Ablation Difficulty Score: Proposal of a new tool to predict success rate of percutaneous ablation for hepatocarcinoma
Conci S, D'Onofrio M, Bianco A, Campagnaro T, Martone E, De Bellis M, Longo C, Dedoni S, Vittoria D'Addetta M, Ciangherotti A, Pedrazzani C, Dalbeni A, Campagnola P, Mansueto G, Guglielmi A, Ruzzenente A.
Eur J Radiol. 2022 Jan;146:110097. doi: 10.1016/j.ejrad.2021.110097
Hepatocellular carcinoma (HCC) accounts for about 90% of primary liver cancer. Its incidence is increasing worldwide, representing the fourth most frequent cause of cancer-related death globally [1]. According to Barcelona Clinic Liver Cancer (BCLC) guidelines, local ablation is one of the curative treatment options available for HCC at the moment [2,3]. Success rates of local ablative techniques (LAT) range from 80% to 98,7% [4, 5, 6], regardless of the high rate of necrosis in the ablated area.
The authors of this study analyzed retrospectively the outcome of 585 nodules treated with radiofrequency ablation in 282 patients from 2010 to 2020, with the objective of developing an ablation difficulty score (ADS) to improve patient selection and treatment allocation. Ablation with microwave device, guided by CT-scan or fusion imaging or performed by laparotomy / laparoscopy were not included. Other exclusion criteria were the presence of macrovascular invasion and patients with follow up imaging not performed in their local radiology department.
Preoperative imaging, either CT or MRI, were used to measure the shortest distance between the edge of the nodule and the liver capsule, and to the major vascular structures. Nodules with distance ≤ 5 mm to vascular structures were defined perivascular, and those with distance ≤ 5 mm to liver surface sub-capsular.
A contrast-enhanced CT 30 days after the procedure was the imaging technique used to assess the ablation success. Incomplete ablation (IA) was defined as residual tumor on the edge of the ablated area. Failure ablation was considered after two consecutive procedures with IA. Ablation success was established as the absence of residual tumor after up to two consecutive procedures.
This study reported an ablation success rate of 85.5%. Univariate and multivariate analysis revealed that nodule’s size > 20 mm, isoechoic nodule appearance, sub-capsular location, perivascular location, and non-cirrhotic liver parenchyma were significantly related to failure ablation. Each one of these factors was awarded 1 point and the ADS was built up with a score from 0 to 5. Three categories of risk were established: low risk (ADS 0), intermediate risk (ADS 1), and high risk (ADS ≥ 2), with an ablation success rate of 93.5%, 85.8%, and 71.3% respectively. The cumulative local tumor progression (LTP) free survival rates at 1-year were 90.2%, 80.6%, and 72.3% for low, intermediate, and high-risk group, respectively. Only nodule size, isoechoic appearance, and perivascular location resulted to be independent factors for LTP free survival rates on univariate and multivariate analysis.
We believe that this study is relevant. On the one hand, LAT remains a widely used curative treatment for HCC thanks to its high success rate, feasibility and low postoperative morbidities [7,8]. On the other hand, the proposed ADS scoring system is a very simple and easy-to-use tool that provides additional and relevant information to guide HCC treatment decisions, reserving LAT in high-risk (ADS ≥2) nodules only for patients not suitable for surgery or liver transplantation.
The study had some limitations. Firstly, a potential risk of selection bias owing to the retrospective single-center design of this study. Secondly, only nodules treated with radiofrequency ablation were considered. Also, ablation with microwave devices or advanced local ablative techniques, such as ablation guided by fusion imaging, CT scan or CEUS, were not included in this study. The latter may explain the lower ablation success rate obtained for those nodules which location or imaging characteristics made it difficult to position the ablation needle.
In conclusion, the establishment of a score to assist in deciding the optimal treatment for HCC is a good step forward to improve patient selection, however, we believe that further studies are needed to address the limitations and to corroborate the results of this study.
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Ali Boukhoubza is a third-year radiology resident at the Hospital Universitari i Politècnic La Fe in Valencia, Spain. He completed his medical degree at University of Granada in 2018. He has a wide range of interests in interventional radiology with a special focus on interventional oncology and liver locoregional therapies.
Comments may be sent to: AliBoukhoubza@gmail.com