Beyond total mesorectal excision: The emerging role of minimally invasive surgery for locally advanced rectal cancer

Abstract

Multivisceral resection and/or pelvic exenteration represents the only potential curative treatment for locally advanced rectal cancer (LARC); however, it poses significant technical challenges, which account for the high risk of morbidity and mortality associated with the procedure. As complete histopathologic resection is the most important determinant of patient outcomes, LARC often requires an extended resection beyond the total mesorectal excision plane to obtain clear resection margins. In an era when laparoscopic surgery and robot-assisted surgery are becoming commonplace, the optimal approach to extensive pelvic interventions remains controversial. However, acceptance of the suitability of minimally invasive surgery is slowly gaining traction. Nonetheless, there is still a lack of evidence in the literature about minimally invasive approaches in multiple and extensive surgical resections, highlighting the need for research studies to explore, validate, and develop this issue. This editorial aims to provide a critical overview of the currently available applications and challenges of minimally invasive abdominopelvic surgery for LARC. Furthermore, we discuss recent developments in the field of robotic surgery for LARC, with a specific focus on new innovations and emerging frontiers.

Key Words: Robotic surgery; Pelvic exenteration; Multivisceral resection; Rectal cancer; Total mesorectal excision

Core Tip: Locally advanced rectal cancer (LARC) poses a distinctive challenge for surgical resection. It is of paramount importance to define the extent of surgery and to decide whether to perform a minimally invasive procedure. Minimally invasive surgery provides adequate guidance for the surgeon to achieve complex and multiple resections with clear margins; however, no consensus regarding the optimal approach exists. Here, we assess the evidence and emerging role of robotic assistance in multivisceral pelvic exenteration beyond total mesorectal excision for LARC, where difficult operative challenges and ergonomics might be encountered.

INTRODUCTION

The benchmark of surgical strategy for patients with rectal adenocarcinoma is a total mesorectal excision (TME)-based approach. Nevertheless, locally advanced rectal cancer (LARC), when the tumor extends beyond the mesorectal envelope, remains an issue in rectal cancer treatment. If detected, cumbersome surgical handling with en-bloc multivisceral pelvic excision of both the neoplasia and its adjacent organs, beyond the well-defined pattern of TME, should be considered as the only potentially curative option.

In this issue of the World Journal of Gastrointestinal Surgery, a valuable paper by Chan et al[1] assesses the feasibility and safety of minimally invasive multivisceral resections (miMVRs) for LARC. Its main goal is to compare postoperative outcomes between robotic and laparoscopic MVR/pelvic exenteration (PE).

At the time of diagnosis, almost 6%-10% of all rectal carcinomas involve the contiguous organs, making complex multivisceral resective strategies the standard of surgical care in a relatively high percentage of cases[2]. MVR/PE surgery for LARC is a challenging and extensive approach associated with significant perioperative morbidity, mortality, and complication rates[3]. Technical difficulties may arise owing to narrow access, leading to improper visualization and delineation of anatomical planes and critical structures in the spatially strained pelvis. Over the past few years, computer-assisted technologies have promoted considerable advancements in minimally invasive approaches to TME for rectal cancers[4]. However, to date, the optimal approach to extensive pelvic surgeries remains controversial, necessitating a shared effort to gain evidence-based knowledge about it. Chan et al’s manuscript adds to the current evidence on the feasibility of minimally invasive surgery (MIS) for LARC, stating that extensive pelvic resections can be achieved using a robotic-assisted approach with satisfactory oncological outcomes. In addition, it allows for the preservation of urinary and intestinal function, thus maintaining premorbid quality of life[1].

Even though randomized trials comparing two different procedures, namely laparoscopic and robotic MVR/PE, are complex to conduct, subject to variability in surgeon expertise, and dependent on the operator and team setting, this manuscript underlines interesting findings and highlights two substantial trends that have arisen regarding robotic surgery: (1) Even though the robotic approach usually results in improved outcomes compared to open procedures, its advantages have been more difficult to document when compared with the laparoscopic approach; and (2) even though the cost-efficiency of several robot-assisted procedures has been questioned, the spread of robotic technology seems to have considerably increased the number of patients who undergo minimally invasive procedures.

APPLICATIONS AND CHALLENGES

The Beyond-TME approach is considered more of a surgical strategy than a strictly outlined procedure. It is, therefore, of paramount importance to carefully plan the intervention and adequately select patients for surgery. Over the last few decades, MIS has found extensive application in several fields of gastrointestinal oncologic surgery. Clinical trials have consistently shown that it can substantially reduce the risk of postoperative complications, the length of hospital stay, and total healthcare costs. Moreover, locally advanced malignancies have been known to be associated with higher surgical complication rates compared to their confined counterparts, as they often require exenterative operations, which may result in considerable morbidity and functional sequelae.

MIS has been shown to bear almost the same oncological outcomes as the open approach, while no difference in perioperative morbidity or complication rates between the approaches has been demonstrated[5]. This might indicate that a certain rate of complications in PE is unavoidable due to technical difficulties and complexity, regardless of the chosen approach. Nevertheless, as the minimally invasive approach to extensive pelvic surgeries becomes more frequent and surgeons’ experience with these techniques evolves, morbidity rates may decrease. To date, preliminary evidence has shown that postoperative outcomes are comparable across different centers, although higher complication rates have been reported in larger case series, perhaps reflecting the real complexity of multivisceral resective pelvic surgery. Nonetheless, MIS can be performed without affecting the adequacy of oncological resection status.

