Imaging Evaluation Following 90Y Radioembolization of Liver Tumors: What Radiologists Should Know

Abstract

Radioembolization using beta-emitting yttrium-90 microspheres is being increasingly used for the treatment of primary and metastatic liver cancers. It is a form of intra-arterial brachytherapy which delivers intense radiation to liver tumors with little embolic effect; this mode of action results in unique post-treatment imaging findings. It is important to understand these imaging findings to avoid misinterpretation of tumor response and to determine further management of the disease. Herein, we discuss the current concepts for assessing tumor response, common post-treatment imaging features, and associated complications following radioembolization.

Keywords: Liver cancer; Post-treatment imaging; Radioembolization; Selective internal radiation therapy; Yttrium-90.

Fig. 1. 67-year-old man with HCC.

A. Pre-treatment CT image shows hypervascular tumor in right lobe of liver. B. ^99mTc-MAA SPECT/CT after delivery of ^99mTc-MAA into right hepatic artery shows high activity in tumor (arrowheads) but weak activity in liver parenchyma, which would predict good response to radioembolization. C. CT scan of arterial phase 1 month after ⁹⁰Y radioembolization shows loss of enhancement in tumor, suggesting tumor necrosis (arrowheads). Note wall edema and mucosal rent of gallbladder (arrow). Despite this abnormal imaging finding of gallbladder, this patient did not have any clinical symptoms or laboratory abnormality suggesting acute cholecystitis, and therefore, no interventional treatment was performed for gallbladder. HCC = hepatocellular carcinoma, SPECT = single photon emission computed tomography, ^99mTc-MAA = technetium-99m macroaggregated albumin

Fig. 2. 68-year-old man with HCC.

A. Pre-treatment MR image shows large hypervascular mass (arrowheads) in right lobe of liver. B. PET/CT image immediately after ⁹⁰Y radioembolization demonstrates high activity of ⁹⁰Y microspheres in tumor. Note defect in activity in medial part of tumor (dotted circle). C. CT scan taken 1 month after ⁹⁰Y therapy shows intra-tumoral nodular enhancement in medial portion (arrowhead). This lesion had grown up slowly on subsequent CT scan, and was treated by chemoembolization 6 months after ⁹⁰Y radioembolization. PET = positron emission tomography, ⁹⁰Y = yttrium-90

Fig. 3. 80-year-old woman with intrahepatic cholangiocarcinoma.

A. Pre-treatment CT scan shows 3.5 cm mass (arrowheads) in right lobe of liver. B. PET/CT image immediately after ⁹⁰Y radioembolization reveals high activity in tumor as well as in surrounding hepatic parenchyma. C. Arterial phase CT image 2 months after ⁹⁰Y radioembolization shows 7 cm low-attenuating area (arrowheads) in treated lobe that may represent necrosis of tumor and peritumoral parenchyma. This size discrepancy between pre- and post-treatment images should not be interpreted as tumor progression. D. One year follow-up CT image shows shrinkage of treated lesion with liver surface retraction.

Fig. 4. 82-year-old man with HCC.

A. Pre-treatment CT scan shows hypervascular mass (arrowheads) in left lobe of liver. B. CT scan 2 months after ⁹⁰Y therapy shows persistent enhancement of tumor (arrowheads). Tumor size was slightly decreased. C. CT scan 6 months after ⁹⁰Y radioembolization shows reduced tumor size and decreased tumor enhancement (arrowheads). CT scan 1 year after ⁹⁰Y radioembolization shows further decrease in size and enhancement of tumor (data not shown). This patient did not receive any additional treatment.

Fig. 5. 57-year-old woman with liver metastases from neuroendocrine tumor.

A. Pre-treatment MR image shows 10 cm tumor (arrowheads) in left lobe of liver, 3 cm tumor in caudate lobe (arrow), and 4 cm tumor in right lobe (open arrowhead). B. CT scan 1 month after ⁹⁰Y radioembolization shows loculated perihepatic ascites (arrow) beside right lobe. Note disappearance of enhancement of tumor in right lobe (open arrowhead) and residual enhancing portion of tumor in left lobe (arrowhead). As residual enhancement on early follow-up is common imaging feature, no additional treatment was performed for this finding. C. CT scan 11 months after ⁹⁰Y radioembolization demonstrates increased enhancing nodular lesion (arrowhead) within treated tumor which suggests tumor recurrence. Chemoembolization was performed using iodized oil, and follow-up image shows nodular dense accumulation of iodized oil within recurrent tumor (data not shown).

Fig. 6. 37-year-old man with HCC.

