Abstract
Minimally invasive total mesorectal excision (TME) for rectal cancer can be performed via transanal TME (TaTME) or robotic TME (R-TME), yet comparative evidence in predominantly non-obese Asian cohorts remains limited. We evaluated a consecutive retrospective cohort during our institutional transition from TaTME to R-TME. Between 2016 and 2022, 109 patients with mid- or low-rectal adenocarcinoma underwent curative TaTME (n = 40) or R-TME (n = 69). The primary analysis used propensity score matching (37 pairs) based on age, sex, and tumor location. Outcomes included pathologic margins and lymph-node yield, perioperative results, and 3-year progression-free survival (PFS) and overall survival (OS). In the matched cohort, pathologic outcomes were comparable, with similar circumferential resection margin/distal margin positivity and lymph-node yield; distal margin length showed a nonsignificant trend toward being longer after TaTME (median 1.8 vs. 1.5 cm; P = 0.079). R-TME required longer operative time (median 330 vs. 251 min; P < 0.001) but was associated with less blood loss (30 vs. 90 mL; P = 0.014) and shorter hospital stay (7 vs. 8 days; P = 0.016); conversion occurred in 13.5% after TaTME versus 0% after R-TME (P = 0.054). Three-year OS and PFS did not differ between groups (log-rank P = 0.701 and P = 0.898, respectively), and results were consistent in a sensitivity analysis restricted to 2019–2020. Limitations include retrospective design, modest sample size, and temporal confounding. In this transition cohort, TaTME and R-TME achieved comparable short-term oncologic and survival outcomes; R-TME offered perioperative advantages, while TaTME showed a trend toward a longer distal margin that warrants cautious interpretation.
Supplementary Information
The online version contains supplementary material available at 10.1007/s11701-026-03241-8.
Keywords: Rectal cancer, TaTME, Robotic TME, Distal margin
Introduction
Surgical treatment of rectal cancer remains technically demanding because of the confined bony pelvis and the proximity of critical neurovascular structures. Achieving an optimal total mesorectal excision (TME) can be challenging, particularly for mid- and low-rectal tumors.
TME, introduced in the mid-1980s, remains the benchmark operation for reducing local recurrence and improving oncological cure. The technique entails sharp dissection along the visceral pelvic fascia—the so-called “holy plane” first described by Heald—so that the rectum and its enveloping lymphovascular mesentery are removed en bloc [1]. Perfecting TME can be technically formidable owing to limited pelvic space and patient- and tumor-specific factors that obscure this plane.
The minimally invasive era has seen open TME largely superseded by laparoscopic TME. Randomized controlled trials such as COLOR II, COREAN and CLASICC have consistently shown that laparoscopic surgery offers better short-term recovery while achieving long-term oncologic outcomes equivalent to open surgery [2–4]. Magnified, angled optics and the pneumoperitoneum afford better visualization and instrument maneuverability in the narrow pelvis; yet dissection of mid- and low-rectal tumors in obese male patients often remains challenging.
Transanal TME (TaTME) was developed to address these limitations. The first clinical report, published in 2010, described a TaTME in a 76-year-old woman with low rectal cancer [5]. By approaching the “holy plane” from the anal canal, TaTME circumvents the constraints of a narrow, adipose pelvis, enabling direct distal transection and a rendezvous with the abdominal dissection. Contemporary series have shown TaTME to improve specimen quality, reduce conversion rates and enhance selected short-term outcomes relative to laparoscopic TME [6, 7].
Robotic surgery has advanced in parallel. Since the first report of robotic TME (R-TME) in 2006 [8], uptake has accelerated—particularly after release of the fourth-generation da Vinci Xi system in 2014. Three-dimensional high-definition vision, tremor-free wristed instruments with seven degrees of freedom and superior ergonomics underpin its appeal [9]. Compared with laparoscopy, R-TME has been associated with lower conversion rates, more reliable nerve preservation in male or obese pelvis, and equivalent or slightly better margin status [10]. Although a 2017 randomized trial did not meet its primary endpoint, it reported lower conversion rates in obese (BMI > 30) and male subgroups treated robotically [11].
Both TaTME and robotic TME have emerged as advanced alternatives to conventional laparoscopy, yet their comparative benefit remains uncertain. In Asian practice, where severe obesity is less prevalent, real-world platform transitions may influence outcomes and case selection. We therefore evaluated a consecutive single-center cohort treated during our program’s transition from TaTME to robotic TME, comparing perioperative, pathologic, and 3-year oncologic outcomes for mid- and low-rectal adenocarcinoma.
Methods
Patients
This retrospective study was conducted at Taichung Veterans General Hospital, a tertiary referral center in central Taiwan. The study protocol was approved by the Institutional Review Board of Taichung Veterans General Hospital (TCVGH-IRB No.: CE25540A). Our colorectal unit evaluates approximately 600 newly diagnosed colorectal cancer patients annually. The hospital’s electronic database was queried for all consecutive patients with histologically confirmed rectal adenocarcinoma between January 2016 and December 2022. We then identified patients who underwent curative-intent surgery for mid- or low-rectal cancer and received either TaTME or R-TME with primary anastomosis; the patient selection process is summarized in Fig. 1. Mid- or low-rectal adenocarcinoma was defined on rigid proctoscopy as a tumor with its distal edge ≤ 8 cm from the anal verge and located at or below the second rectal valve (Houston valve). Data were extracted by the hospital’s Clinical Information Center as a de-identified dataset. We performed a complete-case analysis by excluding records with missing prespecified key variables (baseline clinical factors, core pathological parameters [CRM/DM status and lymph-node yield], and outcome measures; see Fig. 1 for numbers and reasons). Individuals younger than 18 years and those requiring emergency operations were excluded. Eligible cases were assigned to the TaTME or R-TME group according to the procedure performed. Patient-level variables included age, sex, body-mass index, Eastern Cooperative Oncology Group (ECOG) performance status, diabetes mellitus, chronic kidney disease, and receipt and type of neoadjuvant treatment (none, radiotherapy alone, or chemoradiotherapy). Neoadjuvant treatment consisted of long-course or short-course radiotherapy, with chemotherapy added when clinically indicated (oral fluoropyrimidine or FOLFOX). Surgery was typically performed 8–12 weeks after completion of radiotherapy. Pathologic variables included circumferential resection margin (CRM) status, distal margin (DM) status and length, and lymph node yield. Perioperative variables included operative time, estimated blood loss, conversion to open surgery, diverting stoma creation, length of stay, and early clinical outcomes (overall complications graded by the Clavien–Dindo classification, unplanned return visits, and 30-day readmissions).
