient (high vs low CMV risk group, HR=26.7; 95% CI=3.4-210.8; P=< .01). Overall infection-related mortality was only 1.1% (1/86) for SVIs and 2.3% (2/86) for IFIs. Our data indicate that RIC allo-SCT does not carry a lower risk of SVIs and IFIs than MAC allo-SCT in pediatric recipients.

Low toxicity of a conditioning with 8-Gy total body irradiation, fludarabine and cyclophosphamide as preparative regimen for allogeneic hematopoietic stem cell transplantation in pediatric hematological malignancies

We here report the efficacy and toxicity of a conditioning regimen with fractionated 8-Gy TBI, fludarabine, and cyclophosphamide in allogeneic HSCT for pediatric hematological malignancies. Among 22 children who received related or unrelated HSCT, nine were transplanted with refractory disease and/or from HLA two or more loci-mismatched family donors. None of the patients developed graft failure. The Seattle grading system revealed that 18 patients had no RRT, and the remaining patients had grade I gastrointestinal toxicity alone. The estimated overall survival and leukemia-free survival at two yr were 57.1% and 48.0%, respectively, in 10 patients with acute lymphoblastic leukemia; 91.7% and 71.3%, respectively, in 12 patients with myeloid leukemia. The incidence of TRM was 4.8% at two yr. The rates of RRT above grade II and TRM in an 8-Gy TBI-containing regimen were significantly lower than the data of historical control patients who underwent 12-Gy TBI and cyclophosphamide with or without etoposide. The intermediate-dose TBI-based conditioning regimen may confer successful engraftment combined with minimized RRT, although its efficacy should be further evaluated.

Fludarabine-melphalan as a preparative regimen for reduced-intensity conditioning allogeneic stem cell transplantation in relapsed and refractory Hodgkin's lymphoma: the updated M.D. Anderson Cancer Center experience

BACKGROUND

The role of reduced-intensity conditioning allogeneic stem cell transplantation in relapsed/refractory Hodgkin's lymphoma remains poorly defined. We here present an update of our single-center experience with fludarabine-melphalan as a preparative regimen.

DESIGN AND METHODS

Fifty-eight patients with relapsed/refractory Hodgkin's lymphoma underwent RIC and allogeneic stem cell transplantation from a matched related donor (MRD; n=25) or a matched unrelated donor (MUD; n=33). Forty-eight (83%) had undergone prior autologous stem cell transplantation. Disease status at transplant was refractory relapse (n=28) or sensitive relapse (n=30).

RESULTS

Cumulative day 100 and 2-year transplant-related mortality rates were 7% and 15%, respectively (day 100 transplant-related mortality MRD vs. MUD 8% vs. 6%, p=ns; 2-year MRD vs. MUD 13% vs. 16%, p=ns). The cumulative incidence of acute (grade II-IV) graft-versus-host disease in the first 100 days was 28% (MRD vs. MUD 12% vs. 39%, p=0.04). The cumulative incidence of chronic graft-versus-host disease at any time was 73% (MRD vs. MUD 57% vs. 85%, p=0.006). Projected 2-year overall and progression-free survival rates are 64% (49-76%) and 32% (20-45%), with 2-year disease progression/relapse at 55% (43-70%). There was no statistically significant differences in overall survival progression-free survival, and disease progression/relapse between MRD and MUD transplants. There was a trend for the response status pretransplant to have a favorable impact on progression-free survival (p=0.07) and disease progression/relapse (p=0.049), but not on overall survival (p=0.4)

CONCLUSIONS

Fludarabine-melphalan as a preparative regimen for reduced-intensity conditioning allogeneic stem cell transplantation in progression-free survival Hodgkin's lymphoma is associated with a significant reduction in transplant-related mortality, with comparable results in MRD and MUD allografts. Optimizing pretransplant response status may improve patients' outcome.

Stem cell transplantation in Europe: trends and prospects

The aim of the present study was to identify trends in numbers of European patients treated with autologous and allogeneic haematopoietic stem cell transplantation (HSCT) as well as to provide anticipated transplant rates for the upcoming years. The following indications were considered: haematological malignancies (acute leukaemias, myeloproliferative disorders, lymphoproliferative disorders and multiple myeloma), solid tumours and non-malignant diseases. Numbers of patients treated from 1990 to 2004 were extracted from the European Group for Blood and Marrow Transplantation database, extrapolated to 2012 using mathematic models and adjusted to the literature study and expert opinion. In Europe, a 13% raise in HSCT utilisation is to be expected from 2005 to 2010, mostly due to the growing application of reduced-intensity conditioning regimens followed by allogeneic HSCT. Growing transplant rates are likely to exert health expenditure budgets and put pressure on health care providers and health insurers in Europe. Therefore, the rapid expansion would ideally imply a simultaneous increase in HSCT budgets.

