Abstract
Background/Aim: While some research has revealed the potential short-term advantages of robot-assisted low anterior resection (LAR) in patients with mid-to-low rectal cancer, studies focusing on the permanent stoma rate remain limited.
Patients and Methods: We conducted a retrospective analysis on a continuous series of patients with non-metastatic mid-to-low rectal cancer. Between 2016 and 2020, these patients underwent either robot-assisted or traditional laparoscopic LAR at a single center. We used a propensity score matching technique, and the participants were matched in a 1:2 ratio and a caliper of 0.05.
Results: After matching, our cohort consisted of 44 patients from the robot-assisted LAR group and 88 from the laparoscopic LAR group. The long-term results, such as overall survival, cancer-free survival, and local and distant recurrence rates were similar between the two groups. However, the robot-assisted group exhibited a notably shorter average post-surgery hospitalization (10.8 vs. 16.7 days, p=0.001), reduced incidence of anastomotic leakage (11.4% vs. 37.5%, p<0.001), fewer patients requiring a permanent stoma (13.6% vs. 29.5% p=0.044), and significantly lower occurrences of grade III Clavien-Dindo surgical complications. Furthermore, the robot-assisted procedures had a diminished frequency of firing three or more staplers (2.3% vs. 26.1%, p=0.001). A multivariate logistic regression indicated that robot-assisted LAR is independently associated with a reduced risk of permanent stoma (odds ratio=0.28, p=0.033, 95% confidence interval=0.087-0.901).
Conclusion: In patients with mid-to-low rectal cancer, robot-assisted LAR, despite comparable long-term survival and recurrence rates, displayed reduced complications, including fewer instances of anastomotic leakage and permanent stoma requirements than its laparoscopic counterpart. These findings imply the potential superiority of robot-assisted surgical techniques for mid-to-low rectal patients.
Introduction
Surgical resection remains a key treatment for rectal cancer, with a shift from open surgery to minimally invasive approaches. Traditional laparoscopy, though effective, faces challenges in the narrow pelvis due to rigid instruments and limited dexterity. In contrast, robot-assisted resection offers advantages by improving precision, overcoming counter-intuitive motion, reducing assistant dependence, and providing reliable safety even in elderly patients (1, 2).
While robot-assisted surgery offers greater instrument flexibility, especially in narrow spaces, it also comes with higher costs compared to laparoscopy (3). Therefore, stronger evidence is needed to justify its clinical use. Randomized trials have shown similar outcomes between robotic and laparoscopic rectal resections in terms of total mesorectal excision (TME) quality, morbidity, and conversion rates (4-6). Some studies suggest short-term benefits of robot-assisted LAR for mid-to-low rectal cancer (7), but conflicting results across trials (8) make definitive conclusions difficult.
Few studies have evaluated long-term permanent stoma outcomes after these procedures. Therefore, this study compares the safety, efficacy, and long-term stoma status of robot-assisted versus laparoscopic low anterior resection for mid-to-low rectal cancer, using propensity score matching to adjust for confounders.
Patients and Methods
The Chang Gung Medical Foundation Institutional Review Board approved this study (IRB No. 202301006B0). This study was performed in accordance with the Declaration of Helsinki. We collected and analyzed the data of 1162 patients with rectal cancer who underwent surgery at the Division of Colorectal Surgery, Chang Gung Memorial Hospital, Linkou, from January 1, 2016, to December 31, 2020 (Figure 1). Before the surgery, we performed preoperative evaluations such as colonoscopy, chest-pelvis computed tomography (CT), pelvic magnetic resonance imaging (MRI), rectal sonography (if needed), and essential laboratory tests (including serum carcinoembryonic antigen). We also prospectively recorded each patient’s clinical characteristics, such as age, sex, comorbidities (cardiovascular disease, cirrhosis, etc.), tumor location, and the neoadjuvant chemoradiation regimens.
Flow diagram of the study population. LAR: Low anterior resection; CRC: colorectal cancer; GIST: gastrointestinal stromal tumor; NET: neuroendocrine tumor; taTME: Transanal Total Mesorectal Excision.
