PET/CT reveals treatment effect in kids with CF

FDG PET/CT showed post-treatment inflammatory changes in pediatric patients with cystic fibrosis (CF), and these changes correlated with lung function, sputum neutrophil counts and CF-CT scores, according to a study published online in Radiology on July 24.

Anti-inflammatory therapies have been developed to target inflammation associated with the progression of CF. However, measures to assess the effectiveness of these therapies are lacking as existing approaches are invasive, variable or require long follow-up or large numbers of patients. Previous research has suggested that FDG uptake as shown via FDG PET/CT imaging correlates with inflammation and neutrophil burden.

Reshma Amin, MD, of the Hospital for Sick Children in Toronto, and colleagues designed an observational study to determine if FDG PET/CT could be used to show a treatment effect from intravenous antibiotics for pulmonary exacerbation in CF.

A total of 20 CF patients between the ages of 6 and 18 years were enrolled and underwent FDG PET/CT imaging on day 1 and day 14 of admission. Images were reviewed by three board-certified nuclear medicine physicians blinded to the patients’ diagnosis and whether images were pre- or post-therapy. The study included 10 control patients.

Mean SUV_max at baseline was 5.9 for patients with CF before therapy and 2.0 for control patients. Although mean SUV_max decreased significantly with treatment among CF patients it remained significantly higher than in control subjects.

At baseline, average SUV_mean significantly differed between patients with CF and the control group. The measure decreased with treatment, and did not statistically differ between the two groups after treatment.  

According to Amin and colleagues, sputum analysis showed that changes in absolute neutrophil count significantly correlated with SUV_mean but not SUV_max.

“Our results show that different values generated by FDG PET studies provide information on different aspects of lung disease (i.e., diffuse and focal inflammation). The former can be measured with SUV_mean and the latter with SUV_max,” Amin et al wrote.

The researchers acknowledged the burden and risk of radiation exposure among this population and emphasized it should be taken into consideration as physicians evaluate imaging strategies.

Amin and colleagues concluded, “[FDG PET/CT] could potentially facilitate the progression of new CF therapeutics, as the increased sensitivity may afford shorter study durations and smaller sample sizes. Moreover, new PET/magnetic resonance imaging units may further reduce the dose by avoiding CT radiation exposure.”