Review for 10.1186/s12876-017-0694-6 (2017)

Reviewer ’s report  
 
Title:  Primary tumor location predicts poor clinical outcome with cetuximab in RAS wild -type 
metastatic colorectal cancer  
 
Version: 0 Date: 31 May 2017 
 
Reviewer:  M. Peeters  
 
Reviewer’s report:  
 
In this manuscript, the authors describe the impact of primary tumor location in RAS WT 
patients treated with cetuximab as salvage treatment. Therefore, a retrospective analysis was 
performed on 170 RAS WT  patients. Mutation analysis for KRAS, NRAS, BRAF, and PIK3CA 
was performed using the Sequenom MassARRAY technology platform (OncoMap). Tumor 
location was determined and Kaplan Meier analyses were performed for overall and progression -
free survival.  
 
Overal l, this article is scientifically valid, performed with suitable methods. However, the 
number of patients with right colon cancer are rather limited.  
 
 
Essential comments to the author:  
 
- General remark: Numbers of patients with RC are very small (n=23) fo r the RAS WT 
population. It is mentioned once in the conclusion, but please be cautious with conclusions. 
Especially when subpopulations are being studied, for example in the BRAF mutant population 
the number of patients with RC is small (n=9 for RC and n= 8 for LC). You report no significant 
difference, but I wonder whether it is possible to reach statistical significance with these low 
numbers. I would suggest to mention the patient numbers in your results section. Same remark 
for the BRAF WT population (n =14 for RC). I would suggest to mention also in the results 
section that the amount of patients is rather small.  
 
- You mention prognostic and predictive value of PTL in introduction and discussion. Recently, 
many studies have been published on the predict ive value of PTL on anti -EGFR therapy where 
the anti -EGFR arm is compared to a control group (other treatment arm). I would suggest to 
discuss these studies. There was a special session on this topic on last year's ESMO congress.  
 
- There are 2 different abstracts (one on the first page, one on page 3). In the results section of 
the abstract on the first page, the PFS results are different than in the results section of the 
manuscript. Same for the p -values for both PFS and OS.  
 
- Material & Methods, p7, b elow Tumor locations: hepatic flexure should be mentioned for RC 
group (compare with Figure 1).  
 
- Discussion, halfway p11: when referring to NCIC CO.17, it is stated: …, showed that benefit in 
terms of PFS was limited in patients with LC cancer in KRAS ex on 2 WT population. LC should 
be replaced by RC, I think.  
 
- Table 1: Not all numbers are rounded in the same way. For example, histology and stage at 
presentation,.. In addition, numbers of histology in table 1 are not corresponding to the numbers 
describ ed in Results section, p9, patient characteristics.  
 
 
Minor comments to the author:  
 
- Materials & Methods, p6, below Patients: declaration of HeNsinki instead of Helsinki. Same 
mistake at the end of the manuscript: Declarations, p16, below ethics approval and consent to 
participate  
 
- Materials & Methods, p6, below Genotyping: and an MALDI -TOF mass spectrometer -> 
should be: a MALDI -TOF mass spectrometer  
 
- Results, p9, below Patient characteristics, first sentence: RAS -wild type -> should be RAS 
wild-type 
 
- Results, p9, Molecular information according to PTL: Refer to Table 1  
 
- Discussion, halfway p12: .. a negative prognostic indictor -> should be indicator (?)  
 
- Figure 2, B and D: Progression Free - Survival -> Progression -free Survival  
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
Yes 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Unable to assess  
 
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  
 
Qualit y of written English  
Please indicate the quality of language in the manuscript:  
 
Acceptable  
 
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, fees, funding, or salary from an 
organisation that may in any way gain or lose financially from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that may in any w ay gain or lose 
financially from the publication of this manuscript, either now or in the future?  
 
3. Do you hold or are you currently applying for any patents relating to the content of the 
manuscript?  
 
4. Have you received reimbursements, fees, funding, or sal ary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
 
5. Do you have any other financial competing interests?  
 
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer  no to all of the above, write 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
I declare that I have no competing interests  
 
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