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Keywords:

  • cytomegalovirus;
  • unrelated;
  • non-myeloablative stem cell transplantation;
  • infection;
  • related

Abstract

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Summary.  Little is known about the impact of cytomegalovirus (CMV) infections that occur after human leucocyte antigen (HLA)-matched unrelated donor (MUD) non-myleoablative haematopoietic stem cell transplantation (HCT). We analysed the incidence, onset and outcomes of CMV infections in 59 recipients of MUD and in 109 recipients of HLA-matched related donor (MRD) allogeneic HCT following non-myeloablative conditioning containing 2 Gy total body irradiation and fludarabine. In CMV seropositive recipients, antigenaemia occurred in 68% (MUD) and in 49% (MRD, P = 0·08); there were no differences in the maximum levels of CMV antigenaemia and the time to cessation with antiviral therapy. CMV viraemia by culture was more common in MUD compared with MRD HCT recipients in univariate analysis (26% vs. 6%, P = 0·01), however, this difference was not detectable after controlling for other factors. The rates of CMV disease in the first 100 d were similar in MUD (9%) and MRD (5%) HCT recipients. CMV disease tended to occur earlier in the MUD compared with the MRD recipients (median day 41 vs. day 80). Beyond day 100, rates of CMV disease remained similar in both cohorts (cumulative incidence: MUD 21% and MRD 14%). The 30-d and 1-year survivals after CMV disease diagnosis were not significantly different in both groups. Thus, there appeared to be a trend toward increased CMV reactivation in MUD compared with MRD non-myeloablative allogeneic HCT recipients; however, these differences did not reach statistical significance in this cohort and preemptive therapy was similarly effective in preventing CMV diseases.

Cytomegalovirus (CMV) infections are the most common viral infections after myeloablative allogeneic haematopoietic cell transplantation (HCT). Although the diagnosis, prophylaxis and treatment have been improved over the last decade (Einsele et al, 1995; Boeckh et al, 1996; Ljungman et al, 1996), CMV infections still contribute significantly to the morbidity and mortality of patients in the early and late post-transplant periods (Husni et al, 1998; Ljungman, 1998). Risk factors for CMV infection after HCT are a positive serostatus for CMV of the recipients before HCT, acute graft-versus-host disease (GVHD), older age and unrelated or related human leucocyte antigen (HLA)-mismatched donor transplants (Einsele et al, 1995; Ljungman et al, 1998).

Non-myeloablative conditioning regimens have recently been developed for allogeneic HCT (Giralt et al, 1997; Slavin et al, 1998; Childs et al, 1999; Sykes et al, 1999; McSweeney et al, 2001). Most of these regimens are characterized by effective pre- and post-transplant immunosuppression and decreased myeloablation. The non-myeloablative regimen that was developed in Seattle consists of low-dose (2 Gy) total body irradiation (TBI) and fludarabine before and mycophenolate mofetil (MMF) and cyclosporine (CSA) for post-transplant immunosuppression (Feinstein et al, 2001; Maris et al, 2001; McSweeney et al, 2001). We have shown previously that in non-myeloablative HLA-matched related donor (MRD) transplants, early CMV and bacterial infections occurred less frequently compared with myeloablative HCT recipients (Junghanss et al, 2002a,b). However, beyond day 100, CMV disease occurred at a higher incidence than in myeloablative HCT recipients, leading to a similar overall incidence of CMV disease at the end of the first year post-transplant (Junghanss et al, 2002a).

Whether recipients of non-myeloablative, HLA-matched unrelated donor HCT have a similar risk of CMV disease and similar temporal course of CMV infections as non-myeloablative, HLA-matched related donor HCT recipients is unknown. In order to determine the incidence, onset and outcome of CMV infections among such patients we performed a retrospective analysis of unrelated and related donor HCT recipients from our institution, who were transplanted following comparable non-myeloablative conditioning regimens.

Patients. Results from 109 consecutive patients (Table I) who had received HLA-MRD allogeneic HCT between December 1997 and November 2001 and 59 patients who had received non-myeloablative HLA-matched unrelated donor (MUD) allogeneic HCT between January 2000 and November 2001 were analysed. Most MRD (93%) and MUD patients (98%) had haematological malignancies. All patients were treated at the FHCRC and received similar surveillance and prevention strategies for infections. Some of the MRD patients have been reported earlier (Junghanss et al, 2002a).

Table I.  HCT patient characteristics.
Patient characteristicsMRD (n = 109)MUD (n = 59)P-value
  1. ALL, acute lymphocytic leukemia; AML, acute myeloid leukemia; CML, chronic myeloid leukemia; CMV, cytomegalovirus; CLL, chronic lymphocytic leukemia; D, donor; HD, Hodgkin's disease; HCT, haematopoietic cell transplantation; MDS, myelodysplastic syndrome; MM, multiple myeloma; MRD, matched related donor; MUD, matched unrelated donor; NHL, non-Hodgkin's lymphoma; PBSC, peripheral blood stem cells; R, recipient; tx, transplantation.

  2. *Other, renal cell carcinoma, melanoma, cervical carcinoma.

Sex (female/male) (%)  39/6137/630·87
Disease (%)
 ALL17 
 AML1125 
 CLL125 
 CML517 
 HD85 
 MDS817 
 MM268 
 NHL2213 
 Other*72 
Diagnosis group (%)   
 Low risk3466<0·0001
 High risk6634 
Median age at tx (years, range)  53 (21–72)53 (1–69)0·45
 <20 years0120·0008
 20–40 years127 
 >40 years8881 
CMV risk group (%)  0·84
 Low (R/D)2629 
 Intermediate (R/D+)1714 
 High (R+/D, R+/D+)5858 
Stem cell source (%)
 Bone marrow019<0·0001
 PBSC10081 

The CMV risk groups were defined based on previous results from myeloablative transplants (Boeckh, 1999): low risk [recipient (R) and donor (D) serologically negative], intermediate risk (R/D+), and high risk (R+/D, R+/D+).

