Reviewer's report
Title:Family history of cancer on survival of patients with gastrointestinal cancer
in northern Iran, using frailty models
Version: 2Date:12 April 2011
Reviewer: Tron Anders Moger
Reviewer's report:
I think that the arguments for using parametric models are clearer now, as it is
established that the assumption of proportional hazards is violated in the Cox
model. This information was missing in the original manuscript. I do not see any
obvious methodological errors in the revised manuscript. I have a couple of
suggestions, though:
1. Table III is very large. You have established that the log-logistic model with
gamma frailty provides the best fit to the data. Why not present the regression
results for this model only in table III, instead of still using space on the
exponential, Weibull and lognormal models?
2. The legend for figures I and II has been improved in the revised manuscript.
However, the legend for Figure II is now very long, and some of it might be
moved to the text e.g. in the second paragraph on p. 7. Also, I expect that all
figures in Figure II show the residual for models with gamma frailty? This is not
clear from the figure legend.
Some sentences still need re-phrasing. For example, I do not understand what
the authors are trying to say in the following two sentences (p. 9, last paragraph):
These models are relatively new in survival and widely studied in the 1990's and
now the subject of many investigations has been allocated. Technical problems
in estimating the parameters have been caused the Cox model to be used less.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Reviewer's report
Title:Family history of cancer on survival of patients with gastrointestinal cancer
in northern Iran, using frailty models
Version: 2Date:12 April 2011
Reviewer: Tron Anders Moger
Reviewer's report:
I think that the arguments for using parametric models are clearer now, as it is
established that the assumption of proportional hazards is violated in the Cox
model. This information was missing in the original manuscript. I do not see any
obvious methodological errors in the revised manuscript. I have a couple of
suggestions, though:
1. Table III is very large. You have established that the log-logistic model with
gamma frailty provides the best fit to the data. Why not present the regression
results for this model only in table III, instead of still using space on the
exponential, Weibull and lognormal models?
2. The legend for figures I and II has been improved in the revised manuscript.
However, the legend for Figure II is now very long, and some of it might be
moved to the text e.g. in the second paragraph on p. 7. Also, I expect that all
figures in Figure II show the residual for models with gamma frailty? This is not
clear from the figure legend.
Some sentences still need re-phrasing. For example, I do not understand what
the authors are trying to say in the following two sentences (p. 9, last paragraph):
These models are relatively new in survival and widely studied in the 1990's and
now the subject of many investigations has been allocated. Technical problems
in estimating the parameters have been caused the Cox model to be used less.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
Please review this paper.
user
Reviewer's report
Title:Family history of cancer on survival of patients with gastrointestinal cancer
in northern Iran, using frailty models
Version: 2Date:12 April 2011
Reviewer: Tron Anders Moger
Reviewer's report:
I think that the arguments for using parametric models are clearer now, as it is
established that the assumption of proportional hazards is violated in the Cox
model. This information was missing in the original manuscript. I do not see any
obvious methodological errors in the revised manuscript. I have a couple of
suggestions, though:
1. Table III is very large. You have established that the log-logistic model with
gamma frailty provides the best fit to the data. Why not present the regression
results for this model only in table III, instead of still using space on the
exponential, Weibull and lognormal models?
2. The legend for figures I and II has been improved in the revised manuscript.
However, the legend for Figure II is now very long, and some of it might be
moved to the text e.g. in the second paragraph on p. 7. Also, I expect that all
figures in Figure II show the residual for models with gamma frailty? This is not
clear from the figure legend.
Some sentences still need re-phrasing. For example, I do not understand what
the authors are trying to say in the following two sentences (p. 9, last paragraph):
These models are relatively new in survival and widely studied in the 1990's and
now the subject of many investigations has been allocated. Technical problems
in estimating the parameters have been caused the Cox model to be used less.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.
assistant