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Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia
Biology of Blood and Marrow Transplantation 12:1277-1284 (2006) 䊚 2006 American Society for Blood and Marrow Transplantation 1083-8791/06/1212-0001$32.00/0 doi:10.1016/j.bbmt.2006.07.011
Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia Alana A. Kennedy-Nasser, Kathryn S. Leung, Anita Mahajan, Heidi L. Weiss, James A. Arce, Stephen Gottschalk, George Carrum, Shakila P. Khan, Helen E. Heslop, Malcolm K. Brenner, Catherine M. Bollard, Robert A. Krance Center for Cell and Gene Therapy, Baylor College of Medicine, The Methodist Hospital and Texas Children’s Hospital, Houston, Texas Correspondence and reprint requests: Alana A. Kennedy-Nasser, MD, Center for Cell and Gene Therapy, Baylor College of Medicine, The Methodist Hospital and Texas Children’s Hospital, Houston, TX 77030 (e-mail: [email protected]). Received May 5, 2006; accepted July 20, 2006
ABSTRACT Matched sibling donor (MSD) bone marrow transplantation is the treatment of choice for pediatric patients with severe aplastic anemia (SAA); however, only about 33% of patients will have an HLA-identical sibling. Alternative donor (AD) transplants may be an option for these patients, but such therapies have been associated with greater incidence of graft failure and graft-versus-host disease (GVHD). We retrospectively analyzed 36 pediatric patients who received 38 bone marrow or peripheral blood stem cell transplants (15 MSD and 23 AD) for SAA at our institution from April 1997 to October 2005. Nineteen AD recipients received reduced intensity conditioning with cyclophosphamide, low-dose total body irradiation, and antithymocyte globulin (ATG) or Campath. The 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients treated with reduced intensity conditioning regimens at a median follow-up of 52 months (range, 6-99 months). No patient receiving Campath, compared with 3 of 9 patients receiving ATG, developed extensive, chronic GVHD. We conclude that, for children with SAA, AD transplantation is as effective as MSD transplantation. Further, compared with ATG, preparatory regimens containing Campath may be associated with a lower incidence of extensive, chronic GHVD. © 2006 American Society for Blood and Marrow Transplantation
KEY WORDS Aplastic anemia
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Pediatric
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Alternative donor stem cell transplantation
INTRODUCTION HLA-identical matched sibling donor (MSD) hematopoietic stem cell transplantation (HSCT) is the treatment of choice for pediatric patients with severe aplastic anemia (SAA). Storb et al [1] reported an 88% event-free survival for 81 patients with SAA receiving MSD transplantation after conditioning with cyclophosphamide and antithymocyte globulin (ATG). Unfortunately, only about 33% of patients have a suitably HLA-matched sibling [1-4]. Results from alternative donor (AD) transplantations have been less encouraging, mainly because of high rates of graft failure and severe graft-versus-host disease (GVHD)
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Campath
[3-5]. Data from the International Bone Marrow Transplant Registry for 732 pediatric patients who underwent transplantation with MSD grafts between 1996 and 2001 showed a 3-year survival of 82% but only 53% survival for 218 pediatric patients who received transplants from unrelated donors [6]. The Center for International Blood and Marrow Transplant Research reported a 30% to 49% 5-year overall survival for 318 AD grafts [7]. Thus, the trend has been to offer immunosuppressive therapy (IST) to pediatric patients with SAA who do not have an MSD and to offer AD transplants only if immunosuppression fails. Although survival rates after IST in children with SAA have been reported to be as high as 80% [8,9], 1277
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treatment failure occurs in 40% to 50% of cases [10]. Further, late clonal complications including myelodysplasia and paroxysmal nocturnal hemoglobinuria may develop in 25% to 45% of patients undergoing IST by 7 to 11 years after therapy [11-14]. Reports for patients who underwent AD transplantation by European groups and the National Marrow Donor Program suggest that high-dose total body irradiation (TBI) regimens, although effective in achieving engraftment, also increase toxicity, so that survival is not improved [15-18]. Deeg et al [19] reported the results of a multicenter, prospective, phase I study in which the minimum effective dose of TBI was determined in patients with SAA undergoing unrelated donor HSCT. They concluded that a TBI dose of 200 cGy in combination with cyclophosphamide and ATG was sufficient for engraftment in matched unrelated donor (MUD) grafts without incurring unacceptable toxicities. At our institution, all patients with SAA and matched siblings receive HSCT. Other patients initially receive IST and, if this fails, they receive AD transplants. We report that MSD and AD HSCT using reduced intensity conditioning regimens have essentially identical outcomes in pediatric patients with SAA.
METHODS Patients
Between April 1997 and October 2005, 36 consecutive pediatric patients with SAA underwent allogeneic HSCT at Texas Children’s Hospital (n ⫽ 35) and The Methodist Hospital (n ⫽ 1) in studies approved by the institutional review boards. SAA was defined as any 2 of the following: neutrophil count ⬍0.5 ⫻ 109/L, platelet count ⬍20 ⫻ 109/L, or reticulocytes ⬍1% and marrow features of severe hypocellularity or moderate hypocellularity (⬍35% cellularity) [20]. All patients had acquired SAA (Table 1). Fanconi anemia was excluded in all patients by using chromosomal breakage studies. The median age at time of transplantation was 9.4 years (range, 1.3-18.4 years; 20 boys and 16 girls). Median times from diagnosis to transplantation were 4.8 months for all patients (range, 1.2-51.6 months), 2.4 months for MSD recipients, and 6 months for AD recipients. This difference reflects that all but 1 of the AD recipients received and failed IST before transplantation. Bone Marrow Donor Selection
Donor characteristics for all transplants are listed in Table 1. Unrelated donors were recruited through the National Marrow Donor Program. DNA-based allele typing for class II DR has been performed since
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Table 1. Patient and Donor Characteristics Patients, n Transplants, n* Age (y), median (range) Female/male, n Possible causes of acquired aplastic anemia, n Idiopathic Hepatitis Paroxysmal nocturnal hemoglobinuria Prior treatment, n Antithymocyte globulin Cyclosporine Steroids Granulocyte colony-stimulating factors Time from diagnosis to transplantation (mo), median (range) Matched sibling donor recipients Alternative donor recipients Type of transplant, n Matched sibling donor Alternative donor Matched unrelated donor Mismatched unrelated donor Mismatched related donor Haploidentical CD34ⴙ cell dose (ⴛ106)/kg, median (range) Matched sibling donors, n Age (y), median (range) Female/male, n Alternative donors, n Age (y), median (range) Female/male, n
36 38 9.4 (1.3-18.4) 16/20 33 1 2 13 15 15 7 4.8 (1.2-51.6) 2.4 6.0 15 23 12 7 3 1 3.7 (0.2-13.7) 15 11 (0.3-22) 6/9 23 35 (23-50) 10/13
*Two patients received second transplants (1 matched sibling donor recipient later received a matched unrelated donor graft and 1 mismatched unrelated donor recipient later received a haploidentical graft).