Fig. 1.
Patient flow diagram. Flowchart of patient selection for mid- or low- rectal cancer undergoing TaTME or robotic TME, with exclusions applied for non-surgical management, surgery elsewhere, ineligibility for elective curative surgery, upper- rectal cancer, laparoscopic/open surgery, incomplete data, and loss to follow-up, resulting in 109 included patients (TaTME n = 40; robotic TME n = 69). TaTME transanal total mesorectal excision, TME total mesorectal excision
All patients were followed postoperatively in the outpatient clinic and received adjuvant therapy in accordance with contemporaneous National Comprehensive Cancer Network (NCCN) guideline recommendations. Surveillance imaging with contrast-enhanced chest/abdomen/pelvis computed tomography was performed every 3–6 months, with pelvic magnetic resonance imaging obtained when clinically indicated. Three-year overall survival (OS) and progression-free survival (PFS) were the primary long-term endpoints. PFS was defined as the time from surgery to the first documented recurrence (local or distant) or death from any cause, whichever occurred first. Recurrence was confirmed based on cross-sectional imaging (CT and/or MRI), and when available, supported by histopathology and/or multidisciplinary tumor board review. RECIST 1.1 was used only for radiologic response assessment in patients with measurable lesions. Sites of first recurrence/progression (local vs. distant) were summarized in the matched cohort.
Procedures
Between 2015 and 2020, TaTME at our center was performed with a two-team laparoscopic technique: one team worked transabdominally and the other transanally. A snug purse-string suture was first secured distal to the tumor, a full-thickness rectotomy was created, and a second purse-string was tied. Copious transanal irrigation was carried out before and after each purse-string. Dissection then proceeded along the mesorectal plane under direct endoscopic vision until it rendezvoused with the abdominal dissection. Introduction of the da Vinci Xi platform in 2018 triggered a progressive transition to R-TME. Robotic procedures are completed entirely transabdominally by a single console surgeon assisted by one bedside operator, following embryological planes from the peritoneal reflection to the pelvic floor to achieve an intact mesorectal specimen. This change was driven by institutional policy favoring robotic surgery and the aim of streamlining operating-room staffing. No two-team TaTME operations have been scheduled since August 2020. The annual distribution of cases is shown in Supplementary Fig. S1.
Statistical analysis
All statistical analyses were performed using SPSS Statistics for Windows, version 22.0 (IBM Corp., Armonk, NY, USA). Continuous variables are presented as medians with interquartile ranges (IQRs) and were compared using the Mann–Whitney U test. Categorical variables are presented as counts (percentages) and were compared using the χ² test or Fisher’s exact test, as appropriate. Tumor location and DM length were illustrated using dot plots. To reduce confounding, propensity score matching (PSM) was performed to create comparable cohorts based on age, sex, and tumor location, yielding 1:1 matched pairs; matched-group comparisons were then conducted. OS and PFS were estimated using the Kaplan–Meier method and compared between groups with the log-rank test. Cox proportional-hazards regression was used to evaluate factors associated with OS and PFS, with results reported as hazard ratios (HRs) and 95% confidence intervals (CIs); multivariable models were fitted using a forced-entry approach (i.e., covariates entered simultaneously). We additionally fitted forced-entry regression models for perioperative outcomes adjusting for calendar year and ERAS protocol. Given the temporal shift in surgical approach, a sensitivity analysis restricted to the overlapping operative years (2019–2020) was performed. All tests were two-sided, and P values < 0.05 were considered statistically significant.
Results
Among 1,436 patients screened, 109 were analyzed (TaTME, n = 40; R-TME, n = 69) (Fig. 1). Propensity score matching yielded 37 pairs for the primary analysis. In the matched cohort, baseline characteristics were well balanced between groups (Table 1), whereas operative year/ERAS implementation remained different. Median follow-up was longer after TaTME than R-TME (48.7 [37.3–68.8] vs. 37.0 [26.7–48.0] months). Pathologic outcomes were similar between groups (Table 2). CRM positivity and DM positivity were uncommon and did not differ, and lymph node yield was comparable. DM length tended to be longer after TaTME (median 1.8 vs. 1.5 cm; P = 0.079).
Table 1.
