Laboratory Diagnosis of Infections in Cancer Patients: Challenges and Opportunities

Abstract

Infections remain a significant cause of morbidity and mortality in cancer patients. The differential diagnosis for these patients is often wide, and the timely selection of the right clinical tests can have a significant impact on their survival. However, laboratory findings with current methodologies are often negative, challenging clinicians and laboratorians to continue the search for the responsible pathogen. Novel methodologies are providing increased sensitivity and rapid turnaround time to results but also challenging our interpretation of what is a clinically significant pathogen in cancer patients. This minireview provides an overview of the most common infections in cancer patients and discusses some of the challenges and opportunities for the clinical microbiologist supporting the care of cancer patients. Cancer is the leading cause of death worldwide, with 8.2 million deaths reported worldwide in 2012 (1). Common treatment options for oncology patients include hematopoietic stem cell transplantation (HSCT), chemotherapeutic drugs, and surgical resection. The first successful HSCT was performed in 1959 by E. Donall Thomas in Cooperstown, NY, with infusion of two acute lymphocytic leukemia (ALL) patients with bone marrow from their disease-free identical twins. Although initially successful, their remission was short-lived, with recurrence of the disease occurring within a few months of the transplant (2). Today, HSCT is a curative therapy for many types of hematologic malignancies and immune deficiency diseases. E. Donall Thomas and Joseph E. Murray received the 1991 Nobel Prize in Physiology or Medicine for their discoveries concerning "organ and cell transplantation in the treatment of human disease."Of note for microbiologists, the history of cancer chemotherapy started as a history of antibiotics with Paul Ehrlich's discovery in 1909 of arsphenamine (Salvarsan), the first effective treatment against Treponema pallidum infection. Paul Ehrlich also evaluated early versions of alkylating agents to treat cancer but with little hope that these drugs would be curative. Decades of investigations and trials have resulted in the current modern chemotherapeutic agents that are curative for large groups of either hematologic malignancies or solid tumors when used in conjunction with surgical resection (3). CANCER AND INFECTIONSInfections remains a significant cause of death in cancer patients, particularly in HSCT recipients (1). Susceptibility to infections is related to a host's ability to reconstitute their immune system following HSCT and/or chemotherapy treatment. The longer it takes a patient to recover, the higher at risk they are of developing infections. In general, the highest risk of infections occurs in allogeneic HSCT recipients and leukemia patients, and the lowest risk occurs in solid-tumor patients on standard chemotherapy (Table 1) (4). The posttransplant period may be divided into three stages: preengraftment (less than 4 weeks), early postengraftment (3 weeks to 3 months), and late poste...

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