The underlying diseases of the patients (Table I) were grouped into high and low risk based on previous findings concerning the risk for CMV infections: high risk was defined as active de novo or relapsed acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) [refractory anaemia with excess of blasts (RAEB) or excess of blasts in transformation (RAEB-T)], acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), non-Hodgkin's lymphoma (NHL), Hodgkin's disease (HD), multiple myeloma (MM) regardless of status, renal cell carcinoma, melanoma, cervical carcinoma, accelerated chronic myeloid leukemia (CML) or blast crisis of CML; low risk was defined as any of the above named diseases with unknown disease status or in remission except for MM, CML chronic phase and MDS [refractory anaemia (RA), RA with ringed sideroblast (RARS)] (Junghanss et al, 2002a).

Most patients in both groups were Caucasians (MUD 88%, MRD 84%, P = 0·51).

Preparative regimens. Patients in the MRD group received low-dose TBI (2 Gy, day 0) followed by CSA and MMF post-transplant (McSweeney et al, 2001). This regimen was modified after the first 38 patients by adding fludarabine 30 mg/m2 body surface area per day on days −4 to −2. All MUD patients received low-dose TBI (2 Gy, day 0) and fludarabine (30 mg/m2 body surface area per day on days −4 to −2) followed by CSA and MMF post-transplant (Niederwieser et al, 2002).

Prophylaxis against graft-versus-host disease. Recipients were assigned to receive CSA, 6·25 mg/kg p.o. b.i.d. from day −3 to +35 for MRD transplants and from day −1 to +100 for unrelated donor transplants. CSA was then tapered, so that the last dose was given on days +56 (related donors) and +180 (unrelated donors) (McSweeney et al, 2001; Niederwieser et al, 2002). Tapering schedules were modified at the discretion of the attending physician if active GVHD was present. MMF was given at a dose of 15 mg/kg p.o. b.i.d. from day 0 to +27 for related donor transplants and through to day 40 with subsequent taper to day 96 for unrelated donor transplants (Niederwieser et al, 2002). After July 2001 MUD patients (n = 12) received MMF 15 mg/kg p.o. t.i.d. through to day +40 with subsequent taper.

Graft-versus-host disease and treatment. Diagnosis and clinical grading of acute graft-versus host disease (aGVHD) were performed according to established criteria (Glucksberg et al, 1974). GVHD was usually treated with prednisolone and/or restart of CSA if it had already been tapered.

Infection prophylaxis. All patients received prophylactic antibiotics (ceftazidime or ciprofloxacin or imipenem) when absolute neutrophil counts (ANC) were <0·5 × 109/l. Patients who were serologically positive for herpes simplex virus (HSV) received prophylactic low-dose acyclovir from day −5 to +30 or resolution of mucositis, whichever occurred earlier (Boeckh et al, 1996). Fluconazole (400 mg/d) was given to all patients from start of conditioning to day +75 after transplant (Marr et al, 2000). Prophylaxis against Pneumocystis jiroveci was performed using trimethoprim–sulfamethoxazole as first-line treatment and dapsone (50 mg/d b.i.d.) as second-line treatment until day 180 after transplant, or until discontinuation of immunosuppression, whichever occurred later (Souza et al, 1999; Boeckh & Marr, 2002).

Infection surveillance. Patients were monitored up to day 365 after transplant for the development of CMV infections and disease. Surveillance from blood samples for CMV (pp65 antigenaemia, blood culture) was performed weekly during the first 3 months (Boeckh et al, 1996). Ganciclovir (5 mg/kg b.i.d.) was given for any positive antigenaemia and continued until day 100 after transplanation; the dose was reduced to 5 mg/kg/d after 1 week or after a decline of antigenaemia was documented, whichever occurred later. Ganciclovir was substituted with foscarnet in patients with neutropenia. After day 100, surveillance and preemptive therapy was recommended weekly to every other week to intermediate and high-risk patients. Patients with suspected pneumonia were evaluated by bronchoalveolar lavages (BAL) and/or lung biopsies. Viral direct antigen-detecting fluorescent assay (DFA) and conventional and shell vial (SV) centrifugation cultures were performed on all BAL, lung biopsies, and autopsy specimens throughout the study period; specimens were submitted for routine bacterial, fungal, and acid-fast bacilli cultures. Patients with suspected gastrointestinal (GI) disease underwent endoscopy and biopsy specimens were tested by viral cultures and histologic examination. CMV disease was treated with ganciclovir (5 mg/kg b.i.d.) for 3 weeks followed by 5 mg/kg/d for an additional 3 weeks; patients with CMV pneumonia also received intravenous immunoglobulin. Foscarnet was given instead of ganciclovir in patients with neutropenia.

Definitions. Previously described definitions for infections were used in this study (Boeckh et al, 1996; Ljungman et al, 2002). The day of onset of an infection was defined as the day when the diagnostic test was performed. CMV antigenaemia was diagnosed on the basis of positive blood pp65 testing and CMV viraemia on the basis of a positive blood culture (BC) or SV centrifugation cultures. CMV pneumonia was diagnosed on the basis of signs and symptoms compatible with a diagnosis of pneumonia (hypoxaemia, X-ray) and a BAL or lung biopsy specimen positive for CMV by DFA, culture or immunohistology. CMV GI disease was diagnosed when GI signs or symptoms occurred and evidence of CMV in the GI tract was diagnosed by culture, immunohistochemistry, or in situ hybridization of biopsy specimens.

