• Dual Energy CT
• Hepatocellular Carcinoma (HCC)
• Spectral Imaging
• treatment response
• Volumetric Iodine Uptake (VIU)
• Y90-Radioembolization

Purpose: To retrospective compare early response to Yttrium 90 radioembolization (Y90) in terms of volumetric iodine uptake (VIU) changes, Response Evaluation criteria for Solid Tumor version 1.1 (RECIST 1.1) and modified RECIST (mRECIST) in patients with intermediate-advanced hepatocellular carcinoma (HCC) and to explore the association of these criteria with survival.
Materials and methods: The study included 24 patients (20 males, 4 females; mean age 63.4 ± 13.5 years, range 43-79) treated with Y90 from February 2013 to December 2015 and evaluated with Dual-Energy Computed Tomography (DECT) and spectral imaging less than one month before the procedure and 1-2 months after treatment. An independent radiologist performed VIU measurements on late arterial phase spectral images before and after treatment. Responders were defined as those showing a reduction in VIU of at least 15%. Another radiologist evaluated target tumor response according to RECIST 1.1 and mRECIST at 1-2 months and 5-6 months follow-up. Cox regression and Kaplan-Meyer analysis were used to explore differences in overall survival between responders and non-responders for each assessment method.
Results: VIU identified a higher number of responders (18 patients, 75%), compared to RECIST 1.1 (3/24 patients at 1-2 months, 12.5%; 5/21 patients, at 5-6 months, 23.8%) and mRECIST (7/24 patients at 1-2 months, 29.2%; 13/21 patients, at 5-6 months, 61.9%). There was no statistically significant correlation between overall survival and RECIST 1.1 (P=0.70 at 1-2 months and P=0.28 at 5-6 months) or mRECIST (P=0.47 at 1-2 months and P=0.67 at 5-6 months) responses, whereas median survival was significantly higher in VIU responders (29.4 months) compared to non-responders (7.4 months) (HR 0.14; 95%CI 0.03-0.51; P = 0.0047).
Conclusions: VIU can be a sensitive parameter in the early identification of tumor response to Y90 treatment in intermediate-advanced HCC patients and is associated with the overall survival, as opposite to mRECIST and RECIST 1.1.