In the treatment of rectal cancer, chemotherapy typically involves a combination of two or more drugs targeting cancer cells. Chemotherapy and radiotherapy can be administered before surgery (neoadjuvant) or after surgery (adjuvant). For Stage 1 rectal cancer, surgical treatment alone may be sufficient. In this stage, chemotherapy is generally not recommended due to the low risk of recurrence after surgery. However, in Stage 2 and Stage 3 rectal cancer, postoperative chemotherapy and radiotherapy are applied to prevent disease recurrence. Additionally, in patients with Stage 2 and Stage 3 rectal cancer, preoperative chemotherapy and radiotherapy may be preferred to shrink the tumor and increase the chances of successful surgery.