Low-dose total body irradiation, fludarabine, and antithymocyte globulin conditioning for nonmyeloablative allogeneic transplantation.

Nonmyeloablative allogeneic peripheral blood progenitor cell transplantation with low-dose total body irradiation (TBI; 200 cGy) plus fludarabine followed by cyclosporine and mycophenolate mofetil results in modest graft rejection rates. Acute and chronic graft-versus-host diseases (GVHD) are also seen and may not differ substantially from those that occur after fully ablative transplantation. Adding antithymocyte globulin (ATG) to pretransplant conditioning produces substantial immunosuppression. Because of its persistence in the circulation, ATG can achieve in vivo T-cell depletion. Twenty-five patients who were not eligible for conventional fully ablative allogeneic stem cell transplantation by virtue of age or comorbidities underwent nonmyeloablative allogeneic transplantation with ATG 15 mg/kg/d days -4 to -1, TBI 200 cGy on a single fraction on day -5, and fludarabine 30 mg/m(2)/d on days -4 to -2. Oral mycophenolate mofetil 15 mg/kg every 12 hours and cyclosporine 6 mg/kg every 12 hours were started on day -5. Grafts were unmanipulated peripheral blood progenitor cells mobilized with filgrastim 10 microg/kg/d and collected on day 5. The median age of the recipients was 57 years (range, 30-67 years); diagnoses were non-Hodgkin lymphoma (n = 11), acute myeloid leukemia (n = 6), multiple myeloma (n = 3), acute lymphoblastic leukemia (n = 2), severe aplastic anemia (n = 1), paroxysmal nocturnal hemoglobinuria (n = 1), and myelodysplastic syndrome (n = 1). The median CD34(+) and CD3(+) contents of the grafts were 7.6 x 10(6)/kg and 1.6 x 10(8)/kg, respectively. Five patients received voluntary unrelated donor grafts. Three patients, 2 with voluntary unrelated donor grafts and 1 with a sib donor, received a 1 antigen-mismatched graft. The rest were fully matched. Twenty-two of 25 patients were evaluable for chimerism. Sixteen had >/=95% donor chimerism. Four patients displayed 80% to 90% donor chimerism, 1 displayed 78%, and 1 displayed 64%. Eleven patients relapsed with their original disease. One patient rejected the graft at 180 days. The median hospital stay was 27 days. Complications included GVHD in 6 patients (3 patients had grade I or II GVHD of skin and liver, and 3 patients had grade III or IV GVHD of liver and gut). Two of the patients with GVHD had mismatched grafts. Transplant-related toxicity was seen in 4 patients and infection in 5 patients. The median length of follow-up was 162 days (range, 17-854 days). Complete remissions were seen in 10 patients. Four patients remained in complete response (CR) at 280 to 595 days. One patient relapsed with non-Hodgkin lymphoma after a CR of 728 days. Of the 25 patients, 16 died (6 of relapsed disease, 4 of GVHD, 3 of infection, and 3 of transplant-related toxicity) and 9 are alive (6 with CR-2 of them after donor leukocyte infusion-and 3 with relapsed disease). The addition of ATG to low-dose TBI and fludarabine nonmyeloablative conditioning was well tolerated and resulted in >80% donor engraftment in this small cohort. As in other series of truly nonmyeloablative transplantation, a high rate of relapse was observed. Donor engraftment may be facilitated by the addition of ATG to low-dose TBI and fludarabine conditioning.     

Unrelated donor hematopoietic stem cell transplantation for patients with hematologic malignancies using a nonmyeloablative conditioning regimen of fludarabine, low-dose total body irradiation, and rabbit antithymocyte globulin.