All patients underwent multidisciplinary team (MDT) discussion before treatment. Those with locally advanced rectal cancer (cT3, cT4, or cN+) received either neoadjuvant concurrent chemoradiation (CCRT) or short-course radiotherapy. CCRT involved a 5-fluoropyrimidine-based regimen (5-FU, capecitabine, or tegafur) with 50.4 Gy in 28 fractions, followed by surgery after 6-8 weeks. Short-course radiotherapy delivered 25 Gy in 5 fractions, with surgery performed 8-10 days later or after additional neoadjuvant chemotherapy. Adjuvant chemotherapy was 5-fluoropyrimidine-based, with oxaliplatin use at the surgeon’s discretion.
The robotic system used was the Da Vinci® Xi (Intuitive Surgical, Sunnyvale, CA, USA) with four robotic arms and one assistant arm. Anastomosis was performed using a 29-mm ILS curved intraluminal stapler (CDH 29, Ethicon) with or without hand-sewn reinforcement, or via coloanal hand-sewn anastomosis, as determined intraoperatively. Distal rectal transection used cartridges, with additional firings if one was insufficient, often due to a narrow pelvis, limited visualization, or angle constraints. Multiple firings are strongly associated with anastomotic leakage (9). ECHELON FLEX™ ENDOPATH® Staplers (Ethicon) with 60 mm or 45 mm green cartridges were used in both robotic and laparoscopic groups, with cartridge size chosen intraoperatively. Air-leak tests were routinely performed; leakage prompted additional sutures or re-anastomosis with a protective stoma if unresolved. Surgeons typically created diverting stomas in patients with low rectal tumors, narrow pelvis, neoadjuvant radiotherapy, or malnutrition (10-13), though final decisions were made intraoperatively.
Anastomotic leakage was diagnosed clinically or radiologically, indicated by diffuse peritonitis, fecal discharge from wounds or drains, pelvic abscess with sepsis, pus-like anal discharge, or rectovaginal fistula. While most cases underwent imaging, patients with diffuse peritonitis often required immediate laparotomy. Initial management involved laparoscopic diversion and drainage, but laparotomy was performed in hemodynamically unstable patients. Other recorded complications included wound infections, postoperative ileus (diagnosed after excluding leakage), and genitourinary issues.
Postoperative data included pathological stage, histology, hospital stay, stoma status, and complications, with standardized follow-up. Local recurrence referred to cancer reappearing in the pelvis; distant metastasis involved spread to organs such as the liver, lungs, or distant lymph nodes. Before stoma closure, digital rectal exams assessed anastomotic integrity and perianal infection; inconclusive cases underwent colonoscopy or contrast studies.
We compared patients who underwent laparoscopic or robot-assisted anterior resection, excluding those who had transanal TME, open surgery, non-curative resection, metastatic or recurrent cancer, emergency surgery, or non-adenocarcinoma histology (e.g., sarcoma, melanoma, gastrointestinal stromal tumors). Patients with upper rectal cancer (>10 cm from the anal verge) were excluded due to low risk of anastomotic leakage and stoma formation. Those who underwent abdominoperineal resection or Hartmann’s procedure were also excluded, as they had no anastomosis and received immediate permanent stomas.
Permanent stomas were defined as those not reversed by the end of follow-up or reopened after closure. The mean follow-up was 40.27 months (median 37.01; max 73.8). Tumor height averaged 7.6 cm and was assessed via colonoscopy and MRI.
Statistical analysis was performed using SPSS v24.0 (SPSS Inc., Chicago, IL, USA). Continuous variables were compared using independent t-tests, and categorical variables using chi-square or Fisher’s exact tests. Kaplan-Meier analysis with log-rank test assessed survival differences. Multivariate logistic regression identified independent predictors of permanent stoma. A p-value <0.05 was considered statistically significant.
Results
A total of 1,162 patients with rectal cancer were initially screened, and 424 patients non-with metastatic mid-to-low rectal cancer were included, divided into a robot-assisted group (n=44) and a laparoscopy group (n=380) (Figure 1). The robot-assisted group had more low rectal tumors (<5 cm from the anal verge) and received more neoadjuvant therapy (Table I). Propensity score matching (1:2 ratio, caliper 0.05) was performed using covariates including tumor height, neoadjuvant radiation, and chemotherapy. After matching, 44 robot-assisted and 88 laparoscopic patients were analyzed, with an average follow-up of 40.27 months (max 73.8).
