Robotic rectal cancer surgery in obese patients may lead to better short-term outcomes when compared to laparoscopy: a comparative propensity scored match study

Laparoscopic colorectal surgery has become the new standard for colorectal diseases as it offers several advantages over open surgery such as shorter hospital stay, earlier return to normal function, less postoperative pain, early mobilisation and improved cosmesis [1‐6]. There is consensus amongst surgeons that obesity increases the technical difficulty of colorectal surgery [7, 8]. Obese patients tend to have a thickened and excessive omentum and mesentery which restricts the space for instrumental manoeuvre, limits access and vision, distorts the surgical planes and can lead to problematic bleeding [9]. With obesity becoming increasingly a major hazard to public health worldwide, colorectal surgeons are likely to encounter and operate on this group of patients in increasing numbers [10, 11].

Laparoscopic rectal surgery is particularly demanding, with studies reporting high conversion rates for rectal surgery and two recent multi-centre randomised control trials (ALaCaRT and ACOSOG Z6051) failing to show that laparoscopic surgery is non-inferior to open surgery [4, 12‐14]. This is because existing laparoscopic instruments have a restricted range of movement compared with that of the surgeons hand and are difficult to use in confined spaces such as the bony pelvis [15, 16]. These limitations are magnified in the obese due to the even greater restriction of available space for manoeuvre in this group of patients.

Robotic surgical systems were designed to overcome the limitations of laparoscopic surgery by providing stable three-dimensional views from a surgeon-controlled camera, angulated instruments with 7° of freedom, markedly improved ergonomics and tremor filtering [15, 17]. These advantages are particularly attractive in rectal surgery, overcoming the challenges of laparoscopic instrumentation and technique in obese patients, where space is limited and accurate dissection in narrow deep cavities is required. However, whether robotic rectal surgery in the obese translates to superior short-term surgical outcomes is hitherto poorly examined. At present, there are only two studies comparing the short-term surgical outcomes of obese patients having laparoscopic and robotic rectal surgery [18, 19], with both studies including smaller sample sizes.

The aim of this study is to build upon current evidence by analysing and comparing the short-term surgical outcomes of obese patients undergoing robotic and laparoscopic rectal resection surgery.

A retrospective analysis of prospectively maintained databases was conducted for this study. Consecutive patients from three centres, two from the UK and one from Portugal, who received minimally invasive rectal cancer surgical resections between 2006 and 2017 were identified. The inclusion criteria included all obese patients (defined as patients with a BMI ≥ 30) receiving laparoscopic or robotic elective rectal resection surgery. The robotic cases were propensity score matched to laparoscopic cases to obtain comparable patients.

All cancer patients were discussed in a multidisciplinary team meeting (MDT) prior to initiating any type of treatment. Magnetic resonance imaging (MRI) scans were reported using the Mercury criteria, and preoperative chemoradiotherapy was given to patients with high risk for local recurrence (threatened circumferential resection margin ≤ 2 mm or T4 in staging MRI). Neo-adjuvant radiotherapy was not used where rectal cancers were considered resectable by total mesorectal excision (TME) with a likelihood of clear margins.

No specific selection criteria were used to allocate patients to laparoscopic or robotic surgery. Applied surgical modality was based on equipment and theatre availability. The robotic approach was the preferred approach following the adoption of robotic surgery in each unit. This was from May 2013 (Unit A), November 2015 (Unit B) and May 2016 (Unit C) for each unit, respectively. All recruited patients signed an informed consent form allowing their data to be used for analysis and its publishing. The requirements for anonymization of personal dataset by the Data Protection Act 1998 were satisfied. According to the Health Research Authority (HRA), this study did not require their approval due to its status as a clinical audit.

Patients included in the study had surgery performed by fully trained laparoscopic and robotic colorectal surgeons. The surgeon from one of the centres (surgeon AP) led a supervised training programme involving the remaining surgeons participating in this study, ensuring that the same standardised modular approach was used throughout. Data collection commenced when the participating surgeons began working in their respective units, between 2006 and 2012 for the UK centres and 2013 for the Portuguese centre. In addition, 15 robotic cases performed by surgeon AP in other centres as part of demonstrating/proctoring cases were included in the study.

A total of 222 obese patients received elective minimally invasive rectal cancer resection surgery (63 robotic, 159 laparoscopic). The 63 robotic cases were propensity score matched with 61 laparoscopic cases to reduce the effect of confounding factors in the analysis.

