The purpose of this study is evaluation of the safety and the efficacy of transanal total mesorectal excision in difficult case.

Difficult case is defined as below;

- If any one of the following (1 or 2 or 3)

1. BMI: 30 or more
2. Tumor size: more than 7cm in long diameter
3. CRM: mesorectal fascia involvement or less than 1 mm on MRI

Subjects will have their rectal cancer removed using a technique combining surgery through the anus and standard laparoscopy. Transanal visualization will be using endoscopy. At the end of the procedure, the rectum will be removed though the anus or ileostomy formation site, the bowel will be re-connected to the anus, and a temporary diverting stoma will be created, which is standard of care following surgery for this type of cancer.

Inclusion Criteria:

• age: 20-80 years

• biopsy-proven adenocarcinoma of the rectum

• clinical staging (c or yc): T0-3, N0-2, M0

• Rectal cancer located 3-12 cm from the anal verge

• ECOG performance status: 2 or less

• If any one of the following (1 or 2 or 3)

  1. BMI: 30 or more
  2. Tumor size: more than 7cm in long diameter
  3. CRM: mesorectal fascia involvement or less than 1 mm on MRI

Exclusion Criteria:

• Synchronous colon cancer or other malignancy
• Obstructing rectal cancer
• Pregnant or breast-feeding
• Receiving any other study agents
• Fecal incontinence
• History of prior colorectal cancer or inflammatory bowel disease