Introduction Patients with MDR-TB may have residual imaging abnormalities after treatment and we have used FDG-PET/CT scanning nearing end of treatment to guide clinical treatment. A previous study reported the presence of MTB mRNA correlates to FDG-PET/CT avid lesions in TB at the end of treatment and in another study FDG-PET/CT has been shown to be a useful biomarker at 2 months of MDR-TB treatment. Aims To describe near end of MDR-TB treatment FDG-PET/CT appearances performed 2010–2019 in a MDR-TB centre and correlate treatment outcomes. Methods Retrospective observational study of 53 MDR-TB patients treated at a tertiary MDR-TB centre of which 21 patients had FDG-PET/CT scans pre-treatment completion to assess persistent CT abnormalities. A FDG-PET/CT analysis was performed visually (6 point visual score) and quantitatively (SUVmax) by a single experienced observer. The CT component of the FDG-PET/CT was compared to the baseline CT scan. Outcome was documented from clinical, microbiological and bronchoalveolar lavage (BAL) data. Results The FDG-PET/CT cohort (n=21, 15 male, average age of 38 years) all had pulmonary TB with 4 having additional extra-pulmonary disease. Initial CT scans showed nodules (95%), cavities (74%), tree-in-bud (90%), and mediastinal/hilar lymphadenopathy (85%). One case had cervical nodal disease, another had bone and cerebral involvement and two further cases had cerebral involvement. Compared to baseline CT scans available all repeat studies showed improvement. Nine cases (43%) had high or very high visual FDG-PET/CT scores (table 1). 7 of the 9 patients with high or very high visual scores had FDG-PET/CT directed BALs and all were AFB and culture negative. 3 patients had a positive non-mycobacterial microbiological result. All patients completed treatment and none had disease recurrence with an average follow-up period of 17 months in those still being followed up. Conclusion There is a mixed FDG-PET/CT pattern near end of MDR-TB treatment despite overall improvement in the CT appearances. 43% cases had high or very high residual FDG-PET/CT visual scores, but none of our patients relapsed during their follow-up period. In a subset of patient with FDG-PET/CT directed BALs none grew MTB but 3 had a positive non-mycobacterial microbiological results.