1997. Class I A and B typing was antigen specific until March 2005, when allele typing was instituted. The median age of ADs was 35 years (range, 23-50 years). The median age of MSDs was 11 years (range, 0.3-22 years). Transplants
Thirty-six consecutive patients with acquired SAA received 38 allogeneic transplants. Fifteen patients initially received MSD transplants and 21 received AD transplants: 11 MUD, 7 mismatched unrelated donor (MMUD), and 3 mismatched related donor. Two of these 36 patients received a second transplant: 1 MSD recipient had late graft failures despite several additional donor cell infusions and 8 years later received a MUD graft after reduced intensity conditioning (for the purpose of statistical analysis, this patient was censored at the time of undergoing MUD transplantation). One patient had a failed engraftment after MMUD transplantation at 17 years of age, and 2 months later received a peripheral blood stem cell transplant from a haploidentical parent.
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Stem Cell Products
The source of stem cells was unmanipulated bone marrow (n ⫽ 34) or CD34⫹-selected peripheral blood (Isolex [Baxter, Irvine, California]; n ⫽ 4; 1 mismatched related donor, 1 MUD, 1 MSD, and 1 haploidentical graft) collected after granulocyte colonystimulating factor mobilization. For marrow a median of 4.97 total nucleated cells/kg (range, 0.79-34.94) and for CD34⫹-selected products a median of 8.02 CD34⫹/kg (range, 6.53-10.10) were infused.
Survival time was calculated from date of transplantation to date of death or date of final patient follow-up in March 2006. Kaplan-Meier survival curves and estimates of survival rates at specific time points in addition to 95% confidence intervals are estimated for each group of patients. RESULTS Tables 2 and 3 list the transplant characteristics and outcomes of MSD and AD recipients.
Transplantation Protocol for MSD HSCT
Fourteen of 15 MSD recipients received cyclophosphamide 50 mg/kg for 4 days (days ⫺5 to ⫺2) and equine ATG (ATGAM) 30 mg/kg for 3 days (days ⫺5 to ⫺3) in accord with the Seattle regimen [1]. One MSD recipient with paroxysmal nocturnal hemoglobinuria received busulfan for 4 days (days ⫺7 to ⫺4) and cyclophosphamide 50 mg/kg for 2 days (days ⫺3 and ⫺2). Transplantation Protocol for AD HSCT
Nineteen of 23 AD recipients received a reduced intensity conditioning regimen consisting of cyclophosphamide 50 mg/kg for 4 days (days ⫺6 to ⫺3) and low-dose TBI (200 cGy for MUD on day ⫺2 and 200 cGy for MMUD recipients on days ⫺2 and ⫺1). Patients who underwent transplantation from 1997 to 2000 received equine ATG (ATGAM) 30 mg/kg for 3 days (days ⫺5 to ⫺3). After 2000, patients received humanized anti-CD52 monoclonal antibodies and Campath-1H (alemtuzumab) in a weight-dependent dose (3 mg for patients 5-15 kg, 5 mg for patients 16-30 kg, and 10 mg for patients ⬎30 kg) daily for 4 days (days ⫺4 to ⫺1). Three patients received fully myeloablative preparative regimens and 1 patient received a subablative regimen of fludarabine 30 mg/m2 on days ⫺5 to ⫺2, Campath 10 mg on days ⫺5 to ⫺2, and low-dose TBI conditioning for a haploidentical peripheral blood stem cell transplant 2 months after failing to engraft from an initial MMUD transplant. In all, 9 AD grafts included ATG in the preparative regimen and 14 included Campath.
Engraftment
Engraftment was defined as a sustained (3-day) neutrophil count ⬎0.5 ⫻ 109/L and unsupported platelet count ⬎20 ⫻ 109/L. Thirty-seven of 38 transplants were evaluable for engraftment. One patient (no. 11) died of a pre-existing Pseudomonas aeruginosa infection only 6 days after MSD transplantation and was therefore unevaluable for engraftment. Thirty-six of 37 (97%) evaluable transplants engrafted. Median time to neutrophil engraftment was 17 days (range, 11-44 days) and median time to platelet engraftment was 32 days (range, 11-282 days). One patient’s engraftment failed (no. 34) after MMUD transplantation using reduced intensity conditioning but was later successful after haploidentical transplantation using a different reduced intensity conditioning regimen. Chimerism Studies
Chimerism was determined on blood and/or bone marrow using fluorescence in situ hybridization probes for sex chromosomes or polymerase chain reaction amplification of specific polymorphic DNA sequences (short tandem repeats). Thirty-four of 36 (94%) evaluable transplant patients had ⬎95% donor chimerism. Seven of 14 (50%) MSD recipients and 17 of 22 (77%) AD recipients were 100% chimeric. One patient had autologous recovery (MSD recipient) and is transfusion independent with 100% recipient cells and 50%-70% bone marrow cellularity with normal cytogenetics. Survival
GVHD and Infectious Prophylaxis
All patients received FK506 or cyclosporine, with or without methotrexate for GVHD prophylaxis. All patients received bacterial and fungal prophylaxis during the peri-transplantation period and all patients received pneumocystis carinii pneumonia prophylaxis. Monitoring of viral and fungal infections was carried out as per institutional standard of care [21]. Statistical Methods
Engraftment rates and incidences of acute and chronic GVHD are reported for each patient group.
Thirty-one of 36 (86.1%) patients have survived to date as transfusion independent, at a median follow-up of 52 months (range, 6-99 months). The 4-year overall survival was 93% in the MSD group compared with 89% in the AD group of patients receiving this reduced intensity regimen. There was no statistical difference between these 2 groups of patients (Figure 1). Five patients died at a median of 52 days after transplantation (range, 6 days to 5.5 years). Four patients died of infection soon after transplantation and 1 patient (no. 16) died 5.5 years after MUD transplantation from chronic GVHD pulmonary complications
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NA indicates not applicable; HSCT, hematopoietic stem cell transplantation; D, donor; R, recipient; M, male; F, female; HLA, human-leukocyte antigens; CMV, cytomegalovirus; EBV, Epstein-Barr virus; GVHD, graft-versus-host disease; MSD, matched sibling donor; Cy, cyclophosphamide; Bu, busulfan; ATG, antithymocyte globulin; FISH, fluorescence in situ hybridization; STR, short tandem repeats. *Patient 1 is also patient 36 in Table 3.
