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`
`Regular Article
`
`TRANSPLANTATION
`
`Rituximab prophylaxis prevents corticosteroid-requiring chronic GVHD
`after allogeneic peripheral blood stem cell transplantation: results of
`a phase 2 trial
`Corey Cutler,1 Haesook T. Kim,2 Bhavjot Bindra,1 Stefanie Sarantopoulos,3 Vincent T. Ho,1 Yi-Bin Chen,4
`Jacalyn Rosenblatt,5 Sean McDonough,1 Phandee Watanaboonyongcharoen,3 Philippe Armand,1 John Koreth,1
`Brett Glotzbecker,1 Edwin Alyea,1 Bruce R. Blazar,6 Robert J. Soiffer,1 Jerome Ritz,1 and Joseph H. Antin1
`
`1Department of Medical Oncology and 2Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, MA; 3University of
`North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, NC; 4Division of Hematology/Oncology, Massachusetts General Hospital, Boston,
`MA; 5Division of Hematology/Oncology, Beth Israel Deaconess Medical Center, Boston, MA; and 6Blood and Marrow Transplantation, University of
`Minnesota, Minneapolis, MN
`
`Key Points
`
`(cid:129) Rituximab prevents steroid-
`requiring chronic graft-vs-host
`disease when given after
`peripheral blood stem cell
`transplantation.
`(cid:129) Overall survival is improved
`with rituximab after allogeneic
`peripheral blood stem cell
`transplantation when
`compared with a control cohort.
`
`B cells are implicated in the pathophysiology of chronic graft-vs-host disease (GVHD),
`and phase 2 trials suggest that B cell depletion can treat established chronic GVHD. We
`hypothesized that posttransplantation B cell depletion could prevent the occurrence of
`chronic GVHD. We performed a 65-patient phase 2 trial of rituximab (375 mg/m2 IV),
`administered at 3, 6, 9, and 12 months after transplantation. Rituximab administration
`was safe without severe infusional adverse events. The cumulative incidences of chronic
`GVHD and systemic corticosteroid-requiring chronic GVHD at 2 years from trans-
`plantation were 48% and 31%, respectively, both lower than the corresponding rates
`in a concurrent control cohort (60%, P 5 .1, and 48.5%, P 5 .015). There was no difference
`in relapse incidence, but treatment-related mortality at 4 years from transplantation was
`significantly lower in treated subjects when compared with controls (5% vs 19%, P 5 .02),
`and overall survival was superior at 4 years (71% vs 56%, P 5 .05). At 2 years from
`transplantation, the B-cell activating factor/B-cell ratio was significantly higher in subjects
`who developed chronic GVHD in comparison with those without chronic GVHD (P 5 .039).
`Rituximab can prevent systemic corticosteroid-requiring chronic GVHD after peripheral blood stem cell transplantation and should be
`tested in a prospective randomized trial. This trial was registered at www.clinicaltrials.gov as NCT00379587. (Blood. 2013;122(8):1510-1517)
`
`Introduction
`
`Chronic graft-versus-host disease (GVHD) is the leading cause of
`late morbidity, impaired quality of life, and mortality after allogeneic
`stem cell transplantation.1-3 Efforts to pharmacologically prevent
`chronic GVHD by extending the period of immunosuppression
`after allogeneic transplantation have not been successful.4,5 The
`use of T-cell depletion, either with in vivo (polyclonal or monoclonal
`antibody therapy)6-8 or ex vivo (T-cell depletion or CD341 selection)9
`methodologies has been shown to prevent chronic GVHD; however,
`this has not been associated with an improvement in overall survival
`because of excess mortality associated with opportunistic infections
`and possibly malignant disease relapse. Finally, allogeneic tolerance
`induction with the use of posttransplantation cyclophosphamide has
`been shown to prevent chronic GVHD, but long-term outcomes have
`not been compared with traditional GVHD prevention strategies.10
`Because prolongation of calcineurin inhibition after transplanta-
`tion does not prevent the occurrence of chronic GVHD, alternative,
`non-T-cell–dependent pathways that can lead to alloreactivity can
`be implicated in the pathogenesis of chronic GVHD in some patients.
