RATIONALE: Colorectal cancer is one of the most common cancers. However, approaches to minimize surgical trauma, preserve anal function, avoid abdominal stoma, and improve quality of life for patients with ultralow rectal cancers were limited. Thus, new technologies are urgently needed to improve the anal preservation rate, reduce the incidence of anastomotic leakage and improve postoperative anal function in patients with ultralow rectal cancer.

PURPOSE: This one-arm multicenter prospective cohort study aims to collect the data of patients with ultralow rectal cancer who undergo sphincter-preserving surgeries, including modified PPS and conventional surgeries, then compare the effects of different operations on clinical outcomes and to see the efficacy and safety of modified PPS surgery when compared with conventional procedures in the treatment of ultralow rectal cancer.

Inclusion Criteria:

1. Histological proof of newly diagnosed primary adenocarcinoma of the rectum
2. The lower edge of tumor < 3 cm from the dentate line
3. Clinical T stage ≤ T3

Exclusion Criteria:

1. The lower edge of tumor < 1 cm from the dentate line
2. Locally advanced stage of tumor
3. Presence of metastatic disease or recurrent rectal tumor
4. Concomitant malignancies
5. Concurrent uncontrolled medical conditions
6. Impaired anal function before surgery
7. Presence of acute bowel obstruction or bowel perforation caused by cancer
8. Pregnancy or breast feeding

Our study population is the patients who diagnosed as low-lying rectal adenocarcinoma cases by preoperative pathology and meet the eligibility criteria.