Radiofrequency ablation of liver cancer: early evaluation of therapeutic response with contrast-enhanced ultrasonography

Contrast enhanced ultrasound of hepatocellular carcinoma

Sonazoid (Daiichi Sankyo, Tokyo, Japan), a second-generation of a lipid-stabilized suspension of a perfluorobutane gas microbubble contrast agent, has been used clinically in patients with liver tumors and for harmonic gray-scale ultrasonography (US) in Japan since January 2007. Sonazoid-enhanced US has two phases of contrast enhancement: vascular and late. In the late phase of Sonazoid-enhanced US, we scanned the whole liver using this modality at a low mechanical index (MI) without destroying the microbubbles, and this method allows detection of small viable hepatocellular carcinoma (HCC) lesions which cannot be detected by conventional US as perfusion defects in the late phase. Re-injection of Sonazoid into an HCC lesion which previously showed a perfusion defect in the late phase is useful for confirming blood flow into the defects. High MI intermittent imaging at 2 frames per second in the late phase is also helpful in differentiation between necrosis and viable hypervascular HCC lesions. Sonazoid-enhanced US by the coded harmonic angio mode at a high MI not only allows clear observation of tumor vessels and tumor enhancement, but also permits automatic scanning with Sonazoid-enhanced three dimensional (3D) US. Fusion images combining US with contrast-enhanced CT or contrast-enhanced MRI have made it easy to detect typical or atypical HCC lesions. By these methods, Sonazoid-enhanced US can characterize liver tumors, grade HCC lesions histologically, recognize HCC dedifferentiation, evaluate the efficacy of ablation therapy or transcatheter arterial embolization, and guide ablation therapy for unresectable HCC. This article reviews the current developments and applications of Sonazoid-enhanced US and Sonazoid-enhanced 3D US for diagnosing and treating hepatic lesions, especially HCC.

Imaging after radiofrequency ablation of hepatic tumors

Radiofrequency ablation (RFA) is now increasingly used as a first-line therapeutic modality for small malignant hepatic tumors in many parts of the world. The importance of radiological imaging at follow-up to assess therapeutic effectiveness, presence of complications, and recurrences cannot be overemphasized, as RFA treatment is minimally invasive and locally applied. A broad spectrum of imaging findings obtained by the use of various modalities has been reported by many investigators. In this review, we describe findings, including chronologic changes of the ablation zones, both local and remote recurrences, and complications that occur after RFA of the liver as well as the advantages and disadvantages of the use of each imaging modality for a specific situation.

Role of Sonazoid-enhanced three-dimensional ultrasonography in the evaluation of percutaneous radiofrequency ablation of hepatocellular carcinoma

OBJECTIVE

We investigated contrast-enhanced three-dimensional ultrasonography (CE 3D US) with contrast agent Sonazoid for evaluating the effect of percutaneous radiofrequency (RF) ablation of hepatocellular carcinomas (HCCs).

METHODS

63 HCCs were treated by US-guided percutaneous RF ablation. CE 3D US after bolus injection of 0.2 mL of Sonazoid was performed 5-7 days before and 1 day after RF ablation. CE 3D computed tomography (CT) was performed 5-7 days before and 1 month after the ablation, and during the follow-up period. Multiplanar images in three orthogonal planes and US/CT angiograms were reconstructed on both modalities. Two blinded observers reviewed the images on both modalities to evaluate the ablation effects.

RESULTS

After RF ablation, the evaluation on CE 3D US and that on CE 3D CT achieved concordance in 61 lesions. Among them, 59 lesions were detected with the absence of tumor vessels and tumor enhancement and evaluated as adequate ablation, and the remaining two lesions were detected with residual tumors. The kappa value for agreement between the findings on the two modalities was 0.65. When 1-month CE 3D CT scans were used as reference standard, the sensitivity, specificity, and accuracy of 1-day CE 3D US for detecting adequate ablation were 97%, 100%, and 97%, respectively.

CONCLUSION

By demonstrating the ablated areas and residual tumors in three dimensions, CE 3D US with Sonazoid was shown to be useful for evaluating the effect of RF ablation of HCCs, and there was good concordance with the results obtained by CE 3D CT.

Radiofrequency ablation of hepatic tumors: lessons learned from 3000 procedures

Radiofrequency ablation has been accepted as the most popular local ablative therapy for unresectable malignant hepatic tumors. For 9 years from April 1999, we performed 3000 radiofrequency ablation procedures for hepatic tumors in our institution. Our results on the safety (mortality, 0.15%/patient) and therapeutic efficacy (5-year survival rate, 58%) are similar to those of previous studies reported, supporting the growing evidence of a clear survival benefit, excellent results for local tumor control and improved quality of life. The most important lesson learned from our 3000 procedures is that the best planning, safe ablation and complete ablation are key factors for patient outcome. Furthermore, multimodality treatment is the best strategy for recurrent hepatocellular carcinoma encountered after any kind of first-line treatment.

Sonography guided percutaneous radiofrequency ablation of hepatocellular carcinoma: effect of cooperative training on the pretreatment assessment of the operation's feasibility

Objective

The aim of this study is to investigate the effects of cooperative training on the pretreatment assessment of the feasibility to perform Ultrasonography (US) guided percutaneous radiofrequency ablation for patients afflicted with hepatocellular carcinoma.

