Scholarly article on topic 'Comparison of Unrelated Cord Blood Transplantation and HLA-Mismatched Unrelated Bone Marrow Transplantation for Adults with Leukemia'

Comparison of Unrelated Cord Blood Transplantation and HLA-Mismatched Unrelated Bone Marrow Transplantation for Adults with Leukemia Academic research paper on "Clinical medicine"

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{"Unrelated cord blood transplantation" / "HLA-mismatched unrelated bone marrow transplantation"}

Abstract of research paper on Clinical medicine, author of scientific article — Yoshiko Atsuta, Yasuo Morishima, Ritsuro Suzuki, Tokiko Nagamura-Inoue, Shuichi Taniguchi, et al.

Recent advances in unrelated cord blood transplantation (UCBT) and high-resolution typing of human leukocyte antigen (HLA) from an unrelated donor have increased choices in alternative donor/stem cell source selection. We assessed HLA-mismatched locus-specific comparison of the outcomes of 351 single-unit UCB and 1,028 unrelated bone marrow (UBM) adult recipients 16 years old or older at the time of transplantation who received first stem cell transplantation with myeloablative conditioning for acute leukemia or myelodysplastic syndromes. With adjusted analyses, HLA 0 to 2 mismatched UCBT showed similar overall mortality (relative risk [RR] = 0.85, 95% confidence interval [CI], 0.68-1.06; P = .149) compared with that of single-HLA-DRB1-mismatched UBMT. UCBT showed inferior neutrophil recovery (RR = 0.50, 95% CI, 0.42-0.60; P < .001), lower risk of acute graft-versus-host disease (RR = 0.55, 95% CI, 0.42-0.72; P < .001), and lower risk of transplantation-related mortality (RR = 0.68, 95% CI, 0.50-0.92; P = .011) compared with single-HLA-DRB1-mismatched UBMT. No significant difference was observed for risk of relapse (RR = 1.28, 95% CI, 0.93-1.76; P = .125). HLA 0 to 2 antigen-mismatched UCBT is a reasonable second alternative donor/stem cell source with a survival outcome similar to that of single-HLA-DRB1-mismatched or other 7 of 8 UBMT.

Academic research paper on topic "Comparison of Unrelated Cord Blood Transplantation and HLA-Mismatched Unrelated Bone Marrow Transplantation for Adults with Leukemia"

ASBMI

American Society for Blood and Marrow Transplantation

Comparison of Unrelated Cord Blood Transplantation and HLA-Mismatched Unrelated Bone Marrow Transplantation for Adults with Leukemia

Yoshiko Atsuta,1 Yasuo Morishima,2'* Ritsuro Suzuki,1 Tokiko Nagamura-Inoue,3 Shuichi Taniguchi,4 Satoshi Takahashi,5 Shunro Kai,6 Hisashi Sakamaki,7 Yasushi Kouzai,8 Naoki Kobayashi,9 Takahiro Fukuda,10 Hiroshi Azuma," Minoko Takanashi,12 Takehiko Mori,13 Masahiro Tsuchida,14 Takakazu Kawase,15 Keisei Kawa,16 Yoshihisa Kodera,17 Shunichi KatoJ^* for the Japan Marrow Donor Program and the Japan