Hematopoietic stem cell chimerism can be established after low-dose conditioning regimens, although the risk of donor cell rejection increases for unrelated donor transplantations. We added pretransplantation rabbit antithymocyte globulin (6 mg/kg) to an established conditioning regimen of fludarabine (90 mg/m2) and single-fraction total body irradiation (200 cGy) followed by postgrafting immunosuppression with cyclosporine A and mycophenolate mofetil for 22 patients with hematologic malignancies. One patient rejected the graft and successfully underwent transplantation with cells from a second donor by using the same conditioning regimen. The actuarial probability of developing acute graft-versus-host disease grade II to IV before day 100 was 40%, although 9 of 14 patients who survived beyond 100 days developed chronic graft-versus-host disease. These data support a hypothesis that the addition of antithymocyte globulin decreases the risk of graft-versus-host and host-versus-graft reactions when combined with a nonmyeloablative conditioning regimen of fludarabine and total body irradiation.     

Posttransplantation cyclophosphamide facilitates engraftment of major histocompatibility complex-identical allogeneic marrow in mice conditioned with low-dose total body irradiation.

Cyclophosphamide (Cy) has been studied extensively for its immunosuppressive properties and is frequently combined with total body irradiation (TBI) as conditioning prior to HLA-identical allogeneic blood or marrow transplantation (alloBMT) in humans. Because Cy is most effective at suppressing host-versus-graft reactions when the drug is given after the transplantation (Mayumi H et al. Transplant Proc. 1986;18:363-369), we investigated whether posttransplantation Cy could prevent rejection of allogeneic marrow in mice conditioned with low-dose TBI. In a mouse model, posttransplantation Cy reduced the dose of TBI required from 500 cGy to < or = 200 cGy for the engraftment of 10 million major histocompatibility complex (MHC)-identical marrow cells in 100% of recipients. In animals conditioned with low-dose TBI and posttransplantation Cy, donor chimerism was proportional to the dose of TBI, was present in multiple hematopoietic lineages, and was associated with the indefinite survival of donor-strain skin grafts. In contrast, animals conditioned with either TBI alone or posttransplantation Cy alone failed to achieve engraftment after alloBMT and contained antidonor cytotoxic T-cells. Although <5% donor chimerism could be induced without TBI by transplanting > or = 50 million MHC-identical cells and administering posttransplantation Cy, the addition of low-dose TBI reduced the dose of donor cells required for alloengraftment and increased long-term donor chimerism to >50%. These data demonstrate that low-dose TBI and posttransplantation Cy cooperate to prevent graft rejection following the transplantation of standard doses of MHC-identical marrow cells.     

Impact of postgrafting immunosuppressive regimens on nonrelapse mortality and survival after nonmyeloablative allogeneic hematopoietic stem cell transplant using the fludarabine and low-dose total-body irradiation 200-cGy.

The development of nonmyeloablative (NM) hematopoietic cell transplantation (HCT) has extended the potential curative treatment option of allografting to patients in whom it was previously contraindicated because of advanced age or comorbidity. Acute and chronic graft versus host disease (GVHD) and its consequent nonrelapse mortality (NRM), remains the major limitation of NM HCT. In this report, we analyzed the outcome of 67 patients (median age, 45 years) with hematologic diseases receiving NM conditioning with fludarabine 90 mg/m(2) and total body irradiation (TBI) 200-cGy, followed by filgrastim-mobilized peripheral blood stem cell transplant from HLA identical (n = 61), 5/6 antigen-matched related (n = 1), 6/6 antigen-matched unrelated (n = 3), and 5/6 antigen-matched unrelated (n = 2) donors. The first cohort of 21 patients were given cyclosporine (CSP) and mycophenolate mofetil (MMF) as postgrafting immunosuppression, whereas the subsequent cohort was given additional methotrexate (MTX) and extended duration of CSP/MMF prophylaxis in an attempt to reduce graft-versus-host disease (GVHD). Sixty-four (95%) patients engrafted and 3 (5%) had secondary graft failure. Myelosuppression was moderate with neutrophil counts not declining below 500/microL in approximately 25% of patients, and with more than half of the patients not requiring any blood or platelet transfusion. The 2-year cumulative interval (CI) of grade II-IV, grade III-IV acute GVHD and chronic GVHD were 49%, 30%, and 34%, respectively. The 2-year probability of NRM, overall (OS), and progression-free (PFS) survival were 27%, 43%, and 28%, respectively. GVHD-related death accounted for 85% of NRM. Compared with patients receiving CSP/MMF, patients receiving extended duration of CSP/MMF with additional MTX in postgrafting immunosuppression had a significantly lower risk of grade III-IV acute GVHD (CI 20% versus 52%; P = .009) and NRM (CI at 2 years: 11% versus 62%; P < .001), without any significant adverse impact on the risk of relapse (CI at 2 years: 59% versus 33%; P = .174) Subgroup analysis of a cohort of patients given MTX/CSP/MMF showed that patients with "standard risk" diseases (n = 21) had a 3-year OS and PFS of 85% and 65%, respectively. This compares favorably to the 41% (P = .02) and 23% (P = .03) OS and PFS, respectively, in patients with "high-risk" diseases (n = 25). In conclusion, the addition of MTX onto the current postgrafting immunosuppression regimen with extended CSP/MMF prophylaxis duration provides more effective protection against severe GVHD, and is associated with more favorable outcome in patients receiving NM fludarabine/TBI conditioning than in patients receiving fludarabine/TBI conditioning with CSP and MMF without MTX.     

