What, where and why: exploring fluorodeoxyglucose-PET's ability to localise and differentiate infection from cancer

Abstract

Patients with cancer are vulnerable to infection and fever, and the causes of these are frequently unclear using conventional diagnostic methods leading to high morbidity and mortality, length of stay and costs of care. FDG-PET/CT, with its unique complementary functional and anatomical information as well as its whole-body imaging capability, has demonstrated use in detecting occult infection in immunocompromised patients, including invasive fungal and occult bacterial infections, as well as defining extent of infection. By demonstrating disease resolution following treatment and allowing earlier cessation of therapy, FDG-PET acts as a key tool for antimicrobial and antifungal stewardship. Limitations include at times poor differentiation between infection, malignancy and sterile inflammation, however, exciting new technologies specific to infectious pathogens may help alleviate that issue. Further prospective randomised research is needed to explore these benefits in a nonbiased fashion.

Optimising Antimicrobial Selection and Duration in the Treatment of Febrile Neutropenia in Children

“…The role of diagnostic imaging, specifically fluorodeoxyglucose positron emission tomography (FDG-PET) combined with computed tomography (CT) or magnetic resonance imaging (MRI), for investigation of prolonged FN is also emerging as a potentially useful tool. 28,29 A retrospective study of children with cancer and prolonged or recurrent FN found that, compared to conventional imaging, FDG-PET/CT identified additional sites of clinically significant infection/inflammation compared to conventional imaging. The study also showed that the FDG-PET results had a clinical impact in 80%, leading to de-escalation or stopping of antibiotics in many patients.…”

Usefulness of 18F‐FDG PET‐CT for the management of invasive fungal infections: A retrospective cohort from a tertiary university hospital

“…18 F-FDG PET-CT has already been reported to detect infiltrates caused by PJP earlier than the standard chest radiograph. 13 In addition, in our study, 18 The concept of "staging" IFI, along the same line as we do with tumours, is beginning to take root. 15 IFI presentation can be very heterogeneous, and multiple organ involvement is not uncommon.…”

“…Several studies have evaluated 18 F-FDG PET-CT in invasive candidiasis, finding that 18 F-FDG PET-CT is more sensitive than CT or ultrasound for detection of dissemination of Candida, particularly of hepatosplenic involvement, 13,16,17 but few have investigated its role in fungal endocarditis. In the case of fungemia, staging should include the evaluation for endocarditis.…”

“…On the contrary, in the present series, where 18 F‐FDG PET‐CT was compared to echocardiography (100%) and CT (69.2%) in 92.9% of episodes of fungemia, it showed an added value at least in 6/13 (46.2%) of them, not only to confirm or rule out endocarditis but to detect other sites of fungal involvement. It is relevant to underline the value of a negative 18 F‐FDG PET‐CT in this setting due to its high negative predictive value for IFI that allows early discontinuation of antifungals, 13 although in native valve endocarditis, it is considered that the diagnosis of endocarditis cannot be excluded in the absence of abnormal 18 F‐FDG uptake 18 . Similar to Sharma et al., 21 who found 18 F‐FDG PET‐CT is particularly useful in cases where other tests were equivocal or with diagnosis of “possible endocarditis”, in our series, 18 F‐FDG PET‐CT was especially helpful in cases with dubious or negative echocardiography.…”

“…One of the cases was a Pneumocystis pneumonia (PJP) that presented as FUO. 18 F‐FDG PET‐CT has already been reported to detect infiltrates caused by PJP earlier than the standard chest radiograph 13 …”