Review for 10.1186/s12876-018-0861-4 (2018)

Reviewer ’s report  
Title: Title of Article: Synchronous polypectomy during endoscopic diagnosis of colorecta l 
cancer - Is the risk of tumour implantation at the polypectomy site significant?  
 
Version: 1 Date: 18 Jul 2018  
 
Reviewer: Michael J. Bartel  
 
Reviewer's report:  
I would like to thank the editor to consider me for reviewing this manuscript.  
 
Tan and colleagues report their results of a retrospective study analyzing the risk of 
metachronous colorectal cancer at prior polypectomy sites. Generally the authors found a low 
risk of metachronous cancer in such sites, with a cancer incidence comparabl e with rates of 
incomplete resection and missed polyps as previously reported by Pohl et al. (Clin Gastroenterol 
Hepatol. 2010 Oct;8(10):858 -64. Colorectal cancers detected after colonoscopy frequently result 
from missed lesions. Pohl H).  
 
This is an impor tant topic and for sure worth to be reported.  
 
However, the major drawback in my opinion is the study concept. It is a rather far -fetched 
comparison between cohorts with complete polypectomy and a cohort with only some removed 
polyps. This is also acknowle dged by the authors in the discussion, as they did not have follow 
up data of all ~3000 patients with cancer resection and no polypectomy. This raises the question 
if such a comparison in this study is valid and if any conclusions can be drawn, beside the fact 
that overall the risk of metachronous colorectal cancer is low as stated above.  
 
I think that the quality of the study could be substantially improved is the authors could provide 
histologic data and genetic mutations of the metachronous colorectal ca ncer and if they were 
100% similar with the prior resected cancer.  
 
Additional suggestions regarding the study conclusions. Based on the study concept and results, I 
don't think that the authors can conclude that it is not contraindicated to remove synchro nous 
polyps and to apply caution to polyps with 5 cm of the primary tumor.  
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
Yes 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
No 
Are the conclusions drawn adequately supporte d by the data shown?  
If not, please explain in your comments to the authors.  
Yes 
Are you able to assess any statistics in the manus cript or would you recommend an 
additional statistical review?  
If an additional statistical review is recommended, please spe cify what aspects require further 
assessment in your comments to the editors.  
I am able to assess the statistics  
Quality of written English  
Please indicate the quality of language in the manuscript:  
Acceptable  
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
1. Have you in the past five years received reimbursements, fees, funding, or salary from an  
organisation that may in any way gain or  lose financial ly from the publication of this 
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financially from the publication of this manuscript, either now or in the future ? 
3. Do you hold or are you currently applying for any patents  relating to the content of the 
manuscript?  
4. Have you received reimbursements, fees, funding, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
5. Do you have any other financial competing interests?  
6. Do you have any non -financial competing interests in relation to this paper?  
If you can answer no to all of the above, write 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
'I declare that I have n o competing interests  
 
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