Morbidity and mortality in patients with malignancies are increased by viral infections. This document is intended to provide guidance for the prophylaxis of viral infections among adult patients with haematological malignancies and solid tumours. However it is anticipated that individual units or practitioners will adopt local antiviral strategies.
Most viral infections in patients with haematologic malignancies or solid tumours result from reactivation of asymptomatic latent infections, predominantly of herpes viruses, such as herpes simplex virus (HSV) and varicella zoster virus (VZV).
The risk of viral reactivation is determined by baseline serostatus. HSV reactivation commonly occurs in the setting of mucositis and neutropenia, whereas VZV is common in therapies that are T cell depleting. The patients at highest risk of reactivating both HSV and VZV are allogeneic stem cell transplant recipients, in particular those who have received T cell depleting conditioning regimens and who remain on long term immunosuppression for graft versus host disease. For those allogeneic transplant recipients, the pre-engraftment period during which mucositis occurs is the time of heightened disease risk. Prophylaxis may be extended beyond this time in patients who experience frequent HSV recurrences.r
Herpes simplex virus (HSV)
Herpes simplex virus is an important pathogen in patients who develop neutropenia and mucositis. HSV infections are primarily reactivation of latent virus. The presence of latent HSV can be determined by pre-treatment HSV serology. Reactivation and infections with HSV occur in 60 to 80% of blood and marrow transplant (BMT) recipients and in unprophylaxed patients with acute leukaemia undergoing induction or re-induction therapy who are seropositive for HSVr. HSV seronegative patients, including those who receive a BMT from a HSV seropositive donor, do not require prophylaxis.r Once a patient has had an HSV reactivation infection requiring treatment, it is recommended that HSV prophylaxis be administered during all future episodes of neutropenia induced by cytotoxic therapy.
Varicella zoster virus (VZV)
The principle risk factor for VZV is impaired cellular immunity. In allogeneic BMT recipients with a history of VZV infection without antiviral prophylaxis, about 30% have VZV disease after reactivation. VZV seropositive patients pre transplant should receive prophylaxis for at least 12 months post allogeneic transplant, as this has been shown to significantly decrease the incidence of VZV disease compared to placebo (5% vs. 26% respectively).r Continuation of prophylaxis beyond this time is recommended in patients with chronic graft versus host disease (cGvHD) who continue on immunosuppression. Prophylaxis may be discontinued when CD4 counts are greater than 200 cells/microL and immunosuppressive therapy ceased.