Normal text size icon Increase text size by 30% icon 

Information for patients having Radiotherapy to the Rectum


The process of informed consent requires patients to receive written information to help them to make a decision about treatment.

This page is a written version of the information your oncology doctor has told you about radiotherapy for rectal cancer. It includes sections on the most commonly asked questions, about the treatment procedure and the side-effects, which may occur with this sort of treatment.

Whilst it is important to make you aware of side-effects associated with the treatment it is equally important to put this into perspective. We hope this information will help you weigh up the benefits of having adequate treatment now against the risks of late side-effects of Radiotherapy treatment.


If you are a pre-menopausal woman and are at any time concerned that you may be pregnant please tell a member of the treatment team as soon as possible.


 This page is only a short summary. Throughout the process the Doctors, Radiographers and Nurses will be there to explain what will happen in more detail and to answer any questions you may have.


If you need further advice please do not hesitate to ask. The bottom of this page has further suggestions of where you may wish to go for help.


What is Radiotherapy?

  • Radiotherapy is the use of high energy x-rays to treat cancer. The x-rays are produced by a machine called a linear accelerator and are able to damage and destroy cancer cells within the treatment area.

  • Radiotherapy also affects normal cells in the area being treated, but they are generally more able to recover than cancer cells.

  • Treatment is usually given regularly over a period of time to have the greatest effect on the cancer cells whilst limiting the damage to normal cells.


When is it used?

Radiotherapy is used:

  • To treat cancer before surgery.

  • To treat cancer after surgery, to make sure that no cells have been left behind.

  • To control symptoms of the disease

It can be used together with chemotherapy.


How is it given?

Radiotherapy is normally given in daily sessions - Monday to Friday as an outpatient and weekends off. The length of your treatment schedule will be discussed with you by your oncology doctor.

Radiotherapy should be given as a continuous daily treatment and therefore appointments ideally should not be missed. If you are too unwell or have an emergency and unable to attend your appointment, you should inform the radiographers as soon as possible.

If any scheduled ‘breaks’ are required during your treatment, such as Bank Holidays etc. you will be informed prior to starting your treatment.


Is there any preparation for the procedure?

In some circumstances, you may be required to follow special dietary instructions or specific bladder and bowel preparations. You will be informed of this before the appointment.


Planning your treatment

The aim of treatment is to treat the tumour whilst sparing as much of the surrounding healthy tissue as possible where it is safe to do so. To do this an individual plan is prepared for each patient. You will have a CT scan in the radiotherapy department and this will be used to prepare and plan your treatment.

CT contrast agent is used to enhance the images produced by CT scans to help with the planning of your radiotherapy treatment. Contrast agents are also called “contrast mediums” and “dyes”. There are different types of contrast agent that can be used. Some are given by injection into a vein (intravenously), others are swallowed.

If this is something that you require, your oncology doctor will talk to you about this and may send you for a blood test prior to your planning appointment.

Once the area for treatment has been decided, small permanent skin marks, the size of a pinhead are made with a needle and ink (tattoos). This enables the Radiographers to achieve an accurate and consistent treatment each day.


What does the treatment involve?

It takes approximately between 10 and 20 minutes to position and treat you. The treatment is given using a machine called a linear accelerator. You lie on a treatment couch. The radiographers position you using laser lights and marks that have been put on your skin or treatment mask.

Once you are in the correct position the radiographers will ask you to stay very still and breathe normally. The machine may be re-positioned (to different angles) during the session by the radiographers. X-Ray pictures will be taken before the radiation beam is switched on. This will allow the radiographers to ensure accurate positioning and treatment delivery.

You will be in the room on your own whilst the radiation beam is on. The treatment team will monitor you on closed circuit television. If at any time you want the attention of the staff, you will be asked to raise your hand.


Will I be radioactive?

No. As soon as the radiation beam is completed all the radiation disappears. Once the treatment is finished you will be free to go home. It will be perfectly safe to be with other people including children.


Will the procedure be painful?

The treatment itself is totally painless. There is nothing to see or feel - you will hear the machine buzzing.

The treatment couch is quite firm to ensure accuracy but you will be made as comfortable as possible in the treatment position.


What side effects can I expect?

The effect of radiotherapy is dependent on the dose that is prescribed, the length and area of your treatment as well as whether you are having any chemotherapy. If you are, then this may have additional effects.

For most patients, side effects usually settle after a few weeks or months but it is possible that some side effects may be permanent and require further medical intervention.

The review radiographer team will be able to advise you on how to ensure side effects are kept to a minimum and any self-help measures. If necessary there are various medications that can be prescribed to help, so it is important to let staff know if you develop any problems.

For the majority of patients, some level of tiredness can be experienced. It is important to keep hydrated and ensure that you rest as and when necessary.


Short term side effects

  • Loss of appetite/nausea & sickness (Dietary support and advice can be provided if required).

  • Increased frequency of passing urine/burning pain on urination (cystitis)

Inform the treatment radiographers if the burning sensation lasts for a few days. The discomfort may be due to infection. If so, we can arrange for some medication to be prescribed and also try to drink more fluid.

  • Diarrhoea/loose and frequent bowel motions

Inform the treatment radiographers if you experience a change in bowel habits. If necessary the radiographers will talk to you about adjusting/altering you diet or medications.

  • Your skin in the treatment area may become sore if the back passage/anus is being treated and the radiographers will advise you on skin care during your treatment.


You will be reviewed regularly whilst you are on treatment. Your medical team will be able to advise you on how to ensure that any side effects are kept to a minimum. If necessary there are various medications that can be prescribed to help you, so it is important to let staff know if you develop any problems.

Long term side effects

Your doctor will have discussed the likelihood of long term side- effects for you. Fortunately major complications of radiotherapy are rare with modern techniques. The following side-effects are known to occur albeit rarely.

  • Changes in the texture or colour of the skin.

  • Bowel changes causing narrowing or scarring, blockage, ulceration, chronic diarrhoea or poor absorption of food.

  • Bladder changes with loss of capacity frequency of urination, blood in the urine, pain or spasm.

  • In men decreased fertility or sterility due to reduced sperm counts. Impotence or sexual dysfunction.

  • In women changes to the ovaries which could cause menopause or infertility in younger women.

  • Changes to the vagina leading to dryness, shrinkage, pain, bleeding, sexual dysfunction.

  • Weakening of the sphincter.

  • Fistulae.


If you have further questions

If you are at all concerned about the treatment, what it involves and what it means for you, do not hesitate to ask at any time.

You will find a number of contact names and numbers at the bottom of this page.


Further advice about your treatment

For advice or further information you can visit the Macmillan Information Centre located in the Centre for Oncology (Ground Floor). Opening times: Mon-Fri 9.00am to 4.00pm - No appointment Necessary or telephone 01604 544211

Our Macmillan Colorectal Cancer Nurse Specialist service is available to support patients, their families and carers by providing information about treatments and investigations. The contact number during office hours is (01604) 523435.

You may call at any stage before, during or following your treatment. The service is available Monday - Friday 9.00am - 4.00pm. If you would like to speak to someone outside the hospital for advice or information Macmillan can be contacted via the website or telephone 0808 808 00 00


Bowel Cancer UK

Offers an information and support service for patients, carers and health professionals. or telephone 020 7940 1760


Beating Bowel Cancer

Offers an information and support service for patients, carers and health professionals. or telephone 020 8973 0011.


