27 Ago PET-CT scan in early evaluation of clinical success in Native Vertebral Osteomyelitis

Background: In bacterial native vertebral osteomyelitis (NVO) there are no reliable markers predicting clinical outcome during a standard 6- (after 2015 IDSA guidelines) or 12-weeks course of antibiotic treatment (ABTx). We determined if PET-CT scan conducted at baseline and at week 2 of treatment could predict the lenght of ABTx in NVO compared to C-Reactive Protein (CRP).
Methods: A retrospective observational study of bacterial NVO cases collected between 2010-2017 was performed. We defined “Response” as clinical cure after a standard ABTx course; “Delayed response” was defined as prolongation of ABTx >12 weeks. PET-CT improvement was defined as Standardized Uptake Value (SUV) decrease ≥25% at week 2 (SUVt15) from baseline (SUVt0).
Results: Thirty-five cases of bacterial NVO were collected (22 Gram +, 6 Gram -, 7 of unknown aetiology treated as pyogenic NVO). Median SUVt0 for aetiologically known and unknown NVO was 6 [IQR=4.7-8.5] and 5 [IQR=4.2-6.7] respectively. In the “Response” group SUVt15 decline was significantly more rapid (p=0.007) than in the “Delayed response” group (p=0.445). CRP at day 15 significantly decreased from baseline in the “Response” compared the “Delayed response” group but no difference was found at day 30 between and within the two groups.
Conclusions: in bacterial NVOs SUVt15 decline of at least 25% from baseline correlates with a standard course of ABTx. SUVt15 may be used as early marker of clinical outcome in patients with bacterial NVO.