External radiotherapy for rectal cancer

About external beam radiotherapy

External beam radiotherapy uses a machine from outside of the body. It directs radiation beams at the cancer to destroy it. This is different to internal radiotherapy. Internal radiotherapy means giving radiotherapy to the cancer from inside the body.

Go to information about internal radiotherapy for rectal cancer

When might you have external radiotherapy for bowel cancer?

You might have radiotherapy for cancer of the back passage (rectal cancer). You don't usually have radiotherapy for cancer of the large bowel (colon cancer) unless your cancer has spread. This is called metastatic bowel cancer.

When do you have external radiotherapy for rectal cancer?

You might have external radiotherapy on its own or with chemotherapy (chemoradiotherapy):

• before or after surgery

• if you want to try to avoid surgery by treating the rectal cancer with radiotherapy or chemoradiotherapy alone. This is called an organ preservation approach. The aim is for no sign of the cancer after treatment. Doctors call this a complete clinical response.

• if your rectal cancer has spread (metastatic bowel cancer)

Before or after surgery

If your doctor thinks you need radiotherapy, you usually have it before surgery. 

There are 2 different courses of radiotherapy, called short and long course radiotherapy. Your doctor will discuss which is the best treatment for you. 

Short course radiotherapy:

You have daily radiotherapy for 5 days and then have:

• surgery straight away (the day after you have completed radiotherapy)

• delayed surgery (at least 6 weeks after radiotherapy)

You don't usually have radiotherapy after surgery. But your doctor might suggest this if you were diagnosed with rectal cancer as an emergency and had an emergency operation. Or if your rectal cancer comes back soon after your surgery.

Long course radiotherapy:

You have daily radiotherapy for 5 to 5 and a half weeks and then you have:

• surgery a few months later (once the radiotherapy has had time to reduce the size of the cancer)

• scans and close monitoring. You might have this if there is no sign of cancer on repeat scans and camera tests (endoscopy). This is called a complete clinical response. You doctor will talk to you about your treatment options.

Long course radiotherapy and chemotherapy together (chemoradiotherapy)

You might have chemotherapy at the same time as long course radiotherapy. This is called chemoradiotherapy. Chemotherapy can make the cancer cells more sensitive to radiation.

You have radiotherapy every weekday for around 5 weeks. And you have a chemotherapy drug called capecitabine or 5-fluorouracil (5FU).

Find out more about chemoradiotherapy

Total neoadjuvant therapy (TNT)

Total neoadjuvant therapy (TNT) means having radiotherapy, or chemoradiotherapy, and chemotherapy all before surgery.

You might have:

• short course radiotherapy followed by chemotherapy

• chemotherapy followed by chemoradiotherapy

• chemoradiotherapy followed by chemotherapy

Metastatic bowel cancer

You might have radiotherapy if your rectal cancer has spread to another part of your body. This is called metastatic or advanced bowel cancer. Radiotherapy can shrink the cancer, relieve symptoms and help you feel more comfortable.

Read about radiotherapy for metastatic bowel cancer

Where do you have it?

You have your treatment in the hospital radiotherapy department. You have it daily, Monday to Friday as an outpatient. A team of therapy radiographers will deliver your treatment.

The radiotherapy room

Radiotherapy machines are very big and could make you feel nervous when you see them for the first time. The machine might be fixed in one position. Or it might rotate around your body to give treatment from different directions. The machine doesn't touch you at any point.

Before your first treatment, your ​radiographers​ will explain what you will 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 while you have treatment.

Before your treatment

Tell the team looking after you if you think you might be pregnant before treatment starts. 

Your radiographers will check you have emptied your bowels. They will let you know when to empty your bladder and if they need you to start drinking water.

When you are in the treatment room, your radiographers help you get into position on the treatment couch. They line up the radiotherapy machine, using the marks on your skin.

Then they leave you alone in the room for a few minutes for the treatment. This is so they aren't exposed to radiation.

During the treatment

You need to lie very still. Your radiographers might take images (x-rays or scans) before your treatment. This is to make sure that you're in the right position. The machine makes whirring and beeping sounds. You won’t feel anything when you have the treatment.

Your radiographers can see 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. You can also talk to them through the intercom or raise your hand if you need to stop or if you're uncomfortable.

You won't be radioactive

This type of radiotherapy won't make you radioactive. It's safe to be around other people, including pregnant women and children.

Travelling to radiotherapy appointments

You might have to travel a long way each day for your radiotherapy. This depends on where your nearest cancer centre is. This can make you very tired, especially if you have side effects from the treatment.

You can ask your radiographers for an appointment time to suit you. They will do their best, but some departments might be very busy. Some radiotherapy departments are open from 7 am till 9 pm.

Car parking can be difficult at hospitals. Ask the radiotherapy staff if you are able to get free parking or discounted parking. They may be able to give you tips on free places to park nearby.

Hospital transport may be available if you have no other way to get to the hospital. But it might not always be at convenient times. It is usually for people who struggle to use public transport. Or who have any other illnesses or disabilities. You might need to arrange hospital transport yourself.

Some people are able to claim back a refund for healthcare travel costs. This is based on the type of appointment and whether you claim certain benefits. Ask the radiotherapy staff for more information about this and hospital transport.

Some hospitals have their own drivers and local charities might offer hospital transport. So do ask if any help is available in your area.

Side effects of radiotherapy

Everyone is different and the side effects vary from person to person. 

The team looking after you will check your wellbeing. They can make adjustments to your treatment or medication if needed. 

Radiotherapy side effects can be early or late side effects. Early side effects happen in the few weeks following treatment. Late side effects happen many months or years after treatment has finished.

Your specialist team will discuss these with you before starting treatment.

Early side effects

The early side effects gradually develop and can get worse during the treatment. They may continue to get worse after your treatment ends but most of the effects begin to improve after 1 or 2 weeks.

Some common side effects of chemoradiotherapy for rectal cancer include:

• inflammation of your bowel causing diarrhoea

• inflammation of your bladder causing stinging and burning (cystitis) when you pass urine

• tiredness and weakness

• itchy, dry, red or sore skin around the back passage (anus)

Find out about the early side effects of radiotherapy for rectal cancer

Late side effects

These may happen many weeks, months or years after treatment finishes. Not everyone will have these side effects.

There are things you can do to deal with any late side effects that you have. Speak to your specialist if they are a problem for you.

• bowel changes such as needing to go for a poo more often or more urgently

• bladder changes such as needing to pee more often

• bone pain in your pelvis

• fertility problems and changes to your sex life

Read more about the possible long term side effects of radiotherapy