Baseline characteristics of patients undergoing TaTME versus robotic TME before and after propensity score matching
| Before matching | p value | After matching | p value | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| TaTME (n = 40) | Robot TME (n = 69) | TaTME (n = 37) | Robot TME (n = 37) | |||||||
| Age | 64.0 | (56.3–71.8) | 60.0 | (47.5–71.0) | 0.098 | 64.0 | (55.0-70.5) | 64.0 | (49.5–72.5) | 0.661 |
| Gender | 0.623 | 0.797 | ||||||||
| Female | 14 | (35.0%) | 21 | (30.4%) | 11 | (29.7%) | 10 | (27.0%) | ||
| Male | 26 | (65.0%) | 48 | (69.6%) | 26 | (70.3%) | 27 | (73.0%) | ||
| BMI | 22.7 | (21.4–26.0) | 23.6 | (21.7–25.8) | 0.563 | 22.7 | (21.3–26.2) | 24.1 | (22.1–25.9) | 0.673 |
| DM | 9 | (22.5%) | 13 | (18.8%) | 0.646 | 8 | (21.6%) | 6 | (16.2%) | 0.553 |
| CKD | 7 | (17.5%) | 9 | (13.0%) | 0.526 | 5 | (13.5%) | 6 | (16.2%) | 0.744 |
| ECOG | 0.470 | 0.234 | ||||||||
| 0 | 27 | (67.5%) | 48 | (69.6%) | 26 | (70.3%) | 23 | (62.2%) | ||
| 1 | 12 | (30.0%) | 16 | (23.2%) | 10 | (27.0%) | 9 | (24.3%) | ||
| 2 | 1 | (2.5%) | 5 | (7.2%) | 1 | (2.7%) | 5 | (13.5%) | ||
| Tumor location (FAV) | 0.305 | 1.000 | ||||||||
| 6–8 | 14 | (35.0%) | 34 | (49.3%) | 14 | (37.8%) | 14 | (37.8%) | ||
| 4–5 | 21 | (52.5%) | 30 | (43.5%) | 20 | (54.1%) | 20 | (54.1%) | ||
| ≤ 3 | 5 | (12.5%) | 5 | (7.2%) | 3 | (8.1%) | 3 | (8.1%) | ||
| Neoadjuvant Tx | 0.025 | 0.060 | ||||||||
| None | 11 | (27.5%) | 28 | (40.6%) | 10 | (27%) | 16 | (43.2%) | ||
| RT | 3 | (7.5%) | 14 | (20.3%) | 3 | (8.1%) | 7 | (18.9%) | ||
| CRT | 26 | (65%) | 27 | (39.1%) | 24 | (64.9%) | 14 | (27.8%) | ||
| Pathological Stage | 0.495 | 0.061 | ||||||||
| 0 | 4 | (10.0%) | 9 | (13.0%) | 2 | (5.4%) | 6 | (16.2%) | ||
| 1 | 13 | (32.5%) | 17 | (24.6%) | 13 | (35.1%) | 7 | (18.9%) | ||
| 2 | 7 | (17.5%) | 11 | (15.9%) | 6 | (16.2%) | 4 | (10.8%) | ||
| 3 | 11 | (27.5%) | 28 | (40.6%) | 11 | (29.7%) | 19 | (51.4%) | ||
| 4 | 5 | (12.5%) | 4 | (5.8%) | 5 | (13.5%) | 1 | (2.7%) | ||
| ERAS protocol | 0 | (0.0%) | 54 | (78.3%) | < 0.001** | 0 | (0.0%) | 29 | (78.4%) | < 0.001** |
| OP year | < 0.001** | < 0.001** | ||||||||
| 2016 | 3 | (7.5%) | 0 | (0.0%) | 3 | (8.1%) | 0 | (0.0%) | ||
| 2017 | 6 | (15.0%) | 0 | (0.0%) | 5 | (13.5%) | 0 | (0.0%) | ||
| 2018 | 12 | (30.0%) | 1 | (1.4%) | 12 | (32.4%) | 0 | (0.0%) | ||
| 2019 | 14 | (35.0%) | 5 | (7.2%) | 12 | (32.4%) | 5 | (13.5%) | ||
| 2020 | 5 | (12.5%) | 12 | (17.4%) | 5 | (13.5%) | 6 | (16.2%) | ||
| 2021 | 0 | (0.0%) | 21 | (30.4%) | 0 | (0.0%) | 10 | (27.0%) | ||
| 2022 | 0 | (0.0%) | 30 | (43.5%) | 0 | (0.0%) | 16 | (43.2%) | ||
| Follow up duration (month) | 49.8 | (39.9–68.9) | 37.7 | (28.1–48.4) | < 0.001** | 48.7 | (37.3–68.8) | 37.0 | (26.7–48.0) | 0.001** |
Chi-square test/Fisher’s exact test or Mann-Whitney U test. Median(IQR) *p < 0.05, **p < 0.01
TaTME: Transanal Total Mesorectal Excision, TME: Total Mesorectal Excision, BMI: Body mass index, DM: Diabetes Mellitus, CKD: Chronic Kidney Disease, ECOG : Eastern Cooperative Oncology Group, FAV: From Anal Verge, Tx: Treatment, RT: Radiotherapy, CRT: Chemoradiotherapy, ERAS: Early Recovery After Surgery, OP: Operation
Table 2.
Perioperative, short-term clinical, and pathologic outcomes in the propensity score–matched cohorts
| TaTME (n = 37) | Robot TME (n = 37) | p value | |||
|---|---|---|---|---|---|
| OP time | 251.0 | (224.5-267.5) | 330.0 | (298.0-374.0) | < 0.001** |
| Blood loss | 90.0 | (30.0-122.5) | 30.0 | (25.0–60.0) | 0.014* |
| Conversion | 5 | (13.5%) | 0 | (0.0%) | 0.054 |
| Diverting ostomy | 35 | (94.6%) | 33 | (89.2%) | 0.674 |
| Complication | 16 | (43.2%) | 11 | (29.7%) | 0.227 |
| Ileus | 5 | (13.5%) | 6 | (16.2%) | 0.744 |
| Leakage | 4 | (10.8%) | 3 | (8.1%) | 1.000 |
| Urinary retention/UTI | 4 | (10.8%) | 4 | (10.8%) | 1.000 |
| Wound infection | 1 | (2.7%) | 1 | (2.7%) | 1.000 |
| Pneumonia | 1 | (2.7%) | 1 | (2.7%) | 1.000 |
| Stroke | 0 | (0.0%) | 0 | (0.0%) | -- |
| Chylous leak | 3 | (8.1%) | 1 | (2.7%) | 0.615 |
| Hospital stay | 8.0 | (6.0–12.0) | 7.0 | (5.0-9.5) | 0.016* |
| Clavien-Dindo classification | 0.409 | ||||
| 0 | 20 | (54.1%) | 27 | (73.0%) | |
| 1 | 6 | (16.2%) | 3 | (8.1%) | |
| 2 | 7 | (18.9%) | 4 | (10.8%) | |
| 3A | 1 | (2.7%) | 0 | (0.0%) | |
| 3B | 3 | (8.1%) | 2 | (5.4%) | |
| 4 | 0 | (0.0%) | 0 | (0.0%) | |
| 5 | 0 | (0.0%) | 1 | (2.7%) | |
| Early Return Visit | 1 | (2.7%) | 0 | (0.0%) | 1.000 |
| 30-day Readmission | 4 | (10.8%) | 2 | (5.4%) | 0.674 |
| permanent stoma | 3 | (8.1%) | 1 | (2.7%) | 0.615 |
| CRM involve | 1 | (2.7%) | 2 | (5.4%) | 1.000 |
| Distal margin involve | 0 | (0.0%) | 0 | (0.0%) | -- |
| Free Distal margin (cm) | 1.8 | (1.3–2.5) | 1.5 | (0.7–2.1) | 0.079 |
| LN harvest | 18.0 | (15.5–23.5) | 18.0 | (16.0–20.0) | 0.458 |
Chi-square test/Fisher’s exact test or Mann-Whitney U test. Median(IQR) *p < 0.05, **p < 0.01
OP: Operative, UTI: Urinary Tract Infection, TaTME: Transanal Total Mesorectal Excision, TME: Total Mesorectal Excision, CRM: Circumferential Resection Margin, LN: Lymph Node
Perioperative and short-term outcomes are summarized in Table 2. Compared with TaTME, R-TME had a longer operative time (median 330 vs. 251 min; P < 0.001) but less blood loss (30 vs. 90 mL; P = 0.014) and a shorter postoperative hospital stay (7 vs. 8 days; P = 0.016). Conversion occurred in 5 patients (13.5%) after TaTME and in none after R-TME (P = 0.054). Overall complications and Clavien–Dindo grade distribution were similar between groups, as were rates of diverting stoma, anastomotic leak, ileus, 30-day readmission. After adjustment for calendar year and ERAS protocol, neither blood loss nor length of stay differed significantly between approaches (Supplementary Table S1).