Cord Blood Bank Network

Recent advances in unrelated cord blood transplantation (UCBT) and high-resolution typing of human leukocyte antigen (HLA) from an unrelated donor have increased choices in alternative donor/stem cell source selection. We assessed HLA-mismatched locus-specific comparison of the outcomes of 351 single-unit UCB and 1,028 unrelated bone marrow (UBM) adult recipients 16 years old or older at the time of transplantation who received first stem cell transplantation with myeloablative conditioning for acute leukemia or myelodysplastic syndromes. With adjusted analyses, HLA 0 to 2 mismatched UCBT showed similar overall mortality (relative risk [RR] = 0.85, 95% confidence interval [CI], 0.68-1.06; P = .149) compared with that of single-HLA-DRB1-mismatched UBMT. UCBT showed inferior neutrophil recovery (RR = 0.50, 95% CI, 0.42-0.60; P < .001), lower risk of acute graft-versus-host disease (RR = 0.55, 95% CI, 0.42-0.72; P < .001), and lower risk of transplantation-related mortality (RR = 0.68, 95% CI, 0.500.92; P =.011) compared with single-HLA-DRB1-mismatched UBMT. No significant difference was observed for risk of relapse (RR = 1.28,95% CI, 0.93-1.76; P = .125). HLA 0 to 2 antigen-mismatched UCBT is a reasonable second alternative donor/stem cell source with a survival outcome similar to that of single-HLA-DRB1-mismatched or other 7 of 8 UBMT.

Biol Blood Marrow Transplant 18: 780-787 (2012) © 2012 American Society for Blood and Marrow Transplantation

KEY WORDS: Unrelated cord blood transplantation, HLA-mismatched unrelated bone marrow transplantation

From the 'Department of HSCT Data Management/Biostatistics Nagoya University Graduate School of Medicine, Nagoya, Japan; 2Department of Hematology and Cell Therapy Aichi Cancer Center Hospital, Nagoya, Japan; Department of Cell Processing & Transfusion, Research Hospital The Institute of Medical Science, The University of Tokyo, and Tokyo Cord Blood Bank Tokyo, Tokyo, Japan; Department of Hematology Toranomon Hospital, Tokyo, Japan; 5Department of Molecular Therapy The Institute of Medical Science The University of Tokyo, Tokyo, Japan; Department of Transfusion Medicine Hyogo College of Medicine, Nishinomiya, Japan; 7Division of Hematology Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan;

Department of Transfusion Medicine, Tokyo Metropolitan Tama Medical Center, Tokyo, Japan; 'Department of Hematology, Sapporo Hokuyu Hospital, Sapporo, Japan; 10Hemato-poietic Stem Cell Transplantation Unit National Cancer Center Hospital, Tokyo, Japan; ''Hokkaido Red Cross Blood Center, Sapporo, Japan; '2The Japanese Red Cross Tokyo Blood Center, Tokyo, Japan; Division of Hematology,

Department of Medicine, Keio University School of Medicine, Tokyo, Japan; Ibaraki Children's Hospital, Mito, Japan; '5Division of Epidemiology and Prevention, Aichi Cancer Center Hospital, Nagoya, Japan; Osaka Medical Center and Research Institute for Maternal and Child Health, Izumi, Japan; '7BMT Center, Japanese Red Cross Nagoya First Hospital, Nagoya, Japan; and Department of Cell Transplantation & Regenerative Medicine, Tokai University School of Medicine, Isehara, Japan. Financial disclosure: See Acknowledgments on page 786. *Y.M. and S. Kato share senior authorship.

Correspondence and reprint requests: Yoshiko Atsuta, MD, PhD, Department of Hematopoietic Stem Cell Transplantation Data Management/Biostatistics, Nagoya University School of Medicine, '-'-20 Daiko-Minami, Higashi-ku Nagoya 46'-0047, Japan (e-mail: y-atsuta@med.nagoya-u.ac.jp). Received July 20, 20''; accepted October 9, 20'' © 20'2 American Society for Blood and Marrow Transplantation '083-879'/$36.00 doi:'0.'0'6/j.bbmt.20''.'0.008

INTRODUCTION

Allogeneic hematopoietic stem cell transplantation (HSCT) is a widely used, curative treatment for hema-tologic malignancies. When available, a human leukocyte antigen (HLA)-identical sibling is the donor of choice. However, only about 30% of candidates eligible for allogeneic HSCT will have such a donor. In addition, older patients with older siblings have more difficulty finding such a donor capable of stem cell donation. High-resolution donor-recipient HLA matching has contributed to the success of unrelated donor marrow transplantation, and the current first recommended alternative donor after an HLA-matched sibling for HSCT is an HLA-A, -B, -C, and -DRB1 8 of 8-allele-matched unrelated donor [1-4]. However, there are still a significant number of patients for which finding an HLA 8 of 8-matched unrelated donor is difficult and for whom a second alternative donor/stem cell source should be found.