`B-cell-dependent processes have thus been implicated following
`
`several lines of evidence: antibodies against minor histocompat-
`ibility antigens have been associated with the occurrence of chronic
`GVHD11; B-cell depletion in the peritransplantation period has been
`correlated with a reduction in chronic GVHD incidence12; and most
`important, B-cell–depletion therapy with rituximab is effective in
`the therapy of established chronic GVHD.13-19 In addition, murine
`models of chronic GVHD and bronchiolitis obliterans have implicated
`donor B-cell alloantibodies in the pathogenesis of this disease.20
`Much work has focused on the potential role of B cells in patho-
`biology of chronic GVHD. It is known that B-cell reconstitution in
`patients with chronic GVHD is delayed, and these patients have
`elevated plasma B-cell activating factor (BAFF) to B-cell ratios.21
`Altered B-cell homeostasis in chronic GVHD is associated with
`persistence of circulating, potentially autoreactive, B cells.21,22
`Further supporting a mechanistic role for B cells in human chronic
`GVHD are studies demonstrating altered signaling through the BAFF-
`associated and B-cell-receptor–associated pathways.23,24
`Recently, in a small series of patients with aggressive B-cell
`malignancies treated with rituximab in the early posttransplantation
`
`Submitted April 10, 2013; accepted June 27, 2013. Prepublished online as
`Blood First Edition paper, July 16, 2013; DOI 10.1182/blood-2013-04-495895.
`
`The publication costs of this article were defrayed in part by page charge
`payment. Therefore, and solely to indicate this fact, this article is hereby
`marked “advertisement” in accordance with 18 USC section 1734.
`© 2013 by The American Society of Hematology
`
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`BLOOD, 22 AUGUST 2013 x VOLUME 122, NUMBER 8
`
`RITUXIMAB PROPHYLAXIS FOR CHRONIC GVHD
`
`1511
`
`period, a reduction in the rate of chronic GVHD was noted25;
`however, patients were treated using a preparative regimen that
`traditionally is associated with low rates of chronic GVHD.26
`Because chronic GVHD occurs more frequently after peripheral
`blood stem cell transplantation,27,28 we conducted a phase 2 trial of
`rituximab given specifically for the prevention of chronic GVHD
`after allogeneic peripheral blood stem cell transplantation.
`
`Methods
`
`This was a prospective, open-label, phase 2 trial of prophylactic rituximab
`given to prevent the occurrence of chronic GVHD after allogeneic stem cell
`transplantation. The clinical trial was approved by the Office for Human
`Research Studies at the Dana-Farber Cancer Institute/Harvard Cancer Center
`and was registered at www.clinicaltrials.gov (NCT00379587). Genentech
`(San Francisco, CA) provided rituximab for all enrolled subjects. Informed
`consent was obtained in accordance with the Declaration of Helsinki.
`The primary objectives of the trial were to determine the incidence of
`chronic GVHD and corticosteroid-requiring chronic GVHD at 1 and 2 years
`after allogeneic stem cell transplantation. Corticosteroid-requiring chronic
`GVHD was added as an end point after the completion of the trial, but
`before data analysis. Secondary objectives were to determine the incidence
`of hematological and nonhematological adverse events when rituximab was
`administered in the posttransplantation setting. Eligible patients were 18
`years of age or greater and received a nonmyeloablative or myeloablative
`transplantation using peripheral blood stem cells from an 8/8 HLA-matched
`donor or single antigen/allele-mismatched donor approximately 100 days
`prior to enrollment. Adequate performance status and organ function was
`required, and subjects were free of uncontrolled infection and active acute
`GVHD at the time of enrollment. Prior resolved acute GVHD was permitted.
`Subjects were required to have evidence of sustained donor chimerism and
`underwent disease restaging to exclude relapse at the time of enrollment.
`Subjects participating in clinical trials of primary GVHD prophylaxis in
`which chronic GVHD was a secondary end point were not enrolled. Any
`subject with evidence of classic chronic GVHD or overlap chronic GVHD
`was ineligible to participate, as was any subject who had previously received
`donor lymphocyte infusions to treat relapse or falling donor chimerism.
