Whether rectal cancer can be preserved depends on the location of rectal tumor, if it is high rectal cancer, such as 10cm or more from the anal verge, it can be completely preserved. However, if the rectal cancer is low, such as below 5cm from the anal verge, it is difficult to preserve the anus. However, if the tumor stage is early T1 or T2, it is possible to preserve anus, and ISR surgery, which is radical surgery for intersphincteric rectal cancer, can be used. If the rectal tumor is about 7cm, the principle of anal preservation is also possible. For low-grade rectal cancer, if anal preservation surgery is performed, the possibility of anastomotic fistula increases significantly, so usually a prophylactic colostomy is needed, and the patient will have to wait until he/she recovers completely, usually 3 months later, to operate again to return the stoma.