-Maunsell HW

Management of rectal cancer has thankfully evolved significantly since those dark days. At present, it is treated in a multimodal fashion with ever-increasing use of effective neoadjuvant and adjuvant treatments; which includes chemotherapy and radiotherapy. Proper oncological surgical excision however remains the cornerstone of treatment. Since introduction of the concept of total mesorectal excision (TME) by Heald et al. [1] in 1982, it has rapidly gained traction and is now the gold standard surgical technique for curative resections [1]. Indeed, when performed satisfactorily with negative margins, TME excision is perhaps the single most important predictor of local recurrence with a corresponding improvement in disease-free survival [2].

The 1990s saw the advent of laparoscopic surgery and it soon made its way to rectal oncological work. There is little doubt that a laparoscopic approach to TME has improved intraoperative visibility significantly compared to the open approach. Results from the CLASICC (Conventional versus Laparoscopic-Assisted Surgery In patients with Colorectal Cancer) and COLOR II (COlorectal cancer Laparoscopic or Open Resection II) trials further support the use of laparoscopic surgery with improved short-term patient outcomes and minimal difference in oncological outcomes [3, 4]. The laparoscopic resection of rectal cancer, particularly in a narrow and deep pelvis is however technically challenging and often requires a prolonged training curve. Commonly cited technical limitations include the rigidity of straight laparoscopic instruments, unstable camera ship, and unsatisfactory ergonomics for the operating surgeon [5].

Robotic assisted surgery (da Vinci Surgical System, Intuitive Surgical, Sunnyvale, CA, USA) was introduced in 2000 and quickly promoted as a means to overcome some of these issues. The nature of rectal surgery with its difficult ergonomics appear well suited to a robotic approach. The articulated instruments, 3-dimensional camera view, and a stable camera platform confer significant advantages to the operating surgeon and should result in finer dissection in the confines of the pelvis [6, 7].

A full robotic approach is however not all rosy. The 2 operative fields (splenic flexure takedown and rectal dissection), potential collisions of robotic arms, lack of tactile feedback and longer operating times are all reported disadvantages of the system. In addition, ROLARR (Robotic vs Laparoscopic Resection for Rectal Cancer) trial also suggests no statistically significant evidence of proposed superiority compared to laparoscopic surgery [8]. However, we must bear in mind that the robotic platform is constantly evolving. Innovative designs such as the use of “smart” staplers, energy device incorporation, and computer-assisted intelligence have already improved the robotic operative experience and will certainly have the potential to further shape the future of surgery [9].

The subsequent development of transanal TME (TaTME) was therefore motivated primarily by all these difficulties surrounding lower rectal dissection. This transanal approach simply offered the shortest distance to approach an otherwise tricky location, allowing an excellent visualization of an adequate distal resection margin in the process.

It is useful at this point to note the key difference between the various modalities discussed. Laparoscopy and robotic assisted surgery are both tools used in the conduct of transabdominal pelvic surgery. This basically means all anatomical concerns that surgeons face in the abdomen and pelvis will continue to persist: a narrow pelvis, an obese patient, and a very distal rectal tumor with uncertain distal transection margins. TaTME on the other hand is an approach, an approach which revolutionizes the way we look at a similar problem. It is thus impossible for us to perform a head-to-head comparison between all 3 modalities on every front.

-Heald RJ

TaTME can really be attributed to 3 key phases in the evolution of rectal cancer management: (1) Dr. Richard J. Heald’s landmark description of the TME plane in 1982, which quickly became a cornerstone of rectal cancer surgery [1]; (2) Dr. Gerhard Buess’s invention of the transanal endoscopic microsurgery (TEMS) platform to allow transanal excision of rectal polyps and early cancers [10]; (3) In 1996, Dr. Gerald Marks championed the notion of giving preoperative radiotherapy for rectal cancer downstaging to increase sphincter preservation. This was followed by transabdominal transanal (TATA) radical proctosigmoidectomy with a coloanal anastomosis as a means to restore bowel continuity and avoid a permanent colostomy [11].

These 3 crucial phases in rectal cancer surgical development essentially created a fertile environment for modern-day TaTME to develop. Other innovative minimally invasive surgery approaches soon followed, all adding to the development of TaTME. Single-incision laparoscopic surgery was developed by Castellucci et al. [12] in 2008 and made its way to colectomies in the same year. Natural orifice transluminal endoscopic surgery (NOTES) emerged and an ever-increasing variety of procedures were completed smoothly in both animal models and clinical patients [13].

The real driver behind the development of TaTME perhaps lies in the simple fact that good rectal cancer surgery is really not easy. There are many considerations: negative resection margins particularly distally, sparing of the sphincter, nerves, and other vital structures and finally performing a safe anastomosis of the neorectum to the distal rectum or anus. All these, while within the limited confines of the deep and potentially narrow pelvis. Surgeons were therefore looking eagerly for a new breakthrough technique.