Reduced intensity allogeneic umbilical cord blood transplantation in children and adolescent recipients with malignant and non-malignant diseases

There is a significant amount of morbidity and mortality following myeloablative umbilical cord blood transplantation (UCBT). Reduced intensity (RI) conditioning offers an alternative to myeloablative conditioning before UCBT. We investigated RI-UCBT in 21 children and adolescents with malignant (n=14), and non-malignant diseases (n=7). RI conditioning consisted of fludarabine (150-180 mg/m2) with either busulfan (< or = 8 mg/kg)+rabbit antithymocyte globulin (R-ATG; n=16) or cyclophosphamide+R-ATG+/-etoposide (n=5). Human leukocyte antigen match: 4/6 (n=13), 5/6 (n=5) and 6/6 (n=3). The median total nucleated cell and CD34+ cell dose per kilogram were 3.58 x 10(7) and 2.54 x 10(5), respectively. The median time for neutrophil and platelet engraftment was 17.5 and 52 days, respectively. There were six primary graft failures (chronic myelogenous leukemia (CML), beta-thalassemia, hemophagocytic lymphohistiocytosis (HLH) and myelodysplastic syndrome (MDS)). The probability of developing grade II to grade IV acute graft-versus-host disease (GVHD) and chronic GVHD was 28.6 and 16.7%, respectively. Incidence of transplant-related mortality (TRM) was 14%. The 5 years overall survival (OS) in all patients was 59.8%. The 5 years OS for patients with average versus poor-risk malignancy was 77.8 versus 22.2% (P=0.03). RI-UCBT may result in graft failure in specific high-risk chemo-naïve patients (CML, beta-thalassemia, HLH and MDS), but in more heavily pretreated pediatric and adolescent recipients results in rapid engraftment and may be associated with decreased severe GVHD and TRM.

Unrelated donor bone marrow transplants for severe aplastic anemia with conditioning using total body irradiation and cyclophosphamide

The outcome of unrelated donor bone marrow transplantation for aplastic anemia is inferior to that of sibling donor bone marrow transplantation because of a higher rate of transplant-related mortality (TRM), which is closely associated with the intensity of pretransplant conditioning to overcome graft rejection. We conducted a prospective trial with an intermediate to high dose of total body irradiation (TBI) in combination with a fixed dose of cyclophosphamide (120 mg/kg) to use for pretransplant conditioning for unrelated donor bone marrow transplantation in adult aplastic anemia. The number of patients who received doses of 1200, 1000, and 800 cGy of TBI were 5, 9, and 26, respectively. The corresponding probabilities of overall survival (OS) at 3 years were 40%, 44%, and 92%, respectively. The incidence of regimen-related toxicity with grade III-IV and graft rejection in the patients who received a dose of 800 cGy of TBI were 0 of 26 patients. The significant factors associated with OS were the TBI dose (800 cGy vs. >or=1000 cGy; P = .001), chronic graft-versus-host disease (less than or equal to limited vs. extensive; P = .013), the method of HLA typing for the donor-recipient matching (serologic typing vs. DNA-based typing; P = .006), and the transfusion amount before transplantation (<or=90 vs. >90 units; P = .020).

Rapid immune reconstitution after a reduced-intensity conditioning regimen and a CD3-depleted haploidentical stem cell graft for paediatric refractory haematological malignancies

The main obstacles to successful haploidentical haematopoietic stem cell transplantation from a mismatched family member donor are delayed immune reconstitution, vulnerability to infections and severe graft-versus-host disease (GvHD). We designed a reduced-intensity conditioning regimen that excluded total body irradiation and anti-thymocyte globulin in order to expedite immune reconstitution after a CD3-depleted haploidentical stem cell transplant. This protocol was used to treat 22 paediatric patients with refractory haematological malignancies. After transplantation, 91% of the patients achieved full donor chimaerism. They also showed rapid recovery of CD3(+) T-cells, T-cell receptor (TCR) excision circle counts, TCRbeta repertoire diversity and natural killer (NK)-cells during the first 4 months post-transplantation, compared with those results from a group of patients treated with a myeloablative conditioning regimen. The incidence and extent of viremia were limited and no lethal infection was seen. Only 9% of patients had grade 3 acute GvHD, while 27% patients had grade 1 and another 27% had grade 2 acute GvHD. This well-tolerated regimen appears to accelerate immune recovery and shorten the duration of early post-transplant immunodeficiency, thereby reducing susceptibility to viral infections. Rapid T-cell reconstitution, retention of NK-cells in the graft and induction of low grade GvHD may also enhance the potential anti-cancer immune effect.

Reduced intensity conditioning using intravenous busulfan, fludarabine and rabbit ATG for children with nonmalignant disorders and CML

The major problems with busulfan/cyclophosphamide (Bu/Cy)-containing conditioning regimens are acute toxicities and graft failure. To decrease acute toxicities, we have prospectively evaluated a reduced intensity conditioning (RIC) regimen using targeted dosing of i.v. busulfan, fludarabine, and rabbit ATG (Bu/Flu/rATG) in children with diagnoses that historically would have been conditioned with Bu/Cy regimens. Nineteen pediatric patients were enrolled in the study. The donors included HLA-matched and one antigen-mismatched unrelated volunteers (n = 11), unrelated cord blood (n = 1), and related donors (n = 7). Four patients developed graft failure, which occurred between 1 and 8.5 months post transplant. All four of them underwent a second transplantation and 3/4 are alive without evidence of disease. The mean follow-up of living patients is 29.5 +/- s.d. 11 months. Despite excellent 2-year post-transplant overall survival (89 +/- s.d.7%) and event-free survival (74 +/- s.d.10%), the study was closed prematurely due to high graft failure rate (21%). Receiving a transplant from a mismatched unrelated donor was identified as a risk factor for graft failure. The Bu/Flu/rATG RIC regimen was very well tolerated, resulted in excellent overall survival, and provided sustained engraftment in patients undergoing transplant from matched sibling and unrelated donors. However, it did not provide sustained engraftment in the majority of children with nonmalignancies undergoing mismatched unrelated donor transplants.