SUV as a Possible Predictor of Disease Extent and Therapy Duration in Complex Tuberculosis

F-FDG PET/CT provides information on disease extension and activity in neoplastic and inflammatory conditions. So far, little is known about whether SUVmax of a reference lesion can allow a prognosis to be given regarding patient-specific outcome parameters in complex cases of tuberculosis (TB).

We retrospectively identified 37 patients (21 men, 16 women; mean age, 50.4 years) who underwent F-FDG PET/CT for the evaluation of active TB before treatment initiation. The aims were to examine whether the reference lesion SUVmax differed between patients with standard (≤9 months) and long-term (>9 months) therapy and to define an SUVmax cutoff distinguishing those groups. In addition, we analyzed the prognostic value of SUVmax with regard to estimation of initial disease extent and lesion distribution pattern.

Median therapy duration was 10 months (interquartile range, 3.25 months), and median SUVmax was 8 (interquartile range, 8.54). SUVmax was significantly (P = 0.036) higher in patients treated longer than 9 months (10.1 vs 5.5). When applying a receiver operating characteristic curve analysis, an SUVmax cutoff value of 10 differentiated the standard and the long-term therapy group with a sensitivity of 50% and a specificity of 78.6% (P = 0.087). Higher SUVmax corresponded with a larger number of affected organ systems (P = 0.012 for ≤/>1). Patients with extrathoracic involvement showed significantly higher SUVmax than did patients with limited intrathoracic disease (P = 0.024) and received significantly longer antimycobacterial therapy (P = 0.011).

Reference lesion SUVmax from pretherapy F-FDG PET/CT may have prognostic properties in complicated cases of TB, especially regarding therapy duration and disease extent.