Imaging of hepatocellular carcinoma after treatment with yttrium-90 microspheres

OBJECTIVE. Yttrium-90 radioembolization is an emerging therapy for unresectable hepatocellular carcinoma (HCC). Although therapeutic response based on size has been evaluated in numerous studies, necrosis has been used as a criterion of response in only a few studies. The purpose of our study was to describe the imaging features of HCC after Y-90 treatment and to compare size criteria (World Health Organization [ WHO] and Response Evaluation Criteria in Solid Tumors [RECIST]) with necrosis criteria and combined criteria (RECIST and necrosis) for assessment of response. MATERIALS AND METHODS. CT images of 42 patients with 76 Y-90-treated HCC lesions were analyzed. We used four response criteria: WHO size, RECIST size, necrosis, and combined criteria (RECIST and necrosis). Imaging features of treated lesions included both nodular and peripheral rim enhancement. Survival was assessed with the Kaplan-Meier method. RESULTS. The response rate was 23% according to RECIST criteria, 26% according to WHO criteria, 57% according to necrosis criteria, and 59% according to combined criteria. Response according to necrosis and combined criteria was detected earlier than response according to size criteria alone. Ten responding lesions initially increased in size. After therapy, enhancing peripheral nodules increased in size in 10 lesions, decreased in size in two lesions, and disappeared in two lesions. Twenty-one of 25 lesions with thin rim enhancement after Y-90 administration responded to treatment. The median survival times were 660 and 236 days for Okuda stage I and Okuda stage II disease, respectively. CONCLUSION. Use of combined size and necrosis criteria may lead to more accurate assessment of response to Y-90 therapy than use of size criteria alone. Imaging features after Y-90 treatment, including size, necrosis, peripheral enhancing nodules, and thin rim enhancement, are described.