The effect of robotic rectal cancer surgery in offering superior short-term outcomes in obese patients when compared to laparoscopy is largely hitherto unknown. Several studies indicate that obesity is a risk factor for worse short-term surgical outcomes in laparoscopic colorectal surgery [27‐29]. However, this is still a subject of debate, with numerous studies demonstrating no difference in short-term outcomes between laparoscopic obese and non-obese colorectal surgery patients [30, 31]. Nevertheless, the role of robotic colorectal surgery in obese patients has only been investigated in a handful of studies [9, 18, 19, 32, 33], with only two comparing the outcomes of obese robotic vs laparoscopic rectal surgery patients [18, 19]. The remaining three studies compared the outcomes of obese versus non-obese patients receiving robotic rectal surgery, with all three studies demonstrating no difference in short-term outcomes between obese and non-obese patients [9, 32, 33].

In the study presented here, both the length of stay and 30-day readmission rate were lower in patients receiving robotic surgery while operation time was longer. However, there were no differences in any of the remaining short-term surgical outcomes between robotic and laparoscopic rectal surgery. Furthermore, surgical approach, whether robotic or laparoscopic, was not found to affect morbidity and mortality. This study demonstrates that robotic rectal surgery in the obese is both safe and feasible with results suggesting a quicker recovery and better short-term readmission profile when compared to laparoscopic surgery in obese patients.

Robotic systems offer superior stable 3D views and ergonomic wristed instruments which are particularly useful when operating in confined spaces such as the pelvis, making the robotic platform especially attractive for rectal surgery. Obese patients tend to have increased intra-pelvic fat, further restricting access, room for manoeuvre and surgical field visibility. By further restricting the available space in the already narrow pelvis, robotic platforms seem ideally suited for this group of patients. This is supported by the initial results of the ROLARR trial (NCT01196000), a large randomised control trial comparing robotic to laparoscopic rectal surgery [34, 35]. Data from this trial was presented at the ASCRS and EAES conferences in June 2015, where conversion rates were lower in the robotic cohort in obese patients [36]. Considering this in conjunction with the high conversion and CRM positive rates in recent multi-centre randomised control trials investigating the role of laparoscopic rectal surgery [12, 13], the role of robotic rectal surgery in the obese patients clearly warrants further investigation.

In a similar study to ours, Gorgun et al. [18] compared 29 robotic with 27 laparoscopic obese rectal surgery patients. In this study, there was no statistically significant differences in operative time between the two groups, although operative times were longer in both cohorts compared to our results (rob vs lap: 329 vs 295 min; p = 0.13). Similarly, Shiomi et al. [19] compared 52 robotic with 30 laparoscopic obese rectal surgery cases and again found no difference in operative time (rob vs lap: 238 vs 252; p = 0.39). In our study, median operative time was 45 min longer in the robotic group. This may in part be explained by the inclusion of several cases where the surgeons and theatre teams were still in the earlier stages of their learning curve, with active training led by the senior surgeon (AP) being undertaken in a number of the included cases. While all consecutive cases are included in the robotic cohort (including all the initial cases at each unit), the laparoscopic cases are selected from a much larger pool spreading over a longer period.

Early studies involving robotic rectal surgery demonstrated that a significant contributor to the prolonged operation time in robotic surgery was due to the time it took to dock and undock the robot, which in part, may have been due to the relative inexperience of the surgeon and theatre staff who were still on the early stages of their learning curve [37‐42]. More recent studies report equivalent operation times between robotic and laparoscopic rectal surgery [43‐46] with some even demonstrating shorter operation times for robotic surgery [47‐50]. Furthermore, the laser target system and improved design of the da Vinci Xi (the latest model by Intuitive Surgical) make docking easier and faster and increase the feasibility of the single docking approach. These features are likely to help further reduce robotic rectal surgery operative times [51].

