Effects of in vitro depletion of T cells in HLA-identical allogeneic marrow grafts

We report results of a pilot study designed to evaluate the effects of in vitro depletion of T lymphocytes from donor marrow in patients receiving HLA-identical marrow grafts for treatment of hematologic malignancies. Twenty patients aged 31 to 50 years were prepared for transplantation with cyclophosphamide (120 mg/kg) and fractionated total body irradiation (12.0 or 15.75 Gy). All received cyclosporine after grafting. The donor marrows were treated with a mixture of eight murine monoclonal antibodies and rabbit serum complement in a manner that achieved a 2- to 3-log depletion of T cells in most patients. Initial engraftment occurred promptly in 19 of the patients, and only three had clinically significant acute graft-versus-host disease. Depletion of donor T cells, however, was associated with an increased incidence of graft failure, which occurred as late as 244 days after transplantation. Graft failure was transient in one patient but apparently was irreversible in seven others. Three of the seven patients had cytogenetic but not morphological evidence of leukemic relapse at the time of graft failure. All seven patients with irreversible graft failure have died, six after receiving second bone marrow transplants. Seven of the eight cases of graft failure occurred among the 11 patients prepared for transplantation with 12.0 Gy of total-body irradiation, and only one occurred among the nine patients with advanced malignancies who received 15.75 Gy of total-body irradiation. This association with irradiation dose suggests that host factors were partly responsible for the graft failures. Because graft failure seldom occurs in irradiated recipients of unmodified HLA- identical allogeneic marrow transplants, it appears that T cells in the donor marrow may serve a beneficial function in helping to maintain sustained engraftment possibly by eliminating host cells that can cause graft failure. Optimal application of in vitro manipulation of donor marrow as a method for preventing graft-versus-host disease will require more effective immunosuppression of the recipient in order to assure sustained engraftment and function of donor stem cells.     

Clinical trial depleting T lymphocytes from donor marrow for matched and mismatched allogeneic bone marrow transplants

Nine patients received T-lymphocyte-depleted histocompatible bone marrow and 28 patients received T-lymphocyte-depleted histoincompatible bone marrow. Eight of nine patients receiving matched bone marrow quickly engrafted without severe graft-versus-host disease (GvHD). None of the eight patients received anti-GvHD prophylaxis medications. Two of these eight patients are currently alive. Nonengraftment and severe GvHD were problems seen in some of the patients given the histoincompatible bone marrow. Additional cytarabine pretransplant permitted engraftment in those patients undergoing histoincompatible transplants for treatment of malignancy, and prednisone and cyclosporine posttransplant reduced the incidence of acute GvHD in those given T-lymphocyte-depleted grafts. Seven of these 28 patients are currently alive. T-lymphocyte-depleted marrow can reduce the occurrence or prevent severe acute GvHD, especially when combined with additional prednisone and cyclosporine; however, the impact on relapse patterns and survival remains to be determined. The occurrence of nonengraftment and treatment-related lymphomas are formidable problems to overcome.     

Bone marrow transplantation for severe aplastic anemia: influence of conditioning and graft-versus-host disease prophylaxis regimens on outcome.

Data for 595 patients with severe aplastic anemia receiving HLA-identical sibling bone marrow transplants were analyzed to determine the effect of pretransplant conditioning and graft-versus-host disease (GVHD) prophylaxis on outcome. Transplants were performed between 1980 and 1987 and reported to the International Bone Marrow Transplant Registry. Three conditioning regimens (cyclophosphamide alone, cyclophosphamide plus limited field radiation, and cyclophosphamide plus total body radiation) were studied; none was associated with superior long-term survival. Three GVHD prophylaxis regimens (methotrexate, cyclosporine, and methotrexate plus cyclosporine) were studied. Recipients of cyclosporine with or without methotrexate had a significantly higher probability of 5-year survival (69%, 95% confidence interval 63% to 74%) than patients receiving methotrexate only (56%, 49% to 62%, P less than .003). Higher survival with cyclosporine resulted from decreased risks of interstitial pneumonia (P less than .0002) and chronic GVHD (P less than .005). Additional risk factors adversely associated with survival included infection pretransplant (P less than .004), use of parous or transfused female donors (P less than .005), older patient age (P less than .005), and 20 or more pretransplant transfusions (P less than .006). These data may prove useful in planning randomized clinical trials and in identifying patients at high-risk of treatment failure.     

