Three major radiotherapy principles for rectal cancer

Radiotherapy is a complete process that includes multiple steps and is complex. Therefore, the following principles must be followed at different stages of radiotherapy for patients with rectal cancer.

Principles of preoperative radiotherapy

Preoperative radiotherapy can kill lesions around the tumor, reduce the size of the tumor, improve the surgical resection rate, and reduce the possibility of tumor spread during surgery.

In preoperative radiotherapy for rectal cancer, the effect of preoperative radiotherapy is relatively ideal for cancerous lesions with a diameter > 2 cm, especially for sessile tumors or poorly differentiated tumors, with a total dose of 20 to 25 Gy/5 times. However, there are still objections to the total dose.

Principles of postoperative radiotherapy

The indication for postoperative radiotherapy is the presence of residual tumor in the local area after surgery. For patients with advanced disease who have not undergone preoperative radiotherapy, but the tumor is found to have penetrated the muscle layer or nearby tissues or metastasized to the pelvic lymph nodes around the intestinal wall during surgery, postoperative radiotherapy is necessary, and the total dose must be ≥50Gy.

For patients whose tumor tissues cannot be completely removed by surgery and whose distant metastasis is not found, postoperative radiotherapy can be performed. Patients who are preparing to receive postoperative radiotherapy can take some measures during the operation, such as pelvic floor reconstruction and peritoneal coverage, which will help the implementation of postoperative radiotherapy.

Principles of intraoperative radiotherapy

If the patient has residual lesions, positive surgical margins, and obvious tumor adhesions during surgery, intraoperative radiotherapy can be used to improve local control rate and survival rate.

The radiotherapy energy is selected to be 9-15 MeV, and the dose is 10-20 Gy. Most patients can accept 15 Gy, and the dose is on the 90% isodose curve.