Information about surgery, personalised treatment options and side effects.

Radiation Therapy

Radiotherapy is a possible treatment for rectal cancer and it is not usually used to treat bowel cancer.

It uses high-energy, highly focused rays to locally treat cancer. These rays will damage the DNA and kill the cancer cell.

How Is Radiotherapy Given?

Radiotherapy can be used in several ways:

  • External beam radiation therapy (EBRT) is delivered from outside of the body by a machine. Each treatment lasts a few minutes and is performed as an outpatient procedure.
  • Internal radiotherapy involves positioning radioactive sources inside or near to the tumour. The use of internal radiotherapy depends on the size of the cancer and where it is in the rectum. The main advantage of this treatment is that it can deliver a high dose of radiation directly to the cancer while limiting damage to surrounding tissues and organs. This treatment is also known as brachytherapy or contact radiotherapy and is not currently available at all cancer centres. You may have to travel to a specialist centre to receive this treatment.
  • Ablation refers to treatments that destroy small (less than 4 cm across) tumours without removing them. There are many different ablation techniques and ablation can be used to treat tumours in other places too.
  • Selective Internal Radiation Therapy (SIRT – also called radioembolisation) SIRT is a targeted treatment for liver tumours that delivers millions of tiny radioactive beads called SIR-Spheres microspheres directly to the liver tumours. Patients with advanced colorectal cancer often present with liver metastases.

You can read more about SIRT in this booklet: CLICK HERE


  • Before surgery (along with chemo) to help shrink a tumour and make it easier to remove. This is specifically needed in patients with rectal cancer according to the stage of the tumour and the location in proximity of the anus. The multidisciplinary review meeting can decide to perform a short course of radiation followed by surgery or for a long course of radiation (for example 5 weeks) in combination with continuous administration of chemotherapy to improve the effect of radiation
  • During surgery: right to the area where the tumour was, to kill any cancer cells that may be left behind. This is called intraoperative radiation therapy (IORT)
  • After surgery: radiation therapy may be used to try to kill any cancer cells that may have been left behind
  • To ease symptoms: for example, if advanced cancer is causing pain
  • Treatment of metastasis: as a treatment to relieve pain caused by cancer that has spread into the bone or brain

Side Effects of Radiation Therapy

  • During radiotherapy side effects may occur in organs that are directly targeted but also in healthy organs that lie close to the region that needs to be irradiated and that cannot be avoided by the X-rays. Side effects are more intense when radiotherapy is administered together with chemotherapy. Use of radiotherapy in addition to surgery also increases the risk of surgical complications.Strategies to maximally prevent and relieve post-radiation reactions are provided by the radiation oncologist.

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