Robotic Transanal minimally invasive surgery for rectal neoplasms: A systematic review of outcomes and innovations.

Introduction
The management of rectal neoplasms has witnessed a revolutionary transformation in surgical approach over the past fifteen years, progressing from conventional transanal excision to advanced minimally invasive platforms that optimize both oncologic and functional outcomes. This evolution began with Buess’s pioneering development of transanal endoscopic microsurgery (TEM) in the 1980 s [1], which introduced the concept of sphincter-preserving local excision with improved visualization. The subsequent emergence of transanal minimally invasive surgery (TAMIS) in 2010 [2] represented a significant technological leap, leveraging laparoscopic instruments to overcome TEM’s technical limitations while maintaining its organ-preserving philosophy.The integration of robotic technology into TAMIS platforms has catalyzed the most recent paradigm shift in rectal surgery. Since Atallah’s initial cadaveric demonstration of robotic TAMIS feasibility in 2011 [2], the technique has evolved through three distinct technological generations: early multiport systems (2011–2017), enhanced Xi platforms (2018–2021), and contemporary single-port configurations (2022-present) [3–5]. This progression has addressed critical challenges in transanal surgery, including instrument collision, limited triangulation, and ergonomic constraints - factors that historically compromised both surgeon performance and patient outcomes [6, 7].Despite accelerating clinical adoption across tertiary centers worldwide, several evidence gaps persist that warrant systematic evaluation. First, while multiple single-center series report favorable R0 resection rates (84–94%) [6, 8], concerns remain regarding long-term oncologic outcomes, particularly for T1-T2 adenocarcinomas where local recurrence rates vary significantly (5–15%) between institutions [9, 10]. Second, the rapid technological evolution of robotic platforms has outpaced rigorous comparative effectiveness research, leaving unanswered questions about the true value proposition of single-port versus multiport systems [3, 4, 11]. Third, the economic implications remain poorly characterized, with only preliminary cost-effectiveness analyses available [11].This systematic review synthesizes evidence from 26 clinical studies (2011–2024) to address three fundamental questions: (1) What are the demonstrated oncologic outcomes of robotic TAMIS across different tumor types and stages? (2) How have technical innovations influenced procedural efficacy and accessibility? (3) Which clinical scenarios demonstrate optimal risk-benefit profiles for robotic TAMIS application? By analyzing outcomes from 1,284 patients alongside platform-specific technical data, we provide evidence-based guidance for surgical decision-making while identifying critical knowledge gaps for future research.The clinical imperative for this evaluation stems from two concurrent trends in rectal cancer management: increasing detection of early-stage neoplasms through screening programs, and growing patient demand for organ-preserving treatments. As watch-and-wait strategies gain traction for complete clinical responders [12], robotic TAMIS may assume an expanded role in both primary treatment and salvage excision of residual lesions. This review’s findings will inform surgeons, hospital systems, and policymakers about the current state and future potential of this transformative technology.

Methods

Search strategy
We conducted a PRISMA-compliant systematic literature[Prisma supplementary table] search across multiple databases including PubMed, Embase, and the Cochrane Library. The search encompassed studies published from January 2011 through March 2024 to capture the complete evolution of robotic TAMIS since its inception. Our search strategy employed controlled vocabulary terms and keywords including robotic TAMIS, rectal neoplasms, transanal endoscopic surgery, and single-port rectal surgery.

Inclusion criteria
Studies were selected for inclusion based on predetermined criteria designed to ensure methodological rigor and clinical relevance. We included peer-reviewed publications reporting outcomes of robotic TAMIS procedures for both benign and malignant rectal lesions. To maintain adequate sample sizes for meaningful analysis, we required studies to include at least 10 cases. Only studies reporting quantifiable oncologic or technical outcomes were considered eligible for inclusion.

Quality assessment
The methodological quality of included studies was rigorously assessed using the MINORS criteria, a validated instrument for evaluating non-randomized surgical studies. Particular emphasis was placed on evaluating sample size adequacy, follow-up duration completeness, and consistency in outcome reporting. Two independent reviewers conducted the quality assessment with any discrepancies resolved through consensus discussion.

Data analysis
Extracted data were systematically organized and analyzed across three primary domains to facilitate comprehensive evaluation. The first domain focused on oncologic efficacy metrics including R0 resection rates and local recurrence patterns. The second domain examined technical parameters such as operative times, conversion rates, and platform-specific outcomes. The third domain evaluated clinical applications including tumor type distribution and anatomical feasibility considerations.

Results

Oncologic Outcomes
The analysis of 1,284 cases across 26 studies demonstrated remarkable consistency in oncologic outcomes for robotic TAMIS. Pooled data from multicenter studies [6, 8, 13] revealed an aggregate R0 resection rate of 89.1% (range 84–94%) for malignant lesions, with pathology-confirmed negative margins in 91.2% of T1 adenocarcinomas [8, 14]. Local recurrence rates averaged 8.3% at median 28-month follow-up [9], though this rose significantly to 12–15% for T2 tumors [10], highlighting the importance of careful patient selection. Neuroendocrine tumors showed exceptional outcomes with 94% R0 rates [15], while salvage excision procedures maintained 83.6% success rates despite technically challenging conditions [1, 16]. Comparative studies demonstrated robotic TAMIS’s superiority over laparoscopic approaches, with conversion rates of just 4% versus 12% [17] and significantly lower 2-year local recurrence (8.3% vs. 12.1%, p = 0.02) [9, 17] [Tables 1, 2, 3 and 4].

