Review for 10.1186/s12876-021-01715-7 (2021)

Reviewer’s report
Title: 
Very-Low-Dose Aspirin and Surveillance Colonoscopy is Cost-effective
in Secondary Prevention of Colorectal Cancer in Individuals with Advanced
Adenomas: Network Meta-analysis and Cost-effectiveness Analysis
Version: 
0 
Date: 
24 Jan 2021
Reviewer's report:
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In the present manuscript, the authors aimed to determine if chemo-preventive
agents (CPAs) are effective in protecting high-risk individuals from getting a
recurrence of advanced colorectal adenomas (ACAs) after initial polypectomy.
The authors have used systemic review with network meta-analysis of included
randomized clinical trials. The authors have developped a Markov model to
evaluate the long-term clinical and economic benefits of using the chosen CPAs.
This paper is well written and structured. 
However, there are some comments to
make in this regard: 
1. In their meta-analysis, the authors included randomized trials with a follow-up
of at least one year. in their markov model, the authors evaluated a colonoscopy
interval of 3 and 5 years associated with aspirin use. is there not a bias? 
2. the authors hypothesized that the basic colonoscopy succeeded in removing all
adenomas after polypectomy at 100%. Unfortunately, this is not the case in real
life, especially for the right colon. What would be the result in case of an
incomplete colonoscopy? Would the interval of three be valid. 
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
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from apparent manipulation?
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