Patient eligibility for hematopoietic stem cell transplantation: a review of patient-associated variables

Assessing patient eligibility for hematopoietic stem cell transplantation (HSCT) remains a complex, multifaceted challenge. Among these challenges, the paucity of comprehensive clinical data to guide decision making remains problematic coupled with unclear trade-offs between patient, disease and local HSCT center factors. Moreover, it is unclear that the modification of poor patient characteristics will improve post-HSCT outcomes. However, the use of Comorbidity Indices and Comprehensive Geriatric Assessments helps meet this challenge, but may be limited by overlapping patient characteristics. The increasing consideration for pre-HSCT psychosocial assessments and interventions remains to be studied. Ultimately, the decision to proceed with a HSCT remains interdisciplinary while considering the available evidence discussed in this review.

GvHD after umbilical cord blood transplantation for acute leukemia: an analysis of risk factors and effect on outcomes

Using the Center for International Blood and Marrow Transplant Research (CIBMTR) registry, we analyzed 1,404 UCBT patients [single (< 18 years) = 810, double (≥ 18 years) = 594] with acute leukemia to define the incidence of acute and chronic graft-vs.-host disease (GVHD), analyze clinical risk factors and investigate outcomes. After single UCBT, 100-day incidence of grades II–IV aGVHD was 39% (95% CI, 36–43%), grades III–IV aGVHD was 18% (95% CI, 15–20%), and 1-year cGVHD was 27% (95% CI, 24–30%). After double UCBT, 100-day incidence of grades II–IV aGVHD was 45% (95% CI, 41%–49%), grades III–IV aGVHD was 22% (95% CI, 19–26%), and 1-year cGVHD was 26% (95% CI, 22–29%). For single UCBT, multivariate analysis showed that absence of anti-thymocyte globulin (ATG) was associated with aGVHD, whereas prior aGVHD was associated with cGVHD. For double UCBT, absence of ATG and myeloablative conditioning were associated with aGVHD, while prior aGVHD predicted for cGVHD. Grades III–IV aGVHD led to worse survival whereas cGVHD had no significant effect on disease-free or overall survival. GVHD is prevalent after UCBT with severe aGVHD leading to higher mortality. Future research in UCBT should prioritize prevention of GVHD.

The incidence, mortality and timing of Pneumocystis jiroveci pneumonia after hematopoietic cell transplantation: a CIBMTR analysis

Pneumocystis jiroveci pneumonia (PJP) is associated with high morbidity and mortality after hematopoietic stem cell transplantation (HSCT). Little is known about PJP infections after HSCT because of the rarity of disease given routine prophylaxis. We report the results of a Center for International Blood and Marrow Transplant Research study evaluating the incidence, timing, prophylaxis agents, risk factors and mortality of PJP after autologous (auto) and allogeneic (allo) HSCT. Between 1995 and 2005, 0.63% allo recipients and 0.28% auto recipients of first HSCT developed PJP. Cases occurred as early as 30 days to beyond a year after allo HSCT. A nested case cohort analysis with supplemental data (n=68 allo cases, n=111 allo controls) revealed that risk factors for PJP infection included lymphopenia and mismatch after HSCT. After allo or auto HSCT, overall survival was significantly poorer among cases vs controls (P=0.0004). After controlling for significant variables, the proportional hazards model revealed that PJP cases were 6.87 times more likely to die vs matched controls (P<0.0001). We conclude PJP infection is rare after HSCT but is associated with high mortality. Factors associated with GVHD and with poor immune reconstitution are among the risk factors for PJP and suggest that protracted prophylaxis for PJP in high-risk HSCT recipients may improve outcomes.

IL15 levels on day 7 after hematopoietic cell transplantation predict chronic GVHD

Chronic GVHD (cGVHD) is an important complication of allogeneic hematopoietic cell transplantation (HCT). As preemptive therapy might be efficacious if administered early post transplant, we set out to determine whether cGVHD can be predicted from the serum level of a biomarker on day 7 or 28. In a discovery cohort of 153 HCT recipients conditioned with BU, fludarabine and rabbit antithymocyte globulin (ATG), we determined serum levels of B-cell-activating factor, vascular endothelial growth factor, soluble TNF-α receptor 1, soluble IL2 receptor α, IL5, IL6, IL7, IL15, γ-glutamyl transpeptidase, cholinesterase, total protein, urea and ATG. Patients with low levels of IL15 (<30.6 ng/L) on day 7 had 2.7-fold higher likelihood of developing significant cGVHD (needing systemic immunosuppressive therapy) than patients with higher IL15 levels (P<0.001). This was validated in a validation cohort of 105 similarly-treated patients; those with low IL15 levels had 3.7-fold higher likelihood of developing significant cGVHD (P=0.001). Low IL15 was not associated with relapse; it trended to be associated with acute GVHD and was associated with low infection rates. In conclusion, low IL15 levels on day 7 are predictive of cGVHD, and thus could be useful in guiding preemptive therapy.

