Efficacy of a Novel Dual-Layer Plastic Stents for Malignant Biliary Obstruction

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I have the following comments to the authors- 

1. In introduction please add appropriate references- for example- in cholangiocarcinoma of the hilar region, various factors influence the choice of biliary drainage method- Lacking reference. Similarly- Endoscopic nasobiliary drainage (ENBD) is recommended for preoperative drainage because of its lower incidence of cholangitis.- lacking reference 

2. No mention of informed consent or IRB or ethics approval. 

3. The results are lacking clarity. No mention about patient demographics- age, BMI, other chronic conditions, Medications etc. Please describe the the 2 patient populations and present them. 

Author Response

Reviewer1

1. In introduction please add appropriate references- for example- in cholangiocarcinoma of the hilar region, various factors influence the choice of biliary drainage method- Lacking reference. Similarly- Endoscopic nasobiliary drainage (ENBD) is recommended for preoperative drainage because of its lower incidence of cholangitis.- lacking reference 

Thank you for your comments. We have added references in introduction. (Page 5, Line 5,9,12)

2. No mention of informed consent or IRB or ethics approval. 

   Thank you for your comments. We have added the details in Methods (Page 9, Line 16-20)

3. The results are lacking clarity. No mention about patient demographics- age, BMI, other chronic conditions, Medications etc. Please describe the 2 patient populations and present them.

Thank you very much for pointing out an important issue. The explanation of Table1 and 2 added to the results. (Page 10, Line 4-6, 15-16) However, as height and weight were not collected this time, BMI could not be calculated.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In the present retrospective study Sekine et al compared a novel two layers plastic stent covered with PTFE to traditional stent (group R vs IS) for malignant biliary obstruction. They did not find any difference in stent re-obstruction. Main comments:

1) Considerring the main result, the sentence in 2^nd line of Conclusions of the Abstract is in disagreement and should be changed.

2) It is unclear whether PTFE stent was the IS or R group.

3) It is unclear which is the difference between placing the stent “above” vs “across” the papilla. All plastic stents should be placed inside the papilla.

4) Please check Table 1, age may be missing. Furthermore, in the table Authors should also report Bismuth classification.

5) Non cases of pancreatic head cancer?

6) In the “statistics” paragraph, there is no mention of Kaplan-Meier curves.

7) Resolution quality of fig 3 is low.

8) Some p values in table 2 are absent.

9) Considering that the main point of PTFE is that it prevents biofilm formation, a more interesting outcome that should be analyzed is infection/cholangitis after stent placement.

10) In case of RBO, was a metallic stent replaced?

Comments on the Quality of English Language

See points 2 and 3

Author Response

Reviewer2

• Considerring the main result, the sentence in 2^ndline of Conclusions of the Abstract is in disagreement and should be changed.

Thank you for your comment. In this study, despite the R group being across the papilla, there was no difference in stent patency duration compared to the IS group. I have made the necessary revisions for clarity. (Page 4, Line 7-8)

• It is unclear whether PTFE stent was the IS or R group.

Thank you very much for pointing out an important issue. PTFE stent was the R group. We added the detail explanation in method. (Page 7, Line 16-17 )

• It is unclear which is the difference between placing the stent “above” vs “across” the papilla. All plastic stents should be placed inside the papilla.

Thank you for your comment. I believe this is an important point. I have added explanations for the terms "above" and "across" in the description of each stent in the Methods section. (Page 7, Line 24-25, Page 8, Line 1-2, 11-13)

• Please check Table 1, age may be missing. Furthermore, in the table Authors should also report Bismuth classification.

Thank you for your comment. We did not collect information on height or weight, so we could not include BMI. The Bismuth classification was not mentioned because this study was not limited to hilar cholangiocarcinoma; it also included cases of limited intrahepatic bile duct obstruction due to HCC and intrahepatic cholangiocarcinoma. (Page 10, Line 11-14) If we are able to accumulate more cases, we would like to conduct an analysis focusing solely on hilar bile ducts and consider the Bismuth classification.

• Non cases of pancreatic head cancer?

This time, we limited the fucus to the obstruction of the hilar and intrahepatic bile ducts, so pancreatic head cancer was not included.

• In the “statistics” paragraph, there is no mention of Kaplan-Meier curves.

Thank you for your comment. I have added a mention of Kaplan-Meier curves in the Statistical Analyses section. (Page 9, Line 1-6, 12-14)

• Resolution quality of fig 3 is low.

   Thank you for your comments. I increased the resolution of fig 3.

• Some p values in table 2 are absent.

Thank you for your comments. We added N.S. (Not Significant) in table 2.

• Considering that the main point of PTFE is that it prevents biofilm formation, a more interesting outcome that should be analyzed is infection/cholangitis after stent placement.

    Thank you very much for pointing out an important issue. In this study, we excluded regular stent exchanges and focused on comparing the incidence of stent obstruction associated with cholangitis. To clarity, we updated the "RBO rate" in Table 2 to "acute cholangitis rate" and added an explanation in the methods section.

• In case of RBO, was a metallic stent replaced?

   Thank you for your comments. In this study, we did not address re-intervention; however, in all cases of obstruction due to cholangitis, the treatment was switched to either endoscopic biliary stenting (EBS) or endoscopic nasobiliary drainage (ENBD), with no metallic stents being placed.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have answered all the questions. 

Reviewer 2 Report

Comments and Suggestions for Authors

Answers were ok