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Radiotherapy treatment

Find out about what happens when you have external radiotherapy for rectal cancer.

You may have external radiotherapy:

  • before surgery
  • after surgery (adjuvant radiotherapy)

This is to lower the risk of the cancer coming back. Radiotherapy before surgery might also shrink the cancer. And make it easier to remove.

Usually, you have radiotherapy at the same time as chemotherapy. Fluorouracil (5FU) or capecitabine chemotherapy can make the cancer cells more sensitive to radiation. Chemotherapy and radiotherapy given together is called chemoradiotherapy.

You have your treatment in the hospital radiotherapy department. You usually have it Monday to Friday. And have a break at the weekend. The treatment can be over 1 to 5 weeks . This depends:

  • on the size of your cancer
  • on the type of cancer
  • on the hospital treating you

You need to travel to the hospital each time you have treatment. Some hospitals have rooms nearby where you can stay in if you have a long way to travel.

You go to the radiotherapy department from your ward if you are staying in hospital.

The radiotherapy room

Radiotherapy machines are very big. Some are fixed in one position, but others rotate around your body.  

Before you start your course of treatment your radiographers explain what you'll see and hear. In some departments the treatment rooms have docks for you to plug in music players. So you can listen to your own music.

Photo of a linear accelerator

Before each treatment session

The radiographers help you to get onto the treatment couch. You might need to raise your arms over your head.

The radiographers line up the radiotherapy machine using the marks on your body. Once you are in the right position, they leave the room.

During the treatment

You need to lie very still. The machine makes whirring and beeping sounds. You can't feel the radiotherapy when you have the treatment. 

Your radiographers can see you and hear you on a CCTV screen in the next room. They can talk to you over an intercom and might ask you to hold your breath or take shallow breaths at times. They will ask you to raise your hand if you need anything but it is important to stay as still as possible. 

You won't be radioactive

External radiotherapy doesn't make you radioactive. It's safe to be with other people throughout your course of treatment, including pregnant women and children.

Travelling to radiotherapy appointments

Tell the radiotherapy department staff if you prefer treatment at a particular time of day. They can try to arrange this.

Car parking can be difficult at hospitals. It’s worth asking the radiotherapy unit staff:

  • if they can give you a hospital parking permit
  • about discounted parking rates
  • where you can get help with travel fares
  • for tips on free places to park nearby

If you have no other way to get to the hospital, the radiotherapy staff might be able to arrange transport for you. But it might not always be at convenient times. Some hospitals have their own drivers or can arrange ambulances. Some charities offer hospital transport.

Side effects

Radiotherapy for rectal cancer can make you tired. It can also make the skin in the treatment area go red and feel sore.

Last reviewed: 
11 Apr 2016
  • Metastatic Colorectal Cancer: ESMO Clinical Practice Guidelines

    Van Cutsem (and others)
    Annals of Oncology, 2014. Vol 25, Issue 3

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