Title: Primary Tumor Resection with or without Metastasectomy for Left- and Right-sided Stage
IV Colorectal Cancer: An Instrumental Variable Analysis
Version: 1 Date: 20 Nov 2021
Reviewer's report:
Overall study has number of strengths, including large sample and sound statistical analysis.
Although this data is already known, such studies add value to existing data especially when
considering lack of strong randomised studies. Authors should be commended for this effort.
Line6- don’t think you can form a definite conclusion like this from this retrospective data. This
is well explained in discussion. But don’t think you can make definite conclusions in abstract.
Suggest use a different acronym for primary tumour resection plus metastatsectomy. Current
form is confusing and difficult to correlate for the reader.
Consistent with the use of MTR and metastasectomy .
Line 9-12 : previous studies have examined this to some extent ; improved
OS after metastasectomy in left than right colon cancers https://doi.org/10.1016/
j.currproblcancer.2020.100637.
What are the unmeasured variables author trying to address by IV method ? Could author make
it more clearer in the methods ?
Why Fig 1 is in pg 16 and 20- I assume this will be corrected later.  Author to review this to
avoid duplication.
Figure 3 : PTR v no PTR  or PTR v no surgery –  Could author make it clear .
Metachronous disease were not included in this study-I wonder whether database doesn’t capture
this ? this is the vast majority of stage 4 CRC therefore exclusion of this cohort is a major
limitation of this study. I suggest to mention this in the abstract and in methods.
Other limitation is the absence of mutation status and not considering this in multivariate model
as these are important prognostic factors. https://doi.org/10.1080/0284186X.2018.1487581. It
will be important to mention this in the limitations.
Is there an approval number from SEER database  or local Ethics approval for this retrospective
study ? Better to quote the reference this in the text.
Title: Primary Tumor Resection with or without Metastasectomy for Left- and Right-sided Stage
IV Colorectal Cancer: An Instrumental Variable Analysis
Version: 1 Date: 20 Nov 2021
Reviewer's report:
Overall study has number of strengths, including large sample and sound statistical analysis.
Although this data is already known, such studies add value to existing data especially when
considering lack of strong randomised studies. Authors should be commended for this effort.
Line6- don’t think you can form a definite conclusion like this from this retrospective data. This
is well explained in discussion. But don’t think you can make definite conclusions in abstract.
Suggest use a different acronym for primary tumour resection plus metastatsectomy. Current
form is confusing and difficult to correlate for the reader.
Consistent with the use of MTR and metastasectomy .
Line 9-12 : previous studies have examined this to some extent ; improved
OS after metastasectomy in left than right colon cancers https://doi.org/10.1016/
j.currproblcancer.2020.100637.
What are the unmeasured variables author trying to address by IV method ? Could author make
it more clearer in the methods ?
Why Fig 1 is in pg 16 and 20- I assume this will be corrected later.  Author to review this to
avoid duplication.
Figure 3 : PTR v no PTR  or PTR v no surgery –  Could author make it clear .
Metachronous disease were not included in this study-I wonder whether database doesn’t capture
this ? this is the vast majority of stage 4 CRC therefore exclusion of this cohort is a major
limitation of this study. I suggest to mention this in the abstract and in methods.
Other limitation is the absence of mutation status and not considering this in multivariate model
as these are important prognostic factors. https://doi.org/10.1080/0284186X.2018.1487581. It
will be important to mention this in the limitations.
Is there an approval number from SEER database  or local Ethics approval for this retrospective
study ? Better to quote the reference this in the text.
Please review this paper.
user
Title: Primary Tumor Resection with or without Metastasectomy for Left- and Right-sided Stage
IV Colorectal Cancer: An Instrumental Variable Analysis
Version: 1 Date: 20 Nov 2021
Reviewer's report:
Overall study has number of strengths, including large sample and sound statistical analysis.
Although this data is already known, such studies add value to existing data especially when
considering lack of strong randomised studies. Authors should be commended for this effort.
Line6- don’t think you can form a definite conclusion like this from this retrospective data. This
is well explained in discussion. But don’t think you can make definite conclusions in abstract.
Suggest use a different acronym for primary tumour resection plus metastatsectomy. Current
form is confusing and difficult to correlate for the reader.
Consistent with the use of MTR and metastasectomy .
Line 9-12 : previous studies have examined this to some extent ; improved
OS after metastasectomy in left than right colon cancers https://doi.org/10.1016/
j.currproblcancer.2020.100637.
What are the unmeasured variables author trying to address by IV method ? Could author make
it more clearer in the methods ?
Why Fig 1 is in pg 16 and 20- I assume this will be corrected later.  Author to review this to
avoid duplication.
Figure 3 : PTR v no PTR  or PTR v no surgery –  Could author make it clear .
Metachronous disease were not included in this study-I wonder whether database doesn’t capture
this ? this is the vast majority of stage 4 CRC therefore exclusion of this cohort is a major
limitation of this study. I suggest to mention this in the abstract and in methods.
Other limitation is the absence of mutation status and not considering this in multivariate model
as these are important prognostic factors. https://doi.org/10.1080/0284186X.2018.1487581. It
will be important to mention this in the limitations.
Is there an approval number from SEER database  or local Ethics approval for this retrospective
study ? Better to quote the reference this in the text.
assistant