95 of 100 donor FISH 100% donor STR 100% donor STR 100% donor STR 96 of 100 donor FISH 491 of 500 donor FISH Autologous recovery 100% donor STR 99% donor STR 100% donor STR NA 100% donor STR 100% donor STR 93% donor STR 100% donor STR Late graft failure Alive Alive, CMV neg Alive Alive Alive Alive, CMV neg Alive Alive Alive Died Alive Alive Alive Alive No No CMV No No No CMV No No No No No No No No Neither ATG ATG ATG ATG ATG ATG Neither ATG ATG ATG ATG ATG ATG ATG 4F/10M 13F/2F 13M/1M 9M/5M 14M/3F 18F/16M 5M/2F 11M/14M 6M/3F 8F/9F 14F/4M 0.3M/1M 22M/17M 12M/13M 3F/1M 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15
6/6 6/6 6/6 10/10 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 10/10
1.2 3.6 1.2 1.2 2.4 2.4 2.4 4.8 1.2 18 2.4 1.2 8.4 2.4 1.2
Cy Cy Cy Cy Cy Cy Cy Bu, Cy Cy Cy Cy Cy Cy Cy Cy
No No No No No No No No No No NA No Grade 1 No No
No Limited No No No No No No No Limited NA No No No No
Disease Status ATG or Campath Conditioning Regimen Time to HSCT (mo) HLA Matched D/R Age (y) Sex Patient No.
Table 2. Transplant Characteristics and Outcomes of Matched Sibling Donor Recipients
Acute GVHD
Chronic GVHD
CMV or EBV Reactivation
Chimerism Studies
A. A. Kennedy-Nasser et al.
resulting in pulmonary failure (Table 4). For patients dying from infection, the causes of death were preexisting pseudomonas (n ⫽ 2), idiopathic pneumonia (n ⫽ 1), and adenovirus complicated by acute GVHD (n ⫽ 1). Ten patients (3 MSD, 7 AD) developed cytomegalovirus (CMV) reactivation without CMV disease. Five patients received ATG or Campath in the conditioning regimen, and frequencies of CMV infection were 36% with Campath and 23% with ATG. Two of these patients died; 1 MUD recipient who received ATG as a result of pre-existing pseudomonas infection and 1 MUD recipient who received Campath died from adenoviral infection. An additional patient who received Campath developed Epstein-Barr viral reactivation, which was treated successfully with rituximab. Graft-versus-Host Disease
Severe, acute GVHD (grade III or IV) developed in 0 of 15 MSD recipients and 4 of 23 AD recipients. Specifically, 2 of 9 AD recipients who received ATG developed severe, acute GVHD compared with 2 of 14 Campath recipients. Extensive, chronic GVHD developed in 0 of 15 MSD recipients and 3 of 23 AD recipients, all 3 of whom received ATG in the preparative regimen. No patient treated with Campath developed extensive, chronic GVHD. One MMUD recipient (no. 23) with hepatitis-associated SAA developed grade IV acute GVHD and extensive, chronic GVHD of the liver, received a liver transplant, and is now well and disease free.
DISCUSSION Although the outcomes after MSD transplantation for pediatric SAA have improved over the years, the results using AD transplants have been less satisfactory. Margolis and Casper [5] reported 55% survival at 33 months for 28 heavily transfused adult and pediatric patients with SAA undergoing AD HSCT using an intensive conditioning regimen. Because of these and similar results [3-7], immunosuppression has remained first-line therapy for patients lacking an HLA-matched sibling. Unfortunately, IST has achieved limited improvement in survival, with high rates of clonal evolution and relapse [8,11-13,22,23]. In addition, delayed time to transplantation presumably due to IST administration has been associated with a poorer outcome in several studies [7,24]. This has led to the use of nonmyeloablative or reduced intensity preparative regimens to improve survival for recipients of AD transplants. The European Group for Blood and Marrow Transplantation Working Party reported 73% survival for 38 adult and pediatric patients when using a reduced intensity conditioning
Patient No.
D/R Age (y) Sex
Type of HSCT
HLA Matched, Mismatched Ag
Time to HSCT (mo)
Conditioning Regimen
ATG or Campath
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34* 35* 36† 37 38
23F/9F ?M/3M 35F/1F 30F/1M 30M/5F 37M/6M 28M/16M 38F/14M 28F/18F 30M/5F 44F/10M 44M/12F 24F/6M 40F/12M 30M/8F 43F/18F 36F/8F 36M/8F 34M/17F 50M/17F 33M/18M 24M/14M 35M/14M
MUD MUD MUD MMRD MMUD MMUD MMUD MMUD MUD MUD MMRD MUD MUD MUD MUD MMRD MMUD MMUD MMUD Haplo MUD MUD MUD
6/6 6/6 6/6 5/6, B 5/6, DRBI 5/6, DRBI 5/6, B 5/6, DRB1 6/6 6/6 5/6, DRB1 6/6 6/6 6/6 6/6 5/6, DRB1 5/6, DRB1 5/6, B 5/6, A 3/6, A, B, DRBI 6/6 8/10, A 6/6
34.8 12 4.8 4.8 21.6 4.8 22.8 3.6 22.8 NA 6 16.8 12 2.4 6 24 3.6 51.6 6 NA NA 9.6 40.8
Cy, TBI AraC, Cy, TBI Cy, TBI AraC, Cy, TBI AraC, Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Flu, TBI Cy, TBI Cy, TBI Cy, TBI
ATG ATG ATG ATG ATG ATG ATG ATG ATG Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath
Acute GVHD Grade No No No No No No Grade No Grade No No No No No No No Grade No No No No No
3
4 4
3
Chronic GVHD
CMV or EBV Reactivation
Disease Status
Chimerism Studies
Ext No No No No No No Ext Ext No Lim No No No No NA No No No No No No No
No No No No No No CMV No CMV CMV CMV No CMV CMV No No CMV No No CMV No EBV No
Died Died Alive Alive Alive Alive Alive, CMV neg Alive Alive, CMV neg Died, CMV neg Alive, CMV neg Alive Alive, CMV neg Alive, CMV neg Alive Died Alive, CMV neg Alive Failed to engraft Alive, CMV neg Alive Alive, EBV neg Alive
100% donor RFLP NA 100% donor STR 100 of 100 donor FISH 100% donor STR 100% donor STR 200 of 200 donor FISH 199 of 200 donor FISH 100% donor STR 200 of 200 donor FISH 100% donor STR 100% donor STR 198 of 200 donor FISH 194 of 200 donor FISH 200 of 200 donor FISH 100% donor STR 100% donor STR 200 of 200 donor FISH NA 100 of 100 donor FISH 100% donor STR 100% donor STR 100% donor STR
Comparable Outcomes of MSD and AD HSCT for Pediatric SAA
Table 3. Transplant Characteristics and Outcomes in Alternative Donor Recipients
NA indicates not available or applicable; HSCT, hematopoietic stem cell transplantation; GVHD, graft-versus-host disease; CMV, cytomegalovirus; EBV, Epstein-Barr virus; D, donor; R, recipient; M, male; F, female; HLA, human-leukocyte antigens; MUD, matched unrelated donor; MMUD, mismatched unrelated donor; MMRD, mismatched related donor; Haplo, haploidentical; Cy, cyclophosphamide; TBI, total body irradiation; AraC, cytarabine arabinoside; Flu, fludarabine; Bu, busulfan; ATG, antithymocyte globulin; Ext, extensive; Lim, limited; RFLP, restriction fragment length polymorphism; FISH, fluorescence in situ hybridization; STR, short tandem repeats; Ag, antigen. *Patients 34 and 35 are the same patient. †Patient 36 is also patient 1 in Table 2.
