Options for Low Rectal Cancer: Robotic Total Mesorectal Excision

Abstract

Low rectal cancers (LRCs) may offer a difficult technical challenge even to experienced colorectal surgeons. Although laparoscopic surgery offers a superior exposure of the pelvis when compared with open approach, its role in rectal cancer surgery has been controversial. Robotic platforms are well suited for difficult pelvic surgery due to its three-dimensional visualization, degree of articulation of instruments, precise movements, and better ergonomics. The robot may be suitable especially in the anatomically narrow pelvis such as in male and obese patients. Meticulous dissection in critical steps, such as splenic flexure takedown, nerve-sparing mesorectal excision, and distal margin clearance, are potential technical advantages. In addition, robotic rectal resections are associated with lower conversion rates to open surgery, less blood loss, and shorter learning curve with similar short-term quality of life outcomes, similar rates of postoperative complications, and equivalent short-term surrogate outcomes compared with conventional laparoscopy. Robotic surgery approach, if used correctly, can enhance the skills and the capabilities of the well-trained surgeon during minimally invasive procedures for LRC.

Minimally invasive surgical approaches in colorectal cancer have been widely adopted to minimize morbidity and enhance recovery. However, low rectal cancers (LRCs; <5 cm of the anal verge) may offer a difficult technical challenge ¹ even to experienced colorectal surgeons. Open total mesorectal excision (TME) is considered the gold standard for rectal cancer resections, but it is associated with limited access for LRC in the narrow and anatomically difficult pelvis. These limitations may lead to potentially lower rates of sphincter-preserving surgery and inadequate resection margins.

Laparoscopic surgery offers a better exposure of the pelvis due to more direct visualization, but its role in rectal cancer surgery has been controversial. While some studies have shown comparable short-term outcomes between open and laparoscopic TME, ^{2 3} others have failed to achieved a noninferiority margin in terms of pathological outcomes. ^{4 5 6} Additionally, limited dexterity due to nonarticulating instrumental and unstable camera use leads to difficulties during TME for LRC. ⁷

Robotic platforms are well suited for difficult pelvic surgery due its three-dimensional visualization, degree of articulation of instruments, precise movements, and better ergonomics. Alternatively, minimally invasive bottom-up techniques, such as transanal TME (TaTME), have been introduced as an alternative for LRC.

This review aims to discuss the technical aspects and advantages of the robotic platform for TME in the context of LRC.

Surgical Technique for Robotic Total Mesorectal Excision

One of the most important aspects to consider in robotic TME is operating room configuration and patient positioning. The daVinci Xi system (Intuitive, CA) facilitates the surgical work in all four quadrants of the abdomen without the need to redock the cart due to anchoring of all robotic arms into a single boom. The robotic cart should be positioned to the left of the patient, allowing the surgeon to have direct access for both splenic flexure takedown and pelvic dissection ( Fig. 1 ).

Fig. 1.

Typical operating room setup for a robotic low anterior resection at our institution. Robotic arms 1 to 4 are indicated. O.R., operating room.

The patient is placed in the lithotomy position, with legs flexed and arms tucked after ensuring safe intravenous access for the anesthesia team. The patient is secured to the bed to prevent injuries when the patient is positioned. At Memorial Hospital, a careful rectal washout is done before drape positioning.

Pneumoperitoneum can be established through an open approach with a Hasson's port or with a Veress' needle in the left upper quadrant. Arm 1 should be positioned in the upper right quadrant during the dissection of the inferior mesenteric artery (IMA) and superior rectal vessels. Arms 2 and 4 are used for the pelvic part of the dissection and are located as seen in Fig. 2 . During pelvic dissection, arm 1 can be positioned in the left lower quadrant for retraction of the vagina or prostate. Trocar 3 is usually used for the camera.

Fig. 2.

Trocar positioning for a robotic low anterior resection. Trocars are numbered according to the numbering of the robotic arms. MCL, midclavicular line.

Once the ports are placed and before robotic cart docking, a general examination of the peritoneum is recommended to rule out metastatic disease. Once the robot is docked and the patient positioned right side and head down, surgery starts with the identification of the inferior mesenteric vein (IMV) at the level of the ligament of Treitz which is divided. The IMV should be ligated immediately below its emergence from inferior pancreatic border for proper mobilization of the colon for the future anastomosis.