Long-term oncologic outcomes were comparable between the matched cohorts. In the propensity score–matched population (n = 74), Kaplan–Meier analysis showed no significant differences between TaTME and R-TME in either OS(log-rank P = 0.701) or PFS (log-rank P = 0.898) (Fig. 2). The 3-year OS rate was 83.1% after TaTME and 79.8% after R-TME, and the 3-year PFS rate was 72.3% and 75.4%, respectively. In the matched cohort, first recurrence/progression events were predominantly distant; local recurrence was rare (Supplementary Table S3). Findings were consistent in a sensitivity analysis restricted to the overlapping operative years (2019–2020), with similar perioperative results (Supplementary Table S2) and no between-group differences in OS (log-rank P = 0.988) or PFS (log-rank P = 0.862) (Fig. 2). In Cox proportional-hazards models, ECOG performance status was independently associated with both OS and PFS, and 30-day readmission also emerged as an adverse prognostic factor, whereas the surgical approach (R-TME vs. TaTME) was not associated with OS or PFS (Tables 3 and 4).
Fig. 2.
Kaplan–Meier survival analyses in matched and sensitivity cohorts. (A, B) OS and PFS in the propensity score–matched cohort (37 vs. 37). (C, D) OS and PFS in the 2019–2020 sensitivity cohort (17 vs. 11). Log-rank P values are shown. OS overall survival; PFS progression-free survival; TaTME transanal total mesorectal excision; TME total mesorectal excision
Table 4.
Univariable and multivariable Cox regression analyses for progression free survival in the propensity score–matched cohort.(N = 74)
| Univariate | Multivariable | |||||
|---|---|---|---|---|---|---|
| HR | 95%CI | pvalue | HR | 95%CI | pvalue | |
| Age | 1.03 | (0.99-1.07) | 0.100 | |||
| Gender | ||||||
| Female | Reference | |||||
| Male | 0.77 | (0.31-1.90) | 0.568 | |||
| BMI | 1.02 | (0.90-1.16) | 0.774 | |||
| DM | 0.64 | (0.19-2.18) | 0.476 | |||
| CKD | 1.55 | (0.52-4.63) | 0.429 | |||
| ECOG | ||||||
| 0 | Reference | Reference | ||||
| 1 | 3.24 | (1.25-8.40) | 0.016* | 3.34 | (1.29-8.69) | 0.013* |
| 2 | 6.50 | (1.94-21.78) | 0.002** | 7.00 | (2.07-23.70) | 0.002** |
| Tumor location (FAV) | ||||||
| 6–8 | Reference | |||||
| 4–5 | 1.06 | (0.43-2.60) | 0.900 | |||
| ≤ 3 | 0.61 | (0.08-4.93) | 0.645 | |||
| Neoadjuvant Tx | 1.35 | (0.52-3.50) | 0.531 | |||
| CRM involve | 3.07 | (0.71-13.34) | 0.135 | |||
| Distal margin involve | -- | |||||
| Distal margin (cm) | 0.80 | (0.47-1.39) | 0.431 | |||
| LN harvest | 1.00 | (0.94-1.06) | 0.964 | |||
| OP time | 1.00 | (1.00-1.01) | 0.224 | |||
| Blood loss | 1.00 | (1.00-1.01) | 0.809 | |||
| Conversion | 0.04 | (0.00-38.40) | 0.364 | |||
| Diverting ostomy | -- | |||||
| 30-day Readmission | 3.02 | (0.88-10.36) | 0.078 | 3.53 | (1.01-12.34) | 0.048* |
| Complication | 2.02 | (0.86-4.77) | 0.109 | |||
| Clavien-Dindo classification | ||||||
| 0–2 | Reference | |||||
| 3–5 | 1.97 | (0.58-6.71) | 0.281 | |||
| ERAS protocol | 0.86 | (0.34-2.15) | 0.742 | |||
| OP year | ||||||
| 2016–2017 | 0.88 | (0.16-4.84) | 0.882 | |||
| 2018 | 1.09 | (0.28-4.25) | 0.907 | |||
| 2019 | 0.33 | (0.06-1.84) | 0.206 | |||
| 2020 | 1.84 | (0.49-6.89) | 0.365 | |||
| 2021 | 1.05 | (0.23-4.73) | 0.946 | |||
| 2022 | Reference | |||||
| Group | ||||||
| TaTME | Reference | |||||
| Robot TME | 1.09 | (0.45-2.64) | 0.844 | |||
Cox proportional hazard regression. *p < 0.05, **p < 0.01
HR: Hazard Ratio, BMI: Body mass index, DM: Diabetes Mellitus, CKD: Chronic Kidney Disease, ECOG : Eastern Cooperative Oncology Group, FAV: From Anal Verge, Tx: treatment, CRM: Circumferential Resection Margin, LN: Lymph Node, OP: Operative, TaTME: Transanal Total Mesorectal Excision, TME: Total Mesorectal Excision
Table 3.
