Introduction

Reduced intensity conditioning regimens were developed to reduce the toxicities associated with HSCT. Incorporating alemtuzumab (Campath-1H^®), a humanized monoclonal antibody to CD52, in reduced intensity regimens has effectively reduced the incidence of severe acute and chronic GVHD.^{1, 2} However, alemtuzumab delays immune reconstitution, resulting in cytomegalovirus (CMV) infection rates as high as 85%, many of which occur very early after transplant.³ This is substantially more than the 40–50% infection rates occurring in recipients of unmanipulated stem cell grafts and represents a major impediment to its use.

We conducted a prospective study of fludarabine, melphalan and alemtuzumab conditioning for patients with advanced hematological malignancies.⁴ We introduced high-dose valacyclovir prophylaxis for participating patients, based on a randomized study of this drug in recipients of myeloablative transplantation and combined it with pre-transplant ganciclovir.⁵ Here, we report the incidence of CMV infection in 85 consecutive patients at risk.

Patients and methods

Patients

All patients were participants in a study of a conditioning regimen for advanced hematologic malignancies, which was approved by the Institutional Review Board. Outcomes in particular patient subsets have been reported elsewhere.⁶ CMV prophylaxis and monitoring was not defined in the study, but was instituted as a unit policy. Therefore, the analysis of CMV infections is retrospective in nature.

Patients were defined as at risk for post transplant CMV infection if either the recipient, or donor, or both were CMV seropositive. Patients at low risk (CMV R-/D-) are not included in this analysis.

Conditioning regimen, post transplant immunosuppression and supportive care

Conditioning consisted of fludarabine 30 mg/m² on days -7 to -3, alemtuzumab 20 mg/day on days -7 to -3, and melphalan 140 mg/m² on day -2. Recipients received unmanipulated G-CSF mobilized stem cells from related or unrelated donors. Bone marrow collections were occasionally accepted from unrelated donors. Post-transplant tacrolimus was given until day 100. Routine infection prophylaxis followed CDC guidelines. Blood products were filtered and irradiated.

CMV surveillance

After transplantation and until hospital discharge, patients were monitored twice a week. Initially, we used a CMV DNA hybrid capture assay (Digene Corporation, Gaithersburg, MD, USA). As of October 2003, we used a real-time PCR-based assay for CMV DNA (magNApure LC, Roche Applied Science). Patients were then monitored approximately weekly to bi-weekly until day +140 in the absence of chronic GVHD, and indefinitely if chronic GVHD was present.

Prophylaxis and treatment of CMV infection

The initial patients received CMV prophylaxis with high-dose intravenous (i.v.) acyclovir at 500 mg/m² every 8 h from day -7 until engraftment, followed by oral acyclovir 800 mg four times daily until day +180.^{4, 7} After seven of the initial eleven patients developed CMV infection, the policy was changed. The large majority of subsequent patients received prophylaxis with ganciclovir 5 mg/kg i.v. twice daily from day -7 until day -2,⁹ acyclovir 500 mg/m² every 8 h i.v. from day -2 until engraftment, followed by high-dose oral valacyclovir 2 g four times daily, until day +210.⁵ The few patients for whom high-dose valacyclovir was cost prohibitive were given acyclovir instead upon recovery. Overall, 18 patients received acyclovir (in seven cases preceded by an induction course of gancyclovir) and 67 received ganciclovir–valacyclovir. Patients with CMV viremia received preemptive treatment with ganciclovir.⁹ Doses of valacyclovir, ganciclovir or acyclovir were proportionately reduced in patients with impaired renal function.

There were no significant differences in median age or diagnosis between the two groups. Only two patients (11%) in the acyclovir group had unrelated donors versus 31 (46%) in the ganciclovir–valacyclovir group (² P=0.01).

Definitions

CMV infection was defined as more than one positive result for either the CMV hybrid capture assay or PCR. CMV disease was documented when either a positive culture or PCR assay was obtained from the broncho-alveolar fluid of a patient with clinical evidence of pneumonitis, or when there was biopsy-proven CMV involvement at other sites (i.e. colon, esophagus, or liver).

Statistical analysis

The cumulative incidence of CMV infection was calculated with the Kaplan and Meier estimate and expressed as probabilities with a 95% confidence interval (CI). Patients were censored at death or disease recurrence. Univariate comparisons used the log-rank test. All P-values are two-sided. Parameters evaluated in univariate analysis included donor type (related versus unrelated) and type of CMV prophylaxis (acyclovir versus valacyclovir). For comparison of time to CMV infection, a rank-sum test was used.