It is mandatory for a low colorectal anastomosis for the colorectal surgeon to complete a full mobilization of the splenic flexure. For that purpose, pancreas exposure is necessary to correctly enter into the lesser sac. Dissection is performed in a medial to lateral fashion until the splenic hilum is reached ( Fig. 3 ). The lateral attachments of the left colon are divided over Gerota's fascia for proper mobilization of the splenic flexure.

Fig. 3.

Medial aspect of the splenic flexure takedown. Dissection is performed over the surface of tail to the pancreas in the direction of the splenic hilum.

To complete splenic flexure mobilization, the omentum is released from the transverse colon beginning at the level marked by the distal transverse colon, and the lesser sac is entered broadly in a supra-mesocolic fashion. Posteriorly, identification of the IMA is needed which can be found following the right iliac artery caudally. For LRC, the IMA can be ligated at its origin or at the level of the bifurcation for a proper lymphadenectomy.

For dissection of the mesorectum, the third robotic arm is useful for retraction. The pelvic peritoneum is opened bilaterally, and sharp dissection is performed with monopolar scissors in the posterior aspect of the mesorectum. Care should be taken to avoid bleeding from presacral veins and hypogastric nerves should be identified and preserved ( Fig. 4 ). The dissection should be performed to the floor of the pelvis (levator ani muscle). Lateral dissection of the mesorectum should be performed carefully for proper control of the rectal stalks and preservation of the inferior hypogastric plexus. The third arm can now be used to first lift the bladder and then the prostate or the vagina. With the anterior pelvic peritoneum now open, the dissection is extended inferior to the cervix or the seminal vesicles. In men, the dissection plane should be posterior of Denonvilliers' fascia, unless en bloc resection is needed in anterior rectal cancers.

Fig. 4.

Posterior dissection in the areolar space between the mesorectum and presacral fascia.

Distal margin can be determined from direct abdominal visualization, by intraoperative colonoscopy and/or digital rectal examination. A robotic stapler device can be used for rectal division ( Fig. 5 ). If a coloanal anastomosis is required, a perineal portion will be necessary for a dissection above the dentate line or via an intersphincteric approach. The anastomosis can be performed using a double-staple technique or a hand-sewn coloanal anastomosis. A diverting loop ileostomy is frequently performed in the right lower quadrant for most LRC.

Fig. 5.

Rectal division using a robotic stapler device at the level of the pelvic floor.

For a complete visualization of the surgical procedure, please see Video 1(available online only).

Advantages of Robotic Total Mesorectal Excision in Low Rectal Cancer

Robotic TME is associated with similar short-term quality of life outcomes, similar rates of postoperative complications, and equivalent short-term surrogate outcomes compared with conventional laparoscopic TME. ^{8 9 10 11} However, there are several details that make the robotic platform our preferred choice in LRC.

Technical Advantages

Robotic platforms offer better visualization and enhanced dexterity in complex minimally invasive pelvic surgery, especially in the anatomically narrow pelvis such as in male and obese patients. ¹²

In addition, proper splenic flexure takedown is a technically demanding laparoscopic procedure, ¹³ with robotic platforms offering more precision and better control during dissection of critical anatomical structures such as the pancreatic tail and splenic hilum. ¹⁴

Anatomical landmarks during an abdominal TME approach have been widely described. The identification of the hypogastric plexus is highly recommended during TME due to the association of urinary and sexual dysfunction, if these structures are injured or damaged. The three-dimensional magnified view, associated with camera stability offered by the daVinci System, helps in recognizing small structures such as the inferior hypogastric plexus. Additionally, the wide range of motion and precision of the robotic instruments allow fine dissection in limited pelvic areas, minimizing collateral damage to surrounding tissues.

Meticulous dissection and clearance of the distal margin is one of the potential pitfalls in TME for LRC. Both open and laparoscopic TME are frequently limited for a full and correct visualization of the distal rectal margin to ensure oncologic clearance. ⁷ The newer robotic stapler device offers more stability and a 120-degree cone of articulation, giving more maneuverability in tight spaces and with potential use ranging from 45- to 60-mm staple line size.

