Microwave ablation treatment of liver cancer with a 2,450-MHz cooled-shaft antenna: pilot study on safety and efficacy

Early assessment of coagulation necrosis after hepatic microwave ablation: a comparison of non-enhanced and enhanced T1-weighted images

PURPOSE

To compare the technical success and accuracy of hepatic microwave ablation (MWA) using non-enhanced and enhanced T1-weighted imaging early after ablation. Patients were evaluated with regard to the ablation zone and local tumor progression (LTP).

METHODS

This retrospective study conducted between September 2014 and December 2015 which consisted of 56 patients with 56 hepatic malignant lesions who underwent percutaneous MWA. Non-enhanced and contrast-enhanced T1-weighted imagings were performed within 2 days after tumor ablation. The efficacy of ablation assessed according to the hyperintense middle zone on non-enhanced T1-weighted images and the non-enhanced area on contrast-enhanced T1-weighted images were compared. The development of LTP during ≥7 months of follow-up served as the end point.

RESULTS

On the non-enhanced T1-weighted images, the ablated region had a characteristic two-zone structure featuring a hyperintense middle zone and a surrounding hypointense band. Among the 56 patients, LTP developed in ten including seven lesions, in which both the non-enhanced T1-weighted and portal-phase images showed incomplete tumor ablation. In two of the remaining three patients, incomplete tumor ablation was detected on the non-enhanced T1-weighted images, whereas the corresponding portal-phase images showed complete ablation. In the remaining patient, no residual tumor was detected on either the non-enhanced T1-weighted or the portal-phase images. In the 46 patients without LTP, there was no evidence of residual tumor on the non-enhanced T1-weighted or portal-phase images obtained early after ablation.

CONCLUSIONS

Non-enhanced T1-weighted images are useful in assessing the therapeutic efficacy of MWA of liver tumors early after the procedure.

Measurement of Intrahepatic Pressure during Microwave Ablation in an Ex Vivo Bovine Liver Model

Background/Aims

We experimented with different ablation methods and two types of microwave antennas to determine whether microwave ablation (MWA) increases intrahepatic pressure and to identify an MWA protocol that avoids increasing intrahepatic pressure.

Methods

MWA was performed using either a single-step standard ablation or a stepwise increment ablation paired with either a 16-gauge (G) 2-cm antenna or a 14G 4-cm antenna. We compared the maximum pressures and total ablation volumes.

Results

The mean maximum intrahepatic pressures and ablation volumes were as follows: 16G single-step: 37±33.4 mm Hg and 4.63 cm³; 16G multistep: 31±18.7 mm Hg and 3.75 cm³; 14G single-step: 114±45.4 mm Hg and 15.33 cm³; and 14G multistep: 106±43.8 mm Hg and 10.98 cm³. The intrahepatic pressure rose during MWA, but there were no statistically significant differences between the single and multistep methods when the same gauge antennae were used. The total ablation volume was different only in the 14G groups (p<0.05).

Conclusions

We demonstrated an increase in intrahepatic pressure during MWA. The multistep method may be used to prevent increased intrahepatic pressure after applying the proper power.

Liver Ablation: Best Practice

Tumor ablation in the liver has evolved to become a well-accepted tool in the management of increasing complex oncologic patients. At present, percutaneous ablation is considered first-line therapy for very early and early hepatocellular carcinoma and second-line therapy for colorectal carcinoma liver metastasis. Because thermal ablation is a treatment option for other primary and secondary liver tumors, an understanding of the underlying tumor biology is important when weighing the potential benefits of ablation. This article reviews ablation modalities, indications, patient selection, and imaging surveillance, and emphasizes technique-specific considerations for the performance of percutaneous ablation.

Value of microwave ablation in treatment of large lesions of hepatocellular carcinoma

OBJECTIVE

Thermal ablative therapies continue to be favored as a safe and effective treatment for patients with non-resectable hepatocellular carcinoma (HCC). Percutaneous microwave ablative therapy, which is a relatively new technique, has the advantage in providing faster ablation of large tumors. This study aimed to evaluate microwave ablation in the treatment of large HCC (5-7 cm) and to assess its effect on local tumor progression, prognostic outcome and patients' survival.

METHODS

In all, 26 patients with large HCC lesions (5-7 cm) were managed in the multidisciplinary clinic of Kasr Al Ainy University hospital using microwave ablation. The treatment was performed with the patient under conscious sedation and analgesia and ultrasonography-guided using an HS AMICA microwave machine operating at frequency of 2450 MHz and a power up to 100 W. Multiple needle insertions were made in one or two sessions according to the size of the lesion. The complete ablation rate, local tumor progression and patients' overall survival were analyzed, and the efficacy and safety of MWA was evaluated.

RESULTS

Complete ablation was achieved in 19/26 (73.1%). Local tumor progression was recorded in five treated lesions (19.2%). Distant tumor progression within the liver was recorded in six patients (23.1%), with a mean survival of 21.5 months. No procedure-related major complications or deaths were observed.

CONCLUSIONS

Percutaneous microwave ablation is safe and effective in the treatment of large HCC tumors. Patients' survival and local tumor control were acceptable.