Univariable and multivariable Cox regression analyses for overall survival in the propensity score–matched cohort (N = 74)
| Univariate | Multivariable | |||||
|---|---|---|---|---|---|---|
| HR | 95%CI | p value | HR | 95%CI | p value | |
| Age | 1.04 | (0.99-1.08) | 0.101 | |||
| Gender | ||||||
| Female | Reference | |||||
| Male | 0.82 | (0.28-2.37) | 0.714 | |||
| BMI | 1.02 | (0.88-1.18) | 0.792 | |||
| DM | 0.56 | (0.13-2.48) | 0.446 | |||
| CKD | 1.65 | (0.47-5.82) | 0.434 | |||
| ECOG | ||||||
| 0 | Reference | Reference | ||||
| 1 | 1.82 | (0.58-5.75) | 0.307 | 1.79 | (0.57-5.65) | 0.322 |
| 2 | 9.02 | (2.58-31.49) | 0.001** | 9.46 | (2.66-33.63) | < 0.001** |
| Tumor location (FAV) | ||||||
| 6–8 | Reference | |||||
| 4–5 | 1.46 | (0.49-4.31) | 0.493 | |||
| ≤ 3 | 1.11 | (0.13-9.65) | 0.922 | |||
| Neoadjuvant Tx | 1.19 | (0.41-3.44) | 0.745 | |||
| CRM involve | 4.31 | (0.97-19.17) | 0.055 | |||
| Distal margin involve | -- | |||||
| Distal margin (cm) | 0.94 | (0.50-1.76) | 0.837 | |||
| LN harvest | 1.01 | (0.95-1.08) | 0.782 | |||
| OP time | 1.00 | (1.00-1.01) | 0.082 | |||
| Blood loss | 1.00 | (0.99-1.01) | 0.920 | |||
| Conversion | 0.04 | (0.00-101.09) | 0.427 | |||
| Diverting ostomy | -- | |||||
| 30-day Readmission | 3.96 | (1.11-14.12) | 0.034* | 4.20 | (1.15-15.34) | 0.030* |
| Complication | 2.22 | (0.83-5.98) | 0.114 | |||
| Clavien-Dindo classification | ||||||
| 0–2 | Reference | |||||
| 3–5 | 1.56 | (0.35-6.86) | 0.559 | |||
| ERAS protocol | 0.60 | (0.19-1.89) | 0.384 | |||
| OP year | ||||||
| 2016–2017 | 0.90 | (0.14-5.53) | 0.905 | |||
| 2018 | 0.65 | (0.12-3.57) | 0.619 | |||
| 2019 | 0.34 | (0.05-2.17) | 0.255 | |||
| 2020 | 1.70 | (0.37-7.74) | 0.490 | |||
| 2021 | 0.76 | (0.12-4.59) | 0.762 | |||
| 2022 | Reference | |||||
| Group | ||||||
| TaTME | Reference | |||||
| Robot TME | 1.03 | (0.37-2.86) | 0.959 | |||
Cox proportional hazard regression. *p < 0.05, **p < 0.01
HR: Hazard Ratio, BMI: Body mass index, DM: Diabetes Mellitus, CKD: Chronic Kidney Disease, ECOG : Eastern Cooperative Oncology Group, FAV: From Anal Verge, Tx: treatment, CRM: Circumferential Resection Margin, LN: Lymph Node, OP: Operative, TaTME: Transanal Total Mesorectal Excision, TME: Total Mesorectal Excision
Discussion
In this study, we compared two advanced surgical approaches for mid- and low-rectal cancer: R-TME and TaTME. We found that both techniques achieved comparable short-term surgical outcomes. Minor differences were observed in operative time, intraoperative blood loss, conversion to open surgery, and length of hospital stay. This suggests that, in the hands of an experienced team, both R-TME and TaTME can yield excellent results.
One notable difference between the techniques was operative time. Consistent with recent meta-analyses [12], the operative time for R-TME in our cohort was approximately 79 min longer than that of the two-team TaTME approach. The robotic platform requires additional setup steps—such as system docking, instrument exchanges, and ensuring a sterile configuration—that add about 20–30 min to the procedure. Even as the surgical team gains experience, these steps still account for roughly 15–20% of total operative time in many reports [13, 14]. Additionally, the surgical workflow differs between approaches. R-TME is typically performed sequentially by a single team, with the abdominal phase completed before low rectal dissection. In contrast, TaTME is often conducted by two teams simultaneously (abdominal and transanal), which shortens overall operative time.
Despite the longer duration, R-TME has not been associated with higher complication rates. Multiple randomized trials and meta-analyses have reported that R-TME does not increase common short-term complications compared with conventional laparoscopic TME. These include surgical site infection, urinary retention, and 30-day postoperative morbidity. In fact, the stable, magnified 3D visualization provided by the robotic system improves surgical precision and has been associated with lower intraoperative blood loss and a reduced risk of conversion to open surgery [15]. Our findings were consistent with these advantages. Although R-TME had lower blood loss and shorter hospital stay in unadjusted matched analyses, these differences were attenuated after adjusting for calendar year and ERAS protocol (Supplementary Table S1), implying an era/ERAS contribution. Even so, the robotic platform may remain advantageous in technically challenging pelvic anatomy or complex cases [16].
Such challenging cases typically include male patients with a narrow pelvis and patients with obesity (BMI ≥ 30 kg/m²). Previous studies have confirmed that a narrow male pelvis and a high BMI can significantly prolong operative time and increase conversion rates in conventional laparoscopic TME [17, 18]. TaTME’s bottom-up perspective provides an improved view of the distal rectum, which can shorten deep pelvic dissection time and help avoid technical difficulties caused by confined space [19]. On the other hand, R-TME leverages high-resolution 3D imaging and wristed instruments with seven degrees of freedom, a combination that has contributed to lower conversion rates and reduced blood loss in numerous comparative studies [20, 21]. Although sex and BMI were recorded (Table 1), the number of high-risk patients was small. Specifically, there were too few patients with a narrow male pelvis or BMI ≥ 30 kg/m² to support a powered subgroup analysis. Consequently, we could not determine the optimal approach for these high-risk subgroups in the present cohort. Future studies with larger, prospectively stratified samples are warranted to clarify whether TaTME or R-TME confers greater benefit in patients with challenging pelvic anatomy or elevated BMI.