The effect of HLA mismatches after bone marrow transplantation from unrelated donors (UBMT) has been well studied, and single mismatched UBM donors are usually selected as a second alternative donor/stem cell source [1-4]. Lee al. [3] showed that a single mismatch, antigen-level, or high-resolution, at HLA-A, -B, -C, or -DRB1 loci was associated with higher mortality and decreased survival. However, the reduction in survival may be acceptable in comparison with the survival rates for currently available alternative treatments. Analyses from the Japan Marrow Donor Program (JMDP) showed better survival in HLA class II mismatched recipients; thus, single-DRB1-mismatched UBM donor is currently a second alternative in Japan [1,2,5].

Recent advances in unrelated cord blood transplantation (UCBT) have provided patients with increased choices for a second alternative donor/stem cell source [6]. Clinical comparison studies of cord blood transplantation and HLA-A, -B, and -DRB1 6 of 6 allele-matched bone marrow transplantation for leukemia from unrelated donors in adult recipients showed comparable results [7-9]. More recently, promising outcomes of UCBT were shown compared with HLA-A, -B, -C, and -DRB1 8 of 8 allele-matched UBMT, the current first alternative donor/stem cell source [10-12].

The aim of this study was to determine the utility of UCBT as a second-alternative donor source in adult patients with acute leukemia or myelodysplastic syndromes. It is common today to perform highresolution typing of HLA for donor selection of unrelated donors; thus, we performed mismatched-allele-specific analyses for comparison of HLA-mismatched UBMT and UCBT in terms of overall survival (OS) and other HSCT outcomes, setting single-DRB1-mismatched UBMT, the current second alternative, as the reference.

PATIENTS AND METHODS

Collection of Data and Data Source

The recipients' clinical data were provided by the Japan Cord Blood Bank Network (JCBBN) and the JMDP [13]. Peripheral blood stem cell donation from unrelated donors was not permitted in Japan during the study period. All 11 cord blood banks in Japan are affiliated with JCBBN. Both JCBBN and JMDP collect recipients' clinical information at 100 days posttransplantation. Patients' information on survival, disease status, and long-term complications including chronic graft-versus-host (cGVHD) disease and second malignancies is renewed annually using follow-up forms. This study was approved by the institutional review board of Nagoya University Graduate School of Medicine.

Patients

The subjects were adult patients of at least 16 years of age with acute myeloid leukemia, acute lymphoblas-tic leukemia, and myelodysplastic syndromes, who were recipients of first UBMT or UCBT with myeloa-blative conditioning. All patients in the UCBT cohort received a single-unit CB. Transplantation years were between 1996 and 2005 for UBMT and between 2000 and 2005 for UCBT to avoid the first 3 years of a pioneering period (1993-1995 for UBMT and 1997-1999 for UCBT). There were no statistically significant differences between UBMT in 1996-1999 and UBMT in 2000-2005 in probabilities of OS (41% versus 44%, at 3 years posttransplantation; P = .86) and in relapse-free survival (RFS) (40% versus 40%, at 3 years posttransplantation; P = .93).

Among 2,253 UBMT recipients with complete HLA high-resolution data, the following recipients with HLA -A, -B, -C, and -DRB1 8 of 8 allele match (n = 1,079) and more than three mismatches (5 of 8 allele match [n = 117], 4 of 8 allele match [n = 24], 3 of 8 allele match [n = 4], 2 of 8 allele match [n = 1]) were excluded. There were no statistically significant differences in risk of mortality or treatment failure (RFS) associated with single high-resolution (allele) versus single low-resolution (antigen) mismatches (data not shown), so in the analyses, allele and antigen mismatches were considered equivalent. HLA matching of cord blood was performed using low-resolution molecular typing methods for HLA-A and -B, and high-resolution molecular typing for HLA-DRB1. Of 557 recipients of CB with complete HLA data, 105 recipients with three mismatches and nine recipients with four mismatches were excluded. A total of 1,028 UBMT recipients (248 HLA class II locus mismatched, 424 HLA class I locus mismatched, and 356 HLA2 loci mismatched) and 351 UCBT recipients (20 HLA-A, -B, low-resolution and -DRB1 matched, 87