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). Am. J. Hematol. 88:874–882, 2013. © 2013 Wiley Periodicals, Inc.     

Graft failure after T-cell-depleted human leukocyte antigen identical marrow transplants for leukemia: I. Analysis of risk factors and results of secondary transplants

Risk factors for graft failure were analyzed in 122 recipients of an allogeneic T-cell-depleted human leukocyte antigen (HLA)-identical sibling marrow transplant as treatment for leukemia. In each case pretransplant immunosuppression included 1,375 to 1,500 cGy hyperfractionated total body irradiation and cyclophosphamide (60 mg/kg/d x 2). No patient received immunosuppression prosttransplant for graft-versus-host disease (GVHD) prophylaxis. Nineteen patients in this group experienced graft failure. The major factors associated with graft failure were transplants from male donors and the age of the patient (or donor). Among male recipients of male donor-derived grafts a low dose per kilogram of nucleated cells, progenitor cells (colony forming unit-GM) and T cells was also associated with graft failure. Additional irradiation to 1,500 cGy, high dose corticosteroids posttransplant, and additional peripheral blood donor T cells did not decrease the incidence of graft failure. In addition, type of leukemia, time from diagnosis to transplant, an intact spleen, or the presence of antidonor leukocyte antibodies did not correlate with graft failure. To ensure engraftment of secondary transplants, further immunosuppression was necessary but was poorly tolerated. However, engraftment and survival could be achieved with an immunosuppressive regimen in which antithymocyte globulin and high dose methylprednisolone were administered both before and after infusions of secondary partially T- cell-depleted marrow grafts.     

Engraftment and survival after unrelated-donor bone marrow transplantation: a report from the national marrow donor program

We analyzed engraftment of unrelated-donor (URD) bone marrow in 5246 patients who received transplants facilitated by the National Marrow Donor Program between August 1991 and June 1999. Among patients surviving at least 28 days, 4% had primary graft failure (failure to achieve an absolute neutrophil count > 5 x 10(8)/L before death or second stem-cell infusion). Multivariate logistic regression analysis showed that engraftment was associated with marrow matched at HLA-A, HLA-B, and DRB1; higher cell dose; younger recipient; male recipient; and recipient from a non-African American ethnic group. More rapid myeloid engraftment was associated with marrow serologically matched at HLA-A and HLA-B, DRB1 match, higher cell dose (in non-T-cell-depleted cases), younger recipient, recipient seronegativity for cytomegalovirus (CMV), male donor, no methotrexate for graft-versus-host disease prophylaxis, and transplantation done in more recent years. A platelet count higher than 50 x 10(9)/L was achieved by 47% of patients by day 100. Conditional on survival to day 100, survival at 3 years was 61% in those with platelet engraftment at day 30, 58% in those with engraftment between day 30 and day 100, and 33% in those without engraftment at day 100 (P <.0001). Factors favoring platelet engraftment were higher cell dose, DRB1 allele match, recipient seronegativity for CMV, HLA-A and HLA-B serologically matched donor, and male donor. Secondary graft failure occurred in 10% of patients achieving initial engraftment, and 18% of those patients are alive. These data demonstrate that quality of engraftment is an important predictor of survival after URD bone marrow transplantation.     

Bone marrow transplantation for Fanconi anemia

Fanconi anemia is a genetic disorder associated with diverse congenital abnormalities, progressive bone marrow failure, and increased risk of leukemia and other cancers. Affected persons often die before 30 years of age. Bone marrow transplantation is an effective treatment, but there are few data regarding factors associated with transplant outcome. We analyzed outcomes of HLA-identical sibling (N = 151) or alternative related or unrelated donor (N = 48) bone marrow transplants for Fanconi anemia performed between 1978 and 1994 and reported to the International Bone Marrow Transplant Registry. Fanconi anemia was documented by cytogenetic studies in all cases. Patient, disease, and treatment factors associated with survival were determined using Cox proportional hazards regression. Two-year probabilities (95% confidence interval) of survival were 66% (58% to 73%) after HLA-identical siblings transplants and 29% (18% to 43%) after alternative donor transplants. Younger patient age (P .0001), higher pretransplant platelet counts (P = .04), use of antithymocyte globulin (P = .005), and use of low-dose (15 to 25 mg/kg) cyclophosphamide plus limited field irradiation (P = .009) for pretransplant conditioning and cyclosporine for graft-versus-host disease prophylaxis (P = .002) were associated with increased survival. Bone marrow transplants are effective therapy for Fanconi anemia. The adverse impact of increasing age and lower pretransplant platelet count on transplant outcome favors earlier intervention, especially when there is an HLA-identical sibling donor.     

