Role of contrast-enhanced ultrasonography in percutaneous radiofrequency ablation of liver metastases and efficacy evaluation

Abstract

Objective: To retrospectively investigate the role of contrast-enhanced ultrasonography (CEUS) in percutaneous radiofrequency ablation (RFA) in patients with liver metastases and evaluate the therapeutic efficacy of RFA assisted by CEUS.

Methods: From May 2004 to September 2010, 136 patients with 219 liver metastatic lesions received CEUS examination 1 h before RFA (CEUS group), and other 126 patients with 216 lesions without CEUS examination in the earlier period were served as a historical control group. The mean tumor size was 3.2 cm and the mean tumor number was 1.6 in the CEUS group, while 3.4 cm and 1.7 in the control group, respectively (P>0.05). The clinical characteristics, recurrence results and survival outcomes were compared between two groups.

Results: In the CEUS group, two isoechoic tumors were not demonstrated on unenhanced ultrasonography (US), and 63 (47%) of 134 tumors examined with CEUS were 0.3 cm larger than with unenhanced US. Furthermore, in 18.4% of 136 patients, additional 1-3 tumors were detected on CEUS. The CEUS group showed higher early tumor necrosis and lower intrahepatic recurrence than the control group. The 3-year overall survival (OS) rate and the 3-year local recurrence-free survival (LRFS) rate in the CEUS group were 50.1% and 38.3%, in contrast to 25.3% and 19.3% in the control group, respectively (P=0.002 and P<0.001).

Conclusions: CEUS provides important information for RFA treatment in patients with liver metastases and better therapeutic effect could be attained.

Keywords: Contrast media; liver metastases; radiofrequency ablation; ultrasonography.

Figure 1

A 66-year-old man with liver metastasis resulted from lung carcinoma underwent RFA treatment in CEUS group. A. The arterial phase on enhanced CT demonstrated a 3.6 cm tumor with peripheral enhancement in the segment II of liver; B. US showed a hypoechoic tumor with obscure margin, about 3.3 cm in diameter (↑); C. The arterial phase on CEUS appeared obviously overall enhancement of the lesion up to 4.7 cm in diameter (↑); D. After overlapping ablation, the therapeutic scope was above 5 cm in diameter; E. Enhanced CT scan after 4 months RFA treatment showed no enhancement of the lesion, indicating complete tumor necrosis

Figure 2

A 52-year-old woman with liver metastasis resulted from esophageal carcinoma underwent RFA in CEUS group. A. US showed an inhomogenous echoic tumor surrounding with halo located proximal to the diaphragm in the left lobe of liver; B. CEUS demonstrated the tumor was significantly enhanced, and a size of 1.4 cm enhanced nodule near it was noticed (↑) in the arterial phase; C. The two tumors both washed out with clear margin (↑) in the parenchyma phase on CEUS; D. Enhanced CT appeared peripheral enhancement of the two tumors in the arterial phase (↑); E. RFA treatment was performed immediately after CEUS. Two tumors were ablated together; F. Enhanced CT scan after 2 months RFA demonstrated the ablated tumor and the surrounding area were not enhanced

Figure 3

A 69-year-old man with colorectal liver metastases underwent RFA treatment in the control group. A. Enhanced MRI showed an obvious peripheral enhanced tumor adjacent to right diaphragm; B. US demonstrated a 4.8 cm hypoechoic tumor with poor-defined margin (↑); C. US-guided percutaneous RFA for the lesion was performed. Hyperechoic area covered over the treated tumor after RFA; D. Three month after RFA treatment, US showed heterogeneous echo of the lesion treated by RFA, which could not differentiate viability from necrosis (↑); E. Arterial phase on CEUS found a strip enhancement at the peripheral of the lesion (↑); F. Delay phase on CEUS demonstrated its wash-out, which highly suggested local recurrence (↑); G. Enhanced MRI confirmed the local enhancement at the same location on CEUS (↑). After that, the liver metastasis progression could not be controlled by repeat RFA therapy and chemotherapy. The patient died of systematic failure 21 months after first RFA therapy

Figure 4

Comparison of survival between two groups after RFA treatment. A. Overall survival of the CEUS group was significantly higher than the control group, P=0.002; B. The LRFS curve showed CEUS group had better survival than the control group, P<0.001

Figure 5

Comparison of survival of patients with tumors larger than 2 cm between two groups after RFA treatment. A. Patients with tumors larger than 2 cm survived longer in the CEUS group than in the control group, P=0.026; B. The LRFS curve in the patients with tumors larger than 2 cm demonstrated higher LRFS in the CEUS group than in the control group, P=0.007

Figure 6

Comparison of survival of patients with solitary and multiple liver metastases between two groups. A. There was no statistical difference in survival of patients with multiple liver metastases between two groups, P=0.524; B. Survival curves of patients with solitary liver metastases showed patients in the CEUS group had obvious longer survival than in the control group, P=0.001

Figure 7

A 63-year-old man with liver metastasis after colorectal cancer surgery underwent RFA in CEUS group. A. Slightly peripheral enhancement was visualized in portal phase on enhanced CT, measuring 3.5 cm in diameter; B. A hyperechoic tumor around by halo was demonstrated in Segment VII in the liver on US, with unclear margin; C. Range of enhancement was up to 4.0 cm in diameter in arterial phase on CEUS (↑); D. Percutaneous RFA was performed immediately after CEUS. E. No enhancement was found in the tumor 12 months after RFA on enhanced CT; F. No viable sign was shown in the tumor 51 months after RFA on enhanced CT. The size of the tumor was down to 2.6 cm in diameter