locus mismatched, and 244 2 loci mismatched) were the subjects for analyses. Both host-versus-graft and graft-versus-host directions were accounted for in terms of HLA mismatch.

HLA Typing

Alleles at the HLA-A, -B, -C, and -DRB1 with unrelated bone marrow donor-recipient pairs and for HLA-DRB1 for unrelated cord blood donor-recipient pairs were identified by the methods described previously [1,5,14]. Serologic or antigen-level typing was performed with a standard two-stage complement-dependent test of microcytotoxicity or low-resolution DNA-based typing usually by collapsing the four-digit typing result back to its first two digits in part.

Definitions

The primary outcome of the analyses was OS, defined as time from transplantation to death from any cause. A number of secondary endpoints were also analyzed. Neutrophil recovery was defined by an absolute neutrophil count of at least 500 cells per cubic millimeter for three consecutive points; platelet recovery was defined by a count of at least 50,000 platelets per cubic millimeter without transfusion support. Diagnosis and clinical grading of acute GVHD (aGVHD) were performed according to the established criteria [15,16]. Relapse was defined as a recurrence of underlying hematologic malignant diseases. Transplantation-related death was defined as death during a continuous remission. RFS was defined as survival in a state of continuous remission.

Statistical Analysis

Descriptive statistical analysis was performed to assess patient baseline characteristics, diagnosis, disease status at conditioning, donor-patient ABO mismatches, preparative regimen, and GVHD prophylaxis. Medians and ranges are provided for continuous variables and percentages for categoric variables. Cumulative incidence curves were used in a competing-risks setting to calculate the probability of aGVHD and cGHVD, relapse, and transplantation-related mortality (TRM) [17]. Gray's test was used for group comparison of cumulative incidences [18]. Adjusted comparison of the groups on OS and RFS was performed with the use of the Cox proportional-hazards regression model [19]. For other outcomes with competing risks, Fine and Gray's proportional-hazards model for subdistribution of a competing risk was used [20]. For neutrophil and platelet recovery, death before neutrophil or platelet recovery was the competing event; for GVHD, death without GVHD and relapse were the competing events; for relapse, death without relapse was the competing

event; and, for TRM, relapse was the competing event [21]. Adjusted probabilities of OS and RFS were estimated using the Cox proportional-hazards regression model, with consideration of other significant clinical variables in the final multivariate models. The variables considered were the patient's age at transplantation, patient's sex, donor-patient sex mismatch, donor-patient ABO mismatch, diagnosis, disease status at conditioning, the conditioning regimen, and the type of prophylaxis against GVHD. Factors differing in distribution between CB and BM recipients and factors known to influence outcomes were included in the final models. Variables with more than two categories were dichotomized for the final multivariate model. Variables were dichotomized as follows: patient age >40 or <40 years at transplantation, recipient's sex, sex-mismatched donor-patient pair versus sex-matched pair, donor-recipient ABO major mismatch versus others for ABO matching, advanced versus standard (first and second complete remission of acute myeloid leukemia, first complete remission of acute lymphoblastic leukemia, or refractory anemia or refractory anemia with ring sidoblasts of myelodysplastic syndromes) risk of the disease, cyclophosphamide, and total-body irradiation (TBI) or busulfan and cyclophosphamide or others for conditioning regimen, and cyclosporine-based versus tacrolimus-based prophylaxis against GVHD. No significant interactions were identified between each variable and HLA disparity/stem cell source groups. All P values were two-sided.

