The role of (18)F-FDG positron emission tomography in the follow-up of liver tumors treated with (90)Yttrium radioembolization

Abstract

In the last years, radioembolization (RE) has emerged as a novel technique for the treatment of malignant hepatic lesions using (90)Y embedded in spheres, which are infused directly into the hepatic arterial circulation. (90)Y-spheres, once implanted in liver, can release a significant radiation burden to neoplastic cells with a relative low dose to normal parenchyma. (90)Y RE results as a combination of embolization and radiation therapy, thus the standard radiologic follow up modalities may be not sufficiently accurate to assess tumor response to treatment. (18)Fluoro-deoxyglucose Positron Emission Tomography ((18)F-FDG PET) detects glucose uptake and metabolic activity in tumor cells. (18)F-FDG PET has become a well established diagnostic tool in many oncological scenarios. Furthermore, PET response criteria (PERCIST) have been recently introduced to categorize the metabolic response to therapy of cancer patients. Several semiquantitative parameters, such as SUVmax and its changes, the Functional Tumor Volume and the Total Lesion Glycolysis can be useful to accurately assess tumor changes after therapy. The purpose of this article is to present the literature on the role of (18)F-FDG PET in the evaluation of patients with primary and secondary liver tumors treated with (90)Y RE.

Keywords: 90Y radioembolization; Liver tumors; PERCIST; PET-CT; function tumor volume; total lesion glycolysis.

Figure 1

¹⁸F-FDG PET performed before ⁹⁰Y radioembolization in a 39 year-old-male patient with colorectal liver metastases. Maximum Intensity Projection (MIP) thick slab (A) showed intense tracer uptake in liver (right and left lobe) associate with ¹⁸F-FDG accumulation in rectum and lung (arrows). Fused axial images well demonstrated hepatic lesions (B) and loco-regional relapse. Patient was considered ineligible to the procedure due to the extensive extra-hepatic disease.

Figure 2

A 67 year-old-male patient with colorectal liver metastases. ¹⁸F-FDG PET MIP before radioembolization (A) showed intense tracer uptake in a gross tumor in the right hepatic lobe (arrow), while no other areas of abnormal tracer accumulation were evident. MIP acquired 6 weeks after ⁹⁰Y spheres administration (B) revealed a significant reduction of the liver mass (arrow). The significant metabolic response is well evident in the axial images acquired before (C) and after (D) the procedure.

Figure 3

A 72 year-old-female patient with chemo-resistant intrahepatic colangiocarcinoma, which had previously undergone surgery and then relapsed. ¹⁸F-FDG MIP (A) acquired before the radioembolization revealed ¹⁸F-FDG uptake in the right hepatic lobe (arrow). ¹⁸F-FDG MIP 6 weeks after therapy (B) depicted an almost complete metabolic response of the hepatic lesion. The significant metabolic response is well evident in the axial images acquired before (C, arrow) and after (D, arrow) the procedure.