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Clinical Transplantation

RESULTS OF DIFFERENT STRATEGIES FOR REDUCING CYTOMEGALOVIRUS-ASSOCIATED MORTALITY IN ALLOGENEIC STEM CELL TRANSPLANT RECIPIENTS1

Ljungman, Per2,3; Aschan, Johan2; Lewensohn-Fuchs, Ilona4; Carlens, Stefan5; Larsson, Kajsa2; Lönnqvist, Berit2; Mattsson, Jonas5; Sparrelid, Elda6; Winiarski, Jacek7; Ringdén, Olle5,8

Author Information

Departments of Hematology, Clinical Virology, Clinical Immunology, Infectious Diseases, Pediatrics, and Transplantation Surgery, Huddinge University Hospital, Karolinska Institutet, Huddinge, Sweden

1Supported by the Swedish Cancer Society.

2Department of Hematology.

3Address correspondence to: Per Ljungman, Department of Hematology, Huddinge University Hospital, SE-14186 Huddinge, Sweden. E-mail: [email protected]

4Department of Clinical Virology.

5Department of Transplantation Surgery.

6Department of Infectious Diseases.

7Department of Pediatrics.

8Department of Clinical Immunology.

Received 20 April 1998.

Accepted 29 July 1998.

  • Free

Abstract

* Abbreviations: ATG, antithymocyte globulin; BMT, bone marrow transplantation; CMV, cytomegalovirus; GVHD, graft-versus-host disease; PCR, polymerase chain reaction; TBI, total body irradiation; TRM, transplant-related mortality.

Cytomegalovirus (CMV*) infection has been one of the most important complications to allogeneic bone marrow transplantation (BMT). For many years, effective management of CMV infection was hampered by slow diagnostic techniques and no effective prophylaxis. During the last decade, several new developments have allowed the use of different strategies for management of CMV infections after BMT. Intravenous immune globulin has been used extensively, although its efficacy has been controversial. Antiviral chemoprophylaxis with acyclovir or ganciclovir was studied in large randomized trials (1-3). Preemptive therapy with ganciclovir or foscarnet based on antigenemia or polymerase chain reaction (PCR) has during the last few years evolved as a widely used preventive strategy (4-7). However, these developments have happened more or less simultaneously; moreover, these strategies have often been used concurrently. Therefore, it has been difficult to assess each development's impact on risk for and outcome of CMV disease in allogeneic BMT recipients. The aims of the present study were to investigate the impacts of factors known at the time of transplant on subsequent CMV disease, CMV-associated mortality, and transplant-related mortality (TRM) and to identify patients with increased risk for development of CMV-associated complications with modern preventive strategies.

PATIENTS AND METHODS

A total of 584 consecutive allogeneic BMT patients who received transplants between 1975 and June 30, 1997 were included in the study. Ten patients received repeat transplants after receiving a second preparative regimen due to rejection or relapse. Thus, 594 transplants were analyzed in the study. Patients who received syngeneic transplants were excluded from the study. Patient characteristics are shown in Table 1.

T1-12
Table 1:
Patient characteristics

Preparative regimens. The BMT procedures have been published previously (8-10). Patients with malignancies were in almost all cases treated with either cyclophosphamide (60 mg/kg for 2 consecutive days) followed by total body irradiation (TBI; 10 Gy) with the lungs shielded to receive a dose of 9 Gy or busulfan (4 mg/kg for 4 consecutive days) followed by cyclophosphamide (60 mg/kg for 2 consecutive days). In a small series of patients receiving T-cell-depleted grafts, the dose of TBI was reduced to 7.5 Gy with a lung dose of 7 Gy in combination with 6 Gy of total lymphoid irradiation. In patients receiving unrelated donor transplants for hematological malignancies, antithymocyte globulin (ATG) or OKT-3 was added before BMT. Patients with aplastic anemia were given cyclophosphamide 50 mg for 4 days and in patients transplanted later than 1988 ATG was added. Children with metabolic disorders were given busulfan and cyclophosphamide as previously described (11). Patients receiving unrelated transplants for nonmalignant diseases have usually been given cyclophosphamide in combination with TBI and ATG or OKT-3 given during the conditioning regimen, although other regimens have been used in individual cases.

