Is Multimodality the “Third Way” in the Challenge Robot Versus Laparoscopy for Liver Resections?

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To the Editor:
We have read with great interest the article by Tsung et al1 from the University of Pittsburgh Medical Center. It definitely contributes to the knowledge on minimally invasive liver resections. In particular, the study develops the question whether robotic surgery might overcome some limits of the laparoscopic approach.
This specific subject has been recently investigated in other series, showing that robotic and laparoscopic surgery obtain comparable feasibility and safety.2–4 The matched comparison by Tsung et al confirms these findings, describing one of the largest experiences to date, made in one of the most important centers worldwide. In addition, Tsung et al have observed that the robot has delivered no significant postoperative benefit, although has allowed completing more operations in a minimally invasive fashion. In fact, although simple, these are very important conclusions that have triggered immediate technical discussion by Montalti et al from the Ghent Group.5
Those positive conclusions in favor of the robot might represent further incentive for centers like ours that are exploring robotic approach6 to provide benefits for their patients despite higher costs. Although simple, these are very important conclusions on a relevant matter, on which we feel the need to comment further.
From a purely surgical point of view, the robotic resections described in the study were partially laparoscopic, as laparoscopy was systematically utilized in the first part of each procedure. Conversely, the laparoscopic group included hand-assisted and hybrid lap-assisted open procedures. These multimodal techniques are clearly well respected and are also advocated by other teams3,7 but introduce difficulties in this specific comparative analysis. The 2 laparoscopic and robotic groups in fact overlap and include hybrid open procedures, generating a fundamental selection bias at risk of invalidating the study results.
In addition, Tsung et al acknowledge a certain degree of selection bias for the comparison of the 2 groups inevitably caused by the single-surgeon intention whether to proceed to laparoscopic versus robotic surgery. In this sense, more information regarding this particular decision-making process and regarding the patients’ eligibility would be very helpful to understand the Pittsburgh group's experience.
In the absence of dedicated statistical matching methodologies (ie, Propensity Score Matching), the matching procedure in our opinion might hide additional bias. It is not clear from the text if that was performed by human selection by a computer routine, and how and when the diagnosis of liver disease was made. BMI was considered at low priority; here it did not show significant differences overall, but interestingly the obese patients with BMI more than 30 kg/m2 in the robotic group were roughly twice the laparoscopy (38.6% vs 21.9%). Tumor location was not included in the matching, as well as the year (or period of years) of surgery; these 2 variables are not mentioned in the study, again potentially undermining both its internal and external validity.
The potential benefits yielded by the increasing experience in early versus late robotic resections are the object of one of the multiple partial/nested and satellite comparisons presented in the article. This plentiful additional information in our view does not help toward the manuscript's original aims. Conversely, it provides ground for redundancy and inconsistencies. For instance, the further subdivision into minor/major resection is occasionally confounding; with the implicit exclusion of the planned hybrid laparoscopic-open procedures, a similar conversion rate (7% vs 8.8%, P = 0.67) is reported, in contrast with the main study conclusions of robotic technique allowing more minimally invasive completions. Nonetheless, this conclusion is in agreement with the general opinion from advocates of robot liver surgery on the potential benefits such as the enhanced vision and dexterity, occasionally allowing meticulous and peculiar surgery.

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