HLA matching. Until 21 July 2001, the donor–recipient pairs for related and unrelated donor transplants were selected on the basis of intermediate-resolution DNA typing to a level at least as sensitive as the serology for HLA-A, B and C and high-resolution matching for HLA-DRB1 and HLA-DQB1 (MUD: n = 47; MRD: n = 100) (Niederwieser et al, 2002). In subsequent patients (MUD: n = 12; MRD: n = 9), donor–recipient pairs were selected on the basis of high resolution matching for HLA-A, B, C, DRB1 and DQB1 (Petersdorf et al, 1998). In the unrelated donor transplant group a total of six class I single allele mismatched were identified retrospectively (i.e. two HLA-A, three HLA-B, one HLA-C). In addition, a single allele DRB3 mismatch, but no DRB1 mismatch was identified.

Statistical analysis. To compare characteristics of MUD and MRD patients, summary statistics including frequency counts and percentages for categorial variables, as well as medians and ranges for ages at transplant were calculated. Comparisons from 2 × 2 tables were made using chi-squared and Fisher's exact tests as appropriate. Median times until onset of events were compared using the Wilcoxon rank sum test. Cumulative incidence curves were produced for CMV antigenaemia and viraemia up to 100 d post-transplant, and for CMV disease up to 365 d post-transplant.

Univariate and multivariable Cox regression models were used to analyse the influence of selected variables on the risks of CMV disease, CMV viraemia and CMV antigenaemia up to day 100 as well as from day 100 to day 365 for CMV disease. Times to CMV disease or viraemia or antigenaemia were the outcomes for the Cox regression models with censoring at the end of follow-up and death and subsequent transplant as competing risks. Positive antigenaemia and aGVHD were entered as time-dependent covariates. Follow-up times in the model examining early CMV disease were censored at day 100. Bivariate models with MRD and MUD as the primary parameter of interest were fit by including each of the other variables in a step-wise fashion. We wished to determine whether certain factors modified the effect of MRD versus MUD, therefore only those variables whose inclusion altered the coefficient estimate of MRD versus MUD by more than 10% were considered to be important covariates where MRD versus MUD was a significant factor.

One year survivals after CMV disease diagnosis among MUD patients were compared with those of MRD patients using a Kaplan–Meier analysis and the log-rank test. P-values <0·05 were considered to be statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Results from 109 MRD HCT recipients were compared with those of 59 MUD HCT recipients. At the time of the analysis all patients had at least 6 months of follow-up. The median follow-up periods after HCT were 12·5 months (range 0·2–50·9) in MRD recipients and 9·8 months (range 0·7–24·7) in MUD recipients.

CMV antigenaemia during the first 100 d after HCT

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

The rates of CMV antigenaemia are shown in Table II and Fig 1. All patients with CMV antigenaemia received preemptive therapy. Within the CMV high-risk group (R+/D, R+/D+) MUD HCT recipients tended to have a higher incidence of CMV antigenaemia compared with MRD HCT recipients but the difference was not statistically significant. The median day of onset of CMV antigenaemia in CMV high risk patients was day 40 (range 10–78) in MUD recipients and day 44 (range 4–95) in MRD HCT recipients, P = 0·57, Fig 1). When only patients receiving fludarabine/TBI were considered, the curve looked similar (data not shown) (P = 0·12, likelihood-ratio).

Table II.  Incidence of CMV infection and disease.
CMV serostatuspp65 AGViraemia (culture)CMV disease
(day 0–100)(day 0–100)day 0–100day 0–365
MRDMUDMRDMUDMRDMUDMRDMUD
  1. *P = 0·01.

  2. D, donor; R, recipient; MRD, matched related donor; MUD, matched unrelated donor.

  3. Values in parentheses are percentages.

D/R1/28 (4)0/171/28 (4)0/170/281/17 (6)0/281/17 (6)
D+/R5/18 (28)2/8 (25)1/18 (6)1/8 (13)0/180/80/180/8
D/R+ or D+/R+31/63 (49)23/43 (68)4/63 (6)*9/34 (26)*3/63 (5)3/34 (9)9/63 (14)7/34 (21)
All37/109 (34)25/59 (42)6/109 (6)10/59 (17)3/109 (3)4/59 (7)9/109 (8)8/59 (14)
image

Figure 1. Incidences of CMV antigenaemia and viraemia. The cumulative incidences of CMV antigenaemia and viraemia in CMV high-risk patients during the first 100 d post-transplant are displayed. MUD HCT recipients tended to have more CMV antigenaemias during the first 100 d post-transplant (P = 0·08) (A). CMV viraemia occurred significantly more often in MUD compared with MRD patients (P = 0·01) (B).

Download figure to PowerPoint

CMV viraemia during the first 100 d after HCT

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Cytomegalovirus viraemia by culture occurred at low rates in CMV low-risk patients with MUD HCT and one patient each with an intermediate risk for CMV disease developed CMV viraemia in each group (P = 0·53, Table II). Within the CMV high-risk group CMV viraemia occurred at significantly higher rates in MUD HCT recipients (Table II, Fig 1). The median days of CMV viraemia onset in the CMV high-risk MUD HCT recipients were day 40 (range 25–70) and day 60 (range 13–95) in CMV high-risk MRD HCT recipients (P = 0·40, Fig 1). When only patients receiving fludarabine/TBI were considered, the curve looked similar (data not shown); however, the difference did not reach statistical significance (P = 0·23, likelihood-ratio).

