Review for 10.1186/s12876-020-01543-1 (2020)

Reviewer’s report
Title: 
Severe weight loss after minimally invasive oesophagectomy is associated
with poor 5-year survival in patients with oesophageal cancer
Version: 
1 
Date: 
17 May 2020
Reviewer's report:
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The papers main limitations are the derivation of the definition of severe weight
loss, and lack of clarity on preoperative weight loss and indications for enteral
nutrition support. Providing clarity on these would help.
Abstract and Introduction: 
Remove that MIE causes "less damage" to the
patients, this is not exactly proven except for culture positive pneumonia (TIME
trial) and "damage" moreover is not a good term.
Methods: 
1. Some clarity on why patients had FT and others did not is required.
Is there no Department criteria or consensus. 
There is inevitable bias introduced
here. Is is that the FT group had more severe weight loss preoperatively, no data
is provided, or considered by the surgeon to be at very high risk of complications
or poor outcome postoperatively?
2. What numbers of patients had nasojej feeding preoperatively, were they all in
FT group postoperatively?
3. Most studies will accept >10% of weight loss as severe malnutrition, you have
based yours on a post- hoc survival analysis as 17% rather than a priori criteria. 
4. Figure 1 should be in Results
Results: 
1. 
To convince re impact of severe weight loss on surival, all pathologic analyses
of severe and moderate weight loss need to be compared, in particular N stage, R
status, and severity of postoperative complications (Clavien Dindo III and IV).
The large difference in pneumonia could significantly impact on 3 month weight
loss , and yet this is not significant on multivariable analysis which is surprising.
It is also extraordinary that pN status was not significant, I have never seen this
before in any publication and would suggest this is rechecked. 
2. 
Since most people use 10% weight loss as significant, and approximately 56%
of your patients (Fig 1) had lost this by 3 months, please look at impact of this
cohort compared with the rest on outcomes, this would add to your data set. 
3. 
For the FT vs non FT analysis the reader will want more detail on preoperative
weight loss, nutritional support, major complications etc before firm conclusions
can be drawn.
Discussion:
1. A > 10% weight loss in over 50% of patients was observed, and over 20% >
17%, in an MIE series. 
This should be discussed directly in the context of
published studies on weight loss in open and MIE. For instance, Scarpa et al and
Wu etc. reporting that MIE prevents decrease in postoperative nutritional status,
your study clearly contradicts this and yet this is not directly discussed.
2. 
Too much of the Discussion (paragraph 3) is about SMI which is not part of
your study. 
The paper should be much more analytical about its own data, if
anything SMI can be mentioned where limitations are acknowledged.
3. 
Also, in paragraph 4, a number of statements are made, but really this should
relate to how it directly relates to your findings, 
did FT not help because the
patient cohorts were different in some way, or were there other factors. 
How can
FT improve outcomes in some studies, and not in yours, this needs to be more
fully addressed. 
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 recommend additional statistical review
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
Declaration of competing interests
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