LAUSR

We read with great interest the systematic review titled “A systematic review of minimally invasive surgery for retrorectal tumors” by Mullaney et al. [1] evaluating the role of minimally invasive surgery for retrorectal tumors. However, we wish to highlight the following issues: The authors have rightly acknowledged the rarity of lesions arising from the retrorectal space, and consequently the scarcity of literature on this subject. Hence, they have decided to include case reports and series, which constituted the majority of their review. Based on their quantitative analyses, they have concluded laparoscopic and robotic approaches to be safe, feasible, with reduced morbidity and length of hospital stay. Whilst case reports are useful in research involving rare conditions, conclusions from quantitative analysis of such data are susceptible to the risk of any causal inference, generalization, publication bias, and overintepretation [2]. A case in point is the fact that the authors chose to interpret the difference in mean operative times as evidence in favour of the minimally invasive approach, whereas they attributed the lower rate of neurological complications published by Nedelcu et al., to “underreporting rather than a true difference in outcome”. In addition, there probably exists considerable heterogeneity in the types of minimally invasive techniques utilized, ranging from totallylaparoscopic to laparoscopically-assisted and single-port procedures. Perhaps the authors could have presented a purely narrative systematic review without attempting to pool any quantitative variables for the included case reports? In the light of scarce literature, coupled with a recently published systematic review on the same subject by Baek et al. [3], we seek the authors’ clarification on the justification for their study, as it may be prudent to avoid repeated reviews of the same literature [4]. Alternatively, a small-scale meta-analysis of these cohort studies could have been performed for operative outcomes such as operating time, complications, length of hospital stay, and mortality. A meta-analysis of weighted pooled proportions or means could have been considered. Incidentally, whilst the authors have made an attempt to assess the study quality, it was unclear which tool or scale was being employed. Given the retrospective study designs, did the authors consider using the Newcastle-Ottawa Scale [5]? In their discussion, the authors opine that the experience of the surgeon in minimally invasive techniques is “one of the most important factors in deciding on a minimally invasive approach”. This statement seems generic and rhetorical, given that there was no description of the actual experience of the surgeons studied. As acknowledged by the authors, this study must be interpreted in the context of these limitations. Any comparative statements or conclusions between open surgery, laparoscopy, and robotic surgery for retrorectal tumors should not be drawn until large-scale cohort studies are being published.