`Rituximab (375 mg/m2 IV) was administered at 100 days, and again at
`6, 9, and 12 months after transplantation. Premedication with H1- and H2-
`blockers and acetaminophen was provided. Corticosteroids were not used
`as premedication. Systemic immunosuppressive medications were tapered
`at the treating clinician’s discretion per institutional standards. Upon the
`occurrence of chronic GVHD, initial and subsequent immunosuppressive
`treatment was administered according to institutional standards as well.
`
`Correlative studies for B-cell reconstitution and BAFF levels
`
`A commercially available sandwich enzyme-linked immunosorbent assay
`(ELISA) was used in order to measure soluble BAFF/Blys levels from
`patient plasma (R&D Systems, Minneapolis, MN). Whole blood or viable
`frozen ficolled peripheral blood mononuclear cells were processed for flow
`cytometry. Lymphocytes were gated by size using forward and side scatter
`criteria. A total of 50 000 lymphocytes were collected for all samples to
`ensure adequate total numbers of B cells for subset analysis. Anti-CD19
`PC7 (Beckman Coulter, Brea, CA) was used per manufacturer’s instructions.
`CD19 expression was analyzed to exclude CD31 cells from the analysis of
`CD38 or CD27 expression. Red blood cells (RBCs) were lysed, and
`leukocytes were fixed prior to fluorescence-activated cell sorter (FACS). A
`MACSQuant Analyzer (Miltenyi Biotech, Auburn, CA) was used, and data
`were analyzed using FlowJo software (Tree Star, Ashland, OR).
`
`Statistical design and analysis
`
`Because of the differences in the incidence rates of chronic GVHD after
`matched, related donor transplantation and matched, unrelated donor
`
`transplantation, this study was designed to accrue these 2 cohorts separately
`but in parallel, with the null hypothesis of a rate of chronic GVHD of 45%
`after matched, related transplantation and 65% after matched, unrelated
`transplantation. The alternative hypothesis was a 20% reduction with the
`use of rituximab in both cohorts. With this hypothesis, using an exact
`binomial distribution, the probability of concluding rituximab promising
`was 0.88 if the true but unknown rate of developing chronic GVHD is 25%
`and 0.09 if the true rate is 45% in matched, related donor transplantation
`and 0.86 if the true but unknown rate of developing chronic GVHD is 45% and
`0.10 if the true rate is 65% in matched, unrelated transplantation. These
`statistical parameters do not apply to the estimates of corticosteroid-requiring
`chronic GVHD.
`Although not part of the original statistical design, a contemporaneous
`control cohort was constructed from our database using patients treated
`during the same time interval who chose not to participate in this trial.
`Control patients were selected randomly from the database using the
`identical selection criteria as for the clinical trial population. A similar
`proportion of recipients of matched, related and unrelated donors as accrued
`in the prospective trial was purposefully chosen for comparison.
`Baseline characteristics were reported descriptively, and compared using
`the x2 test, Fisher’s exact test, or Wilcoxon rank-sum test. Overall survival
`(OS) and progression-free survival (PFS) were calculated using the Kaplan-
`Meier method. OS was defined as the time from stem cell infusion to death
`from any cause. Patients who were alive or lost to follow-up were censored
`at the time last seen alive. PFS was defined as the time from stem cell infusion
`to disease relapse or progression or death from any cause, whichever occurred
`first. Patients who were alive without disease relapse or progression were
`censored at the time last seen alive and progression-free. The log-rank test
`was used for comparisons of Kaplan-Meier curves. The cumulative incidence
`of grade 3 or higher infections was calculated considering death unrelated to
`infections and relapse as competing events. Cumulative incidences of chronic
`GVHD and systemic corticosteroid-requiring chronic GVHD were calculated
`using competing risks reflecting time to relapse or death without developing
`chronic GVHD or corticosteroid-requiring chronic GVHD as competing
`events. Late acute GVHD was not considered to be chronic GVHD unless
`overlap features were present. Similarly, cumulative incidences of nonrelapse
`death and relapse with or without death were calculated using competing
`risks, reflecting time to relapse and time to nonrelapse death, respectively, as
`competing risks. The difference between cumulative incidence curves in the
`presence of a competing risk was tested using the Gray method.29 Potential
`prognostic factors for OS, PFS, and corticosteroid-requiring chronic GVHD
`were examined in the proportional hazards model as well as in the competing
`risks regression model.30 Factors included in the multivariable models
`were age, patient–donor sex mismatch, myeloid disease (Y/N), donor type,
`conditioning intensity, disease relapse index,31 and grades II-IV acute GVHD.