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Figure 1. Probability of 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients who received reduced intensity conditioning. CI indicates confidence interval.
regimen of fludarabine, cyclophosphamide, and ATG [25]. Another study reported 75% survival with durable engraftment using non-TBI preparative regimens for 13 mostly young adult patients with SAA who received AD transplants [26]. Vassiliou et al [27] reported 100% survival with AD HSCT using Campath, low-dose TBI, and cyclophosphamide as reduced intensity conditioning in 8 patients. In addition, low-dose TBI with cyclophosphamide and ATG has been shown to be effective in securing durable grafts with acceptable toxicities in MUD grafts [2]. We find that this reduced intensity conditioning regimen with low-dose TBI achieves stable engraftment and excellent survival. There is concern that these patients may be at risk for secondary malignancies but none has occurred up to 86 months after AD transplantation. After irradiation, the risk for thyroid cancer is expected to be highest in children exposed at an age ⬍5 years [28]. For patients with SAA excluding Fanconi anemia undergoing MSD and AD transplantation [29], the estimated risk for developing any malignancy by 20 years (range, 1.4-221 months) was reported as 14%. The risk of malignancy likely has a linear relation to radiation doses up to 7-8 Gy. Although the risk of malignancy after conditioning regimens that include radiation are of obvious concern, these risks may be little different from those incurred
after IST alone or after transplant-preparative regimens that use only chemotherapy. Lifelong follow-up for all these patients is therefore necessary. Fludarabine has been used in preparative regimens without TBI. Although a survival of 71% to 84% has been noted for patients who received AD transplants [25,30-33], this regimen has led to a reportedly higher incidence of graft failure and GVHD in some studies [30,32]. Although fludarabine-based conditioning regimens remain promising, the incidence of GVHD using our conditioning regimen (especially in the patients who received Campath) appears lower than that in other reported series. Certainly, the long-term (⬎20-year) effects of a fludarabine-based or low-dose TBI-based preparatory regimen have yet to be determined. Campath was substituted for ATG because it allows for predictable depletion of T and B lymphocytes [34,35]. As previously published by our group and others, Campath may be associated with higher rates of viral infections such as CMV and adenovirus [3638]; however, in our patients, there was no CMV disease. Previous studies have shown that AD transplants result in an increased incidence of graft rejection and an increased risk of death from acute GVHD, infection, and pneumonitis when compared with MSD transplantation [25]. However, other groups have noted an association with lower rates of GVHD using Campath [39,40]. Although graft failure has been an ongoing concern in patients with SAA undergoing AD HSCT, in our experience only 1 patient’s engraftment failed and GVHD was minimal in this cohort of patients. None of the patients who received Campath developed extensive, chronic GVHD compared with 3 of 9 ATG recipients in the AD group; however, the sample was too small to determine significance. Many studies have shown that survival after HSCT is improved by shortening the time to transplantation, thereby decreasing blood product exposures and minimizing prior therapy [24,25,41]. In our report, the median time to transplantation was notably longer in the AD than in the MSD group (6 versus 2.4 months). This delay was attributed to the fact that all but 1 of the AD recipients received and failed IST
Table 4. Deaths Patient No.
Age (y) at Time of HSCT
Type of HSCT
Conditioning Regimen
ATG or Campath
Time of Death after HSCT
Cause of Death
11 16 17 25 31
4.0 9.4 3.3 18.4 5.9
MSD MUD MUD MMRD MUD
Cy RI Myeloablative RI RI
ATG ATG ATG Campath Campath
6 d 5.5 y 33 d 52 d 66 d
Pre-existing infection Chronic GVHD, pulmonary failure Pre-existing infection Idiopathic pneumonia Adenovirus, grade IV acute GVHD
RI indicates reduced intensity; HSCT, hematopoietic stem cell transplantation; MSD, matched sibling donor; MMRD, mismatched related donor; MUD, matched unrelated donor; Cy, cyclophosphamide; GVHD, graft-versus-host disease; ATG, antithymocyte globulin.
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before transplantation. However, we observed no effect of time from diagnosis to transplantation on survival, even though AD transplantation was performed later after diagnosis than MSD transplantation. Some preceding IST for these patients may have favored subsequent engraftment when low-intensity conditioning was used. We have shown that a reduced intensity conditioning regimen of cyclophosphamide, low-dose TBI, and ATG or Campath achieves sustained engraftment and excellent survival in pediatric patients with SAA who receive AD transplants. These results are comparable to the outcome for pediatric patients with SAA who received MSD transplants.
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diation, cyclophosphamide and Campath. Br J Haematol. 2001;114:701-705. Lubin JH, Schafer DW, Ron E, Stovall M, Carroll RJ. A reanalysis of thyroid neoplasms in the Israeli tinea capitis study accounting for dose uncertainties. Radiat Res. 2004;161:359368. Deeg HJ, Socie G, Schoch G, et al. Malignancies after marrow transplantation for aplastic anemia and fanconi anemia: a joint Seattle and Paris analysis of results in 700 patients. Blood. 1996;87:386-392. Srinivasan R, Takahashi Y, McCoy JP, et al. Overcoming graft rejection in heavily transfused and allo-immunised patients with bone marrow failure syndromes using fludarabine-based haematopoietic cell transplantation. Br J Haematol. 2006;133: 305-314. Gupta V, Ball SE, Sage D, et al. Marrow transplants from matched unrelated donors for aplastic anaemia using alemtuzumab, fludarabine and cyclophosphamide based conditioning. Bone Marrow Transplant. 2005;35:467-471. Bacigalupo A, Locatelli F, Lanino E, et al. Fludarabine, cyclophosphamide and anti-thymocyte globulin for alternative donor transplants in acquired severe aplastic anemia: a report from the EBMT-SAA Working Party. Bone Marrow Transplant. 2005;36:947-950. Resnick IB, Aker M, Shapira MY, et al. Allogeneic stem cell transplantation for severe acquired aplastic anaemia using a fludarabine-based preparative regimen. Br J Haematol. 2006; 133:649-654.