CMV disease during the first 100 d after HCT

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Early CMV disease was rare in MUD (1/17, 6%; Table II) and MRD (0/28, 0%) low CMV risk HCT recipients (P = 0·38). None of the MUD and MRD patients with intermediate CMV risk developed CMV disease. In CMV high-risk patients who received MUD HCT CMV, disease occurred at similar rates compared with recipients of MRD HCT (3/34, 9% vs. 3/63, 5%, P = 0·42, Fig 2). The median time of disease onset tended to be earlier in MUD [day 41 (range 16–49)] compared with MRD HCT recipients [day 80 (range 79–91), P = 0·10, Fig 2].

image

Figure 2. Incidence of CMV disease during the first year post-transplant. The cumulative incidences of CMV disease in CMV high-risk patients during the first 365 d post-transplant are displayed. CMV disease occurred at similar rates in MUD compared with MRD HCT recipients during the first year post-transplant (P = 0·42). The cumulative incidence of CMV disease at day 100 after HCT was also similar in both groups, respectively (P = 0·42).

Download figure to PowerPoint

During the first 100 d after HCT the proportion of patients with more severe CMV manifestations, i.e. viraemia or disease, was significantly higher in MUD HCT recipients compared with MRD HCT recipients (MUD 10/34, 29% vs. MRD 7/63, 11%, P = 0·02). In this combined analysis the median time of onset of a more severe CMV event was earlier in MUD (day 40; range 16–70) compared with MRD HCT recipients (day 79, range 13–95, P = 0·03).

CMV disease during the first 365 d after HCT

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

When the rate of CMV disease during the first 365 d after HCT was analysed, the incidence of CMV disease in the CMV high-risk group was not significantly different in MUD and MRD HCT recipients (7/34, 21% vs. 9/63, 14%, P = 0·42, Fig 2). The median time of disease onset was 107 d (range 16–164) after MUD HCT compared with 106 d (range 79–168) after MRD HCT (P = 0·61). After day 100, CMV disease occurred in six of the 60 MRD CMV high-risk HCT recipients who did not have early CMV disease (10%) and in four of the 31 MUD HCT recipients (13%) (P = 0·73).

When all patients were considered in a statistical model that included events during the first 365 d, CMV disease was not statistically significantly different between MUD and MRD recipients [hazard ratio (HR) 1·77, 95% confidence interval (CI) 0·68–4·58, P = 0·25].

Clinical course of CMV disease

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

The clinical course of all patients with CMV disease is presented in Table III. The 30-d and 1-year survival after CMV disease was not significantly different between MUD and MRD HCT recipients (1-year, 5/10 vs. 5/8, P = 0·45). Two MRD HCT recipients who had concomitant invasive aspergillosis and one with pulmonary zygomycosis survived the infections.

Table III.  Clinical course of patients with CMV disease.
CasesDay of CMV disease after transplantSourceCo-pathogen present at time of CMV diagnosisGVHD at time of CMV diagnosisDeathTime from CMV diagnosis to death (days)
  1. *Low CMV risk patient, who developed CMV disease.

  2. **Patient developed a second episode of CMV disease on day +179 and died because of this.

  3. ***Patients who had a time period from CMV diagnosis to death of 0 d, had the CMV disease diagnosis established by autopsy and died due to other infections.

  4. BM, bone marrow; GI, gastro-intestinal; pulm, pulmonary; na, not applicable.

MRD
 179PulmPulm. aspergillosisYesNona
 280PulmPulm. aspergillosis and bacteremiaYesYes3
 391PulmPulm. aspergillosisYesNona
 4105PulmPulm. ZygomycesYesNona
 5106PulmPulm. aspergillosisYesYes86**
 6115GI tractBacteremiaYesYes0***
 7127PulmBacteremiaYesNona
 8149PulmPulm. aspergillosisYesYes15
 9168PulmZygomyces and Fusarium sinusitisYesYes0***
10511PulmNoYesNona
MUD
1*13PulmPulm. aspergillosisYesYes21
216PulmNoNoYes127
341PulmPulm. aspergillosisYesYes0***
449GI tractNoYesNona
5107PulmNoNoYes6
6111PulmNoNoNona
7161BMNoNoNona
8164PulmCandidemiaYesYes0***

Severity of CMV antigenaemia

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

In order to determine whether there were differences in CMV antigenaemia, we analysed the quantified test results (CMV-positive cells per slide) comparing MUD with MRD HCT recipients in the different CMV-risk groups. The first and the maximal CMV antigenaemia results were grouped into ≤5, >5, >10, >50 and >100 positive cells per slide and the percentages of patients within each group were compared between MUD and MRD HCT recipients. The denominator for the analyses of the percentages and P-values of maximal and first positive antigenaemia included all patients with antigenaemia. There were no significant differences in the degree of maximal CMV antigenaemias between MUD and MRD HCT recipients in any of these groups. Overall, when all CMV risk group data were analysed together, MUD HCT recipients did not have significantly higher CMV antigenaemia levels (>5 CMV positive cells per slide) compared with MRD HCT recipients [9/25 (36%) vs. 9/37 (24%), P = 0·32]. Examining the numeric quantity of the first positive CMV test of each patient also revealed no significant differences between MUD and MRD recipients in any of the groups (data not shown). Time to cessation of antigenaemia after initiation of preemptive therapy was also not statistically significantly different between MRD and MUD recipients (data not shown).

Graft-versus-host disease

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Acute GVHD grading was available for 107 of 109 MRD HCT recipients (98%) and for 58 of 59 MUD HCT recipients (98%). Acute GVHD greater than grade 1 occurred in 61 of 107 MRD HCT recipients (57%) compared with 42 of 58 MUD HCT recipients (72%, P = 0·05) and it occurred significantly earlier in MUD HCT recipients (median day 25; range 5–76) compared with MRD HCT recipients (median day 43; range 10–107, P < 0·001). Acute GVHD greater than grade 2 occurred at similar rates in MRD (18%) and MUD (16%) HCT recipients (P = 0·71); the median day of onset was 44 (range 15–96) and 27 (range 7–76), respectively.