Prophylaxis against graft-versus-host disease (GVHD). Patients have received several different protocols as GVHD prophylaxis during the study period. The most commonly used regimens were monotherapy with methotrexate or cyclosporine (12), the combination of cyclosporine and methotrexate, or T-cell depletion with monoclonal antibodies (8).

Acute GVHD was defined according to Thomas et al. (13) and usually treated with prednisolone (2 mg/kg). In severe cases, psoralen plus UV-A (PUVA), methotrexate, or ATG was added when indicated.

Diagnosis of CMV disease and CMV infection. The diagnostic techniques for CMV disease have varied during the study period; therefore, all diagnoses of CMV disease were reassessed, and only cases fulfilling recently published definitions were included in the analysis (14).

The diagnostic techniques for CMV infection have also varied during the study period; therefore, it was not meaningful to analyze frequency of CMV infection in this study. Up until 1989, the diagnosis relied on standard virus isolation. Between 1989 and 1992, a rapid isolation technique was used, which was a modification of the detection of early antigen foci or shell vial cell culture technique using a mixture of monoclonal antibodies directed to several different CMV antigens (15). After January 1, 1992, a leukocyte-based PCR technique was used, which has been described previously (16).

Management of CMV infection. During the study period, different strategies were used for prevention of CMV infection. These include two studies of CMV hyperimmune plasma and hyperimmune globulin (17,18) and two studies, one in HLA-identical sibling donors and one in unrelated donor transplants, with high-dose standard immune globulin given weekly until 12 weeks after transplantation (19). High-dose acyclovir was given in two randomized studies. The first study has been published (1). The second study comparing valaciclovir with high-dose aciclovir has not been published.

The strategy of preemptive therapy with either ganciclovir or foscarnet has been used since 1990. From 1990 to 1992, the strategy was based on rapid CMV isolation and, after 1992, on two consecutive blood samples positive for CMV DNA by PCR (7). All patients received CMV-negative screened blood products from 1983 to 1991. After 1991 until 1995, screened blood products were given to seronegative patients who were transplanted from CMV seronegative donors. Thereafter, leukocyte-depleted blood products were used for all patients.

Treatment of CMV disease. Patients were treated for CMV disease as published previously. Initially, foscarnet was given (20). After 1988, patients with CMV pneumonia were given ganciclovir in combination with intravenous immune globulin as published (21). Patients with other types of CMV disease were treated with either ganciclovir or foscarnet, but immune globulin was not given.

Statistical analysis. The study was analyzed as of December 31, 1997. The following factors were analyzed in univariate analysis for their impact on CMV disease, death in CMV disease, and TRM: donor (matched/mismatched family + unrelated), GVHD prophylaxis (single agent vs. combined + T-cell depletion), conditioning regimen (TBI, yes/no), ATG/OKT-3 (yes/no), serologic status of the donor and recipient, age (as a continuous variable), antiviral prophylaxis (high-dose acyclovir or valaciclovir/no prophylaxis), the use of intravenous Ig, and preemptive therapy (based on viremia, PCR, or no preemptive therapy). Stage of disease was analyzed as early (acute leukemia in first complete remission, CML in chronic phase, and nonmalignant diseases) vs. later stages.

Cox models were constructed with the technique of forward variable selection to assess the factors with P-values of <0.10 in univariate analysis. Three different analyses were performed. First, all patients were analyzed together. In a second analysis, patients who were seronegative for CMV and who had a CMV-seronegative donor were excluded, as the risk for CMV infection in this group was very low. In the third analysis, only patients transplanted after January 1, 1992, when PCR-based preemptive therapy was initiated, were included.

RESULTS

CMV disease. The overall probability of CMV disease in the entire patient group was 8.9%. No patient who was seronegative and who had a seronegative marrow donor developed CMV disease. The corresponding probabilities for seronegative patients with seropositive donors, seropositive patients with seronegative donors, and seropositive patients with seropositive donors were 5.4%, 13.7%, and 11.7%, respectively (Fig. 1). In a multivariate Cox model, the use of the preemptive strategy and being CMV-seronegative reduced the risk for CMV disease whereas unrelated or family mismatched donor transplants, older age, and being CMV-seropositive before the BMT significantly increased the risk for development of CMV disease (Table 2). Acyclovir prophylaxis, GVHD prophylaxis, intravenous Ig, stage of disease at BMT, conditioning with TBI, and the serologic status of the marrow donor had no influence on the risk for CMV disease.

