Total mesorectal excision (TME) is the standard of care for rectal cancer, which can be combined with low anterior resection (LAR) in patients with mid-to-low rectal cancer. The narrow pelvic space and difficulties in obtaining adequate exposure make surgeries technically challenging. Four techniques are used to perform the surgery: open laparotomy, laparoscopy, robot-assisted surgery, and transanal surgery. Comparative data for these techniques is required to provide clinical data on the surgical management of rectal cancers by surgery.

The Rectal Surgery Evaluation Trial will be a prospective, observational, case-matched, four-cohort, multicenter trial designed to study TME with LAR using open laparotomy, laparoscopy, robot-assisted surgery, or transanal surgery in high-surgical-risk patients with mid-to-low, non-metastatic rectal cancer. All surgeries will be performed by surgeons experienced in a technique. Oncologic, morbidity and functional outcomes will be assessed in a composite primary outcome, with success defined as circumferential resection margin ≥1 mm, TME grade III, and minimal postoperative morbidity (absence of Clavien-Dindo grade III-IV complications within 30 days after surgery). Secondary endpoints will include the co-primary endpoints over the long-term (2 years), quality of surgery, quality of life, length of hospital stay, operative time, and rate of unplanned conversions.

Inclusion Criteria:

1. Age ≥ 18 years old

2. Rectal adenocarcinoma from middle and lower third (less than 10 cm from the anal verge) with a sphincter saving procedure

3. High risk operative patients (two of these factors as assessed on MRI):

   1. Obese patient with a BMI > 30 (male or female)
   2. Narrow pelvis: inter-tuberous distance < 10 cm
   3. Large tumoral volume with suspicion of close predictive margin (CRM ≤ 1 mm) at diagnosis
   4. Expected coloanal or ultra-low colorectal anastomosis

4. Patients with adequate performance status (Eastern Cooperative Oncology Group Scale score of ≤2)

5. Patient has signed and dated the informed consent before inclusion in the study.

Exclusion Criteria:

1. Patient with a comorbid illness or condition that would preclude the use of surgery.
2. Patients with T4b tumors which impose a pelvectomy
3. Patient requires an abdominal perineal resection (APR)
4. Patients with concurrent or previous invasive pelvic malignant tumors (cervical, uterine, or rectal; excluding the prostate) within 5 years before study enrollment
5. Patient undergoing emergency procedures
6. Planned rectal surgery along with major concomitant procedures (e.g. hepatectomies, other intestinal resections)
7. Metastatic disease
8. Pregnant or suspected pregnancy
9. Patients unwilling to comply with all follow-up study requirements
10. Patient included in another study which impact on the surgical technique or its choice.

high- risk patients with mid-to-low rectal cancer