Clinicopathological factors of patients undergoing robot-assisted and laparoscopy low anterior resection before and after propensity score matching.
Post-matching, both groups had similar clinicopathological characteristics. The robot-assisted group had a shorter hospital stay (10.8 vs. 16.7 days, p=0.001), more use of total 3D laparoscopy, and fewer cases with >3 staple firings (2.3% vs. 26.1%, p=0.001, Table II). Anastomotic techniques were comparable (p=0.882), but fewer patients in the robot group received preventive stomas (43.2% vs. 63.6%, p=0.025) and had significantly fewer permanent stomas (13.6% vs. 29.5%, p=0.044). In the laparoscopy group, 16 of 26 permanent stomas were linked to anastomosis-related issues and eight to recurrence. In the robot group, three of six were anastomosis-related, and two due to recurrence (Table III). The robot group also had lower anastomotic leakage (11.4% vs. 37.5%, p <0.001) and fewer Clavien-Dindo grade III complications (4.5% vs. 34.1%, p<0.001).
Postoperative complications and surgical factors in patients undergoing robot-assisted versus laparoscopic low anterior resection, before and after propensity score matching.
Related conditions for patients with a permanent stoma.
Long-term overall and cancer-free survival were similar between groups (Figure 2). Recurrence rates, sites, and distribution (local vs. distant, single vs. multiple metastases) were comparable (Table IV). Multivariate analysis showed robot-assisted LAR was independently associated with a lower risk of permanent stoma [odds ratio (OR)=0.28, p=0.033; 95% confidence interval (CI)=0.087-0.901] (Table V).
Kaplan-Meier survival analysis comparing robot-assisted and laparoscopic low anterior resection in patients with mid-to-low rectal cancer after propensity score matching. (A) Overall survival. (B) Cancer-free survival.
Distribution of recurrence sites among patients undergoing robot-assisted and laparoscopy low anterior resection.
Multivariate logistic regression identifying predictors of permanent stoma.
Discussion
With the growing use of robotic surgery in rectal cancer, several studies have compared it to laparoscopy (2, 5, 6-8, 14). Avoiding a permanent stoma is vital for patients with rectal cancer due to its impact on self-image, mental health, and overall quality of life (15). However, no prior studies have specifically examined long-term stoma status. This study is the first to address this issue in patients with mid-to-low rectal cancer undergoing robot-assisted or laparoscopic LAR. Our results show that robotic LAR is associated with shorter hospital stays, fewer anastomotic leaks, lower permanent stoma rates, and fewer grade III Clavien-Dindo complications.
Although the anastomotic leakage rate between the robotic and laparoscopic groups was similar after adjustment, the overall adjusted leakage rate (37.5%) was higher than previously reported, such as the 30% by Peel et al. (16). Initially, the laparoscopy group had a lower leakage rate (11.8%), fewer cases with >3 cartridge firings (17.9%), and a similar permanent stoma rate. After matching, the proportion of low rectal tumors rose from 18.4% to 33%, and neoadjuvant radiation from 13.4% to 46.6% in the laparoscopy group (Table I), both known risk factors for leakage (10, 13). Our findings suggest that in patients with similar risk profiles, robotic surgery may reduce cartridge firings and leakage rates, potentially lowering complications, hospital stay, and permanent stoma rates, thus improving outcomes.
While randomized trials have shown comparable TME quality between robot-assisted and laparoscopic anterior resections (8), robotic surgery may offer advantages in mid-to-low rectal cancer, especially in obese or male patients (4, 7, 17). In our study, circumferential and distal margins were similar before adjustment. After adjustment, the robotic group had fewer involved circumferential margins, while the laparoscopy group had longer distal margins. The high rate of radiation and longer distal margins in the laparoscopy group may have masked any advantage in TME quality, resulting in similar local and distant recurrence rates.