No increased mortality from donor or recipient hepatitis B- and/or hepatitis C-positive serostatus after related-donor allogeneic hematopoietic cell transplantation

Limited data exist on allogeneic transplant outcomes in recipients receiving hematopoietic cells from donors with prior or current hepatitis B (HBV) or C virus (HCV) infection (seropositive donors), or for recipients with prior or current HBV or HCV infection (seropositive recipients). Transplant outcomes are reported for 416 recipients from 121 centers, who received a human leukocyte antigen-identical related-donor allogeneic transplant for hematologic malignancies between 1995 and 2003. Of these, 33 seronegative recipients received grafts from seropositive donors and 128 recipients were seropositive. The remaining 256 patients served as controls. With comparable median follow-up (cases, 5.9 years; controls, 6.7 years), the incidence of treatment-related mortality, survival, graft-versus-host disease, and hepatic toxicity, appears similar in all cohorts. The frequencies of hepatic toxicities as well as causes of death between cases and controls were similar. Prior exposure to HBV or HCV in either the donor or the recipient should not be considered an absolute contraindication to transplant.

High incidence of post transplant lymphoproliferative disorder after antithymocyte globulin-based conditioning and ineffective prediction by day 28 EBV-specific T lymphocyte counts

The largest study on post-allogeneic hematopoietic cell transplant lymphoproliferative disorder (PTLD) epidemiology showed a cumulative incidence of 1.7% in patients receiving antithymocyte globulin (ATG). We had noted an apparently higher incidence in our transplant recipients whose conditioning included ATG. Therefore, we formally determined the incidence of PTLD through chart review. We also evaluated whether counts of EBV-specific T lymphocytes measured by cytokine flow cytometry could identify patients at risk of developing PTLD. Among 307 allogeneic transplant recipients, 25 (8.1%) developed PTLD. This was biopsy proven in 11 patients, and was fatal in seven patients. Patient age, EBV serostatus, donor type/match or GVHD did not influence PTLD risk significantly. Median onset of PTLD was 55 (range, 28-770) days post transplant. Day 28 EBV-specific T lymphocyte counts were not significantly different in 11 patients who developed PTLD and 31 non-PTLD patients matched for published risk factors for PTLD. In summary, when using conditioning with thymoglobulin 4.5 mg/kg, the incidence of PTLD is relatively high and cannot be predicted by day 28 cytokine flow cytometry-determined EBV-specific T lymphocyte counts. Thus, in this scenario PTLD prevention may be warranted, for example, using EBV DNAemia monitoring with preemptive therapy.

Hematopoietic cell transplantation for Crohn’s disease; is it time?

AIM: To review all studies in the literature that have assessed Hematopoietic cell transplantation (HCT) and Crohn’s disease (CD) with the ultimate aims of determining if this is a viable treatment option for those with CD. A secondary aim was to review the above literature and determine if the studies shed further light on the mechanisms involved in the pathogenesis of CD.

METHODS: An extensive Medline search was performed on all articles from 1970 to 2005 using the keywords; bone marrow transplant, stem cell, hematopoietic cell, Crohn’s disease and inflammatory bowel disease.

RESULTS: We identified one case in which a patient developed CD following an allogeneic HCT from a sibling suffering with CD. Evidence for transfer of the genetic predisposition to develop CD was also identified with report of a patient that developed severe CD following an allogeneic HCT. Following HCT it was found that the donor (that had no signs or symptoms of CD) and the recipient had several haplotype mismatches in HLA class III genes in the IBD3 locus including a polymorphism of NOD2/CARD15 that has been associated with CD. Thirty three published cases of patients with CD who underwent either autologous or allogeneic HCT were identified. At the time of publication 29 of these 33 patients were considered to be in remission. The median follow-up time was seven years, and twenty months for allogeneic and autologous HCT respectively. For patients who underwent HCT primarily for treatment of their CD there have been no mortalities related to transplant complications.