RESULTS

Patient Characteristics

Table 1 shows characteristics of patients, their disease, and transplantation regimens. Proportions of females, sex-mismatched donor-recipient pairs, and ABO mismatched donor recipient pairs were larger in cord blood recipients (P < .001, P < .001, and P < .001, respectively). UCB recipients were older than recipients of UBM (median age, 37 years versus 34 years; P < .001). A preparative regimen with TBI and cyclophosphamide was used in the majority of patients in all groups, and cytosine arabinoside was supplemented for CB recipients in addition to TBI and cyclophosphamide in about half the recipients with cyclophosphamide and TBI. For GVHD prophylaxis, tacrolimus and short-term methotrexate was used preferentially in BM recipients (61% of DRB1-one-mismatched BM recipients), while cyclo-sporine A and short-term methotrexate was used preferentially in CB recipients (61%). The median follow-up period for survivors was 2.1 years (range, 0.1-6.2) for CB recipients and 5.5 (range, 0.3-11.6) years for BM recipients.

Table 1. Patient, Disease, and Transplantation Characteristics According to Stem Cell Source and Number of Mismatched Loci

Bone Marrow Transplant

Class II One Locus Class I One Locus Two Loci Cord Blood

Mismatch Mismatch Mismatch Transplantation

N(%) N(%) N(%) N(%)

Number of transplantations 248 424 356 351

Patient age at transplantation

Median (range) 36 (16-60) 34 (16-67) 34 (l6-59) 37 (16-58)

Patient sex

Male 151 (61) 241 (57) 2l0 (59) 162 (46)

Female 97 (39) 183 (43) l46 (4l) 189 (54)

Sex matching

Matched l45 (58) 268 (63) 2l7 (6l) 170 (48)

Male to female 52 (2l) 82 (19) 73 (2l) 97 (28)

Female to male 50 (20) 71 (17) 64 (l8) 84 (24)

Unknown 1 (<l) 3(1) 2 (l) 0 (0)

Diagnosis

AML l35 (54) 204 (48) l72 (48) 193 (55)

ALL 78 (3l) 149 (35) l35 (38) 113 (32)

MDS 35 (l4) 71 (17) 49 (l4) 45 (13)

Disease status

Standard l24 (50) 214 (50) l68 (47) 147 (42)

Advanced ll4 (46) 195 (46) l69 (47) I74(50)

Unknown l0 (4) 15(4) l9 (5) 30(9)

ABO matching

Matched ll9 (48) 184 (43) l53 (43) 114(32)

Minor mismatch 53 (2l) 108 (25) 85 (24) 99 (28)

Major mismatch 67 (27) 116 (27) 97 (27) 73 (21)

Bidirectional 8(3) 12(3) l4 (4) 64(18)

Unknown l (<l) 4(1) 7 (2) 1 (<l)

HLA-mismatched number and direction

Matched 20 (6)

One locus mismatched 87 (25)

HVG direction l6 (6) 38 (9) 8 (9)

GVH direction l7 (7) 30 (7) 8 (9)

Both directions 2l5 (87) 356 (84) 7l (82)

Two loci mismatched 244 (70)

Two HVG direction 4 (l) 2(1)

One HVG direction and one GVH direction 6 (2) 4 (2)

Two GVH direction 4 (l) 3 (l)

One both directions and one HVG direction 42 (l2) 40(16)

One both directions and one GVH direction 29 (8) 28 (ll)

Two both directions 27l (76) l67 (68)

No. of nucleated cells infused (x l07/kg)

Median 25.0 24.5 23 2.46

Range 2.40-59.8 2.10-97.5 l.5-66.0 1.41-6.01

Preparative regimen

CY + TBI 94 (38) 168(40) l5l (42) 109 (31)

CY + CA + TBI 46 (l9) 78 (l8) 74 (2l) l24 (35)

CY + BU + TBI 20 (8) 39(9) 27 (8) l5 (4)