Pre-treatment MRI shows hypervascular mass (arrowheads) in segment VI of liver on arterial phase (A) which shows low ADC value of 0.95 mm²/sec (B). On post-radioembolization MRI, mass (arrowheads) shows decrease in size, decrease in arterial enhancement, and peritumoral ring enhancement (C), and increase in ADC value of 1.45 mm²/sec of tumor (arrowheads) (D) which are findings suggestive of good response to treatment. ADC = apparent diffusion coefficient

Fig. 7. 79-year-old man with intrahepatic cholangiocarcinoma.

A. Pre-treatment CT scan of portal venous phase (left) and delayed phase (right) shows small tumor in right lobe (arrowhead). Radioactive microspheres were injected into right hepatic artery (data not shown). B. CT scan of portal venous phase (left) and delayed phase (right) 2 months after ⁹⁰Y radioembolization shows low attenuation on portal venous phase and iso-attenuation on delayed phase of right lobe, indicating type I radiation change. Note mild shrinkage of right lobe and hypertrophy of left lobe. C. CT scan of portal venous phase (left) and delayed phase (right) 4.5 months after ⁹⁰Y radioembolization shows low attenuation on portal venous phase and high attenuation on delayed phase of right lobe, indicating type II radiation change. Note progression of shrinkage of right lobe and hypertrophy of left lobe.

Fig. 8. 67-year-old man with HCC.

A. Pre-treatment CT scan shows large tumor in left lobe (arrowhead) and small tumor in right lobe (arrow). Radiation segmentectomy of segment VIII and radiation lobectomy of left lobe were performed in one session. B. CT scan of arterial phase 2 months after ⁹⁰Y radioembolization shows peritumoral ring enhancement (arrowhead) in left lobe. Due to suspicion of residual tumor, chemoembolization was requested. But, angiography failed to demonstrate tumor staining (data not shown), and therefore, no additional treatment was performed. C. CT scan of arterial phase (left), portal venous phase (middle), and delayed phase (right) 8 months after ⁹⁰Y radioembolization shows persistent peritumoral ring enhancement around left lobe tumor and dystrophic intratumoral calcification (arrow) in right lobe tumor. Note wedge-shaped enhancement (arrowhead) around right lobe tumor and diffuse enhancement (star) of left lateral segment with decreased volume of treated area, indicating type III radiation change after radiation segmentectomy and radiation lobectomy, respectively. At 16 month follow-up after ⁹⁰Y radioembolization, this patient has demonstrated no evidence of tumor recurrence on tumor marker and imaging studies (data not shown).

Fig. 9. 48-year-old man with HCC.

Pre-treatment gadoxetic acid-enhanced MR image of hepatobiliary phase (20 minutes) (A) shows infiltrative tumor (arrowheads) in segment VII of liver. Radioactive microspheres were injected into right hepatic artery (data not shown). On gadoxetic acid-enhanced MRI 3 months after ⁹⁰Y therapy, arterial phase image (B) demonstrates tumor necrosis (arrow) in segment VII and heterogeneous parenchymal enhancement of right lobe, and hepatobiliary phase image (20 minutes) (C) shows diffuse hypointensity of hepatic parenchyma in right lobe which may indicate radiation effect. This parenchymal change should not be misinterpreted as progression of infiltrative tumor.

Fig. 10. 53-year-old man with HCC.

A. Pre-treatment CT image of portal venous phase demonstrates large tumor in segments IV and VIII of liver (arrow). B. On PET/CT immediately after ⁹⁰Y radioembolization, not only tumor but also hepatic parenchyma of segment IV between middle and left hepatic veins (arrowhead) shows increased activity suggesting high uptake of ⁹⁰Y microspheres. During procedure of ⁹⁰Y radioembolization, excessive ⁹⁰Y microspheres were delivered into small tumor-feeding artery whose vascular territory covered this area (data not shown). C. CT scan 3 months after ⁹⁰Y radioembolization shows shrinkage of hepatic tumor (arrow). Note new hypo-attenuating lesion (arrowhead) between middle and left hepatic veins with decrease in volume, which is thought to be radiation necrosis of hepatic parenchyma. This lesion should not be misdiagnosed as new hypovascular tumor. D. CT scan 8 months after ⁹⁰Y radioembolization shows shrinkage of hepatic tumor with dystrophic calcification (arrow).

Fig. 11. 59-year-old man with hepatic metastases from pancreatic neuroendocrine tumor.

CT scan 3 months after ⁹⁰Y radioembolization shows new low-attenuating lesions (arrow) with perivascular distribution in right lobe of liver. This finding is due to perivascular edema related to ⁹⁰Y radioembolization, which should not be misdiagnosed as infiltrative tumor. Note loss of enhancement of tumor (arrowhead).