Role of contrast-enhanced ultrasound in follow-up assessment after ablation for hepatocellular carcinoma

Abstract

Aim: To assess the usefulness of contrast-enhanced ultrasound (CEUS) during follow-up after percutaneous ablation therapy for hepatocellular carcinoma (HCC).

Methods: A total of 141 patients with HCCs who received percutaneous ablation therapy were assessed by paired follow-up CEUS and contrast-enhanced computed tomography (CECT). The follow-up scheme was designed prospectively and the intervals between CEUS and CECT examinations were less than 14 d. Both images of follow-up CEUS and CECT were reviewed by radiologists. The ablated lesions were evaluated and classified as local tumor progression (LTP) and LTP-free. LTP was defined as regrowth of tumor inside or adjacent to the successfully treated nodule. The detected new intrahepatic recurrences were also evaluated and defined as presence of intrahepatic new foci. On CEUS and CECT, LTP and new intrahepatic recurrence both were displayed as typical enhancement pattern of HCC (i.e., hyper-enhancing during the arterial phase and washout in the late phase). With CECT as the reference standard, the ability of CEUS in detecting LTP or new intrahepatic recurrence during follow-up was evaluated.

Results: During a follow-up period of 1-31 mo (median, 4 mo), 169 paired CEUS and CECT examinations were carried out for the 141 patients. For a total of 221 ablated lesions, 266 comparisons between CEUS and CECT findings were performed. Thirty-three LTPs were detected on CEUS whereas 40 LTPs were detected on CECT, there was significant difference (P < 0.001). In comparison with CECT, the numbers of false positive and false negative LTPs detected on CEUS were 6 and 13, respectively; the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and overall accuracy of CEUS in detecting LTPs were 67.5%, 97.4%, 81.8%, 94.4% and 92.3%, respectively. Meanwhile, 131 new intrahepatic recurrent foci were detected on CEUS whereas 183 were detected on CECT, there was also significant difference (P < 0.05). In comparison with CECT, the numbers of false positive and false negative intrahepatic recurrences detected on CEUS were 13 and 65, respectively; the sensitivity, specificity, PPV, NPV and overall accuracy of CEUS in detecting new intrahepatic recurrent foci were 77.7%, 92.0%, 92.4%, 76.7% and 84.0%, respectively.

Conclusion: The sensitivity of CEUS in detecting LTP and new intrahepatic recurrence after percutaneous ablation therapy is relatively low in comparison with CECT.

Keywords: Contrast-enhanced computed tomography; Contrast-enhanced ultrasound; Hepatocellular carcinoma; Microwave ablation; Radiofrequency ablation.

Figure 1

A 57-year-old male patient with hepatocellular carcinoma. Two months after radiofrequency ablation for hepatocellular carcinoma in segment 3 of the liver. On both contrast-enhanced computed tomography (A, B) and contrast-enhanced ultrasound (C, D), the treated lesion (arrow) showed complete necrosis without any enhancement in all vascular phases.

Figure 2

A 70-year-old male patient with hepatocellular carcinoma. Local tumor progression (arrow) was detected 6 mos after radiofrequency ablation in combination with ethanol ablation for hepatocellular carcinoma in segment 5 of the liver. Local tumor progression showed hyper-enhancement in the arterial phase and iso-enhancement in the portal-late phase on contrast-enhanced ultrasound (A, B), whereas hyper-enhancement in the arterial phase and wash-out in the portal-venous phase on contrast-enhanced computed tomography (C, D).

Figure 3

The same patient as shown in Figure 1. A, B: Two months after radiofrequency ablation for hepatocellular carcinoma. A new intrahepatic recurrence (arrow) was detected in segment 4 of the liver, which showed hyper-enhancement in the arterial phase and wash-out in the portal-venous phase on contrast-enhanced computed tomography; C, D: Similar findings were found in the arterial phase and the portal-late phases with contrast-enhanced ultrasound.

Figure 4

A 62-year-old male patient with hepatocellular carcinoma. Two months after percutaneous ethanol ablation for hepatocellular carcinoma in segment 8 of the liver. A, B: The false positive local tumor progression (arrow) was detected. It showed rim-like hyperenhancement in the arterial phase, wash-out in the portal-late phase on contrast-enhanced ultrasound; C, D: On contrast-enhanced computed tomography, the treated area (arrow) showed complete necrosis without any enhancement in all the vascular phases, but several enhanced hepatic vessels around the treated area.

Figure 5

A 54-year-old male patient with hepatocellular carcinoma. Three months after radiofrequency ablation in combination with ethanol ablation for hepatocellular carcinoma in segment 8 of the liver. A: Contrast-enhanced computed tomography showed local tumor progression (arrow) at the periphery of the treated area; B: On contrast-enhanced ultrasound, local tumor progression (arrow) could not be detected, and the treated area was not clearly observed due to unfavorable location near the liver dome.