Clinical extensive chronic GHVD occurred in 61 of 78 evaluable MRD HCT recipients (78%) compared with 28 of 39 evaluable MUD HCT recipients (72%, P = 0·44) and the onset tended to be later in MRD HCT recipients (median day 136; range 88–444) compared with MUD HCT recipients (median day 107; range 86–354, P = 0·09).

Antigenaemia.  In univariate analyses, MUD status was not associated with increased antigenaemia. Significant factors included: CMV seropositivity before transplant (CMV high-risk group) [relative risk (RR) 6·92; 95% CI 3·29–14·59), P < 0·0001] and aGVHD greater than grade 1 (RR 3·40; 95% CI 1·88–5·57, P < 0·0001). In bivariate models, none of these risk factors for early CMV antigenaemia or graft rejection changed the lack of association between donor type and incidence of CMV antigenaemia.

Viraemia.  Univariate and bivariate models were calculated for CMV viraemia. Since there were only 16 viraemia events, models containing more than two factors would have questionable stability using our approach. The following factors were significantly associated with CMV viraemia in univariate analysis: MUD status, use of fludarabine in the conditioning regimen, high-risk CMV serostatus group, and aGVHD (grade 2–4). When bivariate models were fit with these variables (fludarabine, CMV group, GVHD) and MUD versus MDR status, MUD status was no longer significant. However, in a model that included MUD versus MRD status and graft rejection, MUD status remained significant (HR 3·75, 95% CI 1·36–10·34).

CMV disease.  Matched unrelated donor status was not statistically significantly associated with early, late, or all CMV disease in univariate analysis (early HR 2·6, 95% CI 0·58–11·6; late HR 1·34, 95% CI 0·38–4·76; all HR 1·76, 95% CI 0·68–4·58). The use of peripheral blood stem cells (PBSC) as the stem cell source was associated with a decreased risk for early CMV disease (HR 0·16, 95% CI 0·03–0·80, P = 0·06). CMV seropositivity of recipients showed as trend towards an increased risk for early (HR 4·42, 95% CI 0·53–36·69, P = 0·11), and a statistically significant association with late, CMV disease (HR ∞, P < 0·001); when all events before day 365 were considered CMV recipient seropositivity was also associated with CMV disease (HR 11·9, 95% CI 1·59–90·2). Acute GVHD greater than grade 1 was a significant risk factor for early (HR 18·32, 95% CI 1·78–188·49, P = 0·004) and late CMV disease (HR 6·21, 0·79–49·01, P = 0·03). CMV antigenaemia during the first 100 d increased the subsequent risk for early CMV disease (HR 13·93, 95% CI 2·03–95·72, P = 0·004), but was also a risk factor for late CMV disease (HR 7·28, 95% CI 1·55–34·28, P = 0·004). Fludarabine use, age, underlying disease risk and graft rejection were not associated with CMV disease.

In separate bivariate models [including graft rejection, which was more common in MUD recipients (20·3% vs. 6%, P = 0·003)], no risk factors at any time period changed the lack of association between donor type and incidence of CMV disease (early, late, any).

Survival

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

Overall survival at 1 year was 60·5% for MRD and 51·4% for MUD transplants (P = 0·25, log-rank test). Survival based on pretransplant CMV serology is shown in Fig 3.

image

Figure 3. Mortality according to CMV serostatus. Differences were not statistically significant. R, recipient; D, donor.

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Discussion

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

The impact of unrelated donor status on CMV infection after HCT with non-myeloablative conditioning is poorly defined. Therefore, we analysed the occurrence of CMV antigenaemia, viraemia and disease in a cohort of patients who were given HCT from HLA MUD at a single institution following a low-dose TBI-based conditioning regimen. We compared these data with those from HCT recipients who had received a similar non-myeloablative HCT conditioning regimen but had received stem cells from HLA MRD.

Previous studies have shown that early CMV disease after myeloablative MRD HCT occurs in 3·8–6% of patients who were at high risk for CMV disease (CMV seropositivity before HCT), if polymerase chain reaction (PCR) or antigenaemia-based preemptive therapy approaches were applied (Einsele et al, 1995; Boeckh et al, 1999). An 11% incidence of early CMV disease has been reported after MUD myeloablative HCT (Small et al, 1999). Data from the present study showed that, during the first 100 d after non-myeloablative HCT without T-cell depletion, CMV disease occurred at similar rates in MUD and MRD recipients, although there was a trend towards more CMV disease in MUD recipients. This difference was due to a higher incidence of early CMV disease. Two cases of CMV pneumonia occurred before day 20 after transplantation (Table III). Viraemia by culture was more common despite the identical protocol of preemptive antiviral therapy; however, after controlling for fludarabine use, diagnosis risk group, and aGVHD this difference was no longer statistically significant.

Two recent studies have described incidences of CMV infections in cohorts of patients who received T cell depleted, reduced toxicity conditioning regimens followed by allogeneic HCTs (Bainton et al, 2002; Chakrabarti et al, 2002). Whereas Chakrabarti et al (2002) analysed the incidence of CMV infections in patients who received a conditioning regimen consisting of fludarabine, melphalan and alemtuzumab (100 mg, Campath-1H), Bainton et al (2002) analysed the rate of CMV infections following a BEAM (carmustin, cytosine arabinoside, etoposide, melphalan)-Campath regimen ± fludarabine or a fludarabine–melphalan–Campath-based regimen. Similar to our results, both studies found no significant difference in the risks of CMV infections between sibling and unrelated transplants (Bainton et al, 2002; Chakrabarti et al, 2002). However, the rate of CMV infections in both studies was significantly higher compared to ours, ranging from 78% to 92%. Whereas the study reported by Bainton et al (2002) was too small to allow statistical analyses of rates of CMV disease, the multicentre trial (Chakrabarti et al, 2002) reported a CMV disease rate of 6% in CMV high-risk patients. Therefore, it seemed that T-cell depletion during the conditioning regimen lead to more early CMV infections compared with current results, but CMV disease did not occur more frequently. This suggests that the preemptive therapy strategies used in these studies were generally effective.

