Radiotherapy : Radiotherapy uses high energy rays to kill cancer cells. It is often used to treat cancer that started in the back passage (rectum). Usually, the patient is given radiotherapy at the same time as chemotherapy. The chemotherapy makes the cancer cells more sensitive to radiation. The patient may have radiotherapy before or after surgery.
Doctors use radiotherapy before surgery to lower the risk of the cancer coming back after the operation, and to shrink tumours and make them easier to remove completely.