Unrelated donor granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell transplantation after nonmyeloablative conditioning: the effect of postgrafting mycophenolate mofetil dosing.

We previously reported results in 71 patients with advanced hematologic malignancies given HLA-matched unrelated granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell (G-PBMC) grafts after fludarabine 90 mg/m(2), 2 Gy of total body irradiation, and postgrafting mycophenolate mofetil (MMF) 15 mg/kg twice daily and cyclosporine 6.25 mg/kg twice daily orally. Graft rejection was 15%; the cumulative probability of acute graft-versus-host disease (GVHD) was 52%. According to MMF pharmacokinetic studies, which showed a short half-life of its active metabolite, mycophenolic acid, we increased MMF dosing from 15 mg/kg twice daily to 15 mg/kg 3 times daily to increase immunosuppression and reduce the incidence of both graft rejection and acute GVHD. Among 103 patients so treated, graft rejection occurred in 5%, whereas acute GVHD remained at 53%. Outcomes were compared with results of previous G-PBMC recipients given MMF twice daily. Infection rates were slightly higher with MMF 3 times daily than with MMF twice daily. Nevertheless, 2-year nonrelapse mortality and overall and progression-free survivals were similar for MMF 3-times-daily and twice-daily patients (19%, 58%, and 49% versus 20%, 48%, and 37%, respectively). Nonmyeloablative conditioning with postgrafting cyclosporine and MMF given 3 times daily allowed 95% durable engraftment of unrelated donor G-PBMC grafts.     

