1. In a prospective cohort study of 25 patients with prosthetic vascular graft infections treated with systemic antibiotics, the use of FDG-PET/CT for monitoring of metabolic activity within the graft was effective at determining infection status and was used to alter the course of antibiotic therapy in all patients.
Evidence Rating Level: 3 (Average)
Study Rundown: Prosthetic vascular graft infections (PVGI) are associated with high rates of morbidity and mortality and are often treated with both surgical interventions as well as systemic antibiotic therapy. Systemic treatment typically lasts 3-6 months, however, there are no current guidelines for the monitoring of therapeutic response, though common practice trends blood biomarkers such as white blood cell counts and C-reactive protein (CRP) levels. Previous studies have demonstrated the use of positron emission tomography/computed tomography with 18F-fluorodexoyglucose (FDG-PET/CT) to monitor a known infectious site for decreased metabolic activity within the foci of infection. The purpose of this study was to investigate the feasibility of FDG-PET/CT for therapy control in PVGI under the hypothesis that visualization of metabolic activity within a given infected graft may be a superior marker of infection in guiding antibiotic choice and treatment course. Twenty-five patients with known PVGI were recruited and underwent FDG-PET/CT at the time of systemic antibiotic therapy and approximately 6 months after baseline examination. At the conclusion of the trial, 76% of patients had their antibiotic regimen continued for decreased metabolic activity within the infected graft. The treatment regimen was stopped and altered in 8% and 16%, respectively, because of unchanged or increased metabolic activity at the infected graft site. The results of this study support the potential utility of FDG-PET/CT in monitoring the response to systemic antibiotic therapy in PVGI. However, the study is limited by the small sample size and the lack of a control group for comparison of clinically important outcomes such as graft failure or rates of hospitalization. Additional large prospective trials are needed to clarify the utility of FDG-PET/CT in PVGI.
Relevant Reading: Prosthetic Vascular Graft Infection: The Role of 18F-FDG PET/CT
In-Depth [prospective cohort]: The Vascular Graft Cohort Study (VASGRA) is an open, prospective, observational study to determine the feasibility of FDG-PET/CT in therapy monitoring of PVGI. Researchers recruited 25 patients (median age 66 years; range 48-61) with proven PVGI to undergo FDG-PET/CT prior to surgical intervention (baseline) and for follow-up scans 3 to 6 months later. Follow-up scans were performed at a median interval of 170 days (range: 89-249 days) after the initial investigations. Image analysis was performed by calculating maximum standardized uptake values (SUV max) within the graft, and was compared to laboratory markers in the subjects, including CRP values and white blood counts. Among patients with PVGI and no other metabolically active focus, CRP values correlated well with SUV max in the graft region (R2 = 0.67; p = 0.002). At the conclusion of the trial, the use of FDG-PET/CT had an impact on the clinical management of all 25 patients. Treatment was continued in 76% (n = 19) of patients, and stopped or altered in 8% (n = 2) and 16% (n = 4) of patients, respectively. The use of FDG-PET/CT also detected other foci of inflammation (n = 8) including recurrence of rectal carcinoma (n = 1), clinically silent ischemic stroke (n = 1), and spondylodiscitis (n = 1). There was a significant correlation between biochemical markers of inflammation (i.e. CRP) with a subset of patients with no additional foci of inflammation (n = 11; R2 = 0.67; p = 0.002), but not with the entire cohort.
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