03:27 PM Abstract No. 434 Comparison of tumor and liver enhancement on preinterventional MDCT, CBCT, SPECT, and postinterventional PET in patients with HCC undergoing SIRT

Abstract

In radioembolization (SIRT) the activity of tumor and liver is estimated from Technetium99-Human-Serum-Albumin Single Photon Emission Computed Tomography (SPECT), but relative contrast differences can also be calculated from arterial phase Multidetector Computed Tomography (MDCT) or parenchymal phase Cone-beam Computed Tomography (CBCT) (1). The aim of this study was to investigate the agreement of Tumor-Liver-Enhancement-Ratio (TLER) of preinterventional MDCT, CBCT, and SPECT with postinterventional Yttrium90 Positron Emission Tomography (PET) serving as gold standard for dose distribution assessment. A total of 157 patients with hepatocellular carcinoma (HCC) undergoing SIRT (2013-2018) were screened for study inclusion criteria (no prior interventional therapy, viable tumor diameter >3cm). Overall, 33 patients (median of 71ya, 30m), 36 SIRT procedures and 41 tumor lesions were included. Median interval between evaluation and treatment were 15 days. Tumor and liver enhancement was measured on MDCT and CBCT in Hounsfield units, on SPECT in Counts and on PET in mBq/ml by placing a planar Region-of-Interest on a representative tumor part and the adjacent liver. Subgroup analysis of viable tumor diameter <6cm was also performed. TLER and spearman’s rho were calculated using SPSS 25 (significance level *=p<0.05; **=p<0.01; ***=p<0.01). The median (range) of TLER was for MDCT 1.1 (0.7-2.0), CBCT 1.4 (0.8-3.1), SPECT 4.4 (1.4-33.6) and PET 3.4 (0.7-18). Correlation of TLER assessed on PET and SPECT or CBCT was comparable (r=0.33*; r=0.39*) while TLER from SPECT and CBCT correlate moderately (r=0.49**). There was no significant correlation of TLER from PET and MDCT (r=0.27). If viable tumor diameter was smaller than 6 cm, there was a strong correlation of TLER from PET and SPECT (r = 0.68**) or CBCT (r = 0.80***) or even MDCT (r =0.6*). The correlation of TLER from PET and CBCT is at least comparable with TLER from SPECT and better than from MDCT, which might be due to intra-arterial contrast injection. This study indicates that CBCT is comparable to SPECT and might assist preinterventional dose planning, particularly in small tumors.