F1-12
Figure 1:
Probability of CMV disease in patients with different pretransplant CMV serostatus combinations in donors and patients. Don, donor; pos, positive; rec, recipient; neg, negative; SCT, stem cell transplantation.
T2-12
Table 2:
Results of Cox models regarding factors influencing CMV disease, death in CMV disease, and TRM

Because of the very low probability for CMV disease in the seronegative patient/seronegative donor group, a second Cox model was constructed in which these patients were excluded. In this model, the use of preemptive strategy (P<0.001), the use of a mismatched or unrelated donor (P<0.001), and increasing age (P<0.001) had significant influence on the risk for CMV disease. In this cohort of patients, there was no impact on development of CMV disease from seropositivity of the patient, the donor, or both. Finally, we analyzed only patients who were given preemptive therapy based on PCR. The only factor that influenced the risk for CMV disease in this patient cohort was the use of a mismatched or unrelated donor (12.5% vs. 4.4%; P=0.02).

Death in CMV disease. The overall risk for death in CMV disease in all patients was 5.7%. Patients who were seronegative and who had seronegative marrow donors had 0% probability for death in CMV disease. The corresponding probabilities for seronegative patients with seropositive donors, seropositive patients with seronegative donors, and seropositive patients with seropositive donors were 5.5%, 8.7%, and 6.7%, respectively. In a Cox model, the use of preemptive therapy and CMV seronegativity of the patient reduced the risk for death in CMV disease, whereas the use of mismatched or unrelated donors increased the risk (Table 2).

In the second Cox model, in which seronegative patients with seronegative donors were excluded, preemptive strategy (P<o.001) and acyclovir prophylaxis (P=0.04) reduced the risk for death in CMV disease whereas the use of mismatched or unrelated donors (P<0.001), and older age increased the risk (P<0.001). The probability for death in CMV was 1.4% in patients receiving acyclovir prophylaxis, whereas it was 8.0% in patients who did not receive acyclovir.

In patients monitored by PCR, the use of mismatched or unrelated donors was the only significant risk factor for death in CMV disease (P<0.05). The probability for death in CMV disease in patients receiving grafts from matched sibling donors was 1% whereas the corresponding probability for patients receiving grafts from mismatched or unrelated donors was 5.6% (Fig. 2).

F2-12
Figure 2:
Probability of death from CMV disease in patients who underwent transplants from mismatched family or unrelated transplants later than January 1, 1992, and who were given preemptive therapy based on PCR for CMV DNA. SCT, stem cell transplantation.

TRM. In a Cox model including all patients, the use of combined GVHD prophylaxis, preemptive therapy against CMV, receiving a transplant in early stage of disease, and being CMV-seronegative were associated with reduced risk for TRM while receiving grafts from mismatched or unrelated donors and older age were associated with increased risk for TRM (Table 2). In the model excluding the seronegative/seronegative patient-donor combination, the same factors with the exception of CMV serologic status of the patient were associated with TRM, and in the model including only patients monitored with PCR mismatched or unrelated donor BMT (P=0.006) and older age (P=0.001) were significantly associated with TRM.

Overall mortality. In a Cox model including all patients, preemptive therapy against CMV, receiving a transplant in early stage of disease, and being CMV-seronegative were associated with reduced risk for death whereas receiving grafts from mismatched or unrelated donors and older age were associated with increased risk for death.

DISCUSSION

CMV has been one of the most important obstacles to successful allogeneic BMT. Over the last decade, several strategies have been introduced with the goal to prevent development of CMV disease. These include intravenous immune globulin (22), acyclovir prophylaxis (1,23), ganciclovir prophylaxis (2,3), and preemptive therapy based on sensitive diagnostic techniques (4-7). These different options have in randomized trials frequently been used concurrently; thereby, it has been difficult to assess each strategy's impact on the overall outcome regarding CMV disease and death caused by CMV. Furthermore, these strategies are expensive, and combinations increase the cost of the BMT procedure significantly. This was the reason why we performed this analysis on a large cohort of patients transplanted during a period of more than 2 decades to try to identify which of these options that have the greatest impact on CMV disease and if combination of different strategies confer any additional effect on these end points.