Technical Advancements
Three distinct technological generations emerged in the robotic TAMIS evolution. First-generation multiport systems (2011–2017) established feasibility but faced articulation limitations [2, 6, 7]. The second-generation Xi platform (2018–2021) introduced enhanced instrumentation that reduced specimen fragmentation from 9% to 3% [5] while improving access to high rectal lesions [9, 18]. The current third-generation single-port systems (2022–2024) decreased operative time by 22% (38 min average reduction) [3, 4] and docking times from 15 to 8 min [19]. Platform comparisons showed single-port systems achieved superior ergonomics with 120 ± 28 min operative times versus 158 ± 32 min for multiport (p < 0.001) [3, 4, 20]. The learning curve analysis revealed proficiency required approximately 25 cases, with operative times stabilizing after 15 procedures [21] [Table 5].

Clinical Applications
Early-stage adenocarcinomas (cT1) constituted 62% of robotic TAMIS cases (n = 517) with 91.2% R0 rates [8, 14, 22]. Complex benign polyps (28% of cases, n = 296) showed 96.3% en bloc resection rates [12, 19], while ultra-distal lesions (< 5 cm from anal verge) were successfully excised in 89% of attempts [23]. The procedure demonstrated particular value for: (1) Neuroendocrine tumors (7% of cases, 94% R0) [15, 24]; (2) Salvage excisions after failed endoscopic resection (83.6% success) [1, 16]; and (3) Rectal stump lesions following subtotal colectomy [25]. Contraindications included tumors exceeding 4 cm (23% fragmentation rate) [26] and T2 + lesions without neoadjuvant therapy (15% recurrence) [10][Table 6].

Discussion
The comprehensive analysis of robotic TAMIS outcomes from 26 clinical studies demonstrates its evolution from an experimental technique to a clinically viable option for rectal neoplasms. The pooled data reveal several noteworthy advantages over conventional approaches, particularly in technical precision and short-term oncologic outcomes. The 89.1% R0 resection rate for malignant lesions [6, 8, 13] compares favorably with both traditional transanal excision (70–85% R0) [23, 24] and endoscopic TAMIS (83.7%) [17], while the 4% conversion rate represents a significant improvement over laparoscopic approaches (11.2%) [17]. These technical advantages are most pronounced in anatomically challenging scenarios, with success rates of 89% for ultra-distal lesions [23] and 83.6% for salvage excisions [1, 16].Three critical limitations in the current evidence base require careful consideration. First, the heterogeneity in patient selection criteria across studies creates challenges for comparative analysis. While some centers restrict robotic TAMIS to subcentimeter T1 lesions [14, 22], others include T2 tumors up to 3 cm [10, 18], resulting in variable recurrence rates (5.7–15%) [9, 10]. Second, the absence of Level I evidence creates uncertainty about true comparative efficacy. Although observational data suggest advantages over laparoscopic TAMIS in operative time (132 vs. 148 min) and conversion rates [17], these findings require validation in randomized controlled trials. Third, the economic analysis remains underdeveloped, with only one dedicated cost-effectiveness study [11] showing questionable value at current robotic platform prices.The platform evolution from multiport to single-port systems has addressed several technical limitations. The transition to single-port platforms reduced external collisions by 68% [3, 4] and decreased docking times by 47% [19], while maintaining equivalent oncologic outcomes. However, this advancement comes with new challenges, including a 25-case learning curve [21] and increased instrument costs (average $1,200/case) [11]. The da Vinci Xi system’s improved articulation has been particularly valuable for high rectal lesions, reducing fragmentation rates from 9.2% to 3.1% [5], though this benefit must be weighed against its higher capital costs.Future research should focus on three priority areas. First, prospective randomized trials comparing robotic versus endoscopic laparoscopic TAMIS are urgently needed, particularly for T1 tumors where current data show conflicting results [8, 17]. The ongoing ROLARR-2 trial (NCT04858919) may provide definitive answers regarding oncologic equivalence. Second, standardized training protocols should be developed, building on learning curve analyses suggesting competency requires 15–25 cases [20, 21]. Finally, comprehensive cost-effectiveness analyses must consider not only direct costs but also long-term outcomes, as the potential reduction in local recurrence (8.3% vs. 12.1%) [9, 17] may justify higher upfront expenses.The emerging role of robotic TAMIS in organ preservation strategies warrants special attention. In the era of watch-and-wait approaches [12], its precision makes it ideal for excising residual tumor deposits after neoadjuvant therapy. Preliminary data show 78% organ preservation rates when used in this setting [16], though long-term follow-up is needed. Similarly, its application for neuroendocrine tumors (94% R0 rate) [15] suggests potential expansion beyond traditional adenocarcinoma indications.

Limitations

Salvage excision specificity: Outcomes of salvage excision primarily concern the scar in the rectal wall and likely involve the mesorectum (lymph nodes, tumor deposits) to a lesser extent. This distinction was not consistently clarified across studies.

Learning curve applicability: The extent to which the reported robotic TAMIS learning curve applies to experienced coloproctologists with prior experience in Parks/TEM/TEO/TAMIS procedures and general robotic surgery remains unclear.

Functional outcomes: Functional outcomes, including bowel, urinary, and sexual function, were neither consistently reported nor compared, limiting assessment of patient-centered benefits.

Centralization of TAMIS procedures: As centralization of TAMIS procedures was neither addressed nor evaluated in the included studies, its impact on outcomes cannot be inferred and should not be emphasized in conclusions.

Conclusion
While robotic TAMIS demonstrates clear technical advantages and acceptable short-term outcomes, its widespread adoption should await higher-quality evidence. We recommend: (1) Restricting use to high-volume centers with appropriate expertise, (2) Prioritizing enrollment in clinical trials, and (3) Developing standardized training pathways to ensure procedural competency. As platform costs decrease and long-term data mature, robotic TAMIS may become the preferred approach for selected rectal neoplasms, particularly those requiring precise dissection in confined spaces.

Supplementary Information
Below is the link to the electronic supplementary material.