Furthermore, our results show that the median length of stay was 2 days shorter, and 30-day readmission rate was lower in the robotic cohort. This could be secondary to lower post-operative morbidity. Morbidity was assessed in this study by analysing readmission, reoperation and anastomotic leak rates. However, minor post-operative complications were not included (Clavien-Dindo 1–2) as these were not reported in the datasets. It is postulated that minor complications (Clavien-Dindo 1–2) may be reflected in a prolonged hospital stay, which may explain why length of stay was higher in the laparoscopic group. In addition, readmission rates tend to be higher when length of stay is shorter, since patients that are discharged early are more likely to be readmitted with complications that were not picked up during their original hospital stay. Considering that both length of stay and readmission rate were lower in the robotic group, it is reasonable to suggest that this may be due to reduced surgical morbidity. This is supported by two recent studies published by the Cleveland clinic group who reported that length of stay, readmission rate and mortality effectively predict complications [52, 53]. Considering that mortality was equal between the two groups in our study, these studies strengthen our argument that the reduced readmission rate and length of stay in the robotic cohort are due to a lower surgical morbidity profile.

It is worth noting that both Gorgun et al. [18] and Shiomi et al. [19] also demonstrated a reduced length of stay in the robotic group when compared to the laparoscopic cohort (Gordun et al: 6 vs 8 days, p = 0.02; Shiomi et al: 7 vs 9 days, p < 0.001). Both studies found that length of stay was shorter by 2 days in the robotic group, with Shiomi et al. also demonstrating that blood loss and complication rates were lower in the robotic cohort (blood loss: 10.5 vs 34 ml, p = 0.002; complication rate: 9.6 vs 30%, p = 0.04). Considering the results of these studies in conjunction with our results, it is conceivable that robotic rectal surgery in the obese can lead to a quicker recovery and reduced morbidity when compared to laparoscopic surgery.

Notwithstanding operative time, length of stay and readmission rate, there were no other differences in the examined short-term outcomes. Furthermore, in logistic regression analysis, surgical approach (robotic or laparoscopic) was not found to affect morbidity and mortality. However, we should note that the p value neared statistical significance in both univariate and multivariate analysis (univariate p = 0.051, multivariate p = 0.072) when examining whether surgical approach affects morbidity and mortality (Table 4). In the absence of a power calculation being performed, we need to acknowledge the risk of a type 2 error, and therefore, the p value might have been significant if a higher number of patients were recruited.

Our results support the feasibility and safety of robotic rectal surgery in obese patients. In the robotic group, there was no conversion, 30-day mortality or reoperation, and the estimated blood loss was very low. Furthermore, regarding the short-term pathological results, the lymph node yield was acceptable and the CRM margin was negative (R0) in 96.8% of robotic cases, which is superior to that reported in the recent laparoscopic rectal surgery trials (ALaCaRT [12]: lap 93%, open 97%; ACOSOG Z6051 [13]: lap 87.9%, open 92.3%). Additionally, there is perception in the surgical community that prolonged operative times are associated with worse short-term outcomes [54], especially in obese patients due to the prolonged fixed Trendelenburg position. However, this was not the case in our study, and our results suggest that robotic rectal surgery in the obese can lead to similar short-term outcomes and a quicker post-operative recovery regardless of operative time.

The main strengths of our study are that data was collected from three centres from two different countries and is contemporary data, rather than data collected as part of a study that possibly includes an element of performance bias in surgical trials [55]. In addition, due to the propensity score matching, the two cohorts were evenly matched in terms of cohort characteristics, strengthening our results. Additionally, as far as we are aware, this study includes the largest sample size of its kind. Acknowledging its limitations, our study is retrospective in nature and does not report any functional or long-term data. We should also note that all the laparoscopic procedures pre-dated the robotic cases and this could introduce an element of bias in our results. However, we believe this is unlikely since the two surgeons with the longest laparoscopic colorectal practice had completed laparoscopic colorectal fellowships, were experienced laparoscopic surgeons from the outset of their practice and were both trainers for the National Training Programme for Laparoscopic Colorectal Surgery (LAPCO) in the UK [56]. Furthermore, the robotic cohort is more likely to be affected by the learning curve of the surgeons, since all initial cases are included. In addition, the laparoscopic cases underwent the same standardised enhanced recovery programme which was later applied to all the robotic cases. As a result, we believe that by standardising peri-operative care, both groups are comparable and peri-operative care is unlikely to act as a confounding factor when assessing hospital length of stay.

In summary, robotic rectal surgery in the obese could lead to a quicker recovery and improved morbidity profile when compared to laparoscopy, despite being associated with a longer operative time. Larger-scale multi-centre prospective observational studies are required to further investigate this topic. In addition, urogenital function and long-term oncological data need to be included in these studies to illuminate a more holistic comparison.