Radioembolization: technical and clinical analysis of safety

Abstract

Radioembolization is an established antitumoral treatment for both primary liver tumors and liver metastases. Contrary to normal liver tissue, hepatic tumors are almost solely fed by branches of the hepatic artery, allowing for a selective treatment of these tumors by intra-arterial therapies, such as radioembolization. Nonetheless, some of the injected radio-active microspheres will also accumulate in the normal liver parenchyma, inducing local radiation damage. In the first part of this thesis the clinical aspects of radiation-induced liver toxicity and radioembolization-induced liver disease (REILD) are explored, including the commonly used definitions, reporting and incidence of REILD. Also, the differences in the toxicity profile of the commercially available yttrium-90 microspheres are investigated and the use of prophylactic medication. The most important risk factor for REILD seems to be the absorbed radiation dose in the normal liver tissue. And the value of prophylactic medication in radioembolization is questionable. In the second and third part of this thesis the potential added value of different imaging techniques, including hepatobiliary scintigraphy, FDG PET/CT and CT, in the work-up for radioembolization and the response evaluation are investigated. Hepatobiliary scintigraphy is a nuclear imaging technique, allowing for liver function quantification and visualization. After radioembolization there is a decrease in liver function in the treated part of the liver, as well as an increase in liver function of the non-treated liver part(s). FDG PET/CT is widely used for response evaluation after therapy and the FDG activity concentration in the liver is commonly adopted as a reference-tool. However, after radioembolization the FDG activity concentration of the non-tumorous liver parenchyma changes mildly, yet significantly. Knowledge of these changes can help avoid occasional misinterpretation of therapy-response. Besides a clinical and biochemical work-up, each patient undergoes a CT as part of the patient selection. Two CT protocols in the patient workup were compared for the detection of small arterial branches. No significant differences with regard to arterial detection were observed. Also, lesions with more avid enhancement had a better treatment response, regardless of the contrast phase on which the enhancement was measured.