Radiotherapy for rectal cancer

Radiotherapy uses high-energy rays to kill cancer cells. It is often given with chemotherapy. This is called chemoradiation.

Radiotherapy can be given both externally and internally. External radiotherapy uses a large machine to aim high-energy x-rays at the affected area. It is usually given as an outpatient from Monday to Friday for four to five weeks. Internal radiotherapy involves having radioactive material placed inside the body for a set time and then removed.

These treatments do not make you radioactive. It is safe to be with other people throughout your treatment.

Radiotherapy may be given before an operation to remove rectal cancer. It is used to shrink the cancer and reduce the chance of it coming back. If radiotherapy hasn’t been given before surgery, it may be used afterwards if the cancer was difficult to remove or if there is a chance some cancer remains. Radiotherapy is also sometimes used to relieve symptoms if a cancer cannot be cured.

The type of radiotherapy you are given will depend on the type of cancer you have and your individual situation.

What is radiotherapy?

Radiotherapy uses high-energy rays to destroy cancer cells while doing as little harm as possible to normal cells. Radiotherapy only treats the area of the body that the rays are aimed at. It is often given in combination with chemotherapy. This is called chemoradiation. Chemotherapy makes cancer cells more sensitive to radiotherapy.

Radiotherapy does not make you radioactive. It is safe for you to be with other people, including children, throughout your treatment.

How radiotherapy is given

Radiotherapy can be given externally or internally.

External radiotherapy

This is normally given in the hospital radiotherapy department as a series of short, daily sessions. It uses equipment similar to a large x-ray machine. Each treatment takes 10 to 15 minutes. The treatments are usually given Monday to Friday, with a rest at the weekend. Your doctor will discuss the treatment and possible side effects with you.

Internal radiotherapy

This involves having a radioactive material (the source) placed close to or inside the tumour for a limited period of time. This is called high dose rate (HDR) brachytherapy. As with external radiotherapy, high-energy rays are used to kill the cancer cells.

Before the treatment, the rectum needs to be emptied. This involves having a mini enema, where liquid is put into the back passage to empty it. Brachytherapy is usually given under a general anaesthetic and the procedure takes about an hour.

A small number of people with early-stage rectal cancers may be treated with a type of brachytherapy called Papillon treatment. This can be given as an outpatient and does not need a general anaesthetic. It is only available in a few hospitals, so you may need to travel some distance to have it.

HDR brachytherapy is a new treatment, so not all the potential risks and benefits are known. Before you decide to have this treatment, your doctor will explain what is involved and discuss the possible benefits and risks with you. They will also give you written information to help you make your decision.

When radiotherapy is given

Radiotherapy before surgery

Radiotherapy is sometimes given before an operation. The aims are to:

  • shrink the cancer so that it is easier to remove with surgery
  • reduce the chance of the cancer coming back.

You may have a short course of external radiotherapy. It is given once a day, Monday to Friday, the week before surgery.

If the cancer is large, you may have a longer course of radiotherapy that lasts up to six weeks. This is usually given with chemotherapy, which can help make the radiotherapy more effective (chemoradiation).

After a longer course of radiotherapy, you wait for at least six weeks before you have surgery. During this time, the radiotherapy or chemoradiation will continue to work, shrinking the cancer.

Some people with cancer in the middle or lower third of the rectum are offered internal radiotherapy (HDR brachytherapy) before surgery. The aim is to shrink the tumour and reduce the need to remove the anus during surgery.

Brachytherapy may be given in combination with external radiotherapy or on its own. Your doctor will discuss with you whether this treatment may be suitable for you.

Radiotherapy after surgery

If radiotherapy was not given before surgery, you may have it afterwards if:

  • the cancer was difficult to remove
  • some cancer cells may be left behind
  • the cancer had spread through the bowel wall or into nearby lymph nodes.

External radiotherapy is usually given Monday to Friday, for four to five weeks.

Radiotherapy for advanced cancer

External radiotherapy may be used to treat rectal cancer that has spread or come back after treatment. It is most likely to be used to treat cancer in the pelvis (the area between the hip bones). The aim is to shrink the cancer and relieve symptoms such as bleeding or pain.

Radiotherapy can usually only be given once to any particular area of the body, because of the effects it has on healthy tissues close by.

Radiotherapy for cancer in the liver

Specialised radiotherapy techniques are sometimes used to treat bowel cancer that has spread to the liver (secondary liver cancer). These are different to the other types of radiotherapy discussed above. The side effects are also different.

Stereotactic radiotherapy

Stereotactic radiotherapy is given using a specially adapted radiotherapy machine. It is sometimes called CyberKnife™. The machine delivers beams of radiotherapy from many different angles. This allows the doctor to give a very high dose to the tumour, but a very low dose to surrounding tissues.

This treatment is only available in a few large radiotherapy centres. If it is suitable for you, your team will discuss it with you.

Selective internal radiotherapy (SIRT)

SIRT is a type of internal radiotherapy. It may be used when cancer has spread to the liver and surgery is not possible. It can be given on its own or with chemotherapy. It is done under a local anaesthetic.

A doctor injects tiny radioactive beads into a blood vessel close to the tumours. The radiation destroys the blood vessels and stops blood flow to the tumours. Without a blood supply, the tumours shrink and may die. The radiation only travels a few millimetres, so other parts of the liver are not affected and it doesn’t make you radioactive.

SIRT is only suitable for some secondary liver cancers. Your doctor or specialist nurse can talk to you about whether it is suitable for you.

Planning your radiotherapy treatment

You will have a hospital appointment to plan your treatment. You will usually have a CT scan of the area to be treated. During the scan, you need to lie in the position that you will be in for your radiotherapy treatment.

Your radiotherapy team use information from this scan to plan:

  • the dose of radiotherapy
  • the area to be treated.

You may have some small, permanent markings made on your skin. The marks are about the size of a pinpoint. They help the radiographer make sure you are in the correct position for each session of radiotherapy.

These marks will only be made with your permission. If you are worried about them, talk to your radiographer.

Treatment sessions

At the beginning of each session of radiotherapy, the radiographer will position you carefully on the couch and make sure you are comfortable. During your treatment you will be alone in the room, but you can talk to the radiographer who will watch you from the next room.

Radiotherapy is not painful, but you will have to lie still for a few minutes during the treatment.

Back to Radiotherapy explained

Before your radiotherapy

Before you start radiotherapy, your team will explain what your treatment involves and how it may affect you.

Your radiotherapy team

You will meet many different specialists from your radiotherapy team. You may see them before, during and after radiotherapy treatment.