18F-FDG PET-CT for Monitoring Treatment Response in Extra-Pulmonary Tubercular Infections.

Objectives: Prospectively develop a comprehensive TB Imaging strategy through the use of 18F-FDG Pet-CT for monitoring response of Anti-Tubercular Therapy in Extra-pulmonary Tuberculosis.

Methods: F-18 was prepared via O-18 (p, n) F-18 reaction (PET Trace Cyclotron, GE), & F-18 FDG was prepared in the automated GE TRACER laboratory Mx module. F-18 FDG was collected with a small amount of water, then neutralised, purified & sterilized by passing through a 0.22µm Millipore filter into a sterile multidose vial. Twenty five subjects of Extra-Pulmonary Tuberculosis (14 females & 11 males; age between 18-61 years) were enrolled after providing written informed consent. The diagnosis of tuberculosis was made by Biopsy or MRI Correlation. Baseline FDG PET-CT was performed before initiating Tuberculosis treatment. Repeat 18F-FDG PET-CT scan was done at 2 & 6 months post therapy. FDG PET-CT data was analysed by one Nuclear Medicine specialist & one Radiologist, blinded to clinical, bacterial & histo-pathological findings. A site was designated as abnormal FDG activity was found to be more than adjacent normal tissue. The abnormal lesions were quantitatively analyzed using SUV max. The SUV max of the most active lesions was documented.

Results: Out of 25 subjects of extra- pulmonary tuberculosis 9 had Lymph- adenopathy, 7 had Bone disease, 4 had brain lesion, 3 had Genito-Urinary Tract disease & 2 had Gastro- Intestinal disease. 6 patients had Solitary Tubercular lesion while the rest 19 had 2 or more than 2 lesions. 18 patients showed considerable response to Anti- Tubercular Treatment (ATT) while 5 did not show response to ATT. Majority of non-responders had Brain Tuberculosis. The average SUV max values were found to be 15.15 (range: 21.5-2.9) before starting treatment. The Average SUV max was 8.97 (range: 14.1-2.4) after 2 months of ATT & further reduced to 5.44 (range: 9.9-1.2) after 6 months of treatment.

Conclusions: The study suggests that 18F- FDG PET-CT performed before & after starting anti-tubercular treatment helps to differentiate responders from non responders in patients of Extra- pulmonary Tuberculosis. FDG PET-CT helps to determine therapeutic response & can suggest if a change of therapy plan is required. Further studies are needed to confirm whether FDG PET-CT can accurately determine the End-Point of treatment. AcknowledgementsAll authors are grateful to the International Atomic Energy Agency for their support of the Coordinated Research Project (CRP) E15021- “Use of 18F-FDG PET/CT for Imaging TB Patients & Related Conditions (HIV/AIDS, Tuberculosis): Focus on Drug Resistant Extrapulmonary Tuberculosis.”

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