There are various special considerations for treating invasive infections, whether they are bacterial, viral, or fungal, in immunocompromised patients, especially those with cancer and/or those who have undergone hematopoietic cell transplantation (HCT).

Cancer Therapy Advisor spoke with Thomas J. Walsh, MD, director for the Transplantation-Oncology Infectious Diseases Program at the Weill Cornell Medical Center in New York City, NY, to discuss how he diagnoses and treats these particular patients.

Dr Walsh serves as a professor of medicine, pediatrics, microbiology, and immunology and is the chief of the Infectious Diseases Translational Research Laboratory, whose mission it is to develop new strategies for diagnosis, treatment, and prevention of life-threatening infections in immunocompromised patients with cancer, transplantation, and other immunodeficiencies.

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Cancer Therapy Advisor:  When a patient presents with a presumed invasive infection, how do you go about diagnosing the patient?

Dr Walsh: First, we look at the broader picture of the patient. First of all, we want to know the underlying risk factors for any infection. We take a broad differential diagnosis for patients who may have complaints ranging from fever to cough to any one of a number of symptoms that may relate to any one of a number of different systems.

With that, we carefully evaluate by history and by their epidemiology of what their relative risk factors are for infections. For example, patients with a hematologic malignancy may be at much higher risk for serious life-threatening invasive fungal or bacterial infections, or certain viral infections.

Then, we conduct a very careful, meticulous physical examination examining all body systems to ascertain the presence or absence of an invasive infection.

Cancer Therapy Advisor: What is your approach to empiric therapy?

Dr Walsh: The overarching strategy of early treatment is to try to attain the best outcome by reducing morbidity and improving survival. If, for example, a patient with a hematologic malignancy is febrile and neutropenic, we are thinking a bacterial infection, which are certainly more common.

For that, we would make sure we are using an anti-pseudomonal agent, such as ceftazidime, cefepime, and piperacillin/tazobactam. Those are the 3 most commonly used agents for empiric pseudomonal coverage. If there is a gram-positive bacterial infection suspected, perhaps from a catheter exit site infection, then we may be adding vancomycin as initial therapy as well. If patients have ongoing fever despite the antibacterials, they may then be candidates for empiric pre-emptive anti-fungal therapy based upon what we can see on laboratory tests. 

With that, there are a number of agents that could potentially be used, including the liposomal formulation of amphotericin B, an echinocandin, or an azole antifungal. Another strategy beyond empiric therapy that is often used in high-risk patients is prophylaxis.

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You may already have a patient who is receiving antifungal prophylaxis, such as posiconazole, fluconazole, or voriconazole, but resistant organisms can break through that coverage. In that case, we would back that up with liposomal amphotericin B to cover for likely pathogens.