Review for 10.1186/s12876-021-02066-z (2022)

Reviewer’s report
Title: 
Trend of geographical distribution of stomach cancer in Iran from 2004-
2014
Version: 
0 
Date: 
22 Feb 2021
Reviewer's report:
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General Comment. 
This manuscript titled "Trend of geographical distribution of stomach cancer in
Iran from 2004-2014" is a descriptive work, which shows the geographic pattern
of gastric cancer (GC) in Iran.
It uses mapping techniques to illustrate the spatial distribution of GC incidence
rates. As the authors mention, the results are useful information to better
understand the etiology of the disease.
Unfortunately, the authors do not report any results regarding to some possible
conditioning factors of incidence pattern, such as the distribution of Helicobacter
pylor infection or dietary and nutritional habits, including environmental ones,
recognized as promoters of the occurrence. This limits the scope of the
inferences and apparently biases the discussion that the authors present in the
last section.
Background:
Please, update these references. Please update the references. The authors cite
that in the year 2020 .... (page 2, line 30) and use a 2016' publicatio. 
There is abundant and updated bibliography about the epidemiology of gastric
cancer, the authors should make an effort to achieve a more interesting
introduction in this regard.
In my opnion, authors use and abuse 
two or three references in the background
item and that detracts from the quality of 
work.
Methods:
The period of study was 2004-2014. Why the authors did use provinces
population from the 2012 national census? 
They should have used a previous census, their intermediate projections, and the
2012 census. This is an important issue for calculating incidence rates.
The authors do not mention how they calculate incidence rates over time. Is it
annual? for five years? In the next item refer to the rates joining 10 years. why?
Is it due to the instability of the casuistry that the tumor registry receives? With
this decision, the authors lose the possibility of describing the longitudinal
pattern in time associated with the spatial pattern.
The authors could have estimated indices to identify spatial aggregation, or non-
randomness of the occurrence of GC.
How do the authors verify the differences between the rates? 
Which test or statistical model did they use? the statistical aspects are poorly
described. 
This methodological aspect is very incomplete.
Results:
The third paragraph of Results 
cannot be understood since the statistical tools to
achieve these results are not explicit.
Tables and figures should be improved in their design and edition.
Discussion:
The Discussion is very ambitious in terms of the results obtained and far exceeds
the inferences made. As I mentioned previously, this is a purely descriptive work
and the authors should consider the limitations of the results achieved. Although
it is extremely useful information for the Public Health of the country studied, it
is necessary to have other studies to justify some of the lines outlined in this
section.
Reference:
References must be checked.
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Declaration of competing interests
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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?
Yes
Are the methods sufficiently described to allow the study to be repeated?
No
Is the use of statistics and treatment of uncertainties appropriate?
No
Is the presentation of the work clear?
Yes
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
No