Radiotherapy for rectal cancer

You can have radiotherapy externally from a machine. Or you can have it internally from radioactive substance placed inside the body. Internal radiotherapy is also called brachytherapy.

You usually have external radiotherapy for rectal cancer, but it can also be given internally.

Internal radiotherapy gives you radiotherapy from inside the body. It gives a high dose of radiotherapy to the tumour, but the areas nearby get a much lower dose

There are 2 types of internal radiotherapy for rectal cancer:

Some people have brachytherapy after a course of external radiotherapy. Papillon treatment may be used on its own. This is usually if you have early rectal cancer and cannot have surgery or choose not to have it.

You may have external radiotherapy to treat rectal cancer that has spread or has come back after treatment. 

It is most likely to be used to treat cancer in the pelvis. This is the area between the hip bones. The aim is to shrink the cancer and help with symptoms such as bleeding or pain. 

It may also be used to treat symptoms if the cancer has spread to other organs in the body.

Side effects depend on:

• the dose of radiotherapy
• whether it is external or internal
• whether you have chemotherapy as well (chemoradiation).

Side effects usually begin 1 to 2 weeks after starting treatment. They may continue to get worse for a few weeks after treatment, before starting to get better. Side effects usually improve slowly over the next few weeks or more.

Smoking can make side effects worse. If you smoke, try to stop or cut down. 

It is important to tell your radiographer, cancer doctor or specialist nurse if you have side effects. They will give you advice on how to manage them and prescribe treatments that can help.  

We have more general information about the side effects during pelvic radiotherapy treatment.

These are the most common side effects. You may not get all of these.

Tiredness (fatigue) can continue for weeks or a few months after your treatment has finished. You might be more tired if you have to travel to hospital each day. If you are also having other treatment such as chemotherapy or surgery, this can make you more tired.

Try to get as much rest as you can, especially if you have to travel a long way for treatment. Balance this with some physical activity, such as short walks. This will give your more energy. 

Sometimes the skin in the treated area and around it might: 

• feel sore or itchy 
  redden if you have white skin 
  become darker than surrounding skin if you have black or brown skin
  become moist and sometimes blister or peel, usually towards the end of treatment. 

Not everyone will get these side effects. Your radiographer or specialist nurse will give you advice about looking after your skin. Tell them straight away about any skin changes. They can give you advice or treatments if needed, such as creams or dressings. 

During treatment, you are usually advised to: 

• wash your skin gently with mild, unperfumed soap and water 
• gently pat dry and avoid rubbing your skin
• wear loose-fitting clothes made from natural fibres, such as cotton
• follow your radiotherapy team’s advice about moisturising the treated area
• spend some time sitting or lying on your side to help to relieve any discomfort around the back passage and perineum. 

Skin reactions should get better within 4 weeks of treatment finishing. 

You may experience problems with your bowel such as:

• loose stools (poo) or diarrhoea
• passing a lot of wind
• needing to pass stools urgently and more frequently
• cramping pains in your tummy or back passage
• constipation
• tenesmus – the feeling that you need to go to the toilet even if your bowel is empty 
• having some bleeding or mucus coming from the back passage.

Tell your doctor or nurse if you have any of these symptoms.

If you have diarrhoea, your doctor will prescribe anti-diarrhoea tablets to help. You might also be advised to make changes to your diet during radiotherapy. 

Tell your specialist nurse or radiographer if you have any leakage (incontinence). They will give you advice and explain how to look after the skin in that area.

You may have some stinging or pain when you pass stools. Your doctor can prescribe local anaesthetic creams to help with this. Tell your doctor or nurse if you have any pain.

Radiotherapy to the rectal area may cause inflammation of the lining of the bladder. This can make you feel you want to pass urine (pee) more often. It also gives you a burning feeling when you pass urine.

It helps to drink plenty of water and other fluids. Your doctor can prescribe medicine to make passing urine more comfortable.

Most people lose their pubic hair after radiotherapy to the pelvic area. It should grow back after your treatment finishes, although sometimes pubic hair loss might be permanent. 

Sometimes radiotherapy might make the lining of the vagina sore and inflamed. If this happens, you may be advised not to have sex during treatment and for a few weeks afterwards. 

Radiotherapy can make the vagina narrower, less stretchy and drier than before. This can make having sex painful. It can also make having internal examinations difficult in the future. During and after treatment, your nurse may recommend you use vaginal dilators to try to prevent the vagina from narrowing. Dilators are plastic tubes shaped like a tampon. They are available in different sizes that you use with a lubricant.

Vaginal dryness can be relieved with lubricants or creams. Hormone creams can also help with dryness and vaginal narrowing. These are available on prescription from your GP.

If you are still having periods, radiotherapy to the pelvic area may cause the menopause. This means you will not be able to get pregnant. Your doctor can prescribe hormone replacement therapy (HRT) to improve symptoms of the menopause.

Radiotherapy for rectal cancer can affect the ovaries and the lining of the womb. This often means you will not be able to get pregnant or be able to carry a pregnancy after treatment. 

If you would like to have children in the future, talk to your doctor or specialist nurse before you start treatment. There may be options for preserving your fertility. 

We also have information about fertility and cancer treatment.

It is important that you do not get pregnant or make someone pregnant during radiotherapy, and for a few months after it has finished. Your doctors usually recommend that you use contraception during this time. 

Radiotherapy for rectal cancer can cause problems getting or keeping an erection. This is called erectile dysfunction or ED. Your radiotherapy team can explain what is likely to happen. There are different treatments that can help with ED. 

You may also have a sharp pain when you ejaculate. The pain should get better a few weeks after treatment finishes. You might also find that you ejaculate less fluid or none at all.

Radiotherapy to the pelvis might make you infertile (unable to make someone pregnant). It may be possible to have sperm stored before treatment starts. This is called sperm banking. It is important to talk to your cancer doctor or specialist nurse about this before your treatment starts.