肾移植后吗替麦考酚酯联合低剂量他克莫司加皮质激素的应用

背景：足量吗替麦考酚酯联合低剂量他克莫司和皮质激素可能是目前针对肾移植受者的理想治疗方案,该方案因其具有低肾毒性以及较少的不良反应和较强的免疫抑制作用已在临床上开始逐渐普及。 目的：以吗替麦考酚酯联合标准剂量他克莫司加皮质激素为对照,评估吗替麦考酚酯联合低剂量他克莫司加皮质激素在肾移植患者中的疗效和安全性。 方法：210例首次接受单一器官同种异体移植的肾移植成人受者被随机分配到他克莫司标准剂量组(n=104)和他克莫司低剂量组(n=106),并接受12个月的治疗。主要疗效指标包括肾移植后第12个月慢性移植物损伤指数(CADI)以及肾小球滤过率;次要疗效指标主要包括急性排斥反应发生率、治疗失败率以及患者和移植肾的存活率等;同时对新发移植后糖尿病,新发高血压,新发高血脂等安全性指标进行评价。 结果与结论：两组绝大多数患者使用了足量的吗替麦考酚酯(1.5 g/d及以上)。在他克莫司剂量方面,他克莫司标准剂量组大多数受试者的实际血药浓度水平偏低,与低剂量组的实际血药浓度水平类似,由此反映了吗替麦考酚酯联合低剂量他克莫司和皮质激素方案已广泛为目前临床医师接受和使用。因此,两组也表现出类似的疗效和安全性：他克莫司标准剂量组和低剂量组肾移植后12个月肾脏病理改变的平均CADI评分分别为1.82分和2.13分(P=0.081 3),平均肾小球滤过率分别为77.08 mL/min和       80.12 mL/min(P=0.794 9),急性排斥反应发生率分别为2.6%和5.2%(P=0.681 2),患者和移植肾存活率分别高达100%和99.1%(P=1.000 0)。在安全性方面,他克莫司标准剂量组和低剂量组新发移植后糖尿病的比例分别为2.9%和1.9%,新发高血脂的比例分别为2.9%和3.8%。结果显示在吗替麦考酚酯联合他克莫司和皮质激素的肾移植免疫抑制治疗方案中,足量吗替麦考酚酯的使用,可以减少他克莫司的剂量,在保持较强的免疫抑制作用即成功地降低急性排斥反应发生率的同时,显著减少他克莫司所致的肾毒性、高血脂和新发糖尿病等不良反应,较好地达到了疗效和毒性间的平衡。     

Extended mycophenolate mofetil and shortened cyclosporine failed to reduce graft-versus-host disease after unrelated hematopoietic cell transplantation with nonmyeloablative conditioning.

We previously reported data from 103 patients with hematologic malignancies (median age 54 years) who received peripheral blood stem cell (PBSC) grafts from HLA-matched unrelated donors after nonmyeloablative conditioning and were given postgrafting immunosuppression consisting of mycophenolate mofetil (MMF; administered from day 0 until day +40 with taper through day +96) and cyclosporine (CSP; given from day -3 to day +100, with taper through day 180) (historical patients). The incidences of grade II-IV acute and extensive chronic graft-versus-host disease (aGVHD, cGVHD) were 52% and 49%, respectively, and the 1-year probabilities of relapse, nonrelapse mortality (NRM), and progression-free survival (PFS) were 26%, 18%, and 56%, respectively. Here, we treated 71 patients with hematologic malignancies (median age 56 years) with unrelated PBSC grafts and investigated whether postgrafting immunosuppression with an extended course of MMF, given at full dosing until day +150 and then tapered through day +180, and a shortened course of CSP, through day +80, would promote tolerance induction and reduce the incidence of GVHD (current patients). We observed 77% grade II-IV aGVHD and 45% extensive cGVHD (P=.03, and P=.43, respectively, in current compared to historical patients). The 1-year probabilities of relapse, NRM, and PFS were 23%, 29%, and 47%, respectively (P=.89, P=.02, and P=.08 compared to the historical patients). We conclude that postgrafting immunosuppression with extended MMF and shortened CSP failed to decrease the incidence of GVHD among unrelated PBSC recipients given nonmyeloablative conditioning.     

The importance of age, fludarabine, and total body irradiation in the incidence and severity of chronic renal failure after allogeneic hematopoietic cell transplantation.

Nonmalignant late effects, including chronic renal failure (CRF), impair the quality of life of long-term survivors after allogeneic hematopoietic cell transplantation. One of the major risk factors is the use of total body irradiation (TBI) in the preparative regimen; TBI is currently fractionated in an attempt to reduce toxicity. We analyzed 241 patients who had TBI-based preparative regimens for allogeneic hematopoietic cell transplantation. TBI was delivered as a single fraction of 7.5 Gy (7.5S group), 12 Gy in 6 fractions (12F group), or 14.4 Gy in 8 fractions (14.4F group). The cumulative incidence of CRF at 2 years was 12%. Statistical analysis revealed that older age (P < .001) and fludarabine administration (P = .016) had a significant effect on the incidence of CRF. Furthermore, single-fraction TBI was also significantly associated with CRF severity, because 7 (6.3%) of 111 patients in the 7.5S group developed severe CRF, as opposed to 1 (0.8%) of 130 patients in the 12F and 14.4F groups combined (P = .044). However, these conclusions should be regarded as preliminary in view of the retrospective and nonrandomized nature of this study.     