Since 2019 our institution has gradually introduced the Enhanced Recovery After Surgery (ERAS) concept and started to establish related protocols. Most TaTME cases (2016–2019) were managed under conventional perioperative care. In contrast, most R-TME cases (2019–2022) benefited from a fully implemented ERAS pathway. Previous studies have confirmed that ERAS alone can shorten postoperative length of stay by 1–2 days [22, 23]. Therefore, the shorter LOS in the R-TME group may reflect both the robotic platform and ERAS protocols. It may not be attributable to surgical technique alone. Nevertheless, contemporary literature suggests that robotic TME may be particularly well suited to ERAS pathways, potentially contributing to reduced conversion, improved hemostasis, earlier mobilization, and shorter length of stay [24, 25]. Thus, the observed LOS difference may reflect a combined effect of the robotic platform and standardized perioperative care, rather than ERAS alone.
Regarding pathological outcomes, the two techniques demonstrated comparable CRM status and lymph-node yield, indicating comparable oncological safety. Our results mirror those of a 2023 network meta-analysis [26]. DM length showed a nonsignificant trend toward being longer after TaTME. This observation should be interpreted cautiously given the modest sample size and the influence of tumor height on DM management. Margin outcomes, however, is not uniform across centers. Two meta-analyses and a multicenter matched study published in 2025 reported a CRM-positive rate difference of < 1% between TaTME and R-TME [27–29]. Across studies, overall CRM-positive rates ranged from 2% to 7%, without consistent statistical superiority. Taken together, current high-quality evidence suggests that TaTME and R-TME offer broadly comparable margin security, with modest, center-dependent differences. Surgical approach should be tailored to tumor height and patient body habitus, as well as instrument reach. Most importantly, it should reflect the surgeon’s accumulated experience.
High-quality randomized evidence on long-term oncologic outcomes is still lacking. High-quality randomized evidence for direct comparison remains limited. The ongoing COLOR-III and ROLARR trials will provide only indirect comparisons [11, 30]. At present, direct data come from a handful of retrospective series. A 2024 multicenter retrospective study showed no statistically significant difference in 5-year OS or PFS between TaTME and R-TME [31]. Similarly, a 2021 retrospective cohort reported comparable 3-year OS rates—87.6% for TaTME versus 90.4% for R-TME—without reaching statistical significance [20]. Our own data show long-term outcomes that differ little from those reported in these studies.
Learning-curve considerations are pivotal when interpreting our data. Published systematic reviews indicate that TaTME requires 40–70 cases to reach a plateau in operative efficiency and margin quality, whereas R-TME attains proficiency after roughly 30–40 cases [32–34]. Consequently, the 40 TaTME procedures in our series fall within the early implementation phase. This phase is historically associated with greater variability in outcomes. In Norway, concerns about multifocal local recurrence prompted a temporary nationwide moratorium on TaTME [35, 36]. Our transition from TaTME to R-TME was driven primarily by institutional adoption of the robotic platform and operating-room logistics, rather than concerns regarding recurrence in our TaTME experience. Local recurrence was rare in the matched cohort (0 vs. 1 case), and most progression events were distant (Supplementary Table S3). This pattern may reflect the fact that all lead surgeons were already highly experienced in laparoscopic TME and therefore well versed in pelvic anatomy before adopting TaTME or robotic TME. The seemingly more stable short-term results of our R-TME cohort are likewise in line with evidence showing that high-volume laparoscopic surgeons require a shorter robotic learning curve [37].
Limitations of the study
This retrospective, single-center study is subject to selection bias and unmeasured confounding. ERAS implementation coincided with the robotic era, and no TaTME cases were managed under ERAS, leading to potential residual temporal confounding despite year-adjusted models and overlapping-years sensitivity analyses. The modest sample size limits statistical power and generalizability. TME specimen quality grading and functional/quality-of-life outcomes were not routinely available in our records.
Conclusions and future directions
In this consecutive single-center transition cohort, R-TME and TaTME demonstrated comparable short-term safety and 3-year oncologic outcomes for mid- and low-rectal cancer. R-TME was associated with less blood loss, fewer conversions, and a shorter length of stay. DM integrity and other pathologic metrics were similar between approaches. TaTME showed a nonsignificant trend toward a longer DM. These findings support R-TME as a reasonable primary option in predominantly non-obese Asian practice, while TaTME may remain useful in selected cases. Longer follow-up and prospective studies, including evaluation of hybrid robotic–transanal strategies, are warranted.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
We would like to express our sincere gratitude to the Biostatistics Task Force of Taichung Veterans General Hospital, Taichung, Taiwan, for their invaluable support and assistance in the statistical analysis for this study.
Author contributions
All authors contributed to the study. Study conception and design were performed by Chang-Lin Lin, with supervision by Feng-Fan Chiang. Material preparation and data collection were performed by Ming-Cheng Chen, Chun-Yu Lin, Shih-Wei Chiang, Hou-Hsuan Cheng, Shang-Chih Huang and Yen-Chen Shao. Formal analysis and methodology were conducted by Chang-Lin Lin. The first draft of the manuscript was written by Chang-Lin Lin and Wei-Yuan Chen, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
Funding
Open access funding provided by Taichung Veterans General Hospital. The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.
Data availability
Data can be made available from the corresponding author on reasonable request.
Declarations
Competing interests
The authors declare no competing interests.
Ethics approval
This retrospective study protocol was approved by the Institutional Review Board of Taichung Veterans General Hospital (TCVGH-IRB No.: CE25540A).
Consent to participate
The requirement for informed consent was waived by the TCVGH-IRB due to the retrospective design and the use of de-identified data.
Footnotes
Feng-Fan Chiang and Wei-Yuan Chen are co-senior authors.