It came in 2010. Transanal minimally invasive surgery (TAMIS) was introduced that year by Albert et al. [14] as a feasible alternative to TEMS [14]. It proved to be a lot more. The lower cost, flexible, and laparoscopic-based platform which is a lot more intuitive to many modern-day surgeons, proved to be warmly received and resulted in the TaTME movement. The same year saw the first series of 20 patients undergo TaTME successfully by de Lacy et al. [15]. Before long, many other subsequent studies also demonstrated similar successes, proving the safety and feasibility of this innovative “bottom-up” approach [16]. This heralded the evolution of modern-day TaTME as we know it.

-Isaac Newton

Since its inception in 2010, a significant amount of time, effort, and research has been dedicated to gauging its development. The TaTME approach particularly with a “Cecil” approach, incorporating 2 surgical teams has been shown to reduce surgical time significantly with both Chen et al. [17] and Thien et al. [18] reporting up to a 60 minutes reduction in operative time. The direct visualization of the tumor on entry has also brought relief to many surgeons. There were concerns raised though.

The initial concerns quite intuitively were mainly focused around the quality of TME specimen and its ability to consistently deliver good oncological outcomes. Other relevant questions included the ability to minimize pelvic sepsis and of course cancer seeding, having divided bowel from the onset in this technique. Its results can largely be summarized into perioperative outcomes, oncological and functional results.

-Abraham Lincoln

The common theme while evaluating the outcomes of TaTME is an overwhelming need for a structured training program and proctorship during the initial phases of clinical application. As with all new and challenging surgical techniques, the proper evolution of TaTME into a reproducible surgical technique with standardized steps and identification of key anatomical landmarks with consistent results has taken time.

In our experience, we favor the 2-team synchronous approach which allows coordinated retraction of the rectum and a significant reduction in operative time [17]. We also use a flexible transanal platform (Gel-POINT Path, Applied Medical, Rancho Santa Margarita, CA, USA) (Fig. 1A). The initial purse string, which we term the “oncological” purse string is crucial in determining the distal margin and sets the stage for subsequent dissection into the TME plane (Fig. 1B). We perform an early distal washout with betadine thereafter to minimize tumor cell spillage and colonic contamination. Once circumferential full-thickness proctectomy has been performed, we leave the anterolateral areas to the end often resulting in a “winged” appearance with subsequent dissection at the apex of the neurovascular bundle (Fig. 1C) before eventual rendezvous with the abdominal team (Fig. 1D). A running purse string, which we call the “functional” purse string is then performed either laparoscopically or hand-sewn depending on the location facilitating the entry of a transanal circular stapler and anastomosis (Fig. 1E).

There is now consensus on a structured training program for TaTME [36]. Firstly, TaTME should not be offered in every colorectal unit but centralized to specialist centers with a minimum of at least 20 cases per year. A majority verdict was also reached that the top 2 prerequisites to commencing TaTME were completion of advanced laparoscopic training and a minimum of 30 rectal cases performed independently. In addition, a minimum of 5 TEMS or TAMIS cases was proposed as a prerequisite to attempting TaTME. The desirable prerequisites for a trainer for TaTME were at least 30 cases performed independently, provision of training courses with possible cadaveric resources and an academic output of at least 2 papers a year. This was validated in a recent paper by Ho et al. [37], where they reported safe perioperative and oncological outcomes in their medium-sized colorectal unit of around 30 rectal cancer resections a year.

Perhaps the most important is direct clinical proctorship with regular evaluation of pathological quality of resected TME specimens and analysis of clinical outcome data including complications, mortality, and oncological results. With a robust and detailed framework for a structured TaTME training program in place, it can only serve to protect the interests of both patients and surgeons, while providing a platform for quality assurance and academic pursuit.

Beyond the learning curve, the TaTME movement progresses unabated. The combined use of both robotic assisted surgery and TaTME has already been described [38]. Robotic TaTME has also been introduced as a novel technique, incorporating both the benefits of TaTME and use of robotic technology [39]. This can potentially reduce surgical time, shorten the technical learning curve required and also reduce surgeon fatigue, synonymous with long and complex rectal cases [40]. To add to that, transperineal abdominoperineal resection, which involves a concurrent abdominal and perineal team has also been performed in numerous centers worldwide, reporting feasibility, an acceptable perioperative morbidity, and a relatively low rate of perineal wound dehiscence [41]. Further innovation, evolving technology, and experience on standardized techniques will only pave the way for future success and expansion of the TaTME movement.

What is certain, is that the continued development and adoption of TaTME, in the treatment of rectal cancer is here to stay. This is simply because the logic of commencing the most difficult part of the surgery early, starting with transanal to ensure an optimal distal margin is too obvious. The use of TaTME is also not merely confined to rectal cancer surgery. This novel “bottom-up” technique can easily be extended to other disease pathologies as well. Reversal of Hartmann’s procedure, revision of anastomotic strictures, or inflammatory bowel disease surgical management are some of the notable conditions which can benefit from this surgical technique.

The divergent outcomes of this surgical procedure should however warn young surgeons about the perils of adopting this demanding technique on their own. And while we eagerly await the final results of landmark randomized trials like COLOR-III and GRECCAR 11 for TaTME to formally seal its place in the armamentarium of proven rectal surgical techniques [35, 42], it will ultimately still fall on the shoulders of our current experienced minimally invasive rectal cancer surgeons to define limits and the ideal utilization of this very useful “bottom-up” surgical approach.