Nuclear medicine imaging of infection in cancer patients (with emphasis on FDG-PET).

Infections are a common cause of death and an even more common cause of morbidity in cancer patients. Timely and adequate diagnosis of infection is very important. This article provides clinicians as well as nuclear medicine specialists with a concise summary of the most important and widely available nuclear medicine imaging techniques for infectious and inflammatory diseases in cancer patients with an emphasis on fluorodeoxyglucose positron emission tomography (FDG-PET). ⁶⁷Ga-citrate has many unfavorable characteristics, and the development of newer radiopharmaceuticals has resulted in the replacement of ⁶⁷Ga-citrate scintigraphy by scintigraphy with labeled leukocytes or FDG-PET for the majority of conditions. The sensitivity of labeled leukocyte scintigraphy in non-neutropenic cancer patients is comparable with that in patients without malignancy. The specificity, however, is lower because of the uptake of labeled leukocytes in many primary tumors and metastases, most probably as a result of their inflammatory component. In addition, labeled leukocyte scintigraphy cannot be used for febrile neutropenia because of the inability to harvest sufficient peripheral leukocytes for in vitro labeling. FDG-PET has several advantages over these conventional scintigraphic techniques. FDG-PET has shown its usefulness in diagnosing septic thrombophlebitis in cancer patients. It has also been shown that imaging of infectious processes using FDG-PET is possible in patients with severe neutropenia. Although larger prospective studies examining the value of FDG-PET in cancer patients suspected of infection, especially in those with febrile neutropenia, are needed, FDG-PET appears to be the most promising scintigraphic technique for the diagnosis of infection in this patient group.