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Heald RJ (1988) The ‘Holy plane’ of rectal surgery. J R Soc Med 81(9):503–508. 10.1177/014107688808100904 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Jayne DG, Thorpe HC, Copeland J, Quirke P, Brown JM, Guillou PJ (2010) Five-year follow-up of the medical research Council CLASICC trial of laparoscopically assisted versus open surgery for colorectal cancer. Br J Surg 97(11):1638–1645. 10.1002/bjs.7160 [DOI] [PubMed] [Google Scholar]
- 3.van der Pas MH, Haglind E, Cuesta MA, Fürst A, Lacy AM, Hop WC et al (2013) Laparoscopic versus open surgery for rectal cancer (COLOR II): short-term outcomes of a randomised, phase 3 trial. Lancet Oncol 14(3):210–218. 10.1016/s1470-2045(13)70016-0 [DOI] [PubMed] [Google Scholar]
- 4.Jeong SY, Park JW, Nam BH, Kim S, Kang SB, Lim SB et al (2014) Open versus laparoscopic surgery for mid-rectal or low-rectal cancer after neoadjuvant chemoradiotherapy (COREAN trial): survival outcomes of an open-label, non-inferiority, randomised controlled trial. Lancet Oncol 15(7):767–774. 10.1016/s1470-2045(14)70205-0 [DOI] [PubMed] [Google Scholar]
- 5.Sylla P, Rattner DW, Delgado S, Lacy AM (2010) NOTES Transanal rectal cancer resection using Transanal endoscopic microsurgery and laparoscopic assistance. Surg Endosc 24(5):1205–1210. 10.1007/s00464-010-0965-6 [DOI] [PubMed] [Google Scholar]
- 6.Emile SH, Wignakumar A, Horesh N, Garoufalia Z, Rogers P, Zhou P et al (2024) Outcomes of Transanal total mesorectal excision compared to laparoscopic total mesorectal excision: A meta-analysis of randomized controlled trials. Surgery 175(2):289–296. 10.1016/j.surg.2023.10.006 [DOI] [PubMed] [Google Scholar]
- 7.Hou S, Jiang S, Yu R, Hou H, Liu Z, Li L et al (2025) Comparison of efficacy and safety between TaTME and LaTME for middle and low rectal cancer: A meta-analysis of propensity score matching studies. Curr Probl Surg 69:101792. 10.1016/j.cpsurg.2025.101792 [DOI] [PubMed] [Google Scholar]
- 8.Pigazzi A, Ellenhorn JD, Ballantyne GH, Paz IB (2006) Robotic-assisted laparoscopic low anterior resection with total mesorectal excision for rectal cancer. Surg Endosc 20(10):1521–1525. 10.1007/s00464-005-0855-5 [DOI] [PubMed] [Google Scholar]
- 9.Ngu JC, Tsang CB, Koh DC (2017) The Da Vinci xi: a review of its capabilities, versatility, and potential role in robotic colorectal surgery. Robot Surg 4:77–85. 10.2147/rsrr.S119317 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Liu Y, Liu M, Lei Y, Zhang H, Xie J, Zhu S et al (2022) Evaluation of effect of robotic versus laparoscopic surgical technology on genitourinary function after total mesorectal excision for rectal cancer. Int J Surg 104:106800. 10.1016/j.ijsu.2022.106800 [DOI] [PubMed] [Google Scholar]
- 11.Jayne D, Pigazzi A, Marshall H, Croft J, Corrigan N, Copeland J et al (2017) Effect of Robotic-Assisted vs conventional laparoscopic surgery on risk of conversion to open laparotomy among patients undergoing resection for rectal cancer: the ROLARR randomized clinical trial. JAMA 318(16):1569–1580. 10.1001/jama.2017.7219 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Zhu XM, Bai X, Wang HQ, Dai DQ (2025) Comparison of efficacy and safety between robotic-assisted versus laparoscopic surgery for locally advanced mid-low rectal cancer following neoadjuvant chemoradiotherapy: a systematic review and meta-analysis. Int J Surg 111(1):1154–1166. 10.1097/js9.0000000000001854 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Hagen ME, Jung MK, Ris F, Fakhro J, Buchs NC, Buehler L et al (2017) Early clinical experience with the Da Vinci Xi surgical system in general surgery. J Robot Surg 11(3):347–353. 10.1007/s11701-016-0662-0 [DOI] [PubMed] [Google Scholar]
- 14.Somashekhar SP, Deshpande AY, Ashwin KR, Gangasani R, Kumar R (2020) A prospective randomized controlled trial comparing conventional Intuitive® procedure card recommended Port placement with the modified Indian (Manipal) technique. J Minim Access Surg 16(3):246–250. 10.4103/jmas.JMAS_18_19 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Gahunia S, Wyatt J, Powell SG, Mahdi S, Ahmed S, Altaf K (2025) Robotic-assisted versus laparoscopic surgery for colorectal cancer in high-risk patients: a systematic review and meta-analysis. Tech Coloproctol 29(1):98. 10.1007/s10151-025-03141-3 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Luca F, Craigg DK, Senthil M, Selleck MJ, Babcock BD, Reeves ME et al (2018) Sexual and urinary outcomes in robotic rectal surgery: review of the literature and technical considerations. Updates Surg 70(3):415–421. 10.1007/s13304-018-0581-x [DOI] [PubMed] [Google Scholar]
- 17.Tschann P, Brock T, Weigl MP, Clemens P, Brunner W, Attenberger C et al (2023) Tumour, narrow pelvis and surgery specific factors for total mesorectal excision quality and morbidity following rectal cancer resection. BJS Open 7(6). 10.1093/bjsopen/zrad114 [DOI] [PMC free article] [PubMed]
- 18.Zhang Q, Wei J, Chen H (2023) Advances in pelvic imaging parameters predicting surgical difficulty in rectal cancer. World J Surg Oncol 21(1):64. 10.1186/s12957-023-02933-x [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Migaczewski M, Rymarowicz J, Kołodziejska K, Grochowska A, Wysocki M, Twardowska H et al (2023) A longer pelvis is associated with longer operative time in Transanal total mesorectal excision (TME) but not in laparoscopic TME. Results from a retrospective cohort study. Wideochir Inne Tech Maloinwazyjne 18(2):287–297. 10.5114/wiitm.2023.125294 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Feng Q, Yuan W, Li T, Tang B, Jia B, Zhou Y et al (2022) Robotic versus laparoscopic surgery for middle and low rectal cancer (REAL): short-term outcomes of a multicentre randomised controlled trial. Lancet Gastroenterol Hepatol 7(11):991–1004. 10.1016/s2468-1253(22)00248-5 [DOI] [PubMed] [Google Scholar]
