FDG PET for monitoring response to local and locoregional therapy in HCC and liver metastases.

Local ablative therapies and loco-regional therapies are being increasingly used for the purpose of providing local control of primary liver tumors and liver metastases while sparing normal liver tissue. In this manuscript, literature on the use of fluorodeoxyglucose positron emission tomography (FDG PET) to monitor local and loco-regional treatment for hepatocellular carcinoma (HCC) and liver metastases, mainly limited to radiofrequency ablation (RFA) and selective internal radiation therapy (SIRT) is reviewed. Available data obtained primarily in secondary liver tumors and to a lesser extent in HCC support the notion that FDG PET performed early after RFA provides additional information about the efficacy of local tumor ablation by differentiating post-treatment changes from residual or recurrent malignant tumor. In addition, FDG PET was shown to have an added value for the detection of tumor recurrence. Thus, FDG PET imaging may not only improve treatment evaluation but also provide an opportunity for early re-intervention following RFA. Potential problems that might occur when using FDG PET for the purpose of evaluation of RFA are false negative results due to partial volume effect when dealing with small lesions (<1 cm) or due to diabetes and false positive results due to abscess formation. Larger studies are warranted to confirm these promisingWith regard to SIRT, several studies, almost exclusively performed in patients suffering from liver metastases, have addressed the feasibility of using FDG PET for the assessment and quantification of metabolic response of SIRT with (90)Y-microspheres. These studies consistently show that traditional morphological imaging, computed tomography/magnetic resonance imaging, is insensitive in monitoring response, owing to the presence of necrosis, edema, hemorrhage and cystic changes, when compared to metabolic imaging. Thus, in view of the lack of reliability of tumor markers and/or the potential for delineating the presence of extra-hepatic metastatic cancers in these patients, when confirmed by additional studies, FDG PET may prove to be an excellent adjunct for assessing response following SIRT of liver metastases.