Peer review report 2 on “A cost-minimization analysis of first intention laparoscopic compared to open right hemicolectomy for colon cancer”

1. Original submission 1.1. Recommendation Major Revision. 1.2. Comments to the author I offer you the following comments: This study is not a cost-effectiveness study. I would avoid the use of this terms since it is misleading. Present the actual p values instead of P > 0.05, etc. Use laparoscopic instead of LG, the use of this acronym does not reduce the word count and makes the text harder to read English editing is required: there are sentence fragments, missing commas, etc. The following sentence is not clear: “In addition many studies can be criticised for either being small [9,10,17] or excluded patients not suitable for laparoscopic surgery [8, 9].” In addition to what? Please rephrase Elaborate more on the rationale of why you would expect different oncologic outcomes from right hemicolectomies compared to other colorectal procedures. Did any of the trials comparing open vs laparoscopic surgery find differences in oncologic outcomes for right-sided malignancies? The aim is too vague. Better in terms of what? Please clearly state what your main outcome. Again, you did not do a cost-effectiveness analysis, you only estimated the cost. State the setting where the surgeries took place (academic vs community, hospital size, etc), years included. It is not clear if you included open cases done before 2006 by both teams or only after 2006. Please describe the two teams better - were they comparable in terms of experience? What do you mean by “all elective RHCs started with a diagnostic laparoscopy and in some cases a trial dissection”? MDT was not defined when first used. How many laparoscopic patients had a preoperative tattoo? Why weren't all tattooed? You need a table comparing the characteristics of the laparoscopic and open cases. Table 1 is missing the p value. I would only present the two groups you actually compared (whether you did it by intention to treat or not) I would use conversion to open instead of “the indications for an open operation in LG were”. How did you analyse the cases that were converted? As per intention to treat? If so, please state in the methods. Did you assess the distribution of the continuous variables? Were age, operative time, length of stay normally distributed in both groups? If they were, I recommend presenting the results using means and standard deviations otherwise use medians and interquartile ranges. This sentence is confusing: “There was no difference in 30 and 90-day mortality (LG 1.5%, OG 2.5%) but all 3 post-operative deaths occurred after an open operation.” If all deaths occurred in the open group, why is the mortality in the laparoscopic group 1.5%? What do you mean by time taken to give the anaesthetic? Why would you expect to see differences between groups? Were enhance recovery strategies employed? Did they differ between groups? Please describe the follow-up in the methods section. Was any patient lost to follow-up? The cox proportional hazard models were not described in the methods section. Please describe the verifications of the assumptions of the model and how did you deal with competing risk in the case of cancer-specific mortality. What variables were included in the models? Are the hazard ratios unadjusted? I disagree that this study has large sample size, given the rate of events (3 deaths, 24 complications) you are underpowered to detect differences in these outcomes. I wouldn't start the discussion by discrediting your findings listing the limitations. I would present the main findings of your study in the first paragraph, followed by a discussion of these findings in the context of the existing literature, and then I would address the limitations. It seems that the main finding of your study is that the operative room time cost is similar between both groups because the time taken to give the anaesthetic is longer in the open group. This “time to give anaesthetic” is not clearly described in the paper and I clearly do not understand what do you mean by this and why would it differ between groups. I don't think you need Figure 1 I would only present two groups (see comment #11). How did you compare the operative time? There was no mention of ANOVA though you are presenting 3 groups. If you decide to follow my advice and present only 2 groups, you should use either a t-test or a wilcoxon sum rank test according to the distribution of the variable. Figure 3 is missing the number of patients at risk and number of events Please use STROBE criteria for retrospective cohort studies to ensure the reporting of your study is complete 2. First revision 2.1. Recommendation Major Revision. 2.2. Comments to the author Thank you for addressing the previous comments. The manuscript has improved substantially; however, as many changes were made, I have made several new observations. I offer you the following comments: The following sentence is confusing, what is the link between age and right colon cancer: “As the population gets older the proportion of patients with right colon cancers is increasing”. Please rephrase, I think you mean as the population ages the cases of colon cancer increase, but this is not specific to right-sided colon tumours. I suggest you change “less” for “shorter” in this sentence: “There is no doubt that the length of stay (LOS) after laparoscopic surgery is less than after open surgery suggesting that laparoscopic right hemicolectomies may save money.” This argument is not clear: “However, the reduced LOS following the implementation of enhanced recovery protocols and the prevalence of more elderly patients has made the benefit of laparoscopic surgery less compelling [2,3,14].” The use of the term health economics is not correct in this sentence: “To further complicate the health economics not all operations can be completed laparoscopically and it is likely that operations in excluded patients are technically more difficult, take longer, have more post-operative complications and a longer hospital stay”. This would depend on the rate of conversion: “As a consequence the higher theatre costs of a first intention to undertake right hemicolectomies laparoscopically may offset savings made from a reduced LOS.” Please comment on how lower or higher rates of conversion would affect your analysis. If you are plotting overall survival using the Kaplan Meier method, then you are not censoring at time of death because those are your events, you are censoring at the date of last follow-up or the last date of observation (July 1, 2015) Please state in the methods that the analyses were done as per intention to treat. Your study was not designed to compare non-inferiority of oncologic outcomes, therefore the following statement is incorrect: “Our findings show that an intention to perform a right hemicolectomy laparoscopically is oncologically equivalent to open surgery.” You could say you observed similar or no difference in the oncologic outcomes between the two groups. Similarly, this sentence “It is possible that this study was underpowered and a larger study would have shown a difference.” is not necessary as this was not the objective of your study. Spell out numbers less than 10. The key findings of your study are those of the cost minimization and that is what it should be discussed in the first paragraph. Please reword this sentence: “There is little doubt that patients benefit from the laparoscopic approach because it is less invasive with a shorter recovery time” These sentences would be fine for the introduction but are out of place in the discussion: “However, it is uncertain whether or not a laparoscopic right hemicolectomy is economically advantageous for the health care provider because the savings made from a shorter LOS may be offset by the longer procedure time and higher costs of consumables [10,15,16]. Because the outcomes following the laparoscopic and open procedures are equivalent and the benefit to the hospital is the saving from a reduced LOS a cost minimisation analysis was performed [17].” This sentence in the discussion contradicts what you said in the results: “In this series, as in others, the subgroup of right hemicolectomies completed laparoscopically took longer than open operations [8,16,18], but this was offset by a shorter anaesthetic time.” The discussion is missing a paragraph where you discuss the findings of your cost minimization analysis in the context of similar analyses in the literature. Here are a few examples of relevant articles: http://www.ncbi.nlm.nih.gov/pubmed/21656072 http://www.ncbi.nlm.nih.gov/pubmed/15048739 http://www.ncbi.nlm.nih.gov/pubmed/16363014

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