Results

Patient characteristics

Patient characteristics are summarized in Table 1. All patients participated in a prospective study and thus received identical conditioning therapy and GVHD prophylaxis as described above. One patient had sickle cell disease and one had severe aplastic anemia. All others had hematologic malignancies, with acute leukemia or MDS accounting for more than half the cases. Forty-seven patients had matched-related donors, 31 had matched-unrelated donors, six had mismatched-related or -unrelated donors and one had a syngeneic donor. Eighty-one patients were considered at high risk for CMV infection by virtue of recipient seropositivity. Four patients were CMV-negative with a CMV-positive donor and were considered at intermediate risk. The median time of follow-up was nine months (range, 0–38 months). Acute GVHD grade II–IV occurred only in 10 patients.

Table 1 - Patient characteristics.

Full table

Incidence of CMV viremia and disease

Overall, 25 of the 85 patients developed CMV infection for a cumulative incidence of 29% (95% CI: 19–39%) by day +100, and 33% (95% CI: 21–45%) by day +250. Unrelated donor transplantation was not associated with an increased risk for CMV infection (P=0.9). In the ganciclovir–valacyclovir group, the cumulative incidence of CMV infection was 23% (95% CI: 11–34%) by day +100, and 29% (95% CI: 16–42%) by day +250. In the acyclovir group it was 53% (95% CI: 41–65%) by days +100 and +250. This difference was highly significant (log rank P=0.004) (Figure 1). Overall, 15 of 67 ganciclovir–valacyclovir recipients versus 10 of 18 acyclovir recipients developed CMV infection. In the ganciclovir–valacyclovir group, the median time to CMV infection was 45 days (range 19–488 days), and it was 20 days (range 10–389 days) in the acyclovir group (P=0.008). One patient in the acyclovir group and none in the ganciclovir–valacyclovir group developed CMV disease.

Figure 1.

Cumulative incidence of CMV infection. Acyclovir cohort ———, ganciclovir–valacyclovir cohort - - - - -.

Full figure and legend (14K)

Toxicity and dose adjustments

Toxicity of valacyclovir or acyclovir was not prospectively monitored, but no unusual incidence of severe toxicity was noted. In particular, TTP occurred in only one patient in this study and was not associated with administration of valacyclovir.

Discussion

The very high incidence of early CMV infection after alemtuzumab-based conditioning is a side effect of the potent immunosuppression associated with this drug and has hindered its widespread adoption in the USA, despite its excellent activity for GVHD prophylaxis. It results in the need for preemptive CMV treatment in the majority of patients. This is feasible and effective, but impractical, costly and toxic. Ganciclovir, the standard medication requires i.v. administration and causes frequent neutropenia, as does its oral analog valganciclovir. The alternative, foscarnet causes electrolyte abnormalities and renal toxicity and can be difficult to administer.¹⁰ Our initial patients receiving alemtuzumab were given prophylactic acyclovir, but this was not effective in preventing early CMV infection and there was one case of CMV disease. The incidence and median time to onset of CMV infection were very similar to that observed in a British study of fludarabine–melphalan–alemtuzumab conditioning.³ Based on the results of a recent randomized study, we then instituted a policy of prophylactic high-dose valacyclovir after hematologic recovery.⁵ Additionally, we administered pre-transplant ganciclovir, which might prevent cases of very early CMV reactivation^{11, 12} and i.v. acyclovir in the immediate post transplant period. After this policy was instituted, the incidence of CMV infection was dramatically reduced and similar to what we had previously observed using the same conditioning regimen without alemtuzumab.⁸ Time to onset of CMV infection was also much delayed. No further cases of CMV disease were observed and management of our patients was much simplified, despite a significant increase in the proportion of unrelated donor transplant recipients. As previously observed in the randomized study, no unexpected toxicity was noted with the administration of high-dose valacyclovir.⁵ We hypothesize that all components of our antiviral regimen contribute to its efficacy. Ganciclovir and early post-transplant acyclovir prevent early reactivation. High-dose valacyclovir then prevents later reactivation. Expense of valacyclovir is high, but might be offset in part by reduction in the use of i.v. ganciclovir. A formal pharmaco-economic analysis was not performed during our study.

In summary, prophylactic treatment with pre-transplant ganciclovir and post-transplant high-dose valacyclovir represents a simple, well-tolerated intervention that appears to abrogate the excessive incidence of CMV infection in allogeneic transplant recipients receiving pre-transplant alemtuzumab as reported by others³ and as initially experienced in our acyclovir recipients. Our data represent a confirmation in T-cell depleted transplant, of the value of a prophylaxis method that was initially investigated by the European group.⁵

References

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Acknowledgements

Supported in part by a Grant from Berlex pharmaceuticals and by NCI Grant 1-R21 CA 101337-01.