Other TBI regimen 45 (l8) 70(17) 6l (l7) 80 (23)

BU + CY 34 (l4) 54(13) 30 (8) 2l (6)

Other non-TBI regimen 9 (4) 15(4) l3 (4) 2 (l)

GVHD prophylaxisis

Cycrosporine A + sMTX 87 (35) 221 (52) l50 (42) 213 (61)

Cyclosporine A ± other l (<l) 5 (l) 5 (l) 24 (7)

Tacrolimus + sMTX l52 (6l) l9l (45) l93 (54) 76 (22)

Tacrolimus ± other 8(3) 5 (l) 6 (2) 35 (10)

Others 0 (0) 2(<l) 2 (<l) 3 (l)

ALL indicates acute lymphoblastic leukemia; AML, acute myelogenous leukemia; BU, oral busulfan; CA, citarabine; CY, cyclophosphamide; GVH, graft-versus-host; HVG, host-versus-graft; MDS, myelodysplastic syndomes; sMTX, short-term methotrexate.

Outcome

OS and RFS

OS and RFS for CB recipients were similar when compared with that of single-HLA-DRBl-mismatched BM recipients (relative risk [RR] = 0.85, 95% confidence interval [CI], 0.68-1.06; P = .149 for OS and RR = 0.97, 95% CI, 0.92-1.35; P = .747) (Table 2).

The adjusted probabilities of survival at 3 years posttransplantation of CB recipients (47%) were not

different from those of single HLA-DRB1 mismatched BM recipients (41%; P = .19) or single HLA class I-mismatched BM recipients (47%; P = .96), but superior to those of 6 of 8 BM recipients (38%; P = .014) (Figure 1A). Figure 1B shows adjusted RFS curves (42% for CB recipients, 36% for single HLA-DRB1-mismatched BM, 44% for single HLA class I-mismatched BM, and 36% for 6 of 8 BM recipients, at 3 years posttransplant) (P values of comparison between CB and single HLA-DRB1-mismatched BM, CB, and single HLA

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Relapse and TRM

There was no significant increase of relapse rates among CB recipients when compared with DRB1 single-mismatched BM recipients (RR = 1.28, 95% CI, 0.93-1.76; P = .125). The risk of TRM was lower in CB recipients compared with that of single HLA-DRB1-mismatched BM recipients (RR = 0.68, 95% CI, 0.50-0.92; P = .011) (Table 2). The risk of TRM was also lower in CB recipients when compared with 6 of 8 BM recipients (RR = 0.52, 95% CI, 0.39-0.68; P < .001).

Hematologic recovery

Neutrophil and platelet recovery was inferior in CB recipients, as shown in Table 3 (RR = 0.50, 95% CI, 0.42-0.60; P < .001 for neutrophil recovery, RR = 0.52, 95% CI, 0.42-0.63; P < .001 for platelet recovery).

Acute GVHD and chronic GVHD

The risk of grade 2 to 4 or severe (grades 3-4) aGVHD was lower in CB recipients than that of single HLA-DRB1-mismatched BM recipients (RR = 0.55, 95% CI, 0.42-0.72; P < .001 for grade 2 to 4 aGVHD and RR = 0.43, 95% CI, 0.27-0.58; P < .001 for severe aGVHD) (Table 4). Unadjusted cumulative incidence of severe aGVHD was 9% for CB, 19% for single HLA-DRB1-mismatched BM, 18% for single HLA

----DRB1 1mm BM

A/B/C ImmBM 2 mm BM -CB

Years after transplantation

----DRB1 ImmBM

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Year* after transplantation

Figure 1. Adjusted probabilities of OS (A) and RFS (B). The adjusted 3-year probabilities of OS for unrelated cord blood recipients, single-HLA-DRBI-mismatched unrelated bone marrow (UBM) recipients, single-HLA-class-I-mismatched UBM, and 6 of 8 UBM recipients were 47%, 41%, 47%, and 38%, respectively (A). The adjusted 3-year probabilities of RFS were 42%, 36%, 44%, and 36%, respectively (b).

