Utility of Contrast-Enhanced Harmonic Endoscopic Ultrasound for the Guidance and Monitoring of Endoscopic Radiofrequency Ablation

Abstract

Background/aims: Interventional endoscopists may utilize contrast-enhanced harmonic endoscopic ultrasound (CEHEUS) for image guidance during radiofrequency ablation (RFA) because of its capability to delineate real-time tumor perfusion dynamics. The purpose of this study was to assess the utility of CEH-EUS for the guidance and monitoring of endoscopic RFA.

Methods: Nineteen consecutive patients with solid abdominal tumors who underwent CEH-EUS and endoscopic RFA were included. The extent of the ablation was assessed by CEH-EUS at 5 to 7 days after RFA. Additional RFAs were performed under CEH-EUS guidance.

Results: The diagnoses were as follows: nonfunctioning neuroendocrine tumor (n=13), solid pseudopapillary neoplasm (SPN) (n=2), insulinoma (n=1), left adrenal adenoma (n=2), and left adrenal oligometastasis (n=1). Pre-CEH-EUS findings revealed that 17 cases showed hyperenhanced patterns and two cases of SPN showed isoenhanced patterns. CEH-EUS-assisted RFA was technically feasible in all 19 patients. After the first RFA session, seven patients of the treated tumors showed the disappearance of intratumoral enhancement on CEH-EUS, whereas 12 showed residual contrast enhancement. Twelve patients with incomplete ablation were further treated with additional RFA under real-time CEH-EUS guidance. Radiologic complete response was observed in 13 patients (68.4%). Among the 35 ablation procedures, the only adverse events were two episodes of pancreatitis (5.7%; 1 moderate and 1 mild). During the median follow-up of 28 months, the local recurrence rate was 7.7%.

Conclusions: The application of CEH-EUS for RFA could be helpful in assessing early treatment response after ablation and targeting residual viable tumors during additional ablation sessions.

Keywords: Contrast agent; Endosonography; Radiofrequency ablation.

Fig. 1

A pre-CEH-EUS image shows homogeneous hyperenhancement (arrows) of the pancreatic neuroendocrine tumor (A). Five days after radiofrequency ablation, no enhancement (arrowheads) in the arterial phase is seen inside the tumor, compatible with a complete response (B). CEH-EUS, contrast-enhanced harmonic endoscopic ultrasound.

Fig. 2

Conventional gray scale (A) and contrast-specific (ExPHD)-mode (B) after the first session of radiofrequency ablation. The B-mode EUS image (A) shows the adrenal adenoma as a hypoechoic area. The CEH-EUS image clearly shows an enhancing viable tumor for additional ablation (arrows). CEH-EUS, contrast-enhanced harmonic endoscopic ultrasound.

Fig. 3

Conventional gray scale (A) and contrast-specific (ExPHD)-mode (B) during the second session of radiofrequency ablation. An arterial phase CEH-EUS image (B) obtained 5 days after RFA shows peripheral eccentric enhancement, suggesting a viable tumor. CEH-EUS facilitates the accurate targeting of the RFA needle (arrows) into the lesion to be treated. CEH-EUS, contrast-enhanced harmonic endoscopic ultrasound; RFA, radiofrequency ablation.

Fig. 4

(A) Abdominal computed tomography (CT) image obtained before ablation shows a 1.9-cm neuroendocrine tumor in the body of the pancreas (arrow). (B) The axial arterial phase CT image from the 3-month follow-up depicting a no enhancing hypodense lesion (arrow).