New milestone for clinical research about biliary drainage

Abstract

Endoscopic bile duct stenting has been the first-line treatment for bile duct obstruction, regardless of resectability or benign/malignant status,^1-3 although the criteria for evaluating the outcome of bile duct stents have not been adequately explored. For example, since the definition of stent occlusion varied across different articles, a meta-analysis of bile duct stent outcomes was summarized as stent dysfunction in terms of results. Furthermore, while stent occlusion due to tumor invasion was the main stent dysfunction in the case of inserted plastic stents or uncovered self-expandable metallic stents (SEMS), the advent of covered SEMS has made it necessary to consider stent migration or dislocation as a stent dysfunction.^{4, 5} In this context, a need existed for common definitions regarding procedure-related early outcomes for stents, outcomes of stents during follow-up, and adverse events. Previous TOKYO criteria defined terms associated with the technical and clinical success of biliary stenting, recurrent biliary obstruction (RBO) and related factors, and adverse events.⁶ Technical success was defined as the ability of the stent to adequately bypass the planned bile duct stenosis site, and clinical success was defined as a normal or 50% reduction in total bilirubin levels within 14 days of stent placement. In addition, RBO was defined as an outcome measure, including occlusion or deviation, used to assess the duration of stent function from the date of stent placement. An important aspect of RBO was that it focused on symptoms rather than stent patency alone. The time of symptom recurrence due to stent occlusion or deviation was specified as the time of onset of RBO, and this time point was to be used for assessment. The causes of obstruction of the RBO, such as internal growths associated with tumor growth, tumor growths on the edge of the stent, biliary debris or food residues, the direction of stent dislocation or migration (intrahepatic bile duct or duodenal papillary side), and whether pancreatitis or cholecystitis was present, were to be described separately. In addition, items on survival and contingencies other than RBOs have been created and described uniformly to provide an overall clinical picture from the results of clinical studies.

The progress of biliary drainage over the past decade has been so rapid that it has become increasingly difficult to cover it in the previous TOKYO criteria. For example, balloon endoscopy-assisted endoscopic retrograde cholangiopancreatography (ERCP) for cases with altered anatomy has become widely used.⁷ In ERCP for patients with altered anatomy, the rate of reach to the bile duct orifice should be included in the assessment of technical success.⁸ Endoscopic ultrasound-biliary drainage (EUS-BD) is also widely recognized as a common procedure. It does not bypass the bile duct stricture; therefore, the definition of technical success for EUS-BD differs from that for transpapillary biliary drainage.^{9, 10} Plastic stents are also being replaced more regularly in an increasing number of cases in anticipation of shorter periods of occlusion than metal stents. Cholangitis without bile duct obstruction was an important indication for biliary drainage, and the functional success of bile duct stent placement for cholangitis also needed to be defined. A major issue with the previous TOKYO criteria is the lack of definition for clinical success in cases of cholangitis. Clinical success for cholangitis depends on the individual condition, which requires a tailored definition. Revision of the previous TOKYO criteria was desired in response to the significant changes in the environment surrounding biliary drainage.

In this issue of Digestive Endoscopy, Isayama et al.¹¹ reported new TOKYO criteria, including recent advances in biliary drainage and redefined terms related to biliary drainage. The new TOKYO criteria have recently been revised by Isayama et al. for the first time in 10 years.¹¹ Several key points of revision in the new TOKYO criteria can be identified. The new TOKYO criteria categorized the indications into obstructive jaundice and cholangitis and, as before, differentiated the success of biliary drainage into technical and clinical success with bile duct drainage. In the previous TOKYO criteria, it was defined as functional success; however, in the new TOKYO criteria it has been redefined as clinical success. Clinical success has been defined as a decrease or normalization of total bilirubin levels to ≤50% within 14 days in jaundice cases and improvement of cholangitis in cholangitis cases. The new TOKYO criteria further defined the stent-demanding time, with stent improvement during this stent-demanding time as the objective of biliary treatment using a stent. Other additions include the division of the stenosis site into distal and hilar bile duct stenoses, EUS-BD, biliary drainage with small bowel endoscopy for the postoperative intestinal tract, benign bile duct stenosis, definition of intentional stent replacement, and bile duct ablation. Particularly, EUS-BD is a new item, and the route of puncture may be from various sites, including the stomach, duodenum, and small intestine. Adverse events were also described separately for RBOs and other types. In addition, the duration of the late adverse event has been set at 30 days to enable the comparison and examination of early and late adverse events. Recently, neoadjuvant chemotherapy (NAC) for pancreatic cancer has become more common, and the induction rate and discontinuation of NAC due to stent obstruction have also been specified. Therefore, as a basis for further development of biliary drainage in the future, better clinical trials are expected to be conducted, and evidence should be properly evaluated. We hope that this new biliary drainage assessment criteria will be a milestone.

Author A.K. is an Associate Editor of Digestive Endoscopy.

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