`The occurrence of grade II-IV acute GVHD was treated as a time-dependent
`variable in multivariable analysis. The proportional hazards assumption
`was tested, and interaction terms were examined. All tests are 2-sided at
`a significance level of 0.05. All calculations were done using SAS 9.3
`(SAS Institute, Inc., Cary, NC) and R version 2.13.2 (the Comprehensive
`R Archive Network [CRAN] project [http://cran.us.r-project.org/]).
`
`Results
`
`Between December 2006 and October 2010, 65 subjects were
`enrolled and treated on this clinical trial. The data set was locked
`and analyzed in March 2012, when all subjects had at least 2 years
`of posttransplantation follow-up, with a median follow-up of
`48 months.
`The median age of enrolled subjects was 54 years, and 31
`subjects received peripheral blood stem cell grafts from matched,
`related donors. One subject received a 7/8 unrelated donor transplant
`and was analyzed with the 8/8 matched, unrelated donor recipient
`group (n 5 33). Forty of 65 subjects (61.5%) had undergone
`
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`1512
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`CUTLER et al
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`BLOOD, 22 AUGUST 2013 x VOLUME 122, NUMBER 8
`
`Table 1. Baseline clinical characteristics
`
`Rituximab-treated subjects (n 5 65)
`
`Controls (n 5 68)
`
`Age, median (range)
`
`Gender
`
`M
`
`F
`
`Donor gender
`
`M
`
`F
`
`Subject–donor gender
`
`FF
`
`FM
`
`N
`
`39
`
`26
`
`38
`
`27
`
`9
`
`17
`
`54 (19-74)
`
`%
`
`60
`
`40
`
`58.5
`
`41.5
`
`13.8
`
`26.2
`
`N
`
`41
`
`27
`
`39
`
`29
`
`12
`
`15
`
`17
`
`54 (26-70)
`
`%
`
`60.3
`
`39.7
`
`57.4
`
`42.6
`
`17.6
`
`22.1
`
`25
`
`P value
`
`.81
`
`1.00
`
`1.00
`
`.87
`
`MF
`
`MM
`
`Diagnosis
`
`AML
`
`CLL/SLL/PLL
`
`HD
`
`ALL
`
`MDS
`
`MPD
`
`Mixed MDS/MPD
`
`NHL
`
`Disease relapse index
`
`Low
`
`18
`
`21
`
`30
`
`2
`
`1
`
`4
`
`6
`
`4
`
`18
`
`10
`
`27.7
`
`32.3
`
`46.2
`
`3.1
`
`1.5
`
`6.2
`
`11.1
`
`6.2
`
`27.7
`
`15.4
`
`24
`
`31
`
`3
`
`1
`
`5
`
`7
`
`1
`
`20
`
`10
`
`35.3
`
`45.6
`
`4.4
`
`1.5
`
`7.4
`
`10.3
`
`1.5
`
`29.4
`
`14.7
`
`.57
`
`.49
`
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`
`RIC
`
`Stem cell source
`
`PBSC
`
`GVHD prophylaxis regimen
`1/2
`CI1/2
`1/2
`CI
`
`Mtx
`
`other
`
`1/2
`Siro
`
`other
`
`Grade II-IV acute GVHD
`
`Grade III-IV acute GVHD
`
`Corticosteroid use at rituximab initiation/day 100
`
`65
`
`22
`
`43
`
`9
`
`2
`
`5
`
`100
`
`33.8
`
`66.2
`
`13.8
`
`3.1
`
`7.7
`
`68
`
`26
`
`42
`
`12
`
`5
`
`9
`
`100
`
`38.2
`
`61.8
`
`17.6
`
`7.4
`
`13.2
`
`Corticosteroid dose (mg/kg) at rituximab initiation/
`
`0.13
`
`(0.06-0.38)
`
`0.34
`
`(0.11-0.93)
`
`day 100 (median, range)
`
`1.00
`
`.72
`
`.64
`
`.44
`
`.57
`
`.09
`
`ALL, acute lymphoblastic leukemia; AML, acute myeloid leukemia; CI, calcineurin inhibitor; CLL/SLL/PLL, chronic lymphocytic leukemia/small lymphocytic lymphoma/
`prolymphocytic Leukemia; F, Female; HD, Hodgkin Disease; M, Male; MAC, myeloablative conditioning; MDS, myelodysplastic disorder; MPD, myeloproliferative disease;
`MRD, matched, related donor; Mtx, methotrexate; MUD, matched unrelated donor; NHL, non-Hodgkin lymphoma; PBSC, peripheral blood stem cells; RIC, reduced intensity
`conditioning.