Effect of c-mpl ligands after total body irradiation (TBI) with and without allogeneic hematopoietic stem cell transplantation: low-dose TBI does not prevent sensitization.

This study investigates the potential role of the recombinant c-mpl ligands (recombinant human thrombopoietin [rhTPO] and pegylated recombinant human megakaryocyte growth and development factor [PEG-rhMGDF]) on the recovery of platelet counts after TBI with and without allogeneic hematopoietic stem cell transplantation (HSCT) in an established canine model. Initially, 3 cohorts, each with 2 nonirradiated dogs, received increasing doses of rhTPO (5 microg/kg per day; 10 microg/kg per day; 20 microg/kg per day) for 7 days to determine the optimal dose. The dose of 10 microg/kg per day of rhTPO was selected for subsequent studies. Ten dogs then received either rhTPO or placebo for 28 days after 200 cGy TBI without HSCT. The rhTPO group had fewer days with platelet counts <20,000/microL (9.8 days versus 17.8 days, P < .05) and significantly increased granulocyte counts (n = 5) compared to the controls (n = 5). RhTPO-specific antibodies developed in 2 dogs, which caused a significant but transient decrease of the platelet counts. Retreatment of these sensitized dogs with rhTPO resulted in profound transient decreases in platelet counts. In the next study, 20 dogs received either PEG-rhMGDF or placebo for 21 days after 920 cGy TBI and allogeneic HSCT. The median time to platelet recovery (>20,000/microL) for the PEG-rhMGDF group (n = 10) was 14.0 days compared to 15.5 days for the control group (n = 10; log rank, P = .35). There were no significant differences in the total time to platelet counts <20,000/microL or in the time to recover neutrophil counts >500/microL. The effects of rhTPO on recovery of platelet and granulocyte counts after sublethal TBI were modest, and no effects of PEG-rhMGDF were observed on hematopoietic recovery after high-dose TBI and allogeneic HSCT. The significant effect that rhTPO-specific antibodies had on the platelet counts may limit the clinical role of recombinant c-mpl ligands unless sensitization can be prevented.     

Prediction and prevention of transplant-related mortality from pulmonary causes after total body irradiation and allogeneic stem cell transplantation.

Between July 1997 and August 2004, 146 consecutive patients with hematologic malignancies received a T cell-depleted peripheral blood stem cell transplant from an HLA-identical sibling by using total body irradiation (TBI) and cyclophosphamide conditioning regimens. Eighty-five patients received 13.6 Gy of TBI with no lung shielding, and 61 received lung shielding (total lung dose, 6-12 Gy). Ninety-four patients (65.5%) had standard-risk disease; the remainder had more advanced disease or unfavorable diagnoses. Of the 21 transplant-related deaths, 14 were from pulmonary causes (10 idiopathic pulmonary syndromes and 4 from infection) that occurred at a median of 90 days (range, 23-238 days) after transplantation. Independent risk factors for pulmonary transplant-related mortality (PTRM) were pretransplantation diffusion capacity for carbon monoxide (relative risk, 5.7 for diffusion capacity for carbon monoxide <85%), smoking (relative risk, 5.0), and CD34 cell dose (relative risk, 9.4 for a CD34 dose of <5 x 10(6) cells per kilogram). Patients receiving lung shielding had significantly lower PTRM (3.3% versus 14.1%; P = .02) and better overall survival (70% +/- 6% versus 52% +/- 5%; P = .04), but lung shielding was not a significant independent factor for determining PTRM. These results suggest that pulmonary mortality after TBI-based preparative regimens is predictable and that higher CD34 cell doses can reduce the risk.     

