This study targets patients undergoing ultra-low rectal cancer surgery, which requires internal sphincter resection for sphincter-saving procedures. The study compares the staged Turnbull-Cutait Pull-through anastomosis (a delayed transanal pull-through anastomosis without a protective stoma) as the experimental group with traditional anastomosis (hand-sewn/stapled) plus protective ileostomy as the control group. The aim is to assess whether the Turnbull-Cutait Pull-through colon-anal anastomosis is non-inferior to traditional ISR surgery in terms of complications (short-term such as anastomotic leakage/dehiscence, pelvic infection, anastomotic bleeding, ischemic bowel necrosis, bowel obstruction, and long-term complications such as anastomotic stricture, perianastomotic fistula, bowel obstruction, stoma-related complications, and others), postoperative anal function, quality of life, long-term oncologic outcomes, hospital stay duration, and total hospitalization costs.

In recent years, with the increasing understanding of the anatomy and physiological functions of the lower rectum, the biological behavior of rectal cancer tumors, advancements in new surgical technologies, and the application of comprehensive treatment methods, there has been growing emphasis on radical surgical procedures for low rectal cancer that balance oncological safety with anal function preservation. After undergoing total mesorectal excision for low rectal cancer and subsequent coloanal anastomosis, patients often face a high risk of anastomotic leakage and pelvic infection. Therefore, a protective ileostomy is usually performed to divert feces, providing a relatively low-perfusion environment conducive to healing for ultra-low coloanal anastomoses. In the event of an anastomotic leak, the protective stoma can mitigate infection and reduce the likelihood of secondary surgeries. Nevertheless, complications following protective ileostomy, such as dehydration, chronic renal failure, and parastomal hernia, occur at rates as high as 43% . Additionally, complications related to stoma reversal exceed 20% , all of which significantly impact patients' quality of life. Approximately one-fifth of patients with preventive stomas are unable to have their stomas reversed as planned, or may require lifelong stoma formation.

In 1961, Turnbull and Cutait independently reported surgical techniques involving transanal pull-through rectal resection and delayed manual coloanal anastomosis. From a certain perspective, this procedure is the safest reconstructive method, effectively reducing anastomotic leakage-related complications and avoiding the need for a protective stoma. In recent years, its clinical application in challenging rectal cases involving radiation proctitis, complex recto-vaginal/urethral fistulas, salvage surgeries for anastomotic leaks, and low-stage progressive rectal cancer has gained increasing attention and acceptance.In 2020, a multicenter randomized controlled study published in JAMA Surgery found that the delayed anastomosis group (avoiding protective stoma) did not increase the incidence of anastomotic leaks or other complications compared to the standard coloanal anastomosis plus ileostomy group, and exhibited comparable oncological and functional outcomes . Furthermore, a recent systematic review in 2022 included one randomized controlled trial and nine observational studies with a total of 1,743 patients. This study found that staged Turnbull-Cutait anastomosis was associated with a reduced rate of anastomotic leaks.

However, the aforementioned studies and systematic reviews on staged Turnbull-Cutait anastomosis were all based on total mesorectal excision (TME), and there is a paucity of data on postoperative anal function and quality of life following this procedure, necessitating further research. As an extreme sphincter-saving surgery, ISR is currently limited in widespread adoption due to the high incidence of postoperative complications and suboptimal functional outcomes associated with anastomoses located very close to the anal verge. To date, there is a lack of systematic studies applying the Turnbull-Cutait Pull-through anastomosis to ISR procedures. Therefore, it is highly worthwhile to conduct a multicenter prospective randomized controlled study to determine whether the modified Bacon procedure (transanal pull-through, delayed anastomosis) can serve as an effective alternative to ISR-coloanal anastomosis, achieving comparable or lower rates of postoperative complications, as well as equivalent oncological radicality and defecatory function. Such research is urgently needed in this largely unexplored field. If successfully conducted and achieving its objectives, this clinical study could provide highly valuable guidance for clinical practice. Existing reports on the application of the modified Bacon procedure in low rectal cancer are generally small-sample, single-center, retrospective studies with low levels of evidence. This study aims to provide higher-level evidence through a larger-sample, prospective, multicenter, randomized controlled design.

Inclusion Criteria:

1. Histopathologically confirmed high- or moderate-grade adenocarcinoma or villous adenoma with malignancy on preoperative colonoscopy; tumor located ≤ 5 cm from the anal verge; primary tumor size < 5 cm in diameter.
2. All enrolled patients require intersphincteric dissection. PISR surgery must be completed with hand-sewn (preferably) or stapled coloanal anastomosis. The anastomosis should be located near the dentate line (intraoperative photos or videos must be preserved).
3. Both male and female patients aged 18-75.
4. Non-recurrent rectal cancer.
5. No concurrent multiple primary colorectal cancers.
6. Initial staging or post-neoadjuvant therapy stage: T3 above the levator ani, T1-2 below.
7. Liver or lung oligometastases deemed resectable after evaluation by a multidisciplinary team (MDT).
8. Patients may or may not have received neoadjuvant chemoradiotherapy.
9. Patients and families must understand and be willing to participate in this study, providing written informed consent.
10. Good anal function (Wexner incontinence score ≤ 5).

Exclusion Criteria:

1. History of malignant colorectal tumors.
2. Previous colorectal or anorectal surgeries or diseases.
3. Patients requiring emergency surgery due to intestinal obstruction, perforation, or bleeding.
4. Tumor invasion into the external sphincter, levator ani, or adjacent organs requiring combined organ resection.
5. Poor preoperative anal function or incontinence (Wexner incontinence score ≥ 6).
6. History of inflammatory bowel disease (IBD) or familial adenomatous polyposis (FAP).
7. Recent diagnosis of other malignancies.
8. Participation in other clinical trials within the 4 weeks prior to enrollment.
9. ASA classification ≥ IV or ECOG performance status ≥ 2.
10. Severe hepatic, renal, cardiopulmonary, or coagulation dysfunction or serious underlying disease precluding surgery.
11. History of severe mental illness.
12. Pregnant or breastfeeding women.
13. Uncontrolled preoperative infection.
14. Other clinical or laboratory findings making the patient unsuitable for the study, as judged by the investigator.

http://www.medresman.org.cn/login.aspx http://www.medresman.org.cn/html/resman.pdf The Clinical Research Public Management Platform (Research Manager, ResMan) is an Electronic Data Capture (EDC) system that manages the clinical trial processes and records all relevant information, including baseline data of subjects such as demographic information, baseline data collected during enrollment, implementation details during the trial, and outcome data, encapsulated in the Case Record Form (CRF). All this information is recorded online via the internet and transmitted to a central database for management. Only researchers from the study group are allowed to access and operate the trial, while project managers, sponsors, or investors of funded projects have the right to view real-time data but cannot make any changes. Researchers decide whether to disclose research result data. Once data is entered and saved, any subsequent changes are automatically displayed and tracked.

Start Date: 6 months after primary results are published End Date: Data will remain available on the platform indefinitely, with no specified end date

Data will be made available to researchers who meet the following criteria: 1) possess a research plan approved by an Institutional Review Board (IRB); 2) have a clear scientific objective related to this clinical study. Researchers requesting access must submit an application, and upon approval, will receive controlled access. Data will be provided in anonymized form on a secure online data platform.