CONCLUSION: Overall these preliminary data suggest that both allogeneic and autologous HCT may be effective in inducing remission in refractory CD. This supports the hypothesis that the hemolymphatic cells play a key role in CD and that resetting of the immune system may be a critical approach in the management or cure of CD.

Efficacy of donor vaccination before hematopoietic cell transplantation and recipient vaccination both before and early after transplantation

Allogeneic hematopoietic cell transplantation is followed by humoral immunodeficiency. We evaluated whether antibody levels can be improved by recipient vaccination on day -1 and 50 and whether the levels can be further improved by donor vaccination on day -20. A total of 85 patients were randomized or assigned to one of the following strategies of immunization with Streptococcus pneumoniae polysaccharides, Haemophilus influenzae polysaccharide-protein conjugate, tetanus toxoid (protein recall antigen) and hepatitis B surface antigen (protein neo-antigen): (1) donor on day -20, recipient on days -1, +50 and +365 (D(-20)R(-1,50,365)); (2) donor nil, recipient on days -1, +50 and +365 (D(N)R(-1,50,365)); or (3) donor nil, recipient on day +365 (D(N)R(365)). For H. influenzae and tetanus, IgG levels after grafting were the highest in the D(-20)R(-1,50,365) patients, intermediate in the D(N)R(-1,50,365) patients and the lowest in the D(N)R(365) patients. For S. pneumoniae and hepatitis B, antibody levels appeared to be similar in all three patient groups. The results suggest that for polysaccharide-protein conjugate antigens or protein recall antigens, recipient immunization on days -1 and 50 improves antibody levels and that donor vaccination on day -20 further improves the levels. In contrast, neither recipient immunization on days -1 and 50 nor donor immunization on day -20 appears to be efficacious for polysaccharide antigens and poorly immunogenic protein neo-antigens.

Incidence, risk factors, and mortality from pneumonia developing late after hematopoietic stem cell transplantation

The incidence, etiology, outcome, and risk factors for developing pneumonia late after hematopoietic stem cell transplantation (SCT) were investigated in 1359 patients transplanted in Seattle. A total of 341 patients (25% of the cohort) developed at least one pneumonic episode. No microbial or tissue diagnosis (ie clinical pneumonia) was established in 197 patients (58% of first pneumonia cases). Among the remaining 144 patients, established etiologies included 33 viral (10%), 31 bacterial (9%), 25 idiopathic pneumonia syndrome (IPS, 7%), 20 multiple organisms (6%), 19 fungal (6%), and 16 Pneumocystis carinii pneumonia (PCP) (5%). The overall cumulative incidence of first pneumonia at 4 years after discharge home was 31%. The cumulative incidences of pneumonia according to donor type at 1 and 4 years after discharge home were 13 and 18% (autologous/syngeneic), 22 and 34% (HLA-matched related), and 26 and 39% (mismatched related/unrelated), respectively. Multivariate analysis of factors associated with development of late pneumonia after allografting were increasing patient age (RR 0.5 for <20 years, 1.2 for >40 years, P=0.009), donor HLA-mismatch (RR 1.6 for unrelated/mismatched related, P=0.01), and chronic graft-versus-host disease (GVHD; RR 1.5, P=0.007). Our data suggest that extension of PCP prophylaxis may be beneficial in high-risk autograft recipients. Further study of long-term anti-infective prophylaxis based on patient risk factors after SCT appear warranted.

Immunity of patients surviving 20 to 30 years after allogeneic or syngeneic bone marrow transplantation

The duration of immunodeficiency following marrow transplantation is not known. Questionnaires were used to study the infection rates in 72 patients surviving 20 to 30 years after marrow grafting. Furthermore, in 33 of the 72 patients and in 16 donors (siblings who originally donated the marrow) leukocyte subsets were assessed by flow cytometry. T-cell receptor excision circles (TRECs), markers of T cells generated de novo, were quantitated by real-time polymerase chain reaction. Immunoglobulin G(2) (IgG(2)) and antigen-specific IgG levels were determined by enzyme-linked immunosorbent assay. Infections diagnosed more than [corrected] 15 years after transplantation occurred rarely. The average rate was 0.07 infections per patient-year (one infection every 14 years), excluding respiratory tract infections, gastroenteritis, lip sores, and hepatitis C. The counts of circulating monocytes, natural killer cells, B cells, CD4 T cells, and CD8 T cells in the patients were not lower than in the donors. The counts of TREC(+) CD4 T cells in transplant recipients younger than age 18 years (at the time of transplantation) were not different from the counts in their donors. In contrast, the counts of TREC(+) CD4 T cells were lower in transplant recipients age 18 years or older, even in those with no history of clinical extensive chronic graft-versus-host disease, compared with their donors. The levels of total IgG(2) and specific IgG against Haemophilus influenzae and Streptococcus pneumoniae were similar in patients and donors. Overall, the immunity of patients surviving 20 to 30 years after transplantation is normal or near normal. Patients who received transplants in adulthood have a clinically insignificant deficiency of de novo-generated CD4 T cells, suggesting that in these patients the posttransplantation thymic insufficiency may not be fully reversible.

