Performing PET/CT examinations using the radiotracer 18-Fluoro-deoxyglucose (FDG) immediately following localized liver tumor ablation is more effective than contrast-enhanced CT for predicting tumor recurrence, according to results of a study published online in the Journal of Nuclear Medicine.

Previous studies have shown that FDG PET/CT is an effective tool for assessing treatment success or failure involving liver tumor ablation procedures when performed after a period of about three months.

However, its ability to do so prior to that window of time is confounded by inflammation at the point of ablation, said lead author Francois Cornelis, MD, and his colleagues from Memorial Sloan Kettering Cancer Center in New York City.

“After ablation, histologic changes include a central zone of necrosis which is surrounded by a zone of inflammation caused by the recruitment of neutrophils, lymphocytes, and macrophages within a few days to weeks,” they wrote. “FDG uptake due to ablation-related inflammatory changes could lead to a false positive assessment for residual viable tumor.”

To avoid inflammation-related issues that can affect assessments of treatment failure and tumor recurrence, Cornelis and his team set out to compare the predictive performance of FDG PET/CT and contrast enhanced CT imaging acquired immediately after liver tumor ablation—while the patient remains on the procedure table under anesthesia.

The researchers conducted a retrospective study of 25 PET/CT-guided tumor ablations performed on patients for the treatment of liver tumors using both radiofrequency and microwave techniques. Immediate post-ablation FDG PET/CT and contrast-enhanced CT scans were evaluated and subsequently correlated to clinical and imaging outcomes after one year.

Their results showed the accuracy of contrast-enhanced CT immediately following tumor ablation to be 64 percent (16/25) when compared to one-year tumor recurrence rates among study participants. In comparison, FDG PET/CT accurately predicted tumor recurrence in 92 percent (23/25) of cases studied.

“Immediate PET/CT is an accurate predictor of liver metastasis ablation success at 12 months and is superior to immediate [contrast-enhanced CT],” the authors concluded. “This study can serve as the background for new important investigations in order to prospectively validate these initial findings and correlate with pathologic changes and oncologic outcomes.”