Assessment of Treatment Response Following Yttrium-90 Transarterial Radioembolization of Liver Malignancies

Abstract

Transarterial radioembolization using yttrium-90 microspheres is an established and effective treatment for liver malignancies. Determining response to this treatment is difficult due to the radical changes that occur in tissue as a response to radiation. Though accurate assessment of treatment response is paramount for proper patient disposition, there is currently no standardized assessment protocol. Current methods of assessment often consider changes in size, necrosis, vascularity, fluorodeoxyglucose-positron emission tomography FDG-PET metabolic activity, and diffusion using diffusion-weighted magnetic resonance imaging (DWI). Current methods of assessment require a lag time of one to two months post-treatment to determine treatment effectiveness. This delay is a hindrance to obtaining better patient outcomes, giving rise to a need to identify markers for faster determination of treatment efficacy.

Keywords: brachytherapy; fdg-pet; liver cancer; malignant tumour; mri; post-treatment evaluation; radiation therapy; tumour necrosis; tumour vascularity; y90 transarterial radioembolization.

Figure 1. Pretreatment Magnetic Resonance Imaging (MRI)

Axial (a) and coronal (b) T2-weighted images of the liver demonstrate a mildly hyperintense mass in the right hepatic lobe. Precontrast (c), arterial (d), portalvenous (e), and delayed (f) postcontrast T1-weighted images demonstrate heterogeneous early arterial hyperenhancement and subsequent portalvenous / delayed washout of the mass compatible with hepatocellular carcinoma. The diffusion weighted imaging (DWI) (g) and its corresponding apparent diffusion coefficient (ADC) map (h) demonstrate foci of restricted diffusion within the tumor.

Figure 2. Pretreatment Angiogram

Celiac arteriograms before and after embolization of the gastroduodenal artery (a-b) demonstrate conventional celiac vascular anatomy with tumor blush in the right hepatic lobe corresponding to the known hepatocellular carcinoma (HCC). C-D: Selective arteriograms of the hepatic arterial branches supplying the hypervascular HCC.

Figure 3. Liver-Lung Perfusion Scan

Anterior and posterior planar imaging of both chest and abdomen were performed after selective arterial administration of 5 mCi of Tc-99m MAA by the interventional radiologist. Region of interests (ROIs) were placed over the liver and lungs. The planar images demonstrate activity in the right lobe of the liver and no significant activity in the lungs or bowel. Mean calculated lung shunting is 9.23 %.

Figure 4. Post-treatment Magnetic Resonance Imaging (MRI)

Axial (a) and coronal (b) T2-weighted images demonstrate an overall decrease in signal intensity of treated HCC with interval development of hyperintense foci compatible with cystic necrosis. Precontrast (c), arteral (d), portalvenous (e), and delayed (f) postcontrast T1-weighted images demonstrate lack of tumor enhancement compatible with nonviable tumor and necrosis.