Several factors were shown in the past to be associated with CMV disease. The most important of these factors were the CMV serologic status of the patients, serologic status of the donor (in seronegative patients), the use of TBI, older age, and acute GVHD (24,25). In this study, we wanted to assess only those variables known at the time of transplantation; therefore, acute GVHD was not included in the statistical modeling. Instead, we used GVHD prophylaxis and the type of marrow donor in the models. Both factors were previously shown to be important for the development of acute GVHD.

The results of the risk factor analysis for development of CMV disease confirmed the effect of CMV seropositivity of the recipient. Furthermore, although the donor serologic status was not independently associated with CMV disease, the seronegative donor to a seronegative patient combination had a 0% probability of CMV disease. This very low frequency of CMV disease can might be attributed to our use first of screened CMV seronegative blood and thereafter of leukocyte-depleted blood products, which were shown to significantly reduce the risk for transfer of CMV (26,27). We also confirmed the effect of older age as a risk factor for CMV disease, but we could not detect any effect of TBI. Of the two major factors influencing the development of acute GVHD, patients receiving grafts from mismatched or unrelated donors had an increased risk for development of CMV disease whereas no effect was seen of GVHD prophylaxis in this analysis. Finally, of the strategies applied to prevent CMV disease, only the strategy of preemptive therapy based on PCR had an independent effect on CMV disease. This is in agreement with previous studies (5,7). It should be noted that none of the patients in this study was given ganciclovir prophylaxis. A small number of patients received foscarnet as prophylaxis (28), but it did not influence development of CMV disease.

It could be possible that, although the additional modalities to prevent CMV did not have any influence on disease, they might have an impact on outcome of disease. Therefore, death in CMV disease was analyzed. In this model, there was a significant impact by acyclovir prophylaxis when only high-risk patients for CMV disease were analyzed. Interestingly, in the randomized study of acyclovir prophylaxis by Prentice et al. (1), although there was no difference in the risk for CMV pneumonia, there was a difference in mortality in CMV pneumonia in favor of the group receiving high-dose acyclovir prophylaxis.

We also analyzed TRM and overall mortality, and, in both analyses, preemptive therapy and none of the other preventive measures against CMV had significant impact on mortality. It could be argued that other factors not included in the models could have effects paralleling the effect of preemptive therapy, as our use of PCR-based therapy has been introduced in the last 5 years of the study period. It is not possible to exclude the possibility that factors such as better antifungal prophylaxis and therapy or the use of growth factors might have contributed to the reduced TRM (29).

It is clear from the analysis of patients transplanted the last 5 years, in whom the strategy of preemptive therapy based on PCR was used, that CMV is no longer a major problem in patients given HLA-matched grafts. On the other hand, the risk for CMV-associated mortality was still 5.6% in patients receiving grafts from mismatched or unrelated donors, which means that new strategies must be developed. Furthermore, in this group, none of the additional strategies decreased the risk for death in CMV disease.

None of our patients received ganciclovir prophylaxis, which certainly is a possible additional strategy. Only one controlled study has been performed comparing ganciclovir prophylaxis with preemptive therapy based on antigenemia (4). This study showed a reduction in CMV disease at day 100, but the difference had disappeared at day 180 due to late CMV disease. In our study, two out of six patients died during the normal time of ganciclovir prophylaxis (engraftment to day 100), whereas one patient developed CMV disease before engraftment and three patients died inlate CMV disease who had already been treated repeatedly with preemptive therapy. Similar results have been published by Krause et al. (30). Another potential strategy is the infusion of CMV-specific cytotoxic T lymphocytes as pioneered by the Seattle group (31). However, until now, this strategy has only been applicable to patients receiving grafts from sibling donors. Finally, the use of diagnostic techniques with better capacity to differentiate among patients who have signs of CMV reactivation might improve the results. One such strategy is the use of quantitative PCR, which has been shown to have prognostic value in liver transplant patients (32).

The results of this study show that preemptive therapy has reduced the risk for CMV disease, the mortality in CMV disease, and most probably also TRM in patients undergoing allogeneic BMT. High-dose acyclovir or addition of intravenous immune globulin does add give any additional benefit. Better strategies for management of CMV in patients receiving mismatched and unrelated donor transplants are still needed.

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