Early treatment response to sorafenib for rabbit VX2 orthotic liver tumors: evaluation by quantitative contrast-enhanced ultrasound

The aim of our study was to investigate the application of contrast-enhanced ultrasound (CEUS) and its quantification analysis for the prediction of early treatment response of sorafenib on rabbit VX2 liver tumor model. Rabbits were implanted VX2 tumor mass to establish a liver tumor model. Fourteen days after tumor implantation, rabbits presented with single liver tumor were randomly divided into two groups. Rabbits in treatment group were given by gavage once a day for 14 days with sorafenib suspension at a dose of 30 mg/kg, whereas rabbits in control group were given saline by gavage of the same volume. CEUS was performed before treatment and 3, 7, 14 days after treatment for the analysis of tumor size, enhancement pattern, and necrosis range. The time intensity curve (TIC) was used to obtain quantitative parameters of enhancement patterns. Before sorafenib administration, tumor volumes ranged from 0.24 to 0.75 cm³ (mean 0.49 ± 0.18 cm³) in treatment group and 0.24 to 0.44 cm³ (mean 0.30 ± 0.12 cm³) in control group. The dynamic enhancement patterns of tumors were homogeneous hyper-enhancement (n = 8), heterogeneous hyper-enhancement (n = 4), and peripheral rim-like enhancement (n = 2). All tumors of the treatment group presented with peripheral rim-like enhancement with large necrotic area after sorafenib administration, whereas tumors of the control group showed heterogeneous hyper-enhancement (n = 5) and peripheral rim-like enhancement (n = 2). There was a significant difference in area under the curve (AUC) before and after sorafenib treatment (P = 0.045). CEUS may be of value in the evaluation of early therapeutic response after sorafenib administration.