Low dose T-cell lymphocyte infusion combined with marrow T-cell depletion as prophylaxis of acute graft vs host disease for HLA identical sibling bone marrow transplantation

T-cell depletion (TCD) of the bone marrow graft remains the most effective method to prevent severe graft versus host disease after allogeneic bone marrow transplantation. Early studies of HLA-identical sibling transplants showed that although T-cell depletion decreased GVHD, T-cell depleted transplants had higher risks of graft failure and leukemia relapse, leukemia free survival (LFS) was not improved compared to non-T-cell depleted transplants. In order to avoid graft failure and increased risk of relapse associated with this approach, we initiated a pilot study of T-cell depletion of the marrow graft combined with reinfusion of a fixed quantity of CD₂+ peripheral blood T-cells. Depletion technique consisted in negative purging using CD₂ and CD₇ monoclonal antibodies (MoAbs) followed by rabbit complement cytolysis. This approach was associated with an intensified conditioning regimen using total body irradiation, high-dose cytosine arabinoside and melphalan (TAM) for all but one patient. Twenty-one patients were included with a mean age of 40 years. Only one acute severe Graft Versus Host Disease (GVHD) was observed and all patients engrafted. At 63 months, probability of survival is 42.86% with a relapse risk of 19.89%, two patients died from B-cell lymphoproliferative disease, seven other died from the procedure partially because of the use of the TAM as pretransplant regimen. This approach is being pursued by a gene therapy trial using herpes-simplex − 1 thymidine kinase gene expressing peripheral donor T-cells.     

Current status of allogeneic bone marrow transplantation in acquired aplastic anemia

Bone marrow transplantation is an effective therapy for aplastic anemia. Infusion of allogeneic hematopoietic stem cells after high-dose immune suppression restores normal hematopoiesis in most patients and long-term follow-up has confirmed the durability of donor hematopoiesis. However, success of this approach is limited by transplant-related complications, such as graft failure, graft-versus-host disease, and various organ toxicities. Long-term survival rates range from less than 40% to more than 90% in reported series. These rates have improved over the past 20 years due to significant reductions in graft-versus-host disease, interstitial pneumonitis, and early transplant-related mortality. Most long-term survivors have excellent performance status. Late effects such as cataracts, thyroid disorders, joint problems, and therapy-related cancers are observed, especially in patients who received radiation for pretransplant conditioning. Results are best in young patients transplanted with bone marrow from a human leukocyte antigen (HLA)-identical sibling; early transplantation is appropriate in this group. For older patients or those without an HLA-identical related donor, transplants are better reserved for those who fail to respond to immunosuppressive therapy.     

Bone marrow transplantation from related donors other than HLA-identical siblings: effect of T cell depletion

Results of 470 bone marrow transplants from related donors other than genotypically HLA-identical siblings (alternative related donors) were analysed to identify factors associated with transplant outcome and to determine whether T cell depletion improved results. As compared to 3648 transplant from HLA-identical siblings, alternative related donor transplants were associated with increased graft failure, increased acute graft-versus-host disease (GVHD), and lower disease-free survival. The likelihood of adverse outcome correlated with increasing donor-recipient HLA-disparity. In multivariate analysis of alternative related donor transplants, donor age greater than or equal to 30 years, (relative risk [RR] 1.7, p less than 0.006), intermediate and advanced leukemia (RR 1.5 and 1.6, p less than 0.01 and p less than 0.003), infection pretransplant (RR 1.7, p less than 0.005) and 2- and 3-locus donor-recipient HLA-disparity (RR 1.3, p less than 0.04) were associated with increased risks of treatment failure. The 2-year probability of leukemia-free survival after alternative related donor transplants (n = 43) with none of these adverse prognostic features was 44% (95% confidence interval 28-59%) compared to 56% (95% confidence interval 52-59%) for similar patients receiving HLA-identical sibling transplants (n = 868, univariate p less than 0.03). T cell depletion increased graft failure and decreased acute GVHD after alternative related donor transplants but did not improve leukemia-free survival.     