`
`reduced-intensity conditioning, and acute leukemia was the most
`common diagnosis (52.3%), with advanced B-cell malignancies
`accounting for 32.3% of enrolled subjects. All subjects received
`peripheral blood stem cells, but only 13.8% had grades II-IV acute
`GVHD. Only 2 subjects received anti-thymocyte globulin as part
`of their conditioning regimen (Table 1).
`
`Safety and adverse events
`
`A total of 181 doses of rituximab were administered, with a median
`of 3 doses per subject. The reasons to not receive the complete
`
`4 doses included the development of chronic GVHD (18), relapse
`(13), and patient preference (2). Thirty-two subjects completed all
`4 doses of rituximab, including some individuals who had developed
`chronic GVHD during the first year after transplantation.
`There were no grades 3-4 events associated with rituximab
`infusion. There were 2 reports of grades 3-4 thrombocytopenia
`considered possibly or probably related to therapy with rituximab.
`Leukopenia or neutropenia considered possibly or probably related
`to therapy with rituximab was reported in 9 subjects and was
`managed with growth factor where appropriate. Other toxicities are
`shown in Table 2. Hypogammaglobulinemia was not recorded as
`
`Intermediate
`
`High
`
`Very high
`
`Disease status at transplantation
`
`Active
`
`Remission
`
`Donor type
`
`8/8 MRD
`
`8/8 MUD
`
`7/8 mismatched unrelated
`
`Conditioning intensity
`
`MAC
`
`38
`
`15
`
`2
`
`30
`
`35
`
`31
`
`33
`
`1
`
`25
`
`40
`
`58.5
`
`23.1
`
`3.1
`
`46.1
`
`53.8
`
`47.7
`
`50.8
`
`1.5
`
`38.5
`
`61.5
`
`32
`
`22
`
`4
`
`28
`
`40
`
`30
`
`38
`
`28
`
`40
`
`47.1
`
`32.4
`
`5.9
`
`41.2
`
`58.8
`
`44.1
`
`55.9
`
`41.2
`
`58.8
`
`.60
`
`.52
`
`.86
`
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`BLOOD, 22 AUGUST 2013 x VOLUME 122, NUMBER 8
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`RITUXIMAB PROPHYLAXIS FOR CHRONIC GVHD
`
`1513
`
`Table 2. Toxicities and attribution to rituximab
`
`Relation to rituximab
`
`Toxicity
`
`Possible
`
`Probable
`
`Definite
`
`Transaminitis
`
`Hemolysis
`
`Leukopenia/neutropenia
`
`Thrombocytopenia
`
`Constipation
`
`Anemia
`
`Leukopenia/neutropenia
`
`Thrombocytopenia
`
`Alkaline phosphatase elevation
`
`Flu-like syndrome
`
`Leukopenia/neutropenia
`
`Grade
`
`4
`
`5
`
`3
`
`1
`
`3
`
`2
`
`1
`
`4
`
`1
`
`1
`
`1
`
`1
`
`1
`
`1
`
`1
`
`an adverse event, and subjects were permitted to receive replace-
`ment therapy outside of the transplantation center. Ten patients
`experienced 15 episodes of grade 3 or higher infections. The 1- and
`2-year cumulative incidence of grade 3 or higher infections was
`11% and 15%, respectively. There were 2 lethal infections, with 1
`being considered possibly related to rituximab.
`
`entry, and at months 4 and 6 following transplantation (1 and 3
`months following initial rituximab administration). BAFF levels
`were significantly higher in chronic GVHD-free patients at 9 and
`12 months from transplantation (17.7 ng/mL vs 11.2 ng/mL,
`P 5 .033; 16.7 ng/mL vs 8.1 ng/mL, P , .01, respectively); however,
`there was no difference at 18 and at 24 months, at which point
`B cells had reconstituted (Figure 2). Consistent with prior ob-
`servations,21 the BAFF/B-cell ratio was significantly higher in
`chronic GVHD patients than in chronic GVHD-free patients at
`24 months (P 5 .039).