CD34 cell dose in granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cell grafts affects engraftment kinetics and development of extensive chronic graft-versus-host disease after human leukocyte antigen-identical sibling transplantation

A retrospective analysis of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cell (G-PBMC) products harvested from healthy donors indicates significant variability in both the absolute number and relative proportion of CD34, CD3, and CD14 cells obtained. This report examined whether variations in the cellular composition of G-PBMC products correlated with clinical outcomes after myeloablative allogeneic transplantation. The numbers of CD34, CD3, and CD14 cells infused into 181 human leukocyte antigen (HLA)-identical sibling recipients were analyzed with respect to tempo of engraftment, acute graft-versus-host-disease (GVHD), clinical extensive chronic GVHD, overall survival, and disease relapse. Neither acute GVHD, overall survival, nor disease relapse was statistically significantly associated with CD34, CD3, or CD14 cell doses or the CD14 to CD3 ratio. CD3 and CD14 cell doses and CD14 to CD3 ratios did not correlate with the tempo of neutrophil and platelet engraftment. However, increasing CD34 cell numbers were significantly associated with accelerated neutrophil (P =.03) and platelet (P =.01) engraftment. Higher doses of CD34 cells (> 8.0 x 10(6)/kg) were also associated with a significantly increased hazard of clinical extensive chronic GVHD (HR = 2.3, 95% confidence interval [CI] 1.4-3.7, P =.001), but neither CD3 nor CD14 doses were statistically significantly associated with chronic GVHD. It was concluded that CD34 cell dose in G-PBMC grafts appears to affect both the engraftment kinetics and the development of clinical extensive chronic GVHD in HLA-identical sibling recipients but without a demonstrable impact on survival, relapse, and acute GVHD. Given the morbidity associated with extensive chronic GVHD, efforts to further accelerate engraftment in HLA-matched sibling transplants by increasing CD34 cell number in G-PBMC products may be counterproductive.

Factors influencing B lymphopoiesis after allogeneic hematopoietic cell transplantation

In 93 allograft recipients, the numbers of marrow B-cell precursors on days 80 and 365 correlated with the counts of circulating B cells, suggesting that the posttransplantation B-cell deficiency is at least in part due to insufficient B lymphopoiesis. Factors that could affect B lymphopoiesis were evaluated. The number of marrow B-cell precursors on days 30 and 80 was at least 4-fold lower in patients with grade 2 to 4 acute graft-versus-host disease (GVHD) compared with patients with grade 0 to 1 acute GVHD. The number of B-cell precursors on day 365 was 18-fold lower in patients with extensive chronic GVHD compared with patients with no or limited chronic GVHD. The number of B-cell precursors was not related to CD34 cell dose, type of transplant (marrow versus blood stem cells), donor age, or patient age. It was concluded that posttransplantation B-cell deficiency results in part from inhibition of B lymphopoiesis by GVHD and/or its treatment.

Immune reconstitution after allogeneic marrow transplantation compared with blood stem cell transplantation

Allogeneic peripheral blood stem cell grafts contain about 10 times more T and B cells than marrow grafts. Because these cells may survive in transplant recipients for a long time, recipients of blood stem cells may be less immunocompromised than recipients of marrow. Immune reconstitution was studied in 115 patients randomly assigned to receive either allogeneic marrow or filgrastim-mobilized blood stem cell transplantation. Between day 30 and 365 after transplantation, counts of most lymphocyte subsets were higher in the blood stem cell recipients. The difference was most striking for CD4 T cells (about 4-fold higher counts for CD45RA(high) CD4 T cells and about 2-fold higher counts for CD45RA(low/-)CD4 T cells; P <.05). On assessment using phytohemagglutinin and herpesvirus antigen-stimulated proliferation, T cells in the 2 groups of patients appeared equally functional. Median serum IgG levels were similar in the 2 groups. The rate of definite infections after engraftment was 1.7-fold higher in marrow recipients (P =.001). The rate of severe (inpatient treatment required) definite infections after engraftment was 2.4-fold higher in marrow recipients (P =.002). The difference in the rates of definite infections was greatest for fungal infections, intermediate for bacterial infections, and lowest for viral infections. Death associated with a fungal or bacterial infection occurred between day 30 and day 365 after transplantation in 9 marrow recipients and no blood stem cell recipients (P =.008). In conclusion, blood stem cell recipients have higher lymphocyte-subset counts and this appears to result in fewer infections. (Blood. 2001;97:3380-3389)