One other multicentre study analysed the rate of early CMV infections after reduced intensity conditioning (fludarabine plus busulphan or melphalan) for HLA-matched sibling HCT (Martino et al, 2001a, b). In this study, no T-cell depleting antibody was applied and GVHD prophylaxis consisted of CSA and a short-course of methotrexate. The rates of CMV infections and CMV disease in this study were low (21% and 1%, respectively). Similar to our results, this study identified CMV serostatus and the development of moderate to severe GVHD as risk factors for CMV infections. Of interest, in a subsequent comprehensive report, adverse effects of alemtuzumab (i.e. T-cell depletion) on CMV infections were idenitifed when this Spanish (Martino et al, 2001b) and the British (Kottaridis et al, 2000) prospective studies were analysed together (Perez-Simon et al, 2002). Specifically, CMV reactivation occurred at significantly higher rates in alemtuzumab recipients compared to non-alemtuzumab recipients (85% vs. 24%, P < 0·001), emphasizing the important relationship between the degree of T-cell immunity and the development of CMV disease.

Late CMV disease occurred frequently in both MUD and MRD non-myeloablative HCT recipients at risk, especially in patients who had had CMV antigenaemia during the first 100 d. This is in line with data in myeloablative HCT recipients in whom early CMV antigenaemia or PCR positivity was also identified as a risk factor for late CMV disease (Zaia et al, 1997; Boeckh et al, 2003). Only one other study has reported data on late CMV infections after reduced toxicity conditioning regimen so far (Chakrabarti et al, 2002). In that study, late CMV infections occurred more frequently in MUD compared with MRD HCT recipients; however, late CMV disease was not different (Chakrabarti et al, 2002). The high incidence of CMV disease after day 100 in our study emphasizes the need to continue weekly surveillance and preemptive therapy. Although such surveillance was recommended after the patients were referred back to their primary physicians, adherence was incomplete and no complete records exist on the frequency of testing.

In summary, there was a trend towards more CMV antigenaemia in MUD recipients while CMV viraemia occurred at a higher frequency in recipients of MUD compared with MRD non-myeloablative recipients in univariate analysis. The overall incidence of CMV disease did not reach statistical significance between both groups. The lack of statistical significance for CMV disease may have been due to the relatively small sample size. This small sample size also prevented larger multivariable models controlling for a number of variables. Thus, these results should be confirmed in larger studies. This study confirmed that the risk of late CMV disease is substantial and weekly surveillance and preemptive antiviral therapy should be continued in patients at risk for late CMV disease, i.e. those who reactivated CMV during the first 100 d and those with GVHD requiring systemic treatment.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References

We thank the medical, nursing, data processing, and clinical staff for their important contributions to this study through their dedicated care of the patients. We thank the staff and faculty for long-term follow-up and the pathology department for maintaining clinical databases. This study was supported by grants HL36444, HL03701, CA18221, CA18029, CA78902 and CA15704 awarded by the National Institutes of Health, Department of Health and Human Services, Bethesda, MD. C. Junghanss was supported by grant DFG JU 417/1-1, awarded by the German Research Council.

