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Percutaneous image-guided ablation is now a fairly well established first-line treatment modality for eligible hepatocellular carcinomas (HCCs). However, it is interesting that world-side, the adoption of ablation for HCC has had a checkered history with relatively slow acceptance. In retrospect several factors were likely contributary. Despite early attempts at standardization starting with the International Working Group on Image-guided Tumor Ablation,1,2 published outcomes were initially widely discrepant and highly heterogeneous in ablation device, imaging guidance methods, patient selection, provider’s medical specialty, and training background and experience. Now that percutaneous ablation is generally accepted as a potential first-line treatment for HCC, it is important to establish basic guidelines and continue to update such guidelines, across specialties and physician organizations. Therefore, it is commendable that in this issue, an expert panel consisting of both hepatologists and radiologists has reached and published an updated consensus practice guideline document for the performance of image-guided percutaneous ablation of HCCs.3
An interesting component of this document is that in addition to reviewing published literature, the consensus panel also incorporated survey data from existing practitioners, therefore recommendations took into account actual practice patterns of experienced providers. The following are selected recommendations and discussion points.
[Recommendations]
1. The indications… In addition to the stage of the disease, factors such as the location of the tumor, the feasibility of image guidance, whether combination therapy is used, the patient’s liver function, previous treatment history, and overall health status should be considered in an individualized approach.
Patient selection always needs to be considered in the light of not only society guidelines based on tumor stage, but also taking into account individual patient and tumor factors, as well as the provider skills and experience,4 and capabilities of available imaging and ablation devices. For example, while most tumors ≤3 cm are eligible for ablation, 3-5 cm tumors are not out-of-range for very experienced providers especially when coupled with high-end image-guidance5,6 or combined with trans-arterial embolization. Challenges posed by location and adjacent sensitive organs can often be mitigated by combined imaging and use of protective maneuvers.7-10
[Recommendations]
1. Dynamic contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) should be performed as pretreatment imaging tests for local ablation, and the interval between imaging and the procedure should preferably be within 1 month.
It is not uncommon that at the time of the ablation procedure, the tumor burden has changed sufficiently that there needed to be adjustments to the pre-planned technique. In practice depending on local environment, as it is in the United States, there is often delays in referral and scheduling of consults, insurance authorization, and then scheduling of the procedure itself. It may also be difficult to obtain updated scanning depending on insurance and financial burden on the patient. Nevertheless, it is notable that the consensus statement sets a threshold of 1 month for pre-procedure CT or MRI. Having this as a guideline can be very helpful in insurance authorization of repeat imaging, even if one was recently done but past the 1-month threshold.
[Recommendations]
1. Pre-treatment planning ultrasonography (US) examinations should be performed to assess the feasibility of local ablation and establish a treatment plan.
It is always helpful to perform technical feasibility assessment before making a major treatment decision. If a lesion is not visible on gray scale or contrast enhanced ultrasound, either the lesion is not an ablation candidate or the lesion need to be ablated by US fusion guidance or direct CT or MRI guidance depending on availability of equipment and skill set. In practices where all cases are done by CT alone or combined US/CT guidance, for example in many practices in the United States, a pre planning ultrasound may be useful but not mandatory
[Recommendations]
1. Prophylactic administration of antibiotics should be considered while performing local ablation in patients with a history of biliary tractrelated medical conditions.
In general, it is well recognized that patients with surgical bilio-enteric anastomoses are at high risk of abscess formation after liver tumor ablation. Studies have shown that the abscess rate can be mitigated by antibiotic use, including a proposed aggressive antibiotic regimen.11 However, there is not yet consensus as to the coverage and length of antibiotic prophylaxis necessary. The consensus document in this issue advocates a minimum guideline of 10 days of antibiotics, with the surveyed physicians mostly using cephalosporins. It is important however to note that abscess formation has been known to occur up to 2 months after ablation,12 therefore one may also consider extended antibiotic coverage.
[Recommendations]
1. The patient’s bleeding tendency should be reviewed, and any antiplatelet or anticoagulant agent being taken by the patient should be discontinued before local ablation.
For with-holding of anticoagulant agents and thresholds for correction of coagulopathy, the consensus document cites the 2022 Korean Liver Cancer Association-National Cancer Center (KLCA-NCC) practice guidelines for HCC as well as that from the International Society of Interventional Radiology. While it is unknown whether the technique of track ablation at the end of an ablation procedure decreases the risk of bleeding, it appears to have been universally adopted by all surveyed practitioners.
[Recommendations]
1. Local ablation procedures can be effectively performed under US guidance. Assistance can be provided through the use of CT, fluoroscopy, US/CT-MRI fusion techniques, US contrast agents, and artificial ascites/pleural effusion as needed.
