Treatment Response Evaluation in Necrotizing Otitis Externa Using 18 F-FDG-PET Imaging

Objective: This study aims to identify 18 F-FDG-PET imaging features for improving treatment response evaluation in patients with necrotizing otitis externa (NOE), aiding in the difficult differentiation between sterile inflammation and active infection.

Study Design: Retrospective cohort study.

Setting: Tertiary hospital.

Patients: Patients diagnosed with NOE between 2011 and 2022. NOE criteria included otalgia, otorrhea, granulation, and radiological features consistent with osteomyelitis.

Intervention: 18 F-FDG-PET/computed tomography (CT) parameters were derived from manually delineated regions of interest and were evaluated on both pretreatment and end-of-treatment scans.

Main Outcome Measures: Recurrent disease of NOE after end-of-treatment 18 F-FDG-PET scans.

Results: This study comprised 20 NOE patients, including 5 (25%) experiencing recurrent disease after the end-of-treatment scan. The end-of-treatment 18 F-FDG-PET parameters of maximal and peak standardized uptake value (SUVmax and SUVpeak) were significantly higher in recurrent cases ( p = 0.025 and p = 0.025, respectively). Both parameters demonstrated good discrimination ability in predicting recurrence, with optimal cutoffs yielding 100% sensitivity and 67% specificity. Other parameters, including mean SUV and total lesion glycolysis (TLG), did not yield significant results, neither did the calculated difference in uptake between end-of-treatment and pretreatment scans.

Conclusions: SUVpeak on 18 F-FDG-PET was the preferred parameter for treatment response evaluation of NOE at the end-of-treatment scan. A high residual SUVpeak may adequately detect patients at risk for recurrent disease, which may necessitate prolonged treatment, while low SUVpeak is found in patients with low risk for recurrent disease permitting safe treatment cessation.