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 (90 units; P = .020).     

Unrelated donor status and high donor age independently affect immunologic recovery after nonmyeloablative conditioning.

The risk of cytomegalovirus (CMV) infection is higher after HLA-matched unrelated donor (URD) than after HLA-matched related donor (MRD) nonmyeloablative hematopoietic cell transplantation (HCT). We therefore investigated factors affecting immune recovery in 94 patients given HCT from MRDs (n = 51) and URDs (n = 43) after 2-Gy total body irradiation with or without fludarabine and postgrafting immunosuppression with mycophenolate mofetil and cyclosporine. CD4 T cells counts remained below normal values during the first year after HCT in both patient groups. This included abnormally low counts each of naive CD4 T cells and memory CD4 T cells. Conversely, CD8 T cell counts reached the 10th percentile of normal 6 months after HCT in MRD and URD recipients. On day 30 after HCT, URD recipients had lower counts of B cells (P = .02), naive CD4 T cells (P = .04), memory CD4 T cells (P = .005), memory CD8 T cells (P = .005), and CMV-specific T helper cells (P = .007) than had MRD recipients. This delay in CMV-specific immune reconstitution translated into increased frequency of CMV antigenemia among URD recipients during the first 100 days after HCT. Older donor age was associated with low counts of naive CD4 T cells on days 180-365 after HCT (P = .003). Further, low numbers of T cells and CD34(+) cells in the graft and development of acute graft-versus-host disease were associated with impaired immune recovery of naive CD4 T cells and B cells. In summary, immunologic recovery was poor the first year after nonmyeloablative conditioning and was delayed among URD recipients in comparison with MRD recipients. Other factors significantly associated with delayed immune recovery were advanced donor age, low numbers of CD34 and T cells in the graft, and development of graft-versus-host disease.     

Relapse after allogeneic bone marrow transplantation for refractory anemia is increased by shielding lungs and liver during total body irradiation.

Patients with the refractory anemia (RA) subtype of myelodysplastic syndrome who undergo allogeneic bone marrow transplantation (BMT) have a low risk of relapse, but they have a high risk of nonrelapse mortality when prepared with conventional preparative regimens. To try to reduce nonrelapse mortality, we treated 14 RA patients with a modified approach to total body irradiation (TBI) followed by cyclophosphamide (CY) and HLA-identical sibling BMT. Median patient age was 44 years (range, 28 to 65 years). Patients received TBI with shielding of the right lobe of the liver and both lungs followed by electron beam boosts to shielded ribs. Total radiation exposure in nonshielded areas was 12 Gy (n = 10), 10 Gy (n = 3), or 6 Gy (n = 1). After TBI, patients received CY at 120 mg/kg over 2 days, followed by transplantation of unmanipulated bone marrow. All patients initially achieved engraftment with donor cells, although 2 patients had subsequent reemergence of host hematopoiesis without evidence of disease relapse. Five patients died of transplantation-related causes between 22 and 1262 days post-BMT. Four patients relapsed between 157 and 1096 days post-BMT. These 14 patients were compared with 46 historical controls with RA who received conventional CY/TBI or busulfan/CY preparative regimens. Patients in the experimental group had a similar nonrelapse mortality rate compared with the historical control group (29% versus 37%, respectively; P = .8), but a higher relapse rate (34% versus 2%, P = .0004) and a lower disease-free survival (38% versus 61%, P = .16). We conclude that this modified TBI approach is associated with an unacceptably high risk of relapse for patients with RA undergoing BMT.     

The Basel experience with total body irradiation for conditioning patients with acute leukemia for allogeneic bone marrow transplantation.