- 21.Duhoky R, Rutgers MLW, Burghgraef TA, Stefan S, Masum S, Piozzi GN et al (2024) Long-Term outcomes of robotic versus laparoscopic total mesorectal excisions: A Propensity-Score matched cohort study of 5-year survival outcomes. Ann Surg Open 5(2):e404. 10.1097/as9.0000000000000404 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Zhang W, Wang F, Qi S, Liu Z, Zhao S, Zhang N et al (2023) An evaluation of the effectiveness and safety of the enhanced recovery after surgery (ERAS) program for patients undergoing colorectal surgery: a meta-analysis of randomized controlled trials. Wideochir Inne Tech Maloinwazyjne 18(4):565–577. 10.5114/wiitm.2023.131426 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Sauro KM, Smith C, Ibadin S, Thomas A, Ganshorn H, Bakunda L et al (2024) Enhanced recovery after surgery guidelines and hospital length of Stay, Readmission, Complications, and mortality: A Meta-Analysis of randomized clinical trials. JAMA Netw Open 7(6):e2417310. 10.1001/jamanetworkopen.2024.17310 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.El-Ahmar M, Peters F, Green M, Dietrich M, Ristig M, Moikow L et al (2023) Robotic colorectal resection in combination with a multimodal enhanced recovery program - results of the first 100 cases. Int J Colorectal Dis 38(1):95. 10.1007/s00384-023-04380-2 [DOI] [PubMed] [Google Scholar]
- 25.Zou J, Zhu H, Tang Y, Huang Y, Chi P, Wang X (2025) Robotic versus laparoscopic surgery for rectal cancer: an updated systematic review and meta-analysis of randomized controlled trials. BMC Surg 25(1):86. 10.1186/s12893-025-02805-z [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26.Seow W, Dudi-Venkata NN, Bedrikovetski S, Kroon HM, Sammour T (2023) Outcomes of open vs laparoscopic vs robotic vs Transanal total mesorectal excision (TME) for rectal cancer: a network meta-analysis. Tech Coloproctol 27(5):345–360. 10.1007/s10151-022-02739-1 [DOI] [PubMed] [Google Scholar]
- 27.Lee L, de Lacy B, Gomez Ruiz M, Liberman AS, Albert MR, Monson JRT et al (2019) A multicenter matched comparison of Transanal and robotic total mesorectal excision for mid and Low-rectal adenocarcinoma. Ann Surg 270(6):1110–1116. 10.1097/sla.0000000000002862 [DOI] [PubMed] [Google Scholar]
- 28.Chaouch MA, Hussain MI, Jellali M, Gouader A, Mazzotta A, da Costa AC et al (2025) Systematic review and meta-analysis comparing robotic total mesorectal excision versus Transanal total mesorectal excision for rectal cancer. Scand J Surg 114(1):73–83. 10.1177/14574969241271784 [DOI] [PubMed] [Google Scholar]
- 29.Kossenas K, Kouzeiha R, Hashem H, Elshamsy A, Georgopoulos F (2025) Comparing the perioperative, postoperative, and oncological outcomes between robotic and Transanal total mesorectal excision for rectal cancer: an updated systematic review and meta-analysis of prospective studies with a subgroup analysis for overweight patients. J Robot Surg 19(1):276. 10.1007/s11701-025-02460-9 [DOI] [PubMed] [Google Scholar]
- 30.Deijen CL, Velthuis S, Tsai A, Mavroveli S, de Lange-de Klerk ES, Sietses C et al (2016) COLOR III: a multicentre randomised clinical trial comparing Transanal TME versus laparoscopic TME for mid and low rectal cancer. Surg Endosc 30(8):3210–3215. 10.1007/s00464-015-4615-x [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.de’Angelis N, Marchegiani F, Martínez-Pérez A, Biondi A, Pucciarelli S, Schena CA et al (2024) Robotic, transanal, and laparoscopic total mesorectal excision for locally advanced mid/low rectal cancer: European multicentre, propensity score-matched study. BJS Open 8(3). 10.1093/bjsopen/zrae044 [DOI] [PMC free article] [PubMed]
- 32.Milone M, Adamina M, Arezzo A, Bejinariu N, Boni L, Bouvy N et al (2022) UEG and EAES rapid guideline: systematic review, meta-analysis, GRADE assessment and evidence-informed European recommendations on TaTME for rectal cancer. Surg Endosc 36(4):2221–2232. 10.1007/s00464-022-09090-4 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Wong SW, Crowe P (2022) Factors affecting the learning curve in robotic colorectal surgery. J Robotic Surg 16(6):1249–1256. 10.1007/s11701-022-01373-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34.Arquillière J, Dubois A, Rullier E, Rouanet P, Denost Q, Celerier B et al (2023) Learning curve for robotic-assisted total mesorectal excision: a multicentre, prospective study. Colorectal Dis 25(9):1863–1877. 10.1111/codi.16695 [DOI] [PubMed] [Google Scholar]
- 35.Wasmuth HH, Faerden AE, Myklebust T, Pfeffer F, Norderval S, Riis R et al (2020) Transanal total mesorectal excision for rectal cancer has been suspended in Norway. Br J Surg 107(1):121–130. 10.1002/bjs.11459 [DOI] [PubMed] [Google Scholar]
- 36.Riis RN, Riis MH, Benth J, Augestad KM (2023) Beyond the Transanal total mesorectal excision moratorium: local and distant recurrence among patients operated for low rectal tumours-5-year follow-up from a Norwegian university hospital. Br J Surg 110(11):1547–1548. 10.1093/bjs/znad275 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Noh GT, Han M, Hur H, Baik SH, Lee KY, Kim NK et al (2021) Impact of laparoscopic surgical experience on the learning curve of robotic rectal cancer surgery. Surg Endosc 35(10):5583–5592. 10.1007/s00464-020-08059-5 [DOI] [PubMed] [Google Scholar]
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Supplementary Materials
Data Availability Statement
Data can be made available from the corresponding author on reasonable request.