Adding fluorine­-18 fluorodeoxyglucose positron emission tomography to contrast­-enhanced computed tomography may improve the early detection of local tumor progression following thermal ablation or hepatic resection for colorectal liver metastases compared with contrast­-enhanced computed tomography alone.

In a single-­center prospective observational cohort study, researchers evaluated 64 patients with 154 colorectal liver metastases treated with thermal ablation, hepatic resection, or both between June 2020 and December 2021. The patients underwent contrast­-enhanced computed tomography (CECT), carcinoembryonic antigen (CEA) testing, and fluorine­ (F)-18 fluorodeoxyglucose positron emission tomography (PET)/CECT 3 to 5 months posttreatment. Disease progression was confirmed by histopathology when available, multidisciplinary team consensus, or an extended follow­-up of up to 3 years.

Disease progression was identified in 66% of patients at first follow-­up. Local tumor progression occurred in 25% of the patients, new colorectal liver metastases in 25%, and extrahepatic disease in 34%. For detecting local tumor progression, F-18 FDG­ PET/CECT demonstrated greater diagnostic accuracy compared with CECT following both thermal ablation and hepatic resection. The combination approach identified all cases of local tumor progression in both treatment groups, whereas CECT detected fewer than one-­half.

The imaging modalities performed similarly for detecting new colorectal liver metastases. However, F-18 FDG PET/CECT more accurately identified extrahepatic disease compared with CECT alone.

CEA performed poorly as a standalone marker for disease progression. The biomarker produced false-negative results in 43% of patients with disease progression, indicating that normal CEA levels did not reliably exclude recurrent disease.

The researchers noted that the study was limited by its single-­center design, relatively small and heterogeneous treatment groups, potential selection bias, and reliance on multidisciplinary consensus rather than histopathologic confirmation for most reference diagnoses. Larger prospective studies are needed to confirm the findings.

“Adding [F-18] FDG ­PET/CT to standard care (CECT and CEA serum level monitoring) improved the detection of [local tumor progression] after thermal ablation and liver resection and was more accurate for identifying [extrahepatic disease]. However, [F-18] FDG­ PET/CECT offered no added benefit for identifying new [colorectal liver metastases],” wrote lead study author O. D. Bijlstra, of the Department of Surgery at the Leiden University Medical Center in the Netherlands, and colleagues.

The study authors reported no funding and declared no conflicts of interest related to the study.

Source: European Radiology