We are reporting our experience with 13 patients suffering from end stage acute leukemia that were prepared for allogeneic bone marrow transplantation by combined chemotherapy followed by high dose cyclophosphamide (Cy) and total body irradiation (TBI). Only one patient became a long term survivor. Of the evaluable 12 patients, 6 died of interstitial pneumonia, 4 of GvH and 1 of recurrent leukemia. We conclude that adding combined chemotherapy to the standard conditioning program with Cy and TBI probably increases the risk of developing fatal interstitial pneumonia without eliminating the risk of recurrent leukemia. We suggest that allogenic marrow grafts should be performed earlier in the course of refractory acute leukemias, because in patients with end stage disease its chances of being curative are small.     

CD154 blockade and donor-specific transfusions in DLA-identical marrow transplantation in dogs conditioned with 1-Gy total body irradiation.

Stable mixed donor/host chimerism has been reliably established in dogs given a sublethal dose (2 Gy) of total body irradiation (TBI) before and immunosuppression with mycophenolate mofetil (MMF) or rapamycin combined with cyclosporine (CSP) after marrow transplantation from dog leukocyte antigen (DLA)-identical littermates (hematopoietic cell transplantation [HCT]). When TBI was reduced to 1 Gy, only transient engraftment was observed. Here we investigated whether stable engraftment after 1-Gy TBI could be accomplished by reducing host-versus-donor immune responsiveness through preceding CD154 blockade and infusion of donor peripheral blood mononuclear cells (PBMCs). We found that the anti-human CD154 antibody, 5c8, cross-reacted with canine lymphocytes and blocked alloimmune responses in vitro. Based on pharmacokinetic studies, 6 dogs received a single intravenous injection of 5 mg/kg anti-CD154 antibody (on day -5), followed 1 day later by donor PBMCs. On day 0, the dogs were given 1 Gy of TBI and underwent DLA-identical marrow grafts. Postgraft immunosuppression consisted of MMF and CSP. All 6 dogs demonstrated initial engraftment; 3 dogs sustained the engraftment for >26 weeks, whereas 3 dogs rejected their grafts, after 9, 22, and 24 weeks, and survived with autologous recovery. Graft survival was significantly improved over that in 11 historical controls conditioned with 1-Gy TBI and given either MMF or rapamycin with CSP after HCT, all of which rejected their grafts between 3 and 12 weeks (P = .03). Preceding donor PBMC infusion and CD154 blockade improved survival of DLA-identical marrow grafts after 1-Gy TBI.     

Effect of total body irradiation dose escalation on outcome following T-cell-depleted allogeneic bone marrow transplantation.

Prior studies of non-T-cell-depleted (TCD) transplantation have demonstrated a reduction in relapse in patients receiving escalated doses of TBI; however, overall survival in these studies was not significantly improved due to increased treatment-related toxicity seen at the higher doses of irradiation. Toxicity was in part related to an increased incidence of GVHD. Because T-cell depletion of donor bone marrow reduces the incidence of GVHD and other treatment-related complications after allogeneic bone marrow transplantation, it was postulated that TBI dose may be safely escalated in this setting and may decrease the risk of relapse following TCD BMT. Herein, we report the results of a trial assessing the safety and impact of escalated doses of TBI after TCD BMT. Two hundred adults with hematologic malignancies were treated in consecutive cohorts defined by increasing doses of TBI (1400, 1480, and 1560 cGy) in combination with cyclophosphamide. In vitro T-cell depletion using anti-CD6 monoclonal antibody was used for GVHD prophylaxis. The incidence of grade II or greater acute GVHD in patients receiving 1560 cGy (36%) was significantly higher than in patients receiving 1400 cGy (18%) (P = .04) or 1480 cGy (13%) (P = .01). Two-year treatment-related mortality was significantly higher in patients who received 1560 cGy of TBI (33%) than in those who received 1400 cGy (20%) (P = .04) or 1480 cGy (19%) (P = .05). The increased dose of TBI did not reduce the rates of relapse, with the estimated 2-year risk of relapse being 24% (1400 cGy), 24% (1480 cGy), and 31% (1560 cGy) for the 3 cohorts of patients. Overall survival at 2 years was inferior for patients receiving 1560 cGy of TBI (36%) compared with those who received 1400 cGy (55%) or 1480 cGy (58%) (P = .01). We conclude that dose escalation of TBI is associated with increased GVHD and inferior survival following TCD BMT. Future efforts to reduce the risk of relapse after TCD BMT should focus on immunologic methods to induce the graft-versus-leukemia effect after BMT rather than intensification of the ablative regimen by escalation of irradiation dose.     

