This prospective observational cohort study aims to compare the clinical and procedural outcomes of Endoscopic Submucosal Dissection (ESD) and Transanal Minimally Invasive Surgery (TAMIS) for the treatment of early-stage rectal neoplasia. The study will evaluate recurrence rates, en bloc resection rates, R0 resection rates, procedure time, complication rates, and length of hospital stay over a 1-year follow-up period. Data will be collected from patients treated at multiple centers with expertise in ESD and TAMIS.

Colorectal cancer (CRC) is one of the most common malignancies globally, with early-stage rectal neoplasms being increasingly diagnosed due to widespread screening programs. This trend has led to a greater focus on organ-preserving treatment options, with endoscopic submucosal dissection (ESD) and transanal endoscopic surgery (TES) emerging as key techniques for local excision. ESD allows for en bloc resection of superficial lesions with high histological completeness but has a steep learning curve and a higher perforation risk. In contrast, TES, performed using transanal minimally invasive surgery (TAMIS) or transanal endoscopic operation (TEO), facilitates full-thickness excision and is more commonly used in Western surgical practice.

Each technique presents unique advantages and challenges. ESD is minimally invasive, preserves rectal function, and reduces postoperative complications such as fecal incontinence. However, its prolonged procedure time and technical difficulty limit its widespread adoption. TES, utilizing standard laparoscopic instruments, offers superior visualization and facilitates excision of deeper lesions but may lead to rectal wall defects, increased postoperative pain, and anorectal dysfunction. While studies suggest similar en bloc and recurrence rates between the two methods, discrepancies exist in procedural efficiency, hospital stay, and morbidity rates, with ESD potentially offering a shorter hospitalization period in certain cases.

Despite the increasing use of ESD and TES, a clear consensus on the optimal approach for early rectal neoplasms remains lacking. Existing data, primarily from high-volume centers in Asia, may not be fully applicable to Western populations. To address these gaps, this study aims to conduct a prospective, multi-center observational comparison of ESD and TES, assessing key outcomes such as recurrence rates, resection quality, complications, and hospital stay. The findings will contribute to refining treatment strategies and improving clinical decision-making for rectal neoplasm management.

Inclusion Criteria:

• Adult patients (>18 years)
• Non-pedunculated (sessile) lesions larger than 2 cm.
• Lesions located within 15 cm from the anal verge confirmed by sigmoidoscopy or magnetic resonance imaging (MRI)

Exclusion Criteria:

• Evidence of lymph node involvement, T2 rectal tumors, or distant metastasis on preoperative imaging modalities (MRI, ERUS, CT)
• Previous attempt at endoscopic resection
• Previous rectal surgery
• Previous pelvic radiation therapy
• Inflammatory bowel diseases (Crohn's disease, Ulcerative colitis)

Patients diagnosed with rectal neoplasia undergoing treatment with either ESD or TES at participating centers. Patients will be assigned to ESD or TES based on physician preference, patient choice, and institutional availability.

There will be sharing of de-identified individual participant data (IPD) about both the primary and secondary outcomes.

The data will be available to qualified researchers upon reasonable request, starting 6 months after publication of the study results and for up to 5 years.

Data will be shared via a secure data repository, and access will require an approved data-sharing agreement.