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34. Hale G, Cobbold S, Novitzky N, et al. CAMPATH-1 antibodies in stem-cell transplantation. Cytotherapy. 2001;3:145-164. 35. Hale G. The CD52 antigen and development of the CAMPATH antibodies. Cytotherapy. 2001;3:137-143. 36. Chakrabarti S, Mackinnon S, Chopra R, et al. High incidence of cytomegalovirus infection after nonmyeloablative stem cell transplantation: potential role of Campath-1H in delaying immune reconstitution. Blood. 2002;99:4357-4363. 37. Lamba R, Carrum G, Myers GD, et al. Cytomegalovirus (CMV) infections and CMV-specific cellular immune reconstitution following reduced intensity conditioning allogeneic stem cell transplantation with Alemtuzumab. Bone Marrow Transplant. 2005;36:797-802. 38. Myers GD, Krance RA, Weiss H, et al. Adenovirus infection rates in pediatric recipients of alternate donor allogeneic bone marrow transplants receiving either antithymocyte globulin (ATG) or alemtuzumab (Campath). Bone Marrow Transplant. 2005;36:1001-1008. 39. Kottaridis PD, Milligan DW, Chopra R, et al. In vivo CAMPATH-1H prevents GvHD following nonmyeloablative stem-cell transplantation. Cytotherapy. 2001;3:197-201. 40. Gupta V, Ball SE, Yi QL, et al. Favorable effect on acute and chronic graft-versus-host disease with cyclophosphamide and in vivo anti-CD52 monoclonal antibodies for marrow transplantation from HLA-identical sibling donors for acquired aplastic anemia. Biol Blood Marrow Transplant. 2004;10:867-876. 41. Ades L, Mary JY, Robin M, et al. Long-term outcome after bone marrow transplantation for severe aplastic anemia. Blood. 2004;103:2490-2497.
Comparable Outcomes of Matched-Related and Alternative Donor Stem Cell Transplantation for Pediatric Severe Aplastic Anemia Alana A. Kennedy-Nasser, Kathryn S. Leung, Anita Mahajan, Heidi L. Weiss, James A. Arce, Stephen Gottschalk, George Carrum, Shakila P. Khan, Helen E. Heslop, Malcolm K. Brenner, Catherine M. Bollard, Robert A. Krance Center for Cell and Gene Therapy, Baylor College of Medicine, The Methodist Hospital and Texas Children’s Hospital, Houston, Texas Correspondence and reprint requests: Alana A. Kennedy-Nasser, MD, Center for Cell and Gene Therapy, Baylor College of Medicine, The Methodist Hospital and Texas Children’s Hospital, Houston, TX 77030 (e-mail: [email protected]). Received May 5, 2006; accepted July 20, 2006
ABSTRACT Matched sibling donor (MSD) bone marrow transplantation is the treatment of choice for pediatric patients with severe aplastic anemia (SAA); however, only about 33% of patients will have an HLA-identical sibling. Alternative donor (AD) transplants may be an option for these patients, but such therapies have been associated with greater incidence of graft failure and graft-versus-host disease (GVHD). We retrospectively analyzed 36 pediatric patients who received 38 bone marrow or peripheral blood stem cell transplants (15 MSD and 23 AD) for SAA at our institution from April 1997 to October 2005. Nineteen AD recipients received reduced intensity conditioning with cyclophosphamide, low-dose total body irradiation, and antithymocyte globulin (ATG) or Campath. The 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients treated with reduced intensity conditioning regimens at a median follow-up of 52 months (range, 6-99 months). No patient receiving Campath, compared with 3 of 9 patients receiving ATG, developed extensive, chronic GVHD. We conclude that, for children with SAA, AD transplantation is as effective as MSD transplantation. Further, compared with ATG, preparatory regimens containing Campath may be associated with a lower incidence of extensive, chronic GHVD. © 2006 American Society for Blood and Marrow Transplantation
KEY WORDS Aplastic anemia
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Pediatric
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Alternative donor stem cell transplantation
INTRODUCTION HLA-identical matched sibling donor (MSD) hematopoietic stem cell transplantation (HSCT) is the treatment of choice for pediatric patients with severe aplastic anemia (SAA). Storb et al [1] reported an 88% event-free survival for 81 patients with SAA receiving MSD transplantation after conditioning with cyclophosphamide and antithymocyte globulin (ATG). Unfortunately, only about 33% of patients have a suitably HLA-matched sibling [1-4]. Results from alternative donor (AD) transplantations have been less encouraging, mainly because of high rates of graft failure and severe graft-versus-host disease (GVHD)
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Campath
[3-5]. Data from the International Bone Marrow Transplant Registry for 732 pediatric patients who underwent transplantation with MSD grafts between 1996 and 2001 showed a 3-year survival of 82% but only 53% survival for 218 pediatric patients who received transplants from unrelated donors [6]. The Center for International Blood and Marrow Transplant Research reported a 30% to 49% 5-year overall survival for 318 AD grafts [7]. Thus, the trend has been to offer immunosuppressive therapy (IST) to pediatric patients with SAA who do not have an MSD and to offer AD transplants only if immunosuppression fails. Although survival rates after IST in children with SAA have been reported to be as high as 80% [8,9], 1277
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treatment failure occurs in 40% to 50% of cases [10]. Further, late clonal complications including myelodysplasia and paroxysmal nocturnal hemoglobinuria may develop in 25% to 45% of patients undergoing IST by 7 to 11 years after therapy [11-14]. Reports for patients who underwent AD transplantation by European groups and the National Marrow Donor Program suggest that high-dose total body irradiation (TBI) regimens, although effective in achieving engraftment, also increase toxicity, so that survival is not improved [15-18]. Deeg et al [19] reported the results of a multicenter, prospective, phase I study in which the minimum effective dose of TBI was determined in patients with SAA undergoing unrelated donor HSCT. They concluded that a TBI dose of 200 cGy in combination with cyclophosphamide and ATG was sufficient for engraftment in matched unrelated donor (MUD) grafts without incurring unacceptable toxicities. At our institution, all patients with SAA and matched siblings receive HSCT. Other patients initially receive IST and, if this fails, they receive AD transplants. We report that MSD and AD HSCT using reduced intensity conditioning regimens have essentially identical outcomes in pediatric patients with SAA.