Polyclonal hematopoiesis with variable telomere shortening in human long-term allogeneic marrow graft recipients

Donor-derived hematopoiesis was assessed in 17 patients who received allogeneic marrow grafts from HLA-matched siblings between 1971 and 1980. Complete blood counts were normal or near normal in all patients except one. Chimerism analyses, using either dual-color XY-chromosome fluorescence in situ hybridization (FISH) or analysis of variable number tandem repeat loci, indicated that 15 out of 16 patients had greater than 97% donor-derived hematopoiesis, whereas 1 patient had indeterminate chimerism. All 12 recipients of grafts from female donors exhibited polyclonal hematopoiesis by X-linked clonal analysis with the use of molecular probes. Of the 17 recipients, 9 exhibited a less than 1.0-kilobase shortening of granulocyte telomere length compared with their respective donors, according to terminal restriction fragment analysis or flow-FISH with a fluorescein-labeled peptide nucleic acid probe. These data suggest that under standard transplantation conditions, the stem cell proliferative potential is not compromised during hematopoietic reconstitution. (Blood. 2000;96:3991-3994)

Low B-cell and monocyte counts on day 80 are associated with high infection rates between days 100 and 365 after allogeneic marrow transplantation

To ascertain which mononuclear cell subset deficiency plays a role in the marrow transplant recipient's susceptibility to infections, mononuclear cell subset counts were prospectively determined in 108 patients on day 80. Infections occurring between day 100 and 365 were recorded by an investigator blinded to the subset counts. In univariate analyses, the counts of the following subsets showed a significant inverse correlation with infection rates: total B cells, IgD(+) B cells, IgD(-) B cells, total CD4 T cells, CD28(+) CD4 T cells, CD28(-) CD4 T cells, CD45RA(low/-) CD4 T cells and monocytes. In multivariate analyses, the counts of the following subsets remained significantly inversely correlated with the infection rates: total B cells (P =.0004) and monocytes (P =.009). CD28(-) CD8 T-cell counts showed no correlation with infection rates. In conclusion, the susceptibility of patients to infections late posttransplant may be due in part to the slow reconstitution of B cells and monocytes.

B-cell-autonomous somatic mutation deficit following bone marrow transplant

Hematopoietic stem cell transplantation is characterized by a prolonged period of humoral immunodeficiency. We have previously shown that the deficiencies are probably not due to the failure to utilize the appropriate V regions in the pre-immune repertoire. However, a striking observation, which correlated with the absence of immunoglobulin IgD(-) cells and was consistent with a defect in antigen-driven responses, was that rearrangements in bone marrow transplant (BMT) recipients exhibited much less somatic mutation than did rearrangements obtained from healthy subjects. In this paper, we present evidence suggesting that naive B cells obtained from BMT recipients lack the capacity to accumulate somatic mutations in a T-cell-dependent manner compared with healthy subjects. This appears to be a B-cell-autonomous deficit because T cells from some patients, which were not able to support the accumulation of mutations in autologous naive B cells, were able to support accumulation of mutations in heterologous healthy-subject naive B cells.

Reduced dose intravenous immunoglobulin does not decrease transplant-related complications in adults given related donor marrow allografts

