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Reply: Comparison between short and long‐term outcomes after minimally‐invasive versus open primary liver resections for hepatocellular carcinoma

We would like to thank Hu et al. for their interest in our recent study comparing minimally invasive versus open primary liver resection (LR) for hepatocellular carcinoma. The authors highlighted several limitations of our study which we acknowledge are inherent in all retrospective case‐controlled studies and can only be completely mitigated by conducting a prospective randomized controlled study. One of the major limitations of matched‐controlled studies is that not all potentially confounding baseline characteristics can be matched especially when the sample size is limited. Two potential confounding factors mentioned by the authors were patient body mass index (BMI) and tumor location. The impact of BMI on the outcomes of LR has been well‐ reported with contrasting results from different studies. In our opinion and experience, the effect of increasing BMI on the difficulty of LR is related to the increased likelihood of hepatic steatosis and hence increasing mass/volume of the liver and transection surface. Hence, this would result in an increased operation time and blood loss. This is unlike in gastrointestinal surgery whereby the increased adipose tissue around the viscera in obese patients increases the difficulty of the procedure due to the decreased surgical working space and distorts the surgical anatomy making identification of critical structures such as blood vessels in the mesentery more challenging. Although BMI was not included in our study, it was not a major factor in our selection of patients for minimally invasive surgery (MIS). Tumor location is a well‐known and an important determinant of the difficulty of laparoscopic LR and has been included as an important parameter in difficulty scoring systems such as the IWATE score. Tumors in the posterosuperior segments especially segments 7 and 8 are especially difficult to perform laparoscopically due to the unique technical challenges imposed by laparoscopy compared to the open approach. In this study, 41% of the MIS cases were located in the difficult posterosuperior segments. Nonetheless, we, like many other authors, have previously demonstrated that patients benefit from the same advantages of MIS over the open approach even for tumors in in these difficult locations. Finally, the authors also raised the issue of the learning curve effect on the outcomes of MIS‐LR. The impact of the learning curve on the outcomes of MIS‐LR has been studied extensively in the literature and its potential impact was highlighted in our manuscript. We intentionally did not exclude cases during our early institution learning curve as we felt that it is important to demonstrate that MIS‐LR was safe to adopt with minimal detrimental effects on patient outcomes even during the early adoption phase.