`
`Relapse and survival
`
`The median follow-up among surviving patients was 48 months
`(range, 26 to 77 months). The 4-year cumulative incidence of relapse
`was 34%. There was no difference in relapse between CD201
`malignancies and CD202 malignancies in rituximab-treated subjects
`(32% vs 36%). Nonrelapse mortality, an additional surrogate of
`chronic GVHD severity, was very low, with only 2 subjects dying
`of nonrelapse-related causes at 2 years from transplantation with
`a cumulative incidence of 5.1% at 4 years from transplantation. The
`4-year estimates of PFS and OS were 61% and 71%, respectively.
`
`Incidence of chronic GHVD
`
`Comparison with control cohort
`
`The cumulative incidence of clinician-diagnosed chronic GVHD at
`1 and 2 years after transplantation was 38% and 48%, respectively.
`The corresponding figures for related and unrelated donor recipients
`were 29% and 35% for related donors, and 47% and 59% for
`unrelated donors, which were significantly different (P 5 .046)
`(Figure 1A-B).
`We measured the requirement of initiation of systemic cortico-
`steroids as a surrogate for chronic GVHD severity. The cumulative
`incidence of systemic corticosteroid-requiring chronic GVHD was
`only 21.5% and 31% at 1 and 2 years from transplantation, re-
`spectively. The corresponding figures at 1 and 2 years were 16%
`and 23% for related donors, and 26% and 38% for unrelated donors
`(P 5 .17) (Figure 1A-B). At 1 year from transplantation, 19 subjects
`(5 related donors, 14 unrelated donors) were using systemic corti-
`costeroids, and 47.7% of subjects were using some form of systemic
`immunosuppression (38.7% related donors, 55.9% unrelated donors).
`Mucosal chronic GVHD, with ocular and oral involvement, was
`the most common manifestation of chronic GVHD (24.5% and 22.6%
`of subjects, respectively). Because there was much less systemic
`corticosteroid use in these patients, it appeared that mucosal GVHD
`was not considered severe enough to warrant corticosteroids. Notably,
`both cutaneous and myofascial disease, which have previously
`been reported to be responsive to rituximab therapy,13 was noted
`only in 13.2% and 5.7% of subjects, respectively.
`
`Immunophenotypic correlations
`
`B-cell lymphopenia was profound, and B cells were unmeasurable
`during the year following rituximab administration in almost all
`treated subjects. At 18 months from transplantation (6 months
`following the final rituximab administration), B cells remained
`essentially absent, but by 24 months from transplantation, B-cell
`reconstitution was noted. At 24 months from transplantation, the
`median number of B cells in treated patients who did not develop
`chronic GVHD was 138.5 cells/mL in comparison with only
`9.9 cells/mL in treated patients with chronic GVHD (P 5 .047)
`(Figure 2). Serum BAFF levels were not different between patients
`who eventually did and did not develop chronic GVHD at study
`
`After completion of the trial, a contemporaneous control cohort
`was constructed from our database using patients treated during the
`same time interval who chose not to participate in this trial. Baseline
`clinical characteristics of the control cohort can be found in Table 1.
`
`Figure 1. Chronic GVHD incidence. (A) Overall
`incidence of chronic GVHD.
`Dashed line, incidence of all chronic GVHD; solid line, incidence of corticosteroid-
`requiring chronic GVHD. (B) Incidence of chronic GVHD stratified by donor type.
`Dotted line, incidence of all chronic GVHD, matched related donors; solid line,
`incidence of corticosteroid-requiring chronic GVHD, matched related donors; dot-
`dash line, incidence of all chronic GVHD, matched unrelated donors; dashed line,
`incidence of corticosteroid-requiring chronic GVHD, matched unrelated donors.
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`Figure 2. Immunophenotypic outcomes. Bar graph shows median BAFF levels. Open bar, no chronic GVHD; shaded bar, chronic GVHD. Line graph shows median B-cell
`numbers. Dashed line, chronic GVHD; solid line, no chronic GVHD.