Microwave ablation versus transarterial chemoembolization in large hepatocellular carcinoma: prospective analysis

OBJECTIVE

Limited therapies are offered for large hepatocellular carcinoma (HCC). It carries dismal prognosis and efforts tried changing its management from a palliative to a curative mode. Transarterial chemoembolization (TACE) is a palliative procedure that may have survival benefit if compared to non-management of large lesions. Microwave ablation (MWA) has emerged as a relatively new technique with promise of larger and faster ablation. We aim to evaluate the efficacy and safety of percutaneous MWA versus TACE for large tumors (5-7 cm) and to assess their effects on local tumor progression and survival.

PATIENTS AND METHODS

Sixty-four patients with large lesions are managed in our multidisciplinary HCC clinic and were divided into two groups treated either by MWA or TACE. Complete response rate, local recurrence, de novo lesions, and overall survival analysis are compared between both procedures.

RESULTS

Both groups were comparable as regards the demographic and ultrasonographic features. MWA showed higher rates of complete ablation (75%) with fewer sessions, lower incidence of tumor recurrence (p = 0.02), development of de novo lesions (p = 0.03), occurrence of post-treatment ascites (p = 0.003), and higher survival rates (p = 0.04). The mean survival of the microwave group was 21.7 months with actuarial probability of survival at 12 and 18 months 78.2% and 68.4%, respectively. The mean survival of the TACE group was 13.7 months with actuarial probability of survival at 12 and 18 months being 52.4% and 28.6%, respectively.

CONCLUSION

MWA showed better results than TACE in the management of large HCC lesions.

Initial institutional experience of uncooled single-antenna microwave ablation for large hepatocellular carcinoma

AIM

To evaluate the safety, efficacy, and feasibility of a novel microwave generator, designed to deliver automatically adjusted energy by tissue permittivity feedback control into the tumour via an uncooled antenna, in patients with larger hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Fourteen patients with HCC >5 cm in diameter received surgical or percutaneous microwave ablation with more than 12 months of follow-up. Microwave ablation was performed using a 902-928 MHz generator at 28 W; a single 14 G antenna without water-cooled system was used. The patients were followed up with contrast-enhanced CT and serum alpha-foetoprotein to monitor for tumour recurrence at 1 month and then every 3 months after tumour ablation.

RESULTS

The follow-up duration for the 11 male and three female patients (mean tumour size 5.77 cm, range 5-7 cm; mean age 63.8 years) was 15.8 months. The mean ablation time was 2025 s (range 900-3600 s), and the mean ablation session was 2.5 (range 1-4). The complete ablation rate was 85% (17 of 20). Local recurrence rate was 5.8% (1 of 17). All patients survived and the morbidity and mortality rate was 21.4% and 0%, respectively.

CONCLUSIONS

Microwave tissue ablation using this novel system with tissue permittivity feedback control and a single uncooled antenna has a high complete ablation rate and lower morbidity. It proved to be a fast, easy, and effective option for ablation of large (>5 cm) tumours.

Complications of image-guided thermal ablation of liver and kidney neoplasms

Image-guided thermal ablation is a widely accepted tool in the treatment of a variety of solid organ neoplasms. Among the different techniques of ablation, radiofrequency ablation, cryoablation, and microwave ablation have been most commonly used and investigated in the treatment of liver and kidney neoplasms. This article will review complications following thermal ablation of tumors in the liver and kidney, and discuss the risks and clinical presentation of each complication as well as how to treat and potentially avoid complications.

Microwave ablation of hepatic malignancy

Microwave ablation is an extremely promising heat-based thermal ablation modality that has particular applicability in treating hepatic malignancies. Microwaves can generate very high temperatures in very short time periods, potentially leading to improved treatment efficiency and larger ablation zones. As the available technology continues to improve, microwave ablation is emerging as a valuable alternative to radiofrequency ablation in the treatment of hepatic malignancies. This article reviews the current state of microwave ablation including technical and clinical considerations.

Microwave ablation for hepatic malignancies: a call for standard reporting and outcomes

BACKGROUND

Clinical standards of reporting microwave ablation outcomes have not been defined with regard to ablation success, 90-day morbidity, local recurrence after ablation, and nonablation hepatic recurrence. We propose recommendations for microwave ablation reporting and quality standards.

METHODS

Literature review of clinical studies focusing on microwave ablation of primary and metastatic hepatic tumors was reported.

RESULTS

Ablation success remains the highest quality reporting standard with variations in nomenclature, but with a universal agreement of complete destruction of the target lesion within 1 month after initial microwave ablation. Local recurrence after ablation remains highly variable, with reports as low as 2.2% to as high as 22%; standards lack a common, clearly defined distance from the initial target ablated lesion and the requirement that the target lesion be defined as an ablation success before it can be called a recurrence. Nonablation hepatic recurrence, nonhepatic recurrence, and 90-day morbidity and mortality remain limited in the current literature.

CONCLUSIONS

Standardization of hepatic microwave ablation reporting standards are proposed. Current reporting standards in microwave ablation of hepatic malignancies are suboptimal and lack standardization for comparison across institutions.