METHODS Patients
Between April 1997 and October 2005, 36 consecutive pediatric patients with SAA underwent allogeneic HSCT at Texas Children’s Hospital (n ⫽ 35) and The Methodist Hospital (n ⫽ 1) in studies approved by the institutional review boards. SAA was defined as any 2 of the following: neutrophil count ⬍0.5 ⫻ 109/L, platelet count ⬍20 ⫻ 109/L, or reticulocytes ⬍1% and marrow features of severe hypocellularity or moderate hypocellularity (⬍35% cellularity) [20]. All patients had acquired SAA (Table 1). Fanconi anemia was excluded in all patients by using chromosomal breakage studies. The median age at time of transplantation was 9.4 years (range, 1.3-18.4 years; 20 boys and 16 girls). Median times from diagnosis to transplantation were 4.8 months for all patients (range, 1.2-51.6 months), 2.4 months for MSD recipients, and 6 months for AD recipients. This difference reflects that all but 1 of the AD recipients received and failed IST before transplantation. Bone Marrow Donor Selection
Donor characteristics for all transplants are listed in Table 1. Unrelated donors were recruited through the National Marrow Donor Program. DNA-based allele typing for class II DR has been performed since
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Table 1. Patient and Donor Characteristics Patients, n Transplants, n* Age (y), median (range) Female/male, n Possible causes of acquired aplastic anemia, n Idiopathic Hepatitis Paroxysmal nocturnal hemoglobinuria Prior treatment, n Antithymocyte globulin Cyclosporine Steroids Granulocyte colony-stimulating factors Time from diagnosis to transplantation (mo), median (range) Matched sibling donor recipients Alternative donor recipients Type of transplant, n Matched sibling donor Alternative donor Matched unrelated donor Mismatched unrelated donor Mismatched related donor Haploidentical CD34ⴙ cell dose (ⴛ106)/kg, median (range) Matched sibling donors, n Age (y), median (range) Female/male, n Alternative donors, n Age (y), median (range) Female/male, n
36 38 9.4 (1.3-18.4) 16/20 33 1 2 13 15 15 7 4.8 (1.2-51.6) 2.4 6.0 15 23 12 7 3 1 3.7 (0.2-13.7) 15 11 (0.3-22) 6/9 23 35 (23-50) 10/13
*Two patients received second transplants (1 matched sibling donor recipient later received a matched unrelated donor graft and 1 mismatched unrelated donor recipient later received a haploidentical graft).
1997. Class I A and B typing was antigen specific until March 2005, when allele typing was instituted. The median age of ADs was 35 years (range, 23-50 years). The median age of MSDs was 11 years (range, 0.3-22 years). Transplants
Thirty-six consecutive patients with acquired SAA received 38 allogeneic transplants. Fifteen patients initially received MSD transplants and 21 received AD transplants: 11 MUD, 7 mismatched unrelated donor (MMUD), and 3 mismatched related donor. Two of these 36 patients received a second transplant: 1 MSD recipient had late graft failures despite several additional donor cell infusions and 8 years later received a MUD graft after reduced intensity conditioning (for the purpose of statistical analysis, this patient was censored at the time of undergoing MUD transplantation). One patient had a failed engraftment after MMUD transplantation at 17 years of age, and 2 months later received a peripheral blood stem cell transplant from a haploidentical parent.
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Stem Cell Products
The source of stem cells was unmanipulated bone marrow (n ⫽ 34) or CD34⫹-selected peripheral blood (Isolex [Baxter, Irvine, California]; n ⫽ 4; 1 mismatched related donor, 1 MUD, 1 MSD, and 1 haploidentical graft) collected after granulocyte colonystimulating factor mobilization. For marrow a median of 4.97 total nucleated cells/kg (range, 0.79-34.94) and for CD34⫹-selected products a median of 8.02 CD34⫹/kg (range, 6.53-10.10) were infused.
Survival time was calculated from date of transplantation to date of death or date of final patient follow-up in March 2006. Kaplan-Meier survival curves and estimates of survival rates at specific time points in addition to 95% confidence intervals are estimated for each group of patients. RESULTS Tables 2 and 3 list the transplant characteristics and outcomes of MSD and AD recipients.
Transplantation Protocol for MSD HSCT
Fourteen of 15 MSD recipients received cyclophosphamide 50 mg/kg for 4 days (days ⫺5 to ⫺2) and equine ATG (ATGAM) 30 mg/kg for 3 days (days ⫺5 to ⫺3) in accord with the Seattle regimen [1]. One MSD recipient with paroxysmal nocturnal hemoglobinuria received busulfan for 4 days (days ⫺7 to ⫺4) and cyclophosphamide 50 mg/kg for 2 days (days ⫺3 and ⫺2). Transplantation Protocol for AD HSCT
Nineteen of 23 AD recipients received a reduced intensity conditioning regimen consisting of cyclophosphamide 50 mg/kg for 4 days (days ⫺6 to ⫺3) and low-dose TBI (200 cGy for MUD on day ⫺2 and 200 cGy for MMUD recipients on days ⫺2 and ⫺1). Patients who underwent transplantation from 1997 to 2000 received equine ATG (ATGAM) 30 mg/kg for 3 days (days ⫺5 to ⫺3). After 2000, patients received humanized anti-CD52 monoclonal antibodies and Campath-1H (alemtuzumab) in a weight-dependent dose (3 mg for patients 5-15 kg, 5 mg for patients 16-30 kg, and 10 mg for patients ⬎30 kg) daily for 4 days (days ⫺4 to ⫺1). Three patients received fully myeloablative preparative regimens and 1 patient received a subablative regimen of fludarabine 30 mg/m2 on days ⫺5 to ⫺2, Campath 10 mg on days ⫺5 to ⫺2, and low-dose TBI conditioning for a haploidentical peripheral blood stem cell transplant 2 months after failing to engraft from an initial MMUD transplant. In all, 9 AD grafts included ATG in the preparative regimen and 14 included Campath.
Engraftment
Engraftment was defined as a sustained (3-day) neutrophil count ⬎0.5 ⫻ 109/L and unsupported platelet count ⬎20 ⫻ 109/L. Thirty-seven of 38 transplants were evaluable for engraftment. One patient (no. 11) died of a pre-existing Pseudomonas aeruginosa infection only 6 days after MSD transplantation and was therefore unevaluable for engraftment. Thirty-six of 37 (97%) evaluable transplants engrafted. Median time to neutrophil engraftment was 17 days (range, 11-44 days) and median time to platelet engraftment was 32 days (range, 11-282 days). One patient’s engraftment failed (no. 34) after MMUD transplantation using reduced intensity conditioning but was later successful after haploidentical transplantation using a different reduced intensity conditioning regimen. Chimerism Studies
Chimerism was determined on blood and/or bone marrow using fluorescence in situ hybridization probes for sex chromosomes or polymerase chain reaction amplification of specific polymorphic DNA sequences (short tandem repeats). Thirty-four of 36 (94%) evaluable transplant patients had ⬎95% donor chimerism. Seven of 14 (50%) MSD recipients and 17 of 22 (77%) AD recipients were 100% chimeric. One patient had autologous recovery (MSD recipient) and is transfusion independent with 100% recipient cells and 50%-70% bone marrow cellularity with normal cytogenetics. Survival
GVHD and Infectious Prophylaxis
All patients received FK506 or cyclosporine, with or without methotrexate for GVHD prophylaxis. All patients received bacterial and fungal prophylaxis during the peri-transplantation period and all patients received pneumocystis carinii pneumonia prophylaxis. Monitoring of viral and fungal infections was carried out as per institutional standard of care [21]. Statistical Methods
Engraftment rates and incidences of acute and chronic GVHD are reported for each patient group.
