Laparoscopic and robotic total mesorectal excision in overweight and obese patients: multinational cohort study

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Obesity is a major global health concern that strains available healthcare resources. The prevalence of obesity has doubled since 1980 in over 70 countries1 and is known to increase the risk of colorectal cancer2–4. As a result, the demand for curative surgical interventions in overweight and obese individuals is expected to grow. Surgical treatment of these patients poses several challenges, including logistical challenges in the operating theatre (for example suitable operation table) and care of pressure areas. Most importantly, obesity introduces anatomical challenges in gaining access to and keeping an overview of the surgical field while manipulating adipose tissue and a bulky mesocolon. This can be particularly challenging when performing laparoscopic total mesorectal excision (L-TME)5,6. Previous research, for example the ROLARR trial, has indicated that obesity is a risk factor for conversion to open surgery when undertaking rectal cancer resections7. Earlier studies have also shown an association between obesity and increased morbidity8–11. To overcome the challenges in overweight and obese patients, other techniques have been introduced, such as robotic total mesorectal excision (R-TME) and transanal total mesorectal excision (TaTME). Regarding the comparison of surgical techniques in obese individuals, there are studies that suggest an accelerated recovery after the use of the robotic approach; however, no differences in conversion or complication rates were found, probably because of the relatively small sample sizes10,12,13. Besides smaller sample sizes, the learning curve is often not taken into account, despite research demonstrating improvement of surgical outcomes with increased experience7,12,13. Larger-scale multicentre studies with experienced surgeons operating on a cohort of patients with obesity are therefore needed to assess the optimal surgical approach10,12,14. The aim of this study was to compare the conversion rate and postoperative outcomes in obese and overweight patients who underwent either R-TME or L-TME in a cohort from dedicated centres where all surgeons are fully trained and experienced in these surgical techniques. An international multicentre retrospective cohort study assessing patients with rectal cancer and a BMI greater than 25 kg/m2 was performed. This population was nested within two existing cohorts consisting of 2719 patients: the Minimally Invasive Rectal Carcinoma (MIRECA) cohort and the Expert Dutch, French, and United Kingdom Robotic Rectal Cancer Centres (EUREKA) cohort. The MIRECA cohort consists of patients who underwent L-TME in 11 Dutch hospitals between January 2015 and December 2021 and were identified using the prospective obligatory national Dutch Surgical Colorectal Audit database15. Missing or unavailable data were added to the database from local electronic medical records. The EUREKA cohort consists of R-TME patients from five Dutch hospitals, four French hospitals, and one UK hospital who underwent surgery between 2013 and 2022. Dutch centres contributing to the EUREKA collaborative were those Dutch MIRECA centres also offering robotic surgery. French data were contributed from the ROBOT-CR study, intended to record outcomes and standardize care in robotic colorectal surgery in France. UK data were contributed from a single high-volume centre in the UK. All centres in the EUREKA cohort contributed data prospectively, with outcome data added retrospectively. The MIRECA and EUREKA cohort studies both focused on the assessment of outcomes related to the choice of surgical platform, with due attention to the learning curve, defined as 90 cases for L-TME and 40 cases for R-TME and TaTME16–19. The MIRECA and EUREKA cohort studies both had relevant medical ethics committee approvals (MEC-U, AW19.023 W18.100). Eligibility criteria for the MIRECA and EUREKA cohorts are summarized in Table S1. In this study, adult patients were included from both cohorts who had a rectal tumour located within 15 cm of the anorectal junction on MRI. Patients who underwent surgery before the learning-curve requirements were fulfilled, multivisceral resections, emergency surgery, and palliative resection, as well as patients who had a BMI less than 25 kg/m2, were excluded. The primary outcome of this study was the conversion rate to open surgery. Secondary outcomes were 30-day surgical complications (including anastomotic leak) and length of stay. Anastomotic leak was defined according to the International Study Group of Rectal Cancer20 and postoperative complications were graded according to the Clavien–Dindo classification21. Clinical data collected included age, sex, BMI, ASA grade, history of previous abdominal surgery, presence prior stoma, tumour distance from the anorectal junction on MRI, tumour diameter, administration of neoadjuvant (chemo)radiotherapy, preoperative clinical tumour classification (TNM classification), involvement of mesorectal fascia, and type of procedure (Hartmann procedure, low anterior resection with primary anastomosis, or abdominoperineal excision). Intraoperative data collected included procedure length, conversion rate, and perioperative complications. Pathology data on TNM classification, tumour differentiation, and histological tumour type were also collected. Descriptive statistics were computed for patient characteristics and postoperative outcomes. Normally distributed continuous data are presented as mean(s.d.), with Student’s t test used for between-group comparisons. Non-normally distributed continuous data are presented as median (i.q.r.), with the Mann–Whitney U test used for between-group comparisons. Categorical data are presented as n (%), with the chi-squared test used for comparisons. Propensity score matching was used to adjust for possible confounders and decrease selection bias. Matching was performed using 1 : 1 nearest-neighbour matching. The variables used for propensity score matching were: age, sex, ASA grade, BMI, history of previous abdominal surgery, prior stoma, pT stage, pN stage, tumour distance from the anorectal junction on MRI, involvement of the mesorectal fascia, and neoadjuvant therapy. A standardized mean difference (SMD) of less than 0.1 was considered to indicate appropriate matching. Missing data were imputed using multiple imputations. P < 0.050 was considered statistically significant. All analyses were performed using R studio (version 3.1, 2022). A total of 1395 patients were identified as eligible, comprising 907 R-TME patients and 488 L-TME patients (Fig. S1). The median follow-up for this cohort was at least 36 months, with less than 2% missing data. Baseline characteristics before and after propensity score matching are shown in Table 1. There were differences in age (SMD 0.1681), sex (SMD −0.0850), tumour distance from the anorectal junction (SMD 0.1231), prior stoma (SMD −0.1894), history of previous abdominal surgery (SMD 0.1113), involvement of the mesorectal fascia (SMD −0.3371), pN stage (SMD −0.1334), and neoadjuvant therapy (SMD −0.0758). After propensity score matching, 488 patients remained in each group. The SMD did not exceed 0.05, indicating that the quality of matching was good. Baseline characteristics of the patients Values are n (%) unless otherwise indicated. L-TME, laparoscopic total mesorectal excision; R-TME, robotic total mesorectal excision; SMD, standardized mean difference; i.q.r., interquartile range. Baseline characteristics of the patients Values are n (%) unless otherwise indicated. L-TME, laparoscopic total mesorectal excision; R-TME, robotic total mesorectal excision; SMD, standardized mean difference; i.q.r., interquartile range. In the matched cohort, the conversion rate was lower in the R-TME group compared with the L-TME group (19 (3.9%) versus 38 (7.8%) respectively; P = 0.014). A restorative low anterior resection was performed more frequently in the R-TME group compared with the L-TME group (307

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