Endobiliary radiofrequency ablation: promising but not fully standardized

Radiofrequency ablation (RFA) has a variety of indications for benign, premalignant, and malignant diseases. RFA induces tumor necrosis and possible enhancement of the immune response [1].

In the field of biliopancreatic endoscopy, the indications for RFA have evolved over the past decade. Pancreatic RFA delivery can be performed by endoscopic ultrasound with promising results, especially for small neuroendocrine tumors [2].

“The work of Inoue et al. presents promising results concerning stent patency and patient survival after endobiliary radiofrequency ablation for malignant hilar biliary obstruction – but RFA might not yet be ready for prime time.”

Intrabiliary RFA is applied by advancing dedicated catheters over the wire in order to deliver targeted treatment to biliary strictures. Proposed indications for endobiliary RFA are the treatment of malignant biliary strictures (common bile duct and hilum), the ablation of intraductal extension of ampullary adenomas after endoscopic snare papillectomy [3], and the recanalization of occluded self-expandable metal stents (SEMSs).

According to the available evidence, which comes mainly from observational studies, RFA can improve biliary stent patency and may also be associated with longer survival [4] [5]. Ablation of intraductal ampullary adenomas seems promising in selected cases, obtaining 70 % eradication after a 12-month follow-up [3]. The true advantage of RFA to recanalize occluded SEMS is not known due to the absence of a cost-effective analysis, especially when compared with insertion of a new SEMS.

In this issue of Endoscopy, Inoue et al. [6] evaluate a retrospective series of patients with malignant hilar biliary obstruction (MHBO) treated by endobiliary RFA and subsequent biliary drainage with two uncovered SEMSs. The authors included 41 consecutive patients with MHBO not related to compression from lymph node metastasis; the main MHBO etiologies were cholangiocarcinoma (65.9 %) and gallbladder cancer (22 %). The majority of patients (85.4 %) had complex Bismuth type III or IV hilar strictures. RFA was deployed before SEMS insertion using the Habib bipolar probe (EndoHPB; Boston Scientific, Marlborough, Massachusetts, USA) with 7 W of power for 90 seconds. Immediately after RFA, two uncovered SEMSs, 8 mm in diameter, were placed in the “target” left and right intrahepatic ducts in the side-by-side configuration, with the distal end above the level of the papilla. Technical success rate was 95.1 % (one failure to pass the RFA probe through the stricture and one failure to reach the target stricture). Early adverse events were limited to a single case of cholangitis (2.4 %), while the incidence of late adverse events, other than recurrent biliary obstruction (RBO), was 7.7 % (3/39; cholecystitis, nonocclusion cholangitis, and liver abscess). The rate of RBO (defined as recurrent jaundice and/or cholangitis along with biliary dilatation on imaging studies) was 38.5 % (15 /39), after a median time of 230 days. The authors had previously reported a shorter median patency time (140 days) when draining MHBO with bilateral SEMS placement without RFA [7]. Interestingly, Inoue et al. found that the median time to RBO was longer for strictures > 15 mm than those ≤ 15 mm (314 vs. 156 days; P  = 0.02), as a result of a better effect of RFA on longer strictures. This difference was attributed to the design of the Habib probe; the 8-Fr bipolar catheter has two 8-mm ring electrodes, placed 8 mm apart, thus obtaining a more effective ablation for strictures longer than 16 mm (see Fig. 4 in the paper [6]).

Recently, a dedicated RFA generator (Viva Combo; StarMed, Seoul, Korea) with 18 and 33 mm long RFA catheters was introduced [8]. This generator allows precise Watt setting, target temperature, and impedance control, whereas the Habib probe is connected to an electrosurgical unit in which only Watt setting is possible.

The work of Inoue et al. is relevant as it focuses on the application of endobiliary RFA in a selected group of patients with MHBO, demonstrates the safety of the procedure, and presents promising results concerning stent patency and patient survival.

Some issues are still open and need a more robust explanation. 1) The optimal power for endobiliary RFA is not well defined: the proposed range is 7–10 W for a duration of 90–120 seconds; standardization of these settings is expected. 2) Published series have included heterogeneous stricture etiology: it is possible that the best result with RFA can be achieved in cholangiocarcinoma compared with other biliary strictures secondary to extrinsic compression (i. e. pancreatic cancer, lymph node metastases). 3) Metastatic patients have been included in published series (i. e. 68 % in the Inoue paper): Can endobiliary RFA prolong survival in these patients? Is a patient with local disease that is nonoperable due to age or comorbidities the preferred candidate for RFA treatment? 4) Cases of delayed and fatal hemobilia, possibly secondary to the fall of the eschar after RFA, have been reported: the safety of RFA in the region of the hepatic hilum, where major vessels are present, needs further evaluation and adjustment of Watt and temperature. 5) RFA can enhance the immune response against the tumor [1] [2]: this interesting and promising effect requires further evaluation in the field of endobiliary applications.

In conclusion, continued investigations on endobiliary RFA is required including the testing of new catheters and generator settings, defining indications, and confirming the promising results. Maybe endobiliary RFA is not yet ready for prime time.

Publication History

Article published online:
24 June 2020

• References

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