The recommendation speaks to the essence of technical skills necessary for good ablation outcomes. Ultrasound is currently the dominant imaging guidance modality mostly because it is real-time. And issues of poor visibility are now mitigated by the availability of contrast agents. Interestingly in Korea Kupffer agents are commercially available and is the preferred contrast by most practitioners, while such agents are still not commercially available in the United States. Regardless, it is still not uncommon for lesions to be suboptimal in visibility, especially when such visibility needs to be complete throughout the entire lesion and adjacent tissue in order to achieve adequate safety margin. When such issues arise, it is best to enlist of the assistance of other imaging for combined visualization, fusion navigation, or switch to CT or MR guidance altogether.
It is interesting that the document discussed three of the more popular ablation modalities, radiofrequency ablation, microwave ablation, and cryo-ablation, with their advantages and disadvantages, without specifically endorsing any single one alone. This underscores the importance of imaging and targeting skills rather than the ablation energy source in determining the therapeutic outcomes of ablation procedures.
As for artificial ascites/pleural effusion, these are techniques amongst a growing set of adjunctive procedures that can protect adjacent sensitive organs or structures. These add-on procedures include thermocouple monitoring, balloon interposition, biliary perfusion, and artificial pneumoperitoneum. While these are admittedly more complicated and usually best done with CT assistance, they are nevertheless worthwhile to consider before precluding ablation as a potential treatment option.
[Recommendations]
1. Appropriate local and sedative anesthetic agents should be administered during the procedure to alleviate pain and ensure safe progress.
2. To prevent complications from the procedure and anesthesia, and to perform appropriate emergency measures, vitals, including oxygen saturation, pulse rate, blood pressure, and electrocardiogram should be monitored, and equipment necessary for resuscitation, including oxygen and a crash cart, should be prepared.
Pain control for ablation varies greatly between practices and regions. The survey conducted for development of this document showed that most operators administered sedatives themselves, while 31.4% performed procedures with an anesthesiologist, and 17.1% of operators used only local anesthetic primarily for cryoablation. Pain is not only a comfort issue for the patient, but also a safety issue, and local practice patterns appear to dictate how pain control is done. In the United States, most academic practices have migrated from conscious sedation to anesthesiologist supported deep monitored sedation or general anesthesia. One additional advantage of intubation general anesthesia is the ability to freeze diaphragmatic motion, which can be beneficial in challenging cases where precision image guidance relies on lack of motion.
[Recommendations]
1. Swift post-procedure imaging is required to determine the technical success and the occurrence of complications. Re-treatment or additional treatment may be performed based on the outcome.
This recommendation is critical to ensure good ablation outcomes. Immediate assessment with the intention to act on that assessment during the same treatment session or hospitalization has been shown to minimize local tumor recurrence.13 One of the most important technical goals of an ablation is to achieve a minimum of 5 mm circumferential safety or ablation margin, but there is virtually no way to do this accurately in three dimensions without good volumetric imaging assessment, even for experienced imagers with cognitive registration and interpretation skills. It remains to be seen how a multitude of 3D visualization software tools will be used to help in this assessment. In general, immediate post ablation imaging is done by contrast enhanced CT. If however MRI is available it is likely the best modality for direct assessment of the complete safety or ablation margin because of the “tumor ghost” effect embedded within a clearly demarcated ablation zone as well as taking into account the effect of tissue and tumor contraction if present.14,15
[Recommendations]
1. Appropriate evaluation, including additional imaging studies, must be performed to rule out serious complications if persistent abnormal symptoms and clinical signs are reported after local ablation.
Although major complications are rare, most respondents to the survey monitored patients carefully for 4-6 hours after ablation, with management of nausea, pain, and any complications. In most practices immediate follow up contrast enhanced CT is performed in this recovery period if not already done during the procedure itself.
[Recommendations]
1. Regular follow-up is necessary after local ablation, including imaging studies such as contrast-enhanced CT or MRI examinations, as well as blood tests that include tumor markers. It is also important to establish follow-up intervals…
Regular follow up is necessary not only to determine local treatment response and possible local tumor progression, it is also the continuation of the expected surveillance strategy for all patients with risk factors for HCC. The use of tumor markers is controversial in addition to imaging, although they can be more sensitive and specific than imaging alone in some patients in early detection of local recurrence or appearance of new tumor remote from the treated area.16 According to the survey of experienced providers in developing this document, general practice is to have the first follow up at 1 month post ablation, then 3-6 months intervals for at least 2 years.
The authors are to be commended in generating such practice guidelines as joint publications in their respective medical specialties. Although regional and practice pattern differences remain, the consensus allows and takes into account such differences, and drills down to basic principles that all ablationists can adhere to in order to provide high quality service to their patients.
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