Nuclear Medicine Imaging of Infection in Cancer Patients (With Emphasis on FDG-PET)

Abstract

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).67 Ga-citrate has many unfavorable characteristics, and the development of newer radiopharmaceuticals has resulted in the replacement of 67 Gacitrate 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. The Oncologist 2011;16:980 -991

Use of FDG PET/CT for investigation of febrile neutropenia: evaluation in high-risk cancer patients

“…The delay experienced by some patients in awaiting a scan (beyond day 5-7 of the febrile episode) may have reduced the sensitivity of FDG PET/CT for detection of infection. The presence of neutropenia appears not to compromise the sensitivity of this technique and has an advantage over conventional nuclear medicine infection scanning, where the requirement for radiolabelling of white blood cells may not be met in the setting of low circulating numbers of leucocytes [16]. Radiolabelled anti-granulocyte monoclonal antibodies, or their fragments, have been used to image infectious diseases [17].…”

Sepsis in head and neck cancer patients treated with chemotherapy and radiation: Literature review and consensus

“…White Indium 111 -labeled blood-cell scans and indium 111 Immunoglobulin-G have poor sensitivity and specificity, whereas Technetium scans seems to be more useful, owing to its high specificity (93-94%), but it has a poor sensitivity (40-75%) [77]. Finally, Fluorodeoxyglucose positron-emission tomography (FDG-PET) scans have a high sensitivity (95%) and a good specificity (88%) in identifying septic sources in patients with fever of unknown origin [77][78][79]. [80][81][82].…”

[11C]Para-Aminobenzoic Acid: A Positron Emission Tomography Tracer Targeting Bacteria-Specific Metabolism

“…While these studies are generally sensitive for infection in immunocompetent patients, they rely on indirect methods for detection of infection, limiting specificity. These exams are also difficult to interpret when infection is suspected in the setting of recent surgery, trauma or malignancy 3 . Additionally, they can be falsely negative when patients are unable to mount a sufficient response to infection as is often the case in immunosuppressed or immunodeficient patients 4,5 .…”