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The Cancer Patient
Risk Factors In the cancer patient, the major factor in the pathogenesis of fungal infection is nosocomial impairment of the immune system, especially neutropenia due to chemotherapy or irradiation. The type, dose, and duration of the anticancer drugs administered can help identify patients at high risk of infection. Not all patients with cancer and not all anticancer drugs are associated with immunosuppression. While drugs such as cyclophosphamide, fluorouracil, and vinblastine cause bone-marrow suppression, bleomycin and tamoxifen have little or no effect on neutrophil count. Other drugs frequently given, including prednisone, inhibit the humoral and cell-mediated immune responses. Irradiation and malnutrition decrease T-lymphocyte function.
Other risks discussed previously as environmental factors, including antibiotics, indwelling catheters, surgery, chemotherapy-induced mucosal ulceration, and exposure to ICU environments are also important in the pathogenesis of infection, particularly in combination with neutropenia. Finally, there is growing evidence that potentially immunosuppressive viral infections (cytomegalovirus or CMV) are risks for both candidiasis [19] and aspergillosis [20].
Incidence and Mortality In one study, histologic evidence of fungal infection at autopsy was noted in 5% of patients with solid tumors, 12% of patients with lymphoma, and up to 25% of patients with leukemia [21]. In the absence of prophylaxis, Candida spp are the most common fungal pathogens in cancer patients. Between January 1, 1988, and December 31, 1992, 491 episodes of candidemia were identified at the M. D. Anderson Cancer Center [22]. By 3-month follow-up, 52% of the patients had died. Neutropenia, higher APACHE III score, and visceral dissemination were associated with poor prognosis. For many years C albicans was the most common species causing infection. However, in a recent review of 1,479 cancer patients, C albicans accounted for only 54% of infections [23]. Increases in infection caused by other Candida spp, namely C glabrata and C krusei, are being reported with increasing frequency. The Invasive Fungal Infection Group of the European Organisation for Research and Treatment of Cancer (EORTC) reported 249 episodes of candidemia (90 in patients with solid tumors, 159 in patients with hematologic malignancies) in centers throughout Europe over a 2-year period [24]. Overall 30-day mortality was 39%. This study confirmed the nosocomial nature of the candidemia: 50% of the patients had nonadvanced underlying disease, and only 10% of the episodes occurred outside the hospital.
Invasive aspergillosis is infrequent in patients with solid tumors, accounting for less than 1% of all infections [25]. Infection is mainly seen in patients with prolonged periods of neutropenia and most often reported in patients with acute leukemia. The mortality rate is very high. Emerging fungal pathogens such as Fusarium species and Trichosporon beigelii cause life-threatening infections, particularly in patients with hematologic malignancies.
Course Number: V035B.043001
This CME Expires on July 1, 2003; no tests will be accepted after this date.
This course is accredited by
The University of Pittsburgh School of Medicine, Center for Continuing Education
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