Thirty-one of 36 (86.1%) patients have survived to date as transfusion independent, at a median follow-up of 52 months (range, 6-99 months). The 4-year overall survival was 93% in the MSD group compared with 89% in the AD group of patients receiving this reduced intensity regimen. There was no statistical difference between these 2 groups of patients (Figure 1). Five patients died at a median of 52 days after transplantation (range, 6 days to 5.5 years). Four patients died of infection soon after transplantation and 1 patient (no. 16) died 5.5 years after MUD transplantation from chronic GVHD pulmonary complications
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NA indicates not applicable; HSCT, hematopoietic stem cell transplantation; D, donor; R, recipient; M, male; F, female; HLA, human-leukocyte antigens; CMV, cytomegalovirus; EBV, Epstein-Barr virus; GVHD, graft-versus-host disease; MSD, matched sibling donor; Cy, cyclophosphamide; Bu, busulfan; ATG, antithymocyte globulin; FISH, fluorescence in situ hybridization; STR, short tandem repeats. *Patient 1 is also patient 36 in Table 3.
95 of 100 donor FISH 100% donor STR 100% donor STR 100% donor STR 96 of 100 donor FISH 491 of 500 donor FISH Autologous recovery 100% donor STR 99% donor STR 100% donor STR NA 100% donor STR 100% donor STR 93% donor STR 100% donor STR Late graft failure Alive Alive, CMV neg Alive Alive Alive Alive, CMV neg Alive Alive Alive Died Alive Alive Alive Alive No No CMV No No No CMV No No No No No No No No Neither ATG ATG ATG ATG ATG ATG Neither ATG ATG ATG ATG ATG ATG ATG 4F/10M 13F/2F 13M/1M 9M/5M 14M/3F 18F/16M 5M/2F 11M/14M 6M/3F 8F/9F 14F/4M 0.3M/1M 22M/17M 12M/13M 3F/1M 1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15
6/6 6/6 6/6 10/10 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 6/6 10/10
1.2 3.6 1.2 1.2 2.4 2.4 2.4 4.8 1.2 18 2.4 1.2 8.4 2.4 1.2
Cy Cy Cy Cy Cy Cy Cy Bu, Cy Cy Cy Cy Cy Cy Cy Cy
No No No No No No No No No No NA No Grade 1 No No
No Limited No No No No No No No Limited NA No No No No
Disease Status ATG or Campath Conditioning Regimen Time to HSCT (mo) HLA Matched D/R Age (y) Sex Patient No.
Table 2. Transplant Characteristics and Outcomes of Matched Sibling Donor Recipients
Acute GVHD
Chronic GVHD
CMV or EBV Reactivation
Chimerism Studies
A. A. Kennedy-Nasser et al.
resulting in pulmonary failure (Table 4). For patients dying from infection, the causes of death were preexisting pseudomonas (n ⫽ 2), idiopathic pneumonia (n ⫽ 1), and adenovirus complicated by acute GVHD (n ⫽ 1). Ten patients (3 MSD, 7 AD) developed cytomegalovirus (CMV) reactivation without CMV disease. Five patients received ATG or Campath in the conditioning regimen, and frequencies of CMV infection were 36% with Campath and 23% with ATG. Two of these patients died; 1 MUD recipient who received ATG as a result of pre-existing pseudomonas infection and 1 MUD recipient who received Campath died from adenoviral infection. An additional patient who received Campath developed Epstein-Barr viral reactivation, which was treated successfully with rituximab. Graft-versus-Host Disease
Severe, acute GVHD (grade III or IV) developed in 0 of 15 MSD recipients and 4 of 23 AD recipients. Specifically, 2 of 9 AD recipients who received ATG developed severe, acute GVHD compared with 2 of 14 Campath recipients. Extensive, chronic GVHD developed in 0 of 15 MSD recipients and 3 of 23 AD recipients, all 3 of whom received ATG in the preparative regimen. No patient treated with Campath developed extensive, chronic GVHD. One MMUD recipient (no. 23) with hepatitis-associated SAA developed grade IV acute GVHD and extensive, chronic GVHD of the liver, received a liver transplant, and is now well and disease free.
DISCUSSION Although the outcomes after MSD transplantation for pediatric SAA have improved over the years, the results using AD transplants have been less satisfactory. Margolis and Casper [5] reported 55% survival at 33 months for 28 heavily transfused adult and pediatric patients with SAA undergoing AD HSCT using an intensive conditioning regimen. Because of these and similar results [3-7], immunosuppression has remained first-line therapy for patients lacking an HLA-matched sibling. Unfortunately, IST has achieved limited improvement in survival, with high rates of clonal evolution and relapse [8,11-13,22,23]. In addition, delayed time to transplantation presumably due to IST administration has been associated with a poorer outcome in several studies [7,24]. This has led to the use of nonmyeloablative or reduced intensity preparative regimens to improve survival for recipients of AD transplants. The European Group for Blood and Marrow Transplantation Working Party reported 73% survival for 38 adult and pediatric patients when using a reduced intensity conditioning
Patient No.
