Review for 10.1186/s12876-021-01692-x (2021)

Reviewer’s report
Title: 
Nomogram for predicting overall survival in colorectal cancer with distant
metastasis
Version: 
2 
Date: 
10 Feb 2021
Reviewer's report:
PEER REVIEWER ASSESSMENTS: 
OBJECTIVE - Full research articles: is there a clear objective that addresses a
testable research question(s) (brief or other article types: is there a clear
objective)?
Yes - there is a clear objective
DESIGN - Is the current approach (including controls and analysis protocols)
appropriate for the objective?
Yes - the approach is appropriate
EXECUTION - Are the experiments and analyses performed with technical rigor
to allow confidence in the results?
Yes - experiments and analyses were performed appropriately
STATISTICS - Is the use of statistics in the manuscript appropriate?
Yes - appropriate statistical analyses have been used in the study
INTERPRETATION - Is the current interpretation/discussion of the results
reasonable and not overstated?
Yes - the author's interpretation is reasonable
OVERALL MANUSCRIPT POTENTIAL - Is the current version of this work
technically sound? If not, can revisions be made to make the work technically
sound?
Probably - with minor revisions
PEER REVIEWER COMMENTS: 
GENERAL COMMENTS: 
The paper is well written and uses the standard of care methods for developing
and creating a nomogram. ROC curves and area under the curve statistics were
evaluated. Calibration was examined. The results are limited by the fact that the
majority of the sample was excluded due to missing data (26,850 with missing
data, 14,197 with complete data). Hence, it is unknown how representative the
sample is of patients with colorectal cancer with distant metastasis. Many
variables may have been missing among people who did not receive much
treatment and hence did not have complete pathologic information. It might not
be unusual for those with advanced colorectal cancer to have limited therapy.
ADDITIONAL REQUESTS/SUGGESTIONS: 
Minor comments: Commas are misplaced in the flow diagram. 
The authors might have a stronger mention that the chemotherapy and radiation
information in SEER is incomplete and this is a limitation of using those
variables (https://seer.cancer.gov/data/ChemotherapyRadiation-SEER-
DUA.pdf).
It might be worth noting that those who did not receive surgery or chemotherapy
might not necessarily have been appropriate candidates for such therapy. Hence,
the surgical and chemotherapy estimates might not be causal. That is, if someone
is not an appropriate candidate for surgery or chemotherapy, receiving such
therapy might not improve their outcomes as the nomogram would suggest.
There is selection bias in the receipt of such therapy; SEER data might not
necessarily allow one to adjust for all variables associated with selection bias.
The authors might mention that there could be substantial missing data bias due
to the amount of missing data. The results might have been different had there
been more complete data.
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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?
Yes
Is the use of statistics and treatment of uncertainties appropriate?
Yes
Is the presentation of the work clear?
No
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes