Review for 10.1186/s12876-018-0926-4 (2019)

Reviewer ’s report  
 
Title:  Cancer ri sk in microscopic colitis: A retrospective cohort study  
 
Version: 0 Date: 19 Sep 2018 
 
Reviewer:  Klas Sjöberg  
 
Reviewer’s report:  
 
The article reports cancer cases in a cohort consisting of 221 patients with microscopis colitis 
(MC). In view of the lack of investigat ions about cancer in MC the article provides valuable 
information about this matter. There are however some aspects that need to be considered.  
 
 
Major  
 
The patients were recruited from a tertiary center. Are there any risk of selection bias, i.e. that 
only more severe cases have been identified?  
 
Comparisons were made with patients undergoing screening colonoscopy, but the cohorts differ 
significantly as can be seen in Table 2. Another comparison was made with the SEER program 
from USA. Couldn't data from the same region be used? There are variatio ns in cancer incidence 
depending on location that could lead to skewed results.  
 
From the data it is concluded that there is no increased cancer risk. The population consists of 
about 200 patients. Based on the cancer incidence the number of patients is ra ther small. 
Conclusions may be drawn when it comes to cancer types that are prevalent in the population but 
not for those that appear more seldom.  
 
The median age of the patients was 64 years (IQR 54 -71). Since most cancers are diagnosed after 
the age of 7 0 I think that the sentence "life time risk" is not quite accurate.  
 
In this investigation the risk for cancer during the life span (until 64 years) is stated. Both 
incident and prevalent cases are included. Consequently, there is no possibility to conside r any 
potential causality; the cancer cases can precede or proceed the onset of MC and the possibility 
of any relationship is hard to establish had there been any increase of any cancer.    
 
 
Minor  
 
Statistics: "Continuous variables are summarized using means " but on page 8 age is reported 
with median values.  
 
Page 7, top, the verb should be in past tense.  
 
Are the  methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
No 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Yes 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
 
Yes 
 
Are you able to assess any statistics in the manuscript or would you recommend an 
additional statistical review?  
If an additional statistical review is recommended, please specify 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 financially from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that may in any way gain or lose 
financially from the public ation 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 no competing interests'  
 
I agree to the open peer review policy of the journal. I understand that my name will  be included 
on my report to the authors and, if the manuscript is accepted for publication, my named report 
including any attachments I upload will be posted on the website along with the authors' 
responses. I agree for my report to be made available unde r an Open Access Creative Commons 
CC-BY license ( http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments 
which I do not wish to be included in my named report can be included as  confidential comments 
to the editors, which will not be published.  
 
I agree to the open peer review policy of the journal