Quantitative Imaging Biomarkers for Y Distribution on Bremsstrahlung SPECT After Resin-Based Radioembolization.

Our purpose was to identify baseline imaging features in patients with liver cancer that correlate with Y distribution on postprocedural SPECT and predict tumor response to transarterial radioembolization (TARE). This retrospective study was approved by the institutional review board and included 38 patients with hepatocellular carcinoma (HCC) ( 23; 18/23 men; mean age, 62.39 ± 8.62 y; 34 dominant tumors) and non-HCC hepatic malignancies ( 15; 9/15 men; mean age, 61.13 ± 11.51 y; 24 dominant tumors) who underwent 40 resin-based TARE treatments (August 2012 to January 2018). Multiphasic contrast-enhanced MRI or CT was obtained before and Bremsstrahlung SPECT within 2 h after TARE. Total tumor volume (cm) and enhancing tumor volume (ETV [cm] and % of total tumor volume), and total and enhancing tumor burden (%), were volumetrically assessed on baseline imaging. Up to 2 dominant tumors per treated lobe were analyzed. After multimodal image registration of baseline imaging and SPECT/CT, Y distribution was quantified on SPECT as tumor-to-normal-liver ratio (TNR). Response was assessed according to RECIST1.1 and quantitative European Association for the Study of the Liver criteria. Clinical parameters were also assessed. Statistical tests included Mann-Whitney Pearson correlation, and linear regression. In HCC patients, high baseline ETV% significantly correlated with high TNR on SPECT, demonstrating greater Y uptake in the tumor relative to the liver parenchyma ( < 0.001). In non-HCC patients, a correlation between ETV% and TNR was observed as well ( = 0.039). Follow-up imaging for response assessments within 1-4 mo after TARE was available for 23 patients with 25 treatments. The change of ETV% significantly correlated with TNR in HCC ( = 0.039) but not in non-HCC patients ( = 0.886). Additionally, Child-Pugh class B patients demonstrated significantly more Y deposition in nontumorous liver than Child-Pugh A patients ( = 0.021). This study identified ETV% as a quantifiable imaging biomarker on preprocedural MRI and CT to predict Y distribution on postprocedural SPECT in HCC and non-HCC. However, the relationship between the preferential uptake of Y to the tumor and tumor response after radioembolization could be validated only for HCC.