Another benefit of the enhanced robotic ergonomic benefits in rectal surgery is in the performance of lateral pelvic lymph–node dissection. Up to 20% of rectal cancers below the peritoneal reflection may metastasize into the lateral compartment. ^{13 15} Suspicious lymph nodes larger than 5 mm after neoadjuvant treatment should be considered for a pelvic sidewall dissection. ¹⁶ The use of the robotic platform for a minimally invasive dissection of the obturator and internal iliac spaces offer more control in an anatomically complex area. ^{16 17}

Intraoperative Outcomes and Learning Curve

Longer operative time has been one of the consistent outcomes in robotic rectal cancer surgery. ^{18 19 20 21} This has been attributed to the docking and changes of robotic instruments during the procedure. However, most of these reports consisted with the use of older robotic platform such as Si system. One of the main advantages of the Xi System, especially for TME in the context of LRC, is the avoidance of redocking of the patient cart with the use of the rotation of the boom. A small comparative study ²² of rectal resections, with the Si versus the Xi systems, showed the latter to be associated with a reduction of operative time.

Robotic rectal resections are associated with reduced estimated blood loss (EBL) when compared with laparoscopic ²⁰ and open resections. ²³ Interestingly, EBL is significantly reduced in obese patients, suggesting a higher value of robotic platforms in laborious interventions in this group of patients. ²⁴

Another potential advantage of the robotic platform is an associated lower conversion rate when compared with a laparoscopic approach. ^{18 25} However, well-designed and high-quality trials are required to clarify effectiveness. ²⁶

It has been well documented that robotic rectal resections have a considerably shorter learning curve than other platforms. Using cumulative sum (CUSUM) analysis, the learning curve for robotic rectal resections ranged from 20 to 25 cases. ^{27 28} In contrast, the learning curve for laparoscopic rectal resection and TaTME ranged from 60 to 80 cases ²⁹ and 50 cases, ³⁰ respectively. Interestingly, it seems that the robotic learning curve did not have an impact on the circumferential resection margin positivity rate. ³¹

Pathological Outcomes

Similar circumferential resection margin positivity rate has been reported for robotic versus laparoscopic TME. ^{18 25} A recent meta-analysis showed a better distal margin for robotic TME over laparoscopic approach. ³² Similarly, robotic resection seems to be a better option to obtain a complete mesorectum and a more complete specimen according to a meta-analysis of 12 articles. ³³ However, based on the quality of the current evidence, it cannot be definitively concluded that one modality is superior for complete TME in rectal cancer.

Complications

Anastomotic leak still remains one of the major complications in TME, especially in LRC, with an incidence that varies between 3 to 30%. ^{34 35 36} Recent meta-analyses have revealed similar morbidity rates for patients undergoing robotic versus laparoscopic rectal TME. ^{21 37} From the perspective of postoperative functional outcomes and late sequelae from rectal cancer surgery, some studies have reported favorable urogenital outcomes, ^{25 38} while other were unable to show any major advantages. ^{18 39 40} To date, there is no categorical evidence that demonstrate a significant advantage for the robotic platform over others in preserving bowel and/or urogenital function.

Finally, when compared with other surgical alternatives to LRC, a recent alarn has been raised for the use of TaTME due to a higher rate of local recurrences ⁴¹ and an increase in uncommon intraoperative complications such as urethral injuries ⁴² or gas embolism. ⁴³ A recent moratorium for TaTME has been proposed in Norway due higher anastomotic leak rates and unfavorable local recurrence rates and growth patterns. ⁴⁴

Conclusion

The robotic platform is a powerful tool that offers more precision, dexterity, and a high-resolution/high-definition view for an optimal view of the operating field during TME for LRC. At its base value, the robot remains a surgical device that if used correctly can enhance the skills and the capabilities of the well-trained and careful surgeon during minimally invasive procedures. The key to achieve good results in rectal cancer patients is the proper combination of patient selection, detailed knowledge of pelvic anatomy, and the adequate expertise to perform such complex procedures.