`
`On the basis of selection criteria, there were no significant differences
`in age, sex, donor sex or match, malignant diagnosis, stem cell
`source, conditioning intensity, or the occurrence of acute GVHD.
`Although there was a trend toward a reduction in the overall
`rate of chronic GVHD when comparing rituximab-treated cases and
`controls (48% vs 60%, P 5 .1), the 2-year cumulative incidence of
`systemic corticosteroid-requiring chronic GVHD was 31% among
`rituximab-treated subjects and 48.5% among controls (P 5 .015)
`(Figure 3A). In a multivariable competing risks regression analysis,
`treating acute GVHD as a time-dependent variable, the use of
`rituximab (hazard ratio, 0.47; 95% confidence interal [CI], 0.23-
`0.99; P 5 .046) and myeloid disease (hazard ratio, 0.37; 95% CI,
`0.17-0.79; P 5 .01) was significantly associated with protection
`from corticosteroid-requiring chronic GVHD, whereas age, donor-
`recipient sex matching, donor type, conditioning intensity, disease
`relapse index, and acute GVHD had no statistically significant
`influence.
`The 4-year cumulative incidence of nonrelapse mortality was 19%
`in the control population, in comparison with 5.1% in rituximab-
`treated subjects (P 5 .02). Of 4 subjects who died of nonrelapse
`causes in the rituximab cohort, the causes of death are chronic GVHD
`(3) and respiratory failure (1). Of 13 patients who died of nonrelapse
`causes in the control cohort, the causes of death are chronic GHVD
`(8) and cardiac, traumatic, secondary malignancy, respiratory failure,
`and unknown (1 each). Of these 13, 10 developed chronic GVHD
`prior to death. The 4-year cumulative incidence of relapse was no
`different between rituximab-treated patients and controls (34% vs
`28%, P 5 .79) (Figure 3B), even when stratified by CD20 status.
`PFS at 4 years was no different (61% vs 53%, P 5 .27); however,
`4-year OS was significantly higher in rituximab-treated subjects
`when compared with controls (71% vs 56%, P 5 .05) (Figure 3C).
`In a multivariable Cox regression analysis examining the same poten-
`tial variables as for the occurrence of steroid-requiring chronic
`GVHD, the use of rituximab (hazard ratio for death, 0.56; 95% CI,
`0.31-1.00; P 5 .048) and high or very high disease relapse index
`(hazard ratio for death, 1.90; 95% CI, 1.02-3.53; P 5 .04) were
`significantly associated with OS.
`
`Discussion
`
`Several lines of evidence implicate B cells in the pathophysiology
`of chronic GVHD.32,33 In this clinical trial, we have demonstrated
`that the posttransplantation administration of rituximab is safe and
`reduces the incidence of systemic corticosteroid-requiring chronic
`GVHD when compared with concurrent controls. Although the
`overall rate of chronic GVHD was only modestly affected and did
`not attain the 20% reduction hypothesized, the majority of patients
`treated with prophylactic rituximab who were affected had only
`mucocutaneous disease that did not require systemic therapy and
`was not associated with excess transplant-associated mortality. In fact,
`we noted an extremely low rate of transplant-associated mortality
`of 5% at 4 years from transplantation in a landmark analysis of
`patients who were enrolled in this clinical trial 3 months after
`transplantation.