Most existing studies compare survival, complications, and permanent stoma rates, but few address long-term stoma outcomes. In our study, robot-assisted LAR patients showed similar long-term survival and recurrence rates but had significantly lower anastomotic leakage (11.4% vs. 37.5%, p<0.001), fewer grade III complications (4.5% vs. 34.1%, p<0.001), and fewer permanent stomas (13.6% vs. 29.5%, p=0.044). These benefits may stem from better 3D visualization and reduced stapler use (18, 19). Robotic surgery also allows independent endoscope control, reducing reliance on assistants. Overall, both approaches achieved comparable oncologic outcomes, consistent with current evidence (8, 14, 20, 21), despite a higher rate of close or involved margins in the laparoscopic group, likely offset by radiotherapy and longer distal margins.
Permanent stomas significantly affect patients’ quality of life, impacting body image and overall well-being (22). Thus, avoiding a permanent stoma is a key goal in rectal cancer treatment. This study is the first to show a lower permanent stoma rate in patients undergoing robot-assisted LAR compared to laparoscopic LAR. While the ROLARR trial reported lower conversion rates in select robotic cases (e.g., male or obese patients) (4), previous studies did not address permanent stoma rates in mid-to-low rectal cancer (4-8).
In both groups, permanent stomas were mainly due to cancer recurrence or anastomotic complications (Table III), consistent with prior findings (23). While resection quality, linked to recurrence and survival, is comparable between robotic and laparoscopic LAR (8, 17), robotic surgery may offer superior anastomotic quality due to better visualization, flexible instruments, and fewer stapler firings. This may reduce anastomotic complications, improve temporary stoma closure rates, and maintain equivalent oncologic outcomes.
Our hospital’s first laparoscopic colorectal surgery was in 2007, and the first robot-assisted case followed in 2010. In this study, conversion rates were similar between the laparoscopy and robotic groups (2.3% vs. 0%, p=0.314), but the robotic group had fewer complications after propensity score matching. These findings suggest that robotic surgery offers advantages and a shorter learning curve when built on prior laparoscopic experience.
Although both groups used the same laparoscopic stapler, the robot-assisted group had a lower rate of multiple cartridge firings. A randomized trial showed similar cartridge use between laparoscopic and robotic staplers in robotic surgery (24), suggesting that the surgical approach matters more than the stapler type. The reduced firing rate in the robotic group likely results from less reliance on assistants and better angles provided by flexible robotic arms, allowing more precise cartridge application.
Study limitations. First, its retrospective, single-center design with propensity score adjustment may still carry selection bias and limit generalizability. The small sample size in the robotic group also affects result robustness. Surgical decisions, including the choice of procedure, chemoradiation type, use of oxaliplatin, and timing of surgery, varied by surgeon, introducing treatment variability. Additionally, the high cost of robotic surgery may have led to selection of healthier patients with higher socioeconomic status, potentially contributing to the lower leakage rate observed in the robotic group.
Enhanced recovery after surgery (ERAS) was not routinely applied during the study period. However, hospital stays (robotic: 10.8±4.8 days; laparoscopic: 16.7±13.9 days) were comparable to previous studies (13 vs. 14 days) (25), though ERAS may shorten stays in current practice. Due to lack of postoperative quality of life data, we could not assess this aspect. Still, existing studies have reported negative impacts of long-term (26) and even temporary stomas (27) on patients with rectal cancer. Therefore, larger prospective randomized trials are needed to validate the benefits and cost-effectiveness of robot-assisted surgery in this context.
Conclusion
Although long-term and cancer-free survival rates are similar, robot-assisted LAR is associated with fewer postoperative complications, shorter hospital stays, and lower permanent stoma rates compared to laparoscopic LAR.
Footnotes
Authors’ Contributions
Hsin Hsu: Data curation, Formal analysis, Writing - original draft. Jeng-Fu You: Supervision, Validation, Visualization. Chun-Kai Liao: Data curation, Investigation. Tzong-Yun Tsai: Data curation, Formal analysis, Investigation, Software. Shu Huan Huang: Conceptualization, Investigation, Methodology, Validation, Visualization, Writing - review & editing.
Conflicts of Interest
All Authors declare no conflicts of interest in relation to this study.
Funding
There was no research support for this study.
Artificial Intelligence (AI) Disclosure
No artificial intelligence (AI) tools, including large language models or machine learning software, were used in the preparation, analysis, or presentation of this manuscript.
- Received March 26, 2025.
- Revision received April 13, 2025.
- Accepted April 22, 2025.
- Copyright © 2025 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).
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