Materials and Methods

In our prospective study, 146 patients with 200 hepatocellular carcinomas were referred for radiofrequency ablation after triage by hepatologists. Three radiologists with different levels of experience performed the planning US before (group I) and after (group II) cooperative training, to evaluate whether radiofrequency ablation was feasible. The feasibility rates considered eligible according to our criteria were evaluated. In addition, we analyzed the reasons for the lack of feasibility were analyzed. The interobserver agreement for the assessment of feasibility before and after training was also calculated.

Results

The overall feasibility rates for both groups was 73%. No significant difference in the feasibility rates was observed. The feasibility rates of each observer for group I were 71% (observer 1), 77% (observer 2) and 70% (observer 3) and those for group II were 73%, 76% and 69%, respectively. In the tumors (n = 164) considered ineligible, the two most common causes for refraining from performing radiofrequency ablation included non-visualization of the tumor (62%) and the absence of a safe route for the percutaneous approach (38%). We found moderate interobserver agreement for all observers before cooperative training and a good agreement after training.

Conclusion

Although the cooperative training did not affect the feasibility rate of each observer, it improved the interobserver agreement for assessing the feasibility of performing US guided radiofrequency ablation, which may reduce unnecessary admission or delayed treatment.

Factors limiting complete tumor ablation by radiofrequency ablation

The purpose of this study was to determine radiological or physical factors to predict the risk of residual mass or local recurrence of primary and secondary hepatic tumors treated by radiofrequency ablation (RFA). Eighty-two patients, with 146 lesions (80 hepatocellular carcinomas, 66 metastases), were treated by RFA. Morphological parameters of the lesions included size, location, number, ultrasound echogenicity, computed tomography density, and magnetic resonance signal intensity were obtained before and after treatment. Parameters of the generator were recorded during radiofrequency application. The recurrence-free group was statistically compared to the recurrence and residual mass groups on all these parameters. Twenty residual masses were detected. Twenty-nine lesions recurred after a mean follow-up of 18 months. Size was a predictive parameter. Patients' sex and age and the echogenicity and density of lesions were significantly different for the recurrence and residual mass groups compared to the recurrence-free group (p < 0.05). The presence of an enhanced ring on the magnetic resonance control was more frequent in the recurrence and residual mass groups. In the group of patients with residual lesions, analysis of physical parameters showed a significant increase (p < 0.05) in the time necessary for the temperature to rise. In conclusion, this study confirms risk factors of recurrence such as the size of the tumor and emphasizes other factors such as a posttreatment enhanced ring and an increase in the time necessary for the rise in temperature. These factors should be taken into consideration when performing RFA and during follow-up.

Percutaneous Radiofrequency Ablation for Recurrent Hepatocellular Carcinoma After Hepatectomy: Long-term Results and Prognostic Factors

BACKGROUND

We evaluated the long-term survival results and safety of percutaneous radiofrequency ablation (RFA) for recurrent hepatocellular carcinoma (HCC) after hepatectomy, and assessed the prognostic factors that can influence its long-term therapeutic results.

METHODS

One hundred and two patients, who had 119 recurrent HCC in their livers, underwent ultrasound-guided percutaneous RFA. All the patients had a history of hepatic resection as a first-line treatment modality for HCC. The mean diameter of the recurrent tumors was 2.0 cm (range, 0.8-5.0 cm). We evaluated the effectiveness rates, local tumor progression rates, survival rates, and complications. We also assessed the prognostic factors of the survival rates by using Cox proportional hazard models.

RESULTS

The primary effectiveness rate was 93.3% (111 of 119). The cumulative rates of local tumor progression at 1, 3, and 5 years were 6.0, 8.6, and 11.9%, respectively. The cumulative survival rates at 1, 2, 3, 4, and 5 years were 93.9, 83.7, 65.7, 56.6, and 51.6%, respectively. Patients with a lower serum alpha-fetoprotein (AFP) level (<or=100 microg/L) before RFA or with small resected tumors (<or=5 cm) demonstrated better survival results (P < .05). There was only one major complication (liver abscess, 1.0% per treatment) during the follow-up period. There were no procedure-related deaths.

CONCLUSIONS

Percutaneous RFA is an effective and safe treatment modality for intrahepatic recurrent HCC after hepatectomy. Serum AFP level before RFA and resected tumor size were significant prognostic predictors of long-term survival.

Percutaneous radiofrequency ablation for early-stage hepatocellular carcinoma as a first-line treatment: long-term results and prognostic factors in a large single-institution series

The purpose of this study was to evaluate the long-term survival results and complications of percutaneous radiofrequency ablation (RFA) in patients with early-stage hepatocellular carcinoma (HCC). Between April 1999 and May 2005, 570 patients with 674 early-stage HCCs underwent percutaneous RFA as a first-line treatment option in a single institution. We evaluated the effectiveness rates, local tumor progression rates, survival rates, and complications. We also assessed the prognostic values of survival rates by using Cox proportional hazard models. The primary technique effectiveness rate was 96.7% (652 of 674). The cumulative rates of local tumor progression at 1, 2, and 3 years were 8.1%, 10.9%, and 11.8%, respectively. The cumulative survival rates at 1, 2, 3, 4, and 5 years were 95.2%, 82.9%, 69.5%, 60.8%, and 58.0%, respectively. Patients with Child-Pugh class A cirrhosis, of younger age (<or=58 years), or having lower AFP level (<or=100 microg/L) demonstrated better survival results (P < 0.05). A total of 11 major complications (1.9% per treatment) were found during the follow-up period. There was no procedure-related death. Percutaneous RFA can be used successfully as a first-line treatment modality for early-stage HCCs. Child-Pugh class, age, and AFP level before RFA were significant prognostic predictors of long-term survival.