Bone marrow transplants from mismatched related and unrelated donors for severe aplastic anemia

For patients with acquired severe aplastic anemia without a matched sibling donor and not responding to immunosuppressive treatment, bone marrow transplantation from a suitable alternative donor is often attempted. We examined risks of graft failure, graft-versus-host disease and overall survival after 318 alternative donor transplants between 1988 and 1998. Sixty-six patients received allografts from 1-antigen and 20 from >1-antigen mismatched related donors; 181 from matched and 51 from mismatched unrelated donors. Most patients were young, had had multiple red blood cell transfusions and poor performance score at transplantation. We did not observe differences in risks of graft failure and overall mortality by donor type. The probabilities of graft failure at 100 days after 1-antigen mismatched related donor, >1-antigen mismatched related donor, matched unrelated donor and mismatched unrelated donor transplants were 21, 25, 15 and 18%, respectively. Corresponding probabilities of overall survival at 5 years were 49, 30, 39 and 36%, respectively. Although alternative donor transplantation results in long-term survival, mortality rates are high. Poor performance score and older age adversely affect outcomes after transplantation. Therefore, early referral for transplantation should be encouraged for patients who fail immunosuppressive therapy and have a suitable alternative donor.     

Marrow transplantation for thalassemia

Ten patients with homozygous beta thalassemia, aged from 1 year 7 months to 13 years, underwent bone marrow transplantation from siblings or parents. The first case received 12 mg/kg busulfan, 120 mg/kg cyclophosphamide, and 300 cGy total body irradiation before transplantation; he survives, with a graft, more than 680 days after transplantation. The other nine patients received 16 mg/kg busulfan and 200 mg/kg cyclophosphamide. Two died of transplantation-related complications on days 30 and 55. Seven survive 170 to 580 days after transplantation. Three of the seven surviving patients have durable engraftment (greater than 230 to greater than 550 days) while four patients have autologous hematopoietic recovery. Four of five patients who had less than 50 prior transfusions achieved engraftment. Only one of five patients who had more than 50 prior transfusions achieved engraftment (P less than 0.05). The six-month actuarial survival was 80%; six-month actuarial disease-free survival was 40%. These data demonstrate that bone marrow transplantation may cure thalassemia, but engraftment may be jeopardized among patients who have been heavily transfused or have received marrow from a donor who is not HLA-identical.     

Bone marrow transplantation in patients with leukaemia previously transfused with blood products from family members

Transfusions are withheld, whenever possible, from patients with aplastic anaemia who are potential bone marrow transplant recipients because of the increased risk of graft failure associated with transfusions prior to transplantation. Family members are specifically excluded as blood product donors to reduce the likelihood of sensitizing the recipient to antigens shared by the blood and bone marrow donor. This policy of not using family members, particularly the HLA-matched bone marrow donor, to provide blood products prior to transplantation has been extended to leukaemia as well. To evaluate this policy we reviewed the outcome of bone marrow transplantation in 18 patients with leukaemia transfused prior to transplantation with platelets and/or leucocytes from related family members. In 15 cases in which the outcome could be evaluated, engraftment was rapid and graft failure did not occur. Transfusion of blood products from related family members to patients with leukaemia prior to transplantation does not appear, therefore, to increase the risk of graft rejection.     

Bone marrow transplantation for an infant with neutrophil dysfunction.

A child with severe neutrophil dysfunction and intractable infections received bone marrow transplants from histocompatible siblings. After a first transplant preceded by cyclophosphamide (CY), antithymocyte serum (ATS) and procarbazine (PCB) preconditioning, there was no evidence for engraftment and autologous marrow function rapidly returned. Cell mediated lysis showed no evidence of patient sensitization against the marrow donor suggesting that graft rejection did not cause the transplant failure. A second transplant was performed utilizing another matched sibling donor. Total body irradiation was added to CY, ATS, and PCB for preconditioning after in vitro studies of the colony forming capacity (CFUc) of the patient's marrow cells showed normal sensitivity to radiation. Full engraftment ensued with correction of granulocyte function abnormalities. The patient eventually died of intractable pulmonary disease. Our experience with this child suggests that cyclophosphamide alone may be insufficient preparation for marrow transplantation in some patients with non-neoplastic hematologic disorders. Experimental and clinical data supporting this contention are reviewed.     

