Hematopoietic Stem Cell Transplant: Infection Control - Episode 8
Roy Chemaly, MD: Two strategies are used to address the impact of cytomegalovirus in stem cell transplant recipients. More than 15, 20 years ago, we did a prophylactic strategy. What does that mean? It means that you start a patient on one of the available drugs to prevent CMV reactivation. The problem with this strategy is, you’re exposing patients, for a certain amount of time—usually up to 3 months, because this is the highest-risk period for CMV infection—to a drug that could be potentially toxic with major side effects. For example, ganciclovir can cause myelosuppression. Valganciclovir, which is the prodrug of ganciclovir, may have the same side effect. Foscarnet, another available drug, can have an impact on kidney function and can cause nephrotoxicities as well as electrolyte imbalances and other serious side effects. We know this based on experience and many published studies.
Because of all of the drawbacks of these drugs, we moved away from the prophylactic regimen around 15 or 20 years ago. Now, most of the centers, if not all, are doing preemptive therapy, or preemptive strategy. What I mean by that is, if you have a good, sensitive test, like a molecular assay or antigenemia test, you test periodically, usually once or twice a week, for CMV in the blood—either at the time of the transplant or around the time of engraftment. You look for CMV reactivation, because patients with CMV reactivation may be asymptomatic.
So, that’s why we do it periodically. We do it once or twice a week, even without symptoms. As soon as we find a positive test, above a certain threshold—which is defined a little bit differently in different centers in the US and in Europe—we start treatment. We wait until we have a positive test, above a certain threshold. Then, we start treatment. It could be a short-duration treatment that is only given until the patient responds to treatment and the CMV viral load goes down, or CMV antigenemia disappears. Then, we may stop the treatment and continue preemptive therapy. We have started using this kind of strategy so that patients are less exposed to toxicities from these drugs. We’re hoping for less incidence of side effects, and major side effects, from these drugs.
Transcript Edited for Clarity