Robot-assisted pelvic surgery has been introduced as a novel approach to potentially overcome the difficulties faced in laparoscopy in rectal cancer management, including pelvic space narrowing, particularly in obese male patients with voluminous neoplasms, as well as the technical limits inherent in laparoscopic surgery itself, such as 2D vision and limited maneuverability of instruments[5]. The robotic approach in pelvic operations allows augmented vision and a stable platform, improving ergonomics for the console surgeon and leading to a minimal conversion rate. However, longer surgical times and increased costs are considerable drawbacks.

Extensive acceptance of MIS for MVR/PE is still lacking for several reasons: the number of patients considered eligible for MIS exenteration is limited, surgeon expertise is scarce, and the steep learning curve may hinder the adoption of MIS as a routine approach for extensive pelvic interventions[4]. Long-term follow-up evidence (> 5 years) or cost-benefit analysis of MIS in this setting is lacking. In this context, it is difficult to determine whether the perioperative advantages counteract the time and cost of performing miMVR. Most existing evidence regarding miMVR is in the form of monocentric case series or retrospective reviews, with no wide multicenter trials conducted thus far. Furthermore, due to the prohibitive cost of robotic surgery in some healthcare systems, the majority of data will be restricted to laparoscopic procedures only.

Since the first description of robotic PE for LARC by Shin et al[6], other authors have published papers on MVR, assessing the role of robotic assistance in this technically demanding surgery. Hino et al[7] published a retrospective study reporting optimal short-term outcomes of robotic-assisted MVR for LARC, affirming the promising role of robotic surgery for such complex resections.

Several guideline recommendations, including those from the European Association of Endoscopic Surgery[8], the Society of American Gastrointestinal and Endoscopic Surgeons[9], and the French Society of Digestive Surgery[10], suggest opting for an open approach when laparoscopic en-bloc resection cannot be achieved. The Japanese Society for Cancer of the Colon and Rectum, in light of insights acquired through the open-label, multi-institutional, randomized JCOG0404 trial[11], recommends careful analysis in determining the indications for MIS in the management of LARCs.

Chan et al[1], together with Hino et al[7], emphasized the role of robotics in the treatment of extended LARC and encouraged a review of surgical guidelines.

Despite the need to improve its application, the overall efficacy of robotic surgery is good, yielding promising results for T4 tumors, with lower postoperative morbidity compared to its laparotomic counterpart. We strongly believe that this technique allows the surgeon to obtain clear resection margins while preserving uninvolved compartments and, hence, functions. However, the choice of MIS should be carefully calibrated based on the characteristics of the patient, the disease burden, and its distribution. An interdisciplinary team should be involved in identifying eligible patients for minimally invasive MVR/PE, for whom an oncological R0 resection is conceivable, as it represents the only potential curative treatment. Accurately selected cases requiring beyond-TME MVR, especially among anatomically challenging patient subtypes with considerable body mass index or a constricted male pelvis, are where the harvested advantages of robotic assistance might translate into oncological and functional benefits, substantially justifying its operating time and associated costs. Moving forward, further multicentric prospective trials on safety, efficacy, and oncological outcomes comparing robotic assistance with laparoscopic and open MVR/PE represent the next immediate step in research priorities.

FUTURE PERSPECTIVES

Noting the challenges faced in its diffusion, we expect that the future perspectives of robotic assistance lie in enhancing the ergonomic and visual aspects of the operating field, as well as improving postoperative outcomes. Moving forward, more studies are required to yield solid evidence for the establishment of the role of robot-assisted surgery in beyond-TME MVR/PE, connecting the interplay between perioperative factors and oncological outcome factors to the overall costs of care.

It is worth noting that the current robotic platforms have recently been integrated with several advanced imaging techniques, representing useful tools for improving the accuracy of surgical dissection and, thus, the adequacy of oncological margin status. Early evidence has shown that indocyanine green fluorescence is a promising method for real-time intraoperative assessment of tissue viability and identification of compartment lymph nodes during robotic dissections. Advances in magnetic resonance imaging software images have fostered 3D modeling to produce actual-size, detailed representations of critical structures that could potentially distinguish fibrotic from diseased tissues. Additionally, the integration of real-time stereotactic navigation on a robotic platform to aid in the identification of critical structures has become achievable. Although nascent and fragmented at this point, these breakthroughs are promising heralds of a new era in robotic surgery, where computer-assisted systems facilitate intraoperative decision-making.

Another aspect that requires attention is promoting patient involvement in future clinical studies on robotic PE surgery. In this era of patient-centered and patient-tailored care, this approach may guide us toward the healthcare systems of the future, which are increasingly patient-driven.

CONCLUSION

MIS approaches for MVR and PE are burgeoning to improve oncological outcomes and reduce perioperative morbidity. Minimally invasive approaches to extensive pelvic surgeries are feasible in select patient groups with favorable anatomy and tumor characteristics in specialized centers. Although challenges in robotic surgical assistance persist, along with limited expertise and a continuous learning curve, this minimally invasive approach to complex pelvic multiorgan resections with significant functional benefits shows a promising role.