Selective depletion of CD8+ T lymphocytes for prevention of graft-versus-host disease after allogeneic bone marrow transplantation

The effects of selectively depleting CD8+ cells from donor bone marrow were assessed in 36 patients receiving transplantation from an HLA-identical sibling as treatment for leukemia. Donor bone marrow underwent ex vivo treatment using anti-Leu-2 monoclonal antibody and complement. Patients received cyclosporine post-transplant for 6 months. Thirty-three patients had initial engraftment. Three failed to have hematologic recovery, and one patient with initial engraftment had late graft failure. The actuarial incidence of grade greater than or equal to 2 acute graft-versus-host disease was 28% +/- 18% and was usually confined to the skin. Of 33 patients with engraftment, 32 were complete chimeras and one had mixed chimerism. The tempo of hematologic and immunologic recovery was comparable with that reported with transplantation of unmodified bone marrow, although CD4+ and CD8+ T cells recovered at comparable rates. The actuarial rate of leukemia relapse was 11% +/- 10%, occurring in three patients with acute leukemia but in none of 13 patients transplanted for chronic myelogenous leukemia. Actuarial survival was 57% +/- 17% at 2 years. These data indicate that after transplantation of marrow depleted of CD8+ cells, engraftment with prompt hematologic and immunologic recovery generally occurs, with a relatively low rate of acute graft-versus-host disease. Graft failure remains a problem despite retention of CD4+ cells within the donor marrow. The lack of leukemia relapse in patients with chronic myelogenous leukemia suggests retention of a graft-versus-leukemia effect, at least for this malignancy.     

Donor-type red blood cell transfusion to deplete isoagglutinins prior to allogeneic stem cell transplantation from ABO major incompatible bone marrow donors

ABO incompatibility affects approximately 40% of allogeneic stem cell transplants in Caucasian patient populations. Because bone marrow (BM), the preferred graft from paediatric sibling donors and for non-malignant diseases, has a red blood cell (RBC) content similar to blood, anti-donor isoagglutinins must either be depleted from the recipient or RBCs removed from the graft. To achieve tolerability of unmanipulated BM grafts, we used controlled infusions of donor ABO-type RBC units to deplete isoagglutinins before the transplant. This retrospective study evaluates the outcomes of 52 ABO major incompatible BM transplants performed at our centre between 2007 and 2019. The use of donor-type RBC transfusions was well tolerated. They effectively reduced isoagglutinins levels, typically achieving target titres after one (60%) or two (29%) transfusions. The approach allowed for successful and uneventful infusions of unmanipulated BM which provided timely engraftment. The transplant outcomes were not inferior to those of a matched-pair control group of patients with ABO-identical donors.     

Cord blood stem cell transplantation for haemoglobinopathies

Despite improvements in supportive care, patients with beta-thalassaemia major or sickle cell disease (SCD) may benefit from haematopoietic stem cell transplantation at some point during their lives. Human leucocyte antigen (HLA)-matched sibling bone marrow donors are not always available and alternative sources of stem cells have been sought, including related and unrelated donor cord blood transplants (CBT). The outcome of CBT from related donors for the treatment of both thalassaemia major and SCD is now approaching that for bone marrow transplantation, with around 90% of patients surviving disease-free. The main complication is graft rejection, which may be reduced by increasing pretransplant immune suppression. Transplant-related mortality following HLA-identical matched related donor CBT is extremely low but is significant in the small series of unrelated and/or mis-matched donor CBT. The principal limitation to extending the use of CB stem cells for the cure of haemoglobinopathies is the need to better understand the mechanisms of action and optimal conditioning regimens used to secure long-term engraftment while minimizing morbidity and mortality. Further biological studies and clinical trials are needed to address this aim.     

