Abstract
1483
Introduction: Advances in modern medicine with overwhelming use of antibiotics as well as immuno-suppressants has resulted in an unwelcome increase in invasive fungal diseases. The utility of functional imaging with 18F-FDG PET/CT in infectious disease is slowly gaining foothold and the precise role in invasive fungal infections is less explored1,2. The aim of the study is to evaluate the role of 18F-FDG PET/CT in characterization, disease extent and response evaluation post treatment.
Methods: Thirty seven whole body (vertex to mid-thigh) 18F-FDG PET/CT studies (in a total of twenty six patients) done for evaluating patients with a clinical/histopathological/culture diagnosis of invasive fungal diseases were retrospectively reviewed. Ten studies were done for the indication of initial evaluation for extent of the disease prior to initiation of antifungal therapy and rest of the twenty seven studies were done for assessing response post treatment (after anti-fungal therapy or combination with additional surgical debridement)/ assessing residual disease post treatment. Follow up was done in all patients with mean follow-up period of 56.9±30.1 months (range 6-96).
Results: The study population consisted of twenty six patients (M:F=21:5) with mean age: 42.9±16.0, range 16-80 years). The diagnosis of invasive fungal infections in these patients included Aspergillosis: 6/26 (invasive 4, nasal 1, ABPA 1), Cryptococcosis: 3/26 (pulmonary 1, lymph nodal 1, disseminated 1), Histoplasmosis: 13/26 (adrenal 6, disseminated 4, gastrointestinal 2, lymph nodal 1) and Mucormycosis in 4/26 (nasal 2, renal 1 and disseminated 1). In studies done for initial evaluation (10/37), 18F-FDG PET/CT localized disease in all known sites of disease (previously identified on conventional imaging). 18F-FDG PET/CT outperformed conventional CT in bringing out additional lesions in 6/10 patients (subcutaneous/ lymph nodal/ gastrointestinal/lung/splenic involvement). In studies done for treatment response (27/37), PET/CT showed complete metabolic response to antifungal therapy in 7/27 patients only. 19/27 had a residual disease in PET/CT with mean SUVmax of 6.5±2.1 (Figure). PET/CT showed progression of the disease despite antifungal therapy in one patient. Based on these findings 20/27 patients in whom FDG showed metabolically active/residual lesions were offered additional antifungal therapy. In follow-up, disease specific mortality was noted in no patients.
Conclusions: The study results show that 18F-FDG PET/CT could bear a major role in revealing extent of disease especially in deep seated and invasive infections and in monitoring treatment response for the early initiation of second line antifungal therapy as well as timely curtailing the costly antifungal therapy.