D/R Age (y) Sex
Type of HSCT
HLA Matched, Mismatched Ag
Time to HSCT (mo)
Conditioning Regimen
ATG or Campath
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34* 35* 36† 37 38
23F/9F ?M/3M 35F/1F 30F/1M 30M/5F 37M/6M 28M/16M 38F/14M 28F/18F 30M/5F 44F/10M 44M/12F 24F/6M 40F/12M 30M/8F 43F/18F 36F/8F 36M/8F 34M/17F 50M/17F 33M/18M 24M/14M 35M/14M
MUD MUD MUD MMRD MMUD MMUD MMUD MMUD MUD MUD MMRD MUD MUD MUD MUD MMRD MMUD MMUD MMUD Haplo MUD MUD MUD
6/6 6/6 6/6 5/6, B 5/6, DRBI 5/6, DRBI 5/6, B 5/6, DRB1 6/6 6/6 5/6, DRB1 6/6 6/6 6/6 6/6 5/6, DRB1 5/6, DRB1 5/6, B 5/6, A 3/6, A, B, DRBI 6/6 8/10, A 6/6
34.8 12 4.8 4.8 21.6 4.8 22.8 3.6 22.8 NA 6 16.8 12 2.4 6 24 3.6 51.6 6 NA NA 9.6 40.8
Cy, TBI AraC, Cy, TBI Cy, TBI AraC, Cy, TBI AraC, Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Cy, TBI Flu, TBI Cy, TBI Cy, TBI Cy, TBI
ATG ATG ATG ATG ATG ATG ATG ATG ATG Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath Campath
Acute GVHD Grade No No No No No No Grade No Grade No No No No No No No Grade No No No No No
3
4 4
3
Chronic GVHD
CMV or EBV Reactivation
Disease Status
Chimerism Studies
Ext No No No No No No Ext Ext No Lim No No No No NA No No No No No No No
No No No No No No CMV No CMV CMV CMV No CMV CMV No No CMV No No CMV No EBV No
Died Died Alive Alive Alive Alive Alive, CMV neg Alive Alive, CMV neg Died, CMV neg Alive, CMV neg Alive Alive, CMV neg Alive, CMV neg Alive Died Alive, CMV neg Alive Failed to engraft Alive, CMV neg Alive Alive, EBV neg Alive
100% donor RFLP NA 100% donor STR 100 of 100 donor FISH 100% donor STR 100% donor STR 200 of 200 donor FISH 199 of 200 donor FISH 100% donor STR 200 of 200 donor FISH 100% donor STR 100% donor STR 198 of 200 donor FISH 194 of 200 donor FISH 200 of 200 donor FISH 100% donor STR 100% donor STR 200 of 200 donor FISH NA 100 of 100 donor FISH 100% donor STR 100% donor STR 100% donor STR
Comparable Outcomes of MSD and AD HSCT for Pediatric SAA
Table 3. Transplant Characteristics and Outcomes in Alternative Donor Recipients
NA indicates not available or applicable; HSCT, hematopoietic stem cell transplantation; GVHD, graft-versus-host disease; CMV, cytomegalovirus; EBV, Epstein-Barr virus; D, donor; R, recipient; M, male; F, female; HLA, human-leukocyte antigens; MUD, matched unrelated donor; MMUD, mismatched unrelated donor; MMRD, mismatched related donor; Haplo, haploidentical; Cy, cyclophosphamide; TBI, total body irradiation; AraC, cytarabine arabinoside; Flu, fludarabine; Bu, busulfan; ATG, antithymocyte globulin; Ext, extensive; Lim, limited; RFLP, restriction fragment length polymorphism; FISH, fluorescence in situ hybridization; STR, short tandem repeats; Ag, antigen. *Patients 34 and 35 are the same patient. †Patient 36 is also patient 1 in Table 2.
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Figure 1. Probability of 4-year overall survival for MSD recipients was 93% versus 89% for AD recipients who received reduced intensity conditioning. CI indicates confidence interval.
regimen of fludarabine, cyclophosphamide, and ATG [25]. Another study reported 75% survival with durable engraftment using non-TBI preparative regimens for 13 mostly young adult patients with SAA who received AD transplants [26]. Vassiliou et al [27] reported 100% survival with AD HSCT using Campath, low-dose TBI, and cyclophosphamide as reduced intensity conditioning in 8 patients. In addition, low-dose TBI with cyclophosphamide and ATG has been shown to be effective in securing durable grafts with acceptable toxicities in MUD grafts [2]. We find that this reduced intensity conditioning regimen with low-dose TBI achieves stable engraftment and excellent survival. There is concern that these patients may be at risk for secondary malignancies but none has occurred up to 86 months after AD transplantation. After irradiation, the risk for thyroid cancer is expected to be highest in children exposed at an age ⬍5 years [28]. For patients with SAA excluding Fanconi anemia undergoing MSD and AD transplantation [29], the estimated risk for developing any malignancy by 20 years (range, 1.4-221 months) was reported as 14%. The risk of malignancy likely has a linear relation to radiation doses up to 7-8 Gy. Although the risk of malignancy after conditioning regimens that include radiation are of obvious concern, these risks may be little different from those incurred
after IST alone or after transplant-preparative regimens that use only chemotherapy. Lifelong follow-up for all these patients is therefore necessary. Fludarabine has been used in preparative regimens without TBI. Although a survival of 71% to 84% has been noted for patients who received AD transplants [25,30-33], this regimen has led to a reportedly higher incidence of graft failure and GVHD in some studies [30,32]. Although fludarabine-based conditioning regimens remain promising, the incidence of GVHD using our conditioning regimen (especially in the patients who received Campath) appears lower than that in other reported series. Certainly, the long-term (⬎20-year) effects of a fludarabine-based or low-dose TBI-based preparatory regimen have yet to be determined. Campath was substituted for ATG because it allows for predictable depletion of T and B lymphocytes [34,35]. As previously published by our group and others, Campath may be associated with higher rates of viral infections such as CMV and adenovirus [3638]; however, in our patients, there was no CMV disease. Previous studies have shown that AD transplants result in an increased incidence of graft rejection and an increased risk of death from acute GVHD, infection, and pneumonitis when compared with MSD transplantation [25]. However, other groups have noted an association with lower rates of GVHD using Campath [39,40]. Although graft failure has been an ongoing concern in patients with SAA undergoing AD HSCT, in our experience only 1 patient’s engraftment failed and GVHD was minimal in this cohort of patients. None of the patients who received Campath developed extensive, chronic GVHD compared with 3 of 9 ATG recipients in the AD group; however, the sample was too small to determine significance. Many studies have shown that survival after HSCT is improved by shortening the time to transplantation, thereby decreasing blood product exposures and minimizing prior therapy [24,25,41]. In our report, the median time to transplantation was notably longer in the AD than in the MSD group (6 versus 2.4 months). This delay was attributed to the fact that all but 1 of the AD recipients received and failed IST
Table 4. Deaths Patient No.
Age (y) at Time of HSCT
Type of HSCT
Conditioning Regimen
ATG or Campath
Time of Death after HSCT
Cause of Death
11 16 17 25 31
4.0 9.4 3.3 18.4 5.9
MSD MUD MUD MMRD MUD
Cy RI Myeloablative RI RI
ATG ATG ATG Campath Campath
6 d 5.5 y 33 d 52 d 66 d
Pre-existing infection Chronic GVHD, pulmonary failure Pre-existing infection Idiopathic pneumonia Adenovirus, grade IV acute GVHD
RI indicates reduced intensity; HSCT, hematopoietic stem cell transplantation; MSD, matched sibling donor; MMRD, mismatched related donor; MUD, matched unrelated donor; Cy, cyclophosphamide; GVHD, graft-versus-host disease; ATG, antithymocyte globulin.
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before transplantation. However, we observed no effect of time from diagnosis to transplantation on survival, even though AD transplantation was performed later after diagnosis than MSD transplantation. Some preceding IST for these patients may have favored subsequent engraftment when low-intensity conditioning was used. We have shown that a reduced intensity conditioning regimen of cyclophosphamide, low-dose TBI, and ATG or Campath achieves sustained engraftment and excellent survival in pediatric patients with SAA who receive AD transplants. These results are comparable to the outcome for pediatric patients with SAA who received MSD transplants.
13.
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15.
16.
17.
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