Table 3. Multivariate Analyses of Neutrophil and Platelet Recovery

Neutrophil Recovery Platelet Recovery

Degree of HLA Mismatch N RR (95% CI) P value RR (95% CI) P value

Bone marrow transplantation Single DRBl (7/8) 248 1.00 1.00

Single A or B (7/8) 137 1.31 (1.04-1.65) .021 l.3l (1.01-1.70) .039

Single C (7/8) 287 l.l9 (0.98-1.43) .069 0.98 (0.79-l.2l) .840

C + DRBl (6/8) l44 0.96 (0.77-1.20) .735 0.79 (0.62-1.02) .065

A/B + C (6/8) l22 l.l4 (0.89-1.45) .307 0.84 (0.63-l.l3) .255

Other two loci (6/8) 90 0.89 (0.68-1.14) .346 0.80 (0.58-l.l0) .l74

Cord blood transplantation 351 0.50 (0.42-0.60) <.001 0.52 (0.42-0.63) <.00l

RR indicates relative risk; CI, confidence interval.

Adjusted by patient age at transplantation >40 versus <40, patient sex, donor-patient sex mismatch versus matched, ABO major mismatch versus others, advanced versus standard disease status at transplant, cyclophosphamide, and total-body irradiation or busulfan and cyclophosphamide for conditioning versus other conditioning regimen, and cyclosporine-based versus tacrolimus-based prophylaxis against graft-versus-host disease.

class I-mismatched BM, and 22% for 6 of 8 BM at 100 days posttransplantation (P < .001 between CB and single HLA-DRB1-mismatched BM) (Figure 2A).

Among recipients who survived at least 100 days posttransplantaton, the risk of developing cGVHD and extensive-type cGVHD was not significantly increased in all HLA disparity groups of CB recipients when compared with that of HLA-DRB1-allele/anti-gen-mismatched BM recipients (RR = 1.36, 95% CI, 0.99-1.88; P = .057 for cGVHD, and RR = 0.86, 95% CI, 0.55-1.34; P = .500 for extensive-type cGVHD). The unadjusted cumulative incidence of extensive-type cGVHD was 17% for CB recipients, 20% for single HLA-DRB1-mismatched BM, 25% for single HLA class I-mismatched BM, and 30% for 6 of 8 BM recipients at year posttransplantation (P = .34 between CB and single HLA-DRB1-mismatched BM) (Figure 2B).

DISCUSSION

Our main objective was to compare OS after transplantation of UCBT and single-HLA-mismatched UBMT and to provide useful data for selection of an appropriate donor and graft source in second stem cell source/donor selection for adults with hematologic malignancy. To the best of our knowledge, this is the first study to involve mismatched allele/antigen-specific analyses including CB for the process of donor selection. Our results suggest that 0 to 2 HLA-mismatched UCB is a reasonable second alternative of choice for adult patients with leukemia, with similar survival to that of single DRB1-mismatched or other 7 of 8 UBM recipients, the current first choice for second alternative donor/stem cells.

Neutrophil and platelet recovery was slower in CB recipients than BM recipients, consistent with the results of previous reports [7-10,12]. This is the major limitation of the use of UCB, and several strategies have been studied to reduce the neutropenic period, such as screening for patients' pretransplantation anti-HLA antibodies and their specificity, transplantation of 2 UCB units if a single UCB unit with an ade-

quate cell dose is not available, or direct infusion of UCB into bone marrow [22-26].

Despite higher HLA disparity at the antigen level (69% 2 antigen mismatch, 25% antigen mismatch, and 6% matched), UCB recipients showed lower incidence of severe aGVHD than single DRB1-mismatched UBM recipients, consistent with other reports that compared UCB with single-mismatched UBM (7 of 8) [8,11,12]. In our study, tacrolimus and short-term methotrexate were used preferentially in BM recipients, whereas cyclosporine A was used in 68% of CB recipients. Prior studies have shown reduced severe aGVHD with tacrolimus, and this difference may have underscored the improved aGVHD control of UCB over mismatched BM in unadjusted analyses [27,28]. It is likely that decreased risk of grade 2 to 4 aGVHD in UCB recipients contributed to decreased risk of TRM among UCB recipients.