References

  1. Top of page
  2. Abstract
  3. Patients and methods
  4. Results
  5. CMV antigenaemia during the first 100 d after HCT
  6. CMV viraemia during the first 100 d after HCT
  7. CMV disease during the first 100 d after HCT
  8. CMV disease during the first 365 d after HCT
  9. Clinical course of CMV disease
  10. Severity of CMV antigenaemia
  11. Graft-versus-host disease
  12. Univariate and multivariable risk factor analyses
  13. Survival
  14. Discussion
  15. Acknowledgments
  16. References
  • Bainton, R.D., Byrne, J.L., Davy, B.J. & Russell, N.H. (2002) CMV infection following nonmyeloablative allogeneic stem cell transplantation using Campath. Blood, 100, 38433844.
  • Boeckh, M. (1999) Current antiviral strategies for controlling cytomegalovirus in hematopoietic stem cell transplant recipients: prevention and therapy. Transplant Infectious Disease, 1, 165178.
  • Boeckh, M. & Marr, K. (2002) Infections in hematopoietic stem cell transplantation. In: Clinical Approach to Infection in the Compromised Host (ed. by R.Rubin & L.S.Young), pp. 527572. Plenum Medical Book Company, New York.
  • Boeckh, M., Gooley, T.A., Myerson, D., Cunningham, T., Schoch, G. & Bowden, R.A. (1996) Cytomegalovirus pp65 antigenemia-guided early treatment with ganciclovir versus ganciclovir at engraftment after allogeneic marrow transplantation: a randomized double-blind study. Blood, 88, 40634071.
  • Boeckh, M., Bowden, R.A., Gooley, T., Myerson, D. & Corey, L. (1999) Successful modification of a pp65 antigenemia-based early treatment strategy for prevention of cytomegalovirus disease in allogeneic marrow transplant recipients. Blood, 93, 17811782.
  • Boeckh, M., Leisenring, W., Riddell, S.R., Bowden, R.A., Huang, M.L., Myerson, D., Stevens-Ayers, T., Flowers, M.E., Cunningham, T. & Corey, L. (2003) Late cytomegalovirus disease and mortality in recipients of allogeneic hematopoietic stem cell transplants: importance of viral load and T-cell immunity. Blood, 101, 407414.
  • Chakrabarti, S., Mackinnon, S., Chopra, R., Kottaridis, P.D., Peggs, K., O'Gorman, P., Chakraverty, R., Marshall, T., Osman, H., Mahendra, P., Craddock, C., Waldmann, H., Hale, G., Fegan, C.D., Yong, K., Goldstone, A.H., Linch, D.C. & Milligan, D.W. (2002) High incidence of cytomegalovirus infection after nonmyeloablative stem cell transplantation: potential role of Campath-1H in delaying immune reconstitution. Blood, 99, 43574363.
  • Childs, R.W., Clave, E., Tisdale, J., Plante, M., Hensel, N. & Barrett, J. (1999) Successful treatment of metastatic renal cell carcinoma with a nonmyeloablative allogeneic peripheral-blood progenitor-cell transplant: evidence for a graft-versus-tumor effect. Journal of Clinical Oncology, 17, 20442049.
  • Einsele, H., Ehninger, G., Hebart, H., Wittkowski, K.M., Schuler, U., Jahn, G., Mackes, P., Herter, M., Klingebiel, T. & Loffler, J. (1995) Polymerase chain reaction monitoring reduces the incidence of cytomegalovirus disease and the duration and side effects of antiviral therapy after bone marrow transplantation. Blood, 86, 28152820.
  • Feinstein, L., Sandmaier, B., Maloney, D., McSweeney, P.A., Maris, M., Flowers, C., Radich, J., Little, M.T., Nash, R.A., Chauncey, T., Woolfrey, A., Georges, G., Kiem, H.P., Zaucha, J.M., Blume, K.G., Shizuru, J., Niederwieser, D. & Storb, R. (2001) Nonmyeloablative hematopoietic cell transplantation. Replacing high- dose cytotoxic therapy by the graft-versus-tumor effect. Annals of New York Academy of Science, 938, 328337.
  • Giralt, S., Estey, E., Albitar, M., van Besien, K., Rondon, G., Anderlini, P., O'Brien, S., Khouri, I., Gajewski, J., Mehra, R., Claxton, D., Andersson, B., Beran, M., Przepiorka, D., Koller, C., Kornblau, S., Korbling, M., Keating, M., Kantarjian, H. & Champlin, R. (1997) Engraftment of allogeneic hematopoietic progenitor cells with purine analog-containing chemotherapy: harnessing graft-versus-leukemia without myeloablative therapy. Blood, 89, 45314536.
  • Glucksberg, H., Storb, R., Fefer, A., Buckner, C.D., Neiman, P.E., Clift, R.A., Lerner, K.G. & Thomas, E.D. (1974) Clinical manifestations of graft-versus-host disease in human recipients of marrow from HL-A-matched sibling donors. Transplantation, 18, 295304.
  • Husni, R.N., Gordon, S.M., Longworth, D.L., Arroliga, A., Stillwell, P.C., Avery, R.K., Maurer, J.R., Mehta, A. & Kirby, T. (1998) Cytomegalovirus infection is a risk factor for invasive aspergillosis in lung transplant recipients. Clinical Infectious Diseases, 26, 753755.
  • Junghanss, C., Boeckh, M., Carter, R.A., Sandmaier, B.M., Maris, M.B., Maloney, D.G., Chauncey, T., McSweeney, P.A., Little, M.T., Corey, L. & Storb, R. (2002a) Incidence and outcome of cytomegalovirus infections following nonmyeloablative compared to myeloablative allogeneic stem cell transplantation, a matched control study. Blood, 99, 19781985.
  • Junghanss, C., Marr, K.A., Carter, R.A., Sandmaier, B.M., Maris, M.B., Maloney, D.G., Chauncey, T., McSweeney, P.A. & Storb, R. (2002b) Incidence and outcome of bacterial and fungal infections following nonmyeloablative compared with myeloablative allogeneic hematopoietic stem cell transplantation: a matched control study. Biology of Blood and Marrow Transplantation, 8, 512520.
  • Kottaridis, P.D., Milligan, D.W., Chopra, R., Chakraverty, R.K., Chakrabarti, S., Robinson, S., Peggs, K., Verfuerth, S., Pettengell, R., Marsh, J.C., Schey, S., Mahendra, P., Morgan, G.J., Hale, G., Waldmann, H., de Elvira, M.C., Williams, C.D., Devereux, S., Linch, D.C., Goldstone, A.H. & Mackinnon, S. (2000) In vivo CAMPATH-1H prevents graft-versus-host disease following nonmyeloablative stem cell transplantation. Blood, 96, 24192425.
  • Ljungman, P. (1998) Immune reconstitution and viral infections after stem cell transplantation. Bone Marrow Transplantation, 21 (Suppl 2), S72S74.