Graft-vs.-host disease (GVHD) and infection are major complications of allogeneic bone marrow transplantation. Intravenous immunoglobulin (IVIg) given at a dose of 500 mg/kg/wk has been shown to decrease the risk of acute GVHD, interstitial pneumonia, and infection in adults early after allogeneic transplantation. The current study is a controlled trial to determine whether a lower total dose of IVIg given with pretransplant loading reduces the incidence of transplant-related complications. In a randomized trial of 241 patients > or =20 years of age who were given related donor marrow allografts, 121 individuals receiving Ig prophylaxis (500 mg/kg/d loading from day -6 to -1 and then 100 mg/kg every 3 days from day 3 to 90) were compared with 120 control patients who did not receive IVIg. Randomization was stratified by human leucocyte antigen-matching, remission status of malignancy, GVHD prophylaxis, and cytomegalovirus (CMV) serology. The study was powered to detect a reduction in acute GVHD by 18% and a decrease in transplant-related mortality by 17%. Pretransplant IVIg loading and posttransplant maintenance achieved median serum IgG levels >1350 mg/dL, which were approximately twofold greater than the untreated controls (p<0.01). White blood cell and platelet recoveries were similar for the two groups, although control patients required fewer units of platelets per day (2.5 vs. 3.3, p = 0.008). No significant differences in the incidence of CMV infection, interstitial pneumonia, or bacteremia were observed. The incidence of acute GVHD did not differ between the two groups; however, acute GVHD was less frequent among IVIg recipients achieving maximum serum IgG levels >3000 mg/dL (60 vs. 79%). Neither transplant-related mortality nor disease-free survival was significantly altered by Ig prophylaxis. However, the cumulative incidence of relapse of malignancy was higher in IVIg recipients than in controls (31 vs. 18%, p = 0.03). Multivariable regression analysis demonstrated a 1.89 increased relative risk of relapse for individuals given IVIg (p = 0.021). We conclude that pretransplant loading and a shorter course and lower total dose of IVIg prophylaxis did not appear to decrease the risk of acute GVHD or mortality among adults receiving related donor marrow transplants. Note, IVIg administration may be associated with an increased risk of recurrent malignancy, a finding that warrants further investigation.

Comparison of two flow cytometric methods enumerating CD4 T cells and CD8 T cells

The enumeration of blood CD4+ (single-positive) T cells by flow cytometry is subject to errors such as counting CD4+ monocytes or CD4+CD8+ (double-positive) T cells as CD4+ T cells. Relatively accurate count can be obtained when CD4+ T cells are defined as CD3+CD4+CD8- mononuclear cells (MNCs), using 3-color flow cytometry. However, using this approach, further classification into CD4+ T cell subsets requires expensive 4-color flow cytometry. In an attempt to enumerate CD4+ T cells using only 2 colors, we have defined CD4+ T cells as MNCs expressing CD4 and not expressing the markers of other MNCs (CD8, CD13, CD14, and CD16) and compared the results to those obtained with the 3-color method in which CD4+ T cells were defined as CD3+CD4+CD8- MNCs. Both methods produced similar results. An analogous approach was undertaken to enumerate CD8+ T cells as MNCs expressing CD8 and not expressing the markers of other MNCs. However, when compared with the percents obtained by the 3-color method in which CD8+ T cells were defmed as CD3+CD4-CD8+ MNCs, the 2-color method overestimated the percent of CD8+ T cells. This was likely due to counting CD8low null cells as CD8+ T cells. When the percentages of CD8high T cells were evaluated, both methods produced similar results. We conclude that the 2-color method is suitable for the enumeration of CD4+ T cells and CD8high T cells and reserves the third color for further enumeration of CD4+ or CD8high T cell subsets.

Allogeneic peripheral blood stem cell transplantation may be associated with a high risk of chronic graft-versus-host disease

Chronic graft-versus-host disease (GVHD) is likely caused by donor T lymphocytes. Because unmodified blood stem cell grafts contain one log more T lymphocytes than unmodified marrow grafts, we evaluated the incidence of chronic GVHD in previously reported 37 blood stem cell recipients and 37 computer-matched historical control marrow recipients (Bensinger et al, Blood 88:2794, 1996). All patients have been followed until death, relapse, or occurrence of chronic GVHD or for a minimum of 2 years. In a univariable proportional hazards regression model, the relative risk of developing clinical chronic GVHD (includes clinical limited and clinical extensive disease) by 2 years posttransplant among the peripheral blood stem cell recipients compared with the marrow recipients was 2.22 (95% confidence interval, 1.04 to 4.74; P = .039). For clinical extensive chronic GVHD, the relative risk was 2.37 (95% confidence interval, 1.07 to 5. 29; P = .035). In multivariable analyses, considering also the covariables of patient age, patient cytomegalovirus serostatus, and donor cytomegalovirus serostatus, the relative risks of clinical chronic GVHD and clinical extensive chronic GVHD were also greater than 2 (P < .05). We conclude that the transplantation of unmanipulated filgrastim-mobilized blood stem cells may result in a relatively high incidence of chronic GVHD.