The goal of this clinical trial is to learn whether a modified single-stapled anastomosis (MST) can reduce anastomotic leakage compared with the conventional double-stapled technique (DST) in adult patients undergoing laparoscopic or robotic low anterior resection for rectal cancer.

The main questions it aims to answer are:

• Does MST lower the incidence of anastomotic leakage after rectal cancer surgery?
• Does MST improve short-term surgical outcomes compared with DST?

Researchers will compare the MST group with the DST group to see if MST leads to fewer anastomotic leaks and safer postoperative recovery.

Participants will:

Receive either MST or DST during minimally invasive rectal cancer surgery Undergo routine postoperative CT scans within one month after surgery to check for symptomatic or asymptomatic anastomotic leakage Attend scheduled follow-up visits and standard postoperative assessments as part of routine rectal cancer care

Anastomotic leakage is one of the most serious complications after low anterior resection (LAR) for rectal cancer. This complication can lead to infection, reoperation, prolonged hospitalization, higher medical costs, and worse long-term oncologic outcomes. Although laparoscopic and robotic surgery have improved short-term recovery compared with open surgery, the risk of anastomotic leakage remains a major concern.

The most commonly used reconstruction method during minimally invasive LAR is the double-stapled technique (DST). In DST, the rectum is transected with a linear stapler and then reconnected with a circular stapler. This creates an intersection between two staple lines, a known weak point that may be prone to leakage due to structural and ischemic vulnerability.

The modified single-stapled technique (MST) eliminates this intersection. Before applying the circular stapler, the two ends of the linear staple line on the rectal stump are brought together using a simple suture. This results in a single, centered staple line that the circular stapler incorporates completely into the anastomosis. Early studies, including a previous randomized trial, suggest that MST significantly reduces anastomotic leakage compared with DST.

This multicenter randomized controlled trial aims to provide high-quality evidence on the effectiveness of MST in reducing anastomotic leakage in patients undergoing laparoscopic or robotic LAR for rectal cancer. A total of 440 adult patients will be enrolled across multiple high-volume university hospitals in South Korea. Participants will be randomly assigned in a 1:1 ratio to receive MST or DST. Randomization will be stratified by sex, neoadjuvant treatment, and study center.

To ensure consistent surgical quality, all participating colorectal surgeons will complete a pre-trial standardization workshop and submit unedited surgical videos for competency review. All surgical procedures will follow standardized steps, and perioperative care will be based on established Enhanced Recovery After Surgery (ERAS) protocols.

The primary outcome is the rate of anastomotic leakage within one month after surgery. All participants will undergo routine abdominopelvic CT scans within this time window to detect both symptomatic and asymptomatic leaks. Secondary outcomes include postoperative complications, operative time, distal resection margin length, hospital stay, and long-term oncologic outcomes such as recurrence and survival. If MST is shown to be superior to DST, this study may support a simple, low-cost, and easily adoptable modification to current surgical practice. MST does not require additional equipment or complex training, making it a potentially valuable technique that can improve patient safety and surgical outcomes in rectal cancer care across diverse clinical settings.

Inclusion Criteria:

• Adult patients with rectal cancer who are scheduled to undergo laparoscopic or robotic low anterior resection
• histologically confirmed rectal adenocarcinoma located within 15cm from anal verge.
• ECOG performance status of 0 to 2
• Any clinical stage

Exclusion Criteria:

• Who have significant comorbidities or history of abdominal surgeries that would preclude a minimally invasive approach
• Bowel obstruction for perforation requiring emergency surgey
• Concurrent, or recent treatment for colorectal or other malignancies within the past five years
• Presence of inflammatory bowel diseases
• Hereditary colorectal cancer syndrome

IPD will not be shared because the dataset contains sensitive clinical information, and secondary distribution is not permitted under the terms of institutional review board approvals and patient consent. Data access is restricted to the study investigators to protect participant privacy.

No additional parties.