`This clinical trial did not use the National Institutes of Health
`(NIH) Staging System for the diagnosis and severity assessment of
`chronic GVHD because the trial was conceived before the NIH
`diagnostic system was initially published,34 and long before this
`staging system was validated.35-37 Similarly, the recommendations
`from the NIH Consensus Conference for the conduct of clinical
`trials in chronic GVHD was not published until after the initiation
`of this trial.38 Faced with the lack of a standardized and recognized
`marker of chronic GVHD severity, we chose 2 end points to measure
`the efficacy of our intervention: the occurrence of any-degree chronic
`GVHD by clinician assessment, and the requirement of systemic
`corticosteroids specifically to treat chronic GVHD, as a surrogate
`for chronic GVHD severity. We felt this latter end point was valid
`because chronic GVHD involving mucocutaneous tissues treated
`with topical therapy alone generally does not impact posttrans-
`plantation survival. In acute GVHD clinical trial designs in which
`corticosteroid-sparing strategies are being tested, it is recommen-
`ded that corticosteroid doses be incorporated into the outcome
`assessment, providing further justification for this end point.39 It
`should be noted that this end point is not entirely objective and
`may be difficult to use in phase 3 clinical trials. As such, in addition
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`BLOOD, 22 AUGUST 2013 x VOLUME 122, NUMBER 8
`
`RITUXIMAB PROPHYLAXIS FOR CHRONIC GVHD
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`1515
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`
`We compared outcomes in subjects treated in this trial with
`those of a contemporaneous control population chosen to match the
`entry criteria for this clinical trial. We specifically chose a similar
`proportion of related and unrelated donor recipients, and included
`several patients who received ATG as part of their GVHD prophylaxis
`regimen. Although we did not note any differences in baseline
`characteristics between enrolled subjects and control patients, bias
`cannot be completely excluded, and only a prospective randomized
`trial can adequately compare outcomes after rituximab adminis-
`tration to outcomes in the absence of rituximab administration.
`Survival outcomes in both rituximab and control populations were
`better than anticipated because they represent landmark analyses of
`patients who survived to day 100 and were eligible to participate
`in a clinical trial. It is possible that control patients were offered
`participation in this clinical trial but chose not to participate because
`of unmeasured morbidity precluding participation.
`We empirically chose the timing and duration of rituximab ad-
`ministration in this study, with a goal of inducing long-lasting B
`lymphopenia prior to the robust recovery of B cells after transplan-
`tation. Repeated dosing was given on the basis of the reported half-
`life of rituximab to ensure B lymphopenia during the first year after
`transplantation. Other experiences have demonstrated the safety of
`even earlier administration of rituximab after transplantation. When
`given prophylactically as early as day 15 after transplantation to
`prevent Epstein-Barr virus (EBV) reactivation in T-cell–depleted
`transplantation, no effect on chronic GVHD incidence was apparent,
`because only donor B cells delivered with the graft were affected,
`and not donor-derived B cells that were generated upon immuno-
`logic recovery.41 Others have also demonstrated cytopenias com-
`monly when rituximab was administered early after T-cell–depleted
`transplantation.19,25 In addition, we did not note excess opportunistic
`infections despite persistent hypogammaglobulinemia, which was
`treated at investigator discretion. Because rituximab administration
`ended at 12 months from transplantation, B-cell recovery occurred
`in the majority of patients between 18 months and 2 years after
`transplantation. We noted an ongoing incidence of chronic GVHD
`during year 2 from transplantation, coinciding with ongoing B-cell
`recovery, suggesting that prolonged rituximab administration during
`year 2 after transplantation or longer may be required to fully prevent
`B-cell-mediated chronic GVHD, or that non-B-cell–dependent
`processes are involved in later chronic GVHD.
`One third of the subjects enrolled in our trial had high-risk
`B-cell malignancies. There was likely biased enrollment for these
`patients, because posttransplantation rituximab has been used in an
`attempt to prevent malignant disease relapse in B-cell malignan-
`cies. One concern was that the elimination of chronic GVHD
`would be associated with loss of a graft-vs-malignancy effect and
`an increase in malignant relapse. We did not note an excess incidence
`of malignant relapse after the administration of rituximab when
`compared with untreated controls, suggesting that the graft-vs-
`malignancy effect is more dependent on T-cell–mediated processes,
`or involves antigen-presenting cells that are not of B-cell lineage, or
`do not express CD20.
`The mechanism through which B cells interact with and control
`T-cell responses is complex and has not been elucidated in chronic
`GVHD. B cells can participate in priming and maintaining antigen-
`specific CD41 T-cell responses,42 so B-cell depletion could be
`associated with antigen-specific T-cell anergy, although other antigen-
`presenting cells are involved in productive immune responses as
`well. An additional mechanism potentially involved in prevention
`of chronic GVHD is the expansion of regulatory T cells, a phe-
`nomenon that has been noted in association with B-cell depletion in
`
`Figure 3. Comparison of rituximab-treated cases and controls. (A) Incidence of
`corticosteroid-requiring chronic GVHD. Solid line, incidence of corticostero