Background
Human herpesvirus-6B (HHV-6B) encephalitis is a severe complication following cord blood transplantation (CBT), with a reported incidence of 7.5% in this study. The disease carries high mortality and morbidity, yet optimal antiviral management remains controversial. This registry-based study from Japan provides critical real-world evidence on the impact of different antiviral regimens—foscarnet (FCN) monotherapy, ganciclovir (GCV) monotherapy, and FCN/GCV combination therapy—on survival outcomes.
Study Design
The study analyzed 3,862 adult CBT recipients registered between January 2019 and December 2023, identifying 289 cases of HHV-6B encephalitis within 100 days post-transplant. Patients received FCN monotherapy (n=190), GCV monotherapy (n=12), or FCN/GCV combination therapy (n=74). Primary endpoints included 1-year survival rates and hazard ratios (HR) for mortality, stratified by neutrophil engraftment status.
Key Findings
Survival Advantages of Combination Therapy
The FCN/GCV group demonstrated a 1-year survival of 63.2%, surpassing FCN monotherapy (52.5%) and GCV monotherapy (41.7%), though the p-value for overall comparison was 0.38. Notably, FCN/GCV was independently associated with improved survival versus FCN monotherapy (HR: 0.60; 95% CI: 0.38–0.95; p=0.031).
Impact of Engraftment Status
Survival benefits were context-dependent: post-engraftment patients showed superior survival with FCN/GCV (68.1% vs. 51.6% for FCN), while pre-engraftment patients fared worse (34.1% vs. 54.6%). This suggests timing of therapy relative to hematologic recovery is critical.
Expert Commentary
“These findings challenge the one-size-fits-all approach to HHV-6B encephalitis,” notes Dr. Takanori Terao, lead author. “The interplay between immune reconstitution and antiviral efficacy underscores the need for dynamic treatment algorithms.” Limitations include retrospective design and small GCV monotherapy cohort.
Conclusion
FCN/GCV combination therapy may offer survival benefits in HHV-6B encephalitis post-CBT, particularly after engraftment. Future randomized trials should validate these findings and explore mechanisms underlying engraftment-dependent efficacy.