Cyclophosphamide combined with antithymocyte globulin in preparation for allogeneic marrow transplants in patients with aplastic anemia

Graft rejection has been a problem after marrow grafts for patients with aplastic anemia who were conditioned with cyclophosphamide (CY). Rejection lessened when patients were given the marrow donor's peripheral blood buffy-coat cells in addition to the marrow, but this result was achieved at the price of more chronic graft-versus-host disease (GVHD). Results with second transplants suggested that CY alternating with antithymocyte globulin (ATG) was more immunosuppressive than CY alone. Therefore, the current study explored CY and ATG without buffy-coat cell transfusions in 39 patients with aplastic anemia given marrow transplants from HLA-identical family members (siblings in 38 cases, father in 1 case). We hoped both to minimize the risks of graft rejection and of chronic GVHD and to improve survival. Patients were 2 to 52 years of age (median, 24.5); 87% had received previous transfusions, and 41% had therapy with immunosuppressive agents before transplant. They were administered four daily doses of CY (total, 200 mg/kg) alternating with three doses of ATG (total, 90 mg/kg) followed by an HLA-identical marrow graft. Methotrexate and cyclosporine were administered to prevent GVHD. Two patients rejected their grafts (5%), and both were successfully retransplanted. Acute (grade 2 or 3) GVHD occurred in 15% and chronic GVHD in 34% of patients. The actuarial survival rate at 3 years was 92%, which compares favorably to the 72% survival rate in 39 historical patients who were matched with current patients for age and risk factors for rejection and GVHD. CY/ATG is a well-tolerated and effective conditioning program for marrow grafting in aplastic anemia that, when combined with GVHD prevention by methotrexate/cyclosporine, results in excellent survival.     

Aplastic anemia treated by allogeneic bone marrow transplantation: a report on 49 new cases from Seattle.

Forty-nine patients with severe aplastic anemia, 33 due to unknown cause, 11 drug or chemical related, 2 associated with hepatitis, 1 with paroxysmal nocturnal hemoglobinuria, and 2 possibly associated with Fanconi syndrome did not show recovery after 0.5-96 (median 2) mo of conventional therapy. Twenty-two were infected and 21 were refractory to random platelet transfusions at the time of admission. All were given marrow grafts from HLA-identical siblings. Forty-five were conditioned for grafting by cyclophosphamide (CY), 50 mg/kg on each of 4 successive days, and four by 1000 rad total body irradiation. All were given intermittent methotrexate therapy within the first 100 days of grafting to modify graft-versus-host disease (GVHD). Three patients died from infection too early to evaluate (days 1-8). Forty-six had marrow engraftment. Of these, 20 are surviving with good peripheral blood counts between 186 and 999 days, and 18 have returned to normal activities. Chronic GCHD is a problem in five. Twelve patients died of infection following rejection of the marrow graft. Twelve patients died with bacterial or fungal infections or interstitial pneumonia and active GVHD or soon following resolution of GVHD. Two patients died with marrow engraftment and no GVHD, one with an interstitial, and the other with a bacterial pneumonia. Thirty-six patients who had received random donor blood transfusions were randomly assigned to receive either CY or procarbazine-antithymocyte globulin-CY as conditioning regimens to test whether the incidence of graft rejection could be decreased. There was no difference in the incidence of graft rejection between the two regimens. In 13 patients with rejection, second transplants were attempted either with the original marrow donor (9 patients) or another HLA-identical sibling (4 patients). Three of these transplants were not evaluable, seven were unsuccessful and three were successful with only one of the three surviving for more than 468 days. In conclusion, the long-term survival of 41% of the patients in the present study is similar to that achieved in our first 24 patients, and confirms the importance of marrow transplantation for the treatment of severe aplastic anemia. Marrow graft rejection, GVHD, and infections continue to be the major causes of failure.     

Allogeneic transplantation using peripheral blood stem cells

Over the past 9 years there has been a remarkable increase in the use of peripheral blood stem cells (PBSC) for allogeneic transplantation, primarily for matched sibling transplants but also increasingly for unrelated donor transplantation. In 1999 over 50% of all sibling transplants and over 25% of unrelated donor transplants reported to the European Group for Blood and Marrow Transplantation (EBMT) used PBSC. The major reason for this increasing use of PBSC relates to the rapid haemopoietic recovery seen which mirrors the advantages of using PBSC in autologous transplantation. This improvement in engraftment is a consequence of the larger number of stem cells that can be collected from G-CSF-mobilized peripheral blood compared to bone marrow. Evidence from randomized trials now shows a survival advantage for the use of PBSC in patients with advanced leukaemia. The reason for this improved survival appears primarily to relate to a reduced risk of transplant-related mortality and, possibly, a reduced risk of relapse, However, these randomized studies have also confirmed that there is an increased risk of chronic graft-versus-host disease associated with PBSC transplantation and further follow-up is required to determine the long-term impact on outcome.