The conventional intersphincteric resection (ISR) for low rectal cancer requires a combined abdominal and perineal approach, and followed with a handsewn coloanal anastomosis, which is time consuming and difficult to accomplish. A complete laparoscopic abdominal approach partial intersphincteric resection has been proved to be a safe and feasible alternative for low rectal cancer treatment, with the advantages of technical convenience and avoiding a permanent ostomy. But there are few reports concerning differences in clinical outcomes between patients with or without neoadjuvant chemoradiotherapy undergoing partial ISR surgery. Therefore, it is necessary to compare the functional outcomes (including anal and sexual function, and postoperative quality of life [QOL]) and oncologic outcomes of patients who underwent completely abdominal approach laparoscopic partial ISR surgery after neoadjuvant chemoradiotherapy, with those who received ISR surgery directly. Furthermore, the operation difficulty between the above two groups is also worthy of intensive study.

Patients with cT1 to cT2 low rectal cancer are directly operated through completely abdominal approach laparoscopic partial ISR surgery. Patients with cT3 low rectal cancer are firstly treated with standard neoadjuvant chemoradiotherapy until down staged to ycT1 to ycT2. The postoperatively functional outcomes and oncologic outcomes between the two groups are compared, including anal and sexual function, QOL and local recurrence rate. The operation difficulty between the above two groups is also investigated, including operation time, the intraoperative and postoperative complications, mesorectum integrity, time for mobilizing the intersphincteric plane, the intactness of the fascia of the levator ani muscle, pubis coccygeus, puborectalis, and external sphincter.

Inclusion Criteria:

• Biopsy-proven moderate or well differentiated adenocarcinoma
• Rullier classification of low rectal cancer (types Ⅱ: juxta-anal tumor)
• Clinical staging: initially staged as T1 -2 or down staged to T1-2 after neoadjuvant chemoradiotherapy;

Exclusion Criteria:

• Without signing informed consent, poor compliance
• Unfit for laparoscopy
• Other serious diseases not suitable for participating in this clinical trial
• A degree of preoperative fecal incontinence
• After preoperative neoadjuvant chemoradiotherapy, the sphincter function, sexual function and others involved in this trail are seriously affected