Increasing the number of HLA mismatches from 7 of 8 to 6 of 8 was associated with an approximately 10% reduction in survival in UBM recipients, which was quite similar to the results from the National Marrow Donor Program [3]. Because we eliminated data from the first 3 pioneering years of unrelated BMT, most of the bone marrow recipients and donors were allele-typed for at least HLA-A, -B, and -DRB1 before transplantation. Survival outcomes of single class I mismatch were not significantly different from those of single class II mismatch in the current analyses. We believe that allele typing of HLA-A, -B, and -DRB1 before transplantation led to better selection of the donor compared with that in the first several years of UBMT. This study includes a large number of fully typed BM and CB recipients, but there are limitations. The choice of stem cell source is influenced by many unmeasured factors that can affect outcome. It is also influenced by the availability of acceptable HLA disparity for unrelated donors and mainly cell dose for cord blood units. Although we have adjusted for known risk factors and disparities between groups, we cannot rule out the influence of potential selection bias, which can only be excluded in a randomized controlled trial. Transplantation years

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Figure 2. Cumulative incidence of grade 3 to 4 aGVHD (A) and extensive-type cGVHD (B). The cumulative incidences of grade 3 to 4 aGVHD at I 00 days posttransplantation for unrelated cord blood recipients, single HLA-DRB I -mismatched unrelated bone marrow (UBM) recipients, and single HLA class I-mismatched UBM were 9%, I 9%, I 8%, and 22% (A). The cumulative incidences of extensive-type cGVHD at I -year posttransplantation were I 7%, 20%, 25%, and 30% (B).

of UBM recipients included from 1996 and 1999, for which there were no significant outcome differences between UBMT performed in 1996 to 1999 and after 2000. In these periods, there were advances including in supportive care and nutritional management, introduction of new antifungal agents, and more frequent use of tacrolimus, which may have affected transplantation outcomes [27-32].

In conclusion, we suggest that 0 or 2 HLA-mismatched UCB is a comparable second alternative for adult patients with leukemia in the absence of the first alternative, an 8 of 8 UBM donor, with survival similar to that of single DRB1-mismatched or other 7 of 8 UBM recipients. UCB may be preferred over single mismatched UBM when a transplantation is needed urgently, considering the short time needed for UCBT.

ACKNOWLEDGMENTS

The authors are grateful for the assistance and cooperation of all the staff members of the collaborating institutes of the Japan Cord Blood Bank Network and Japan Marrow Donor Program. This work was supported by a Research Grant for Tissue Engineering (H17-014), a Research Grant for Allergic Disease and Immunology (H20-015), a Research Grant for Cancer (H19-1), and a Research Grant for Allergic Disease and Immunology (H23-010) from the Japanese Ministry of Health, Labor, and Welfare.

Financial disclosure: The authors have nothing to disclose.

AUTHORSHIP STATEMENT

Contributions: Y.A., Y.M., R.S., and S. Kato designed the study, and wrote the article; Y.A. analyzed results and created the figures; T.N.I., H.A, and M. Takanashi reviewed and cleaned the Japan Cord Blood Bank Network data, and reviewed the results; S. Taniguchi, S. Takahashi, S. Kai., H.S., Y. Kouzai., N.K., T.M., T.F., and Y. Kodera submitted and cleaned the data; M. Tsuchida, K.K., T.K., and Y.M. reviewed and cleaned the Japan Marrow Donor Program data, and reviewed the results.

SUPPLEMENTARY DATA

Supplementary data related to this article can be found online at doi:10.1016/j.bbmt.2011.10.008.

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