  • Ljungman, P., Oberg, G., Aschan, J., Ehrnst, A., Lonnqvist, B., Pauksen, K. & Sulila, P. (1996) Foscarnet for pre-emptive therapy of CMV infection detected by a leukocyte-based nested PCR in allogeneic bone marrow transplant patients. Bone Marrow Transplantation, 18, 565568.
  • Ljungman, P., Aschan, J., Lewensohn-Fuchs, I., Carlens, S., Larsson, K., Lonnqvist, B., Mattsson, J., Sparrelid, E., Winiarski, J. & Ringden, O. (1998) Results of different strategies for reducing cytomegalovirus-associated mortality in allogeneic stem cell transplant recipients. Transplantation, 66, 13301334.
  • Ljungman, P., Griffiths, P. & Paya, C. (2002) Definitions of cytomegalovirus infection and disease in transplant recipients. Clinical Infectious Diseases, 34, 10941097.
  • McSweeney, P.A., Niederwieser, D., Shizuru, J.A., Sandmaier, B.M., Molina, A.J., Maloney, D.G., Chauncey, T.R., Gooley, T.A., Hegenbart, U., Nash, R.A., Radich, J., Wagner, J.L., Minor, S., Appelbaum, F.R., Bensinger, W.I., Bryant, E., Flowers, M.E., Georges, G.E., Grumet, F.C., Kiem, H.P., Torok-Storb, B., Yu, C., Blume, K.G. & Storb, R.F. (2001) Hematopoietic cell transplantation in older patients with hematologic malignancies: replacing high-dose cytotoxic therapy with graft-versus-tumor effects. Blood, 97, 33903400.
  • Maris, M., Woolfrey, A., McSweeney, P.A., Sandmaier, B.M., Nash, R.A., Georges, G., Maloney, D.G., Molina, A., Chauncey, T., Yu, C., Zaucha, J.M., Blume, K.G., Shizuru, J., Niederwieser, D. & Storb, R. (2001) Nonmyeloablative hematopoietic stem cell transplantation: transplantation for the 21st century. Frontiers in Bioscience, 6, G13G16.
  • Marr, K.A., Seidel, K., Slavin, M.A., Bowden, R.A., Schoch, H.G., Flowers, M.E., Corey, L. & Boeckh, M. (2000) Prolonged fluconazole prophylaxis is associated with persistent protection against candidiasis-related death in allogeneic marrow transplant recipients: long-term follow-up of a randomized, placebo-controlled trial. Blood, 96, 20552061.
  • Martino, R., Caballero, M.D., Canals, C., San Miguel, J., Sierra, J., Rovira, M., Solano, C., Bargay, J., Perez-Simon, J., Leon, A., Sarra, J., Brunet, S. & De La, C.R. (2001a) Reduced-intensity conditioning reduces the risk of severe infections after allogeneic peripheral blood stem cell transplantation. Bone Marrow Transplantation, 28, 341347.
  • Martino, R., Caballero, M.D., Canals, C., Simon, J.A., Solano, C., Urbano-Ispizua, A., Bargay, J., Rayon, C., Leon, A., Sarra, J., Odriozola, J., Conde, J.G., Sierra, J. & San Miguel, J. (2001b) Allogeneic peripheral blood stem cell transplantation with reduced- intensity conditioning: results of a prospective multicentre study. British Journal of Haematology, 115, 653659.
  • Niederwieser, D., Maris, M., Shizuru, J.A., Petersdorf, E., Hegenbart, U., Sandmaier, B.M., Maloney, D.G., Storer, B., Lange, T., Chauncey, T., Deininger, M., Poenisch, W., Anasetti, C., Woolfrey, A., Little, M.T., Blume, K.G., McSweeney, P.A. & Storb, R.F. (2003) Low-dose total body irradiation (TBI) and fludarabine followed by hematopoietic cell transplantation (HCT) from HLA-matched or mismatched unrelated donors and postgrafting immunosuppression with cyclosporine and mycophenolate mofetil (MMF) can induce durable complete chimerism and sustained remissions in patients with hematological diseases. Blood.101, 16201629.
  • Perez-Simon, J.A., Kottaridis, P.D., Martino, R., Craddock, C., Caballero, D., Chopra, R., Garcia-Conde, J., Milligan, D.W., Schey, S., Urbano-Ispizua, A., Parker, A., Leon, A., Yong, K., Sureda, A., Hunter, A., Sierra, J., Goldstone, A.H., Linch, D.C., San Miguel, J.F. & Mackinnon, S. (2002) Nonmyeloablative transplantation with or without alemtuzumab: comparison between 2 prospective studies in patients with lymphoproliferative disorders. Blood, 100, 31213127.
  • Petersdorf, E.W., Gooley, T.A., Anasetti, C., Martin, P.J., Smith, A.G., Mickelson, E.M., Woolfrey, A.E. & Hansen, J.A. (1998) Optimizing outcome after unrelated marrow transplantation by comprehensive matching of HLA class I and II alleles in the donor and recipient. Blood, 92, 35153520.
  • Slavin, S., Nagler, A., Naparstek, E., Kapelushnik, Y., Aker, M., Cividalli, G., Varadi, G., Kirschbaum, M., Ackerstein, A., Samuel, S., Amar, A., Brautbar, C., Ben Tal, O., Eldor, A. & Or, R. (1998) Nonmyeloablative stem cell transplantation and cell therapy as an alternative to conventional bone marrow transplantation with lethal cytoreduction for the treatment of malignant and nonmalignant hematologic diseases. Blood, 91, 756763.
  • Small, T.N., Papadopoulos, E.B., Boulad, F., Black, P., Castro-Malaspina, H., Childs, B.H., Collins, N., Gillio, A., George, D., Jakubowski, A., Heller, G., Fazzari, M., Kernan, N., Mackinnon, S., Szabolcs, P., Young, J.W. & O'Reilly, R.J. (1999) Comparison of immune reconstitution after unrelated and related T-cell- depleted bone marrow transplantation: effect of patient age and donor leukocyte infusions. Blood, 93, 467480.
  • Souza, J.P., Boeckh, M., Gooley, T.A., Flowers, M.E. & Crawford, S.W. (1999) High rates of Pneumocystis carinii pneumonia in allogeneic blood and marrow transplant recipients receiving dapsone prophylaxis. Clinical Infectious Diseases, 29, 14671471.
  • Sykes, M., Preffer, F., McAfee, S., Saidman, S.L., Weymouth, D., Andrews, D.M., Colby, C., Sackstein, R., Sachs, D.H. & Spitzer, T.R. (1999) Mixed lymphohaemopoietic chimerism and graft-versus-lymphoma effects after non-myeloablative therapy and HLA-mismatched bone-marrow transplantation. Lancet, 353, 17551759.
  • Zaia, J.A., Gallez-Hawkins, G.M., Tegtmeier, B.R., ter Veer, A., Li, X., Niland, J.C. & Forman, S.J. (1997) Late cytomegalovirus disease in marrow transplantation is predicted by virus load in plasma. Journal of Infectious Diseases, 176, 782785.