Low incidence of transplantation-related acute complications in patients with chronic myeloid leukemia undergoing allogeneic stem cell transplantation with a low-dose (550 cGy) total body irradiation conditioning regimen.

Although allogeneic transplantation is a curative therapy for chronic myeloid leukemia (CML), treatment-related mortality is still a major cause of posttransplantation mortality, especially for patients older than 40 years. We investigated, in a phase II trial, the role of a low-dose (550 cGy) high-dose rate (35 cGy/min) single-exposure total body irradiation (TBI) conditioning regimen for allogeneic peripheral blood stem cell (PBSC) transplantation in patients with CML. Between June 1997 and August 2000, 30 adult patients with CML underwent cytokine-mobilized allogeneic PBSC transplantation from HLA-matched siblings following administration of cyclophosphamide (60 mg/kg per day intravenously on days -2 and -1) and single-dose TBI (550 cGy delivered at 30 cGy/min on day 0). Cyclosporine A alone was administered for prophylaxis against graft-versus-host disease (GVHD). Median patient age was 47 years (range, 21-63 years), with 23 patients (77%) older than 40 years. The preparative regimen was well tolerated. Grade 4 toxicities and oral mucositis were not observed. Graft failure did not occur. Severe acute GVHD was observed in 5 patients (17%). The median follow-up was 23 months (range, 6-39 months). Cytogenetic or hematologic relapse was detected in 3 patients (10%), 2 of whom subsequently entered remission following a taper of immunosuppression. Nonrelapse mortality occurred in 5 patients (17%), and the Kaplan-Meier estimate of survival at 2 years was 83% (95% confidence interval, 70%-97%). In summary, this low-dose TBI-based preparative regimen resulted in uniform donor engraftment, with markedly reduced organ toxicity and nonrelapse mortality, in this relatively older cohort of patients with CML.     

Efficacy of CD34+ stem cell dose in patients undergoing allogeneic peripheral blood stem cell transplantation after total body irradiation.

We estimated the effect of CD34(+) stem cell dose during peripheral blood stem cell transplantation (PBSCT) in predicting mortality after total body irradiation (TBI). Between 1997 and 2004, 146 consecutive patients with hematologic malignancies received fractionated TBI (12-13.6 Gy) in 8 fractions over 4 days before undergoing PBSCT; 61 patients received TBI with reduced radiation dose to the lung (6-9 Gy). The number of CD34(+) cells transplanted was recorded for all patients. A cubic spline representation for CD34(+) dose within a Cox proportional hazards model was used to model the relationship between the CD34(+) dose and mortality. Median follow-up was 44 months (range, 12-90 months). The CD34(+) cell dose ranged from 2.45 to 15.90 x 10(6) cells/kg (median, 5.15 x 10(6) cells/kg). Risk of mortality decreased with CD34(+) doses between 4-8 x 10(6) cells/kg and then began to increase. For all patients, CD34(+) doses of 5.1-12.9 x 10(6)/kg resulted in at least a doubling of median survival associated with the lowest CD34(+) value. In patients treated with lung dose reduction, a similar range of CD34(+) dose (4.3-10.2 x 10(6) cells/kg) produced at least a 5-fold improvement from the survival associated with the lowest CD34(+) dose; however, the relationship between CD34(+) dose and mortality was not statistically different when analyzed by lung dose reduction. A method for assessing risk of mortality by CD34(+) dose as a continuous variable is presented. Risk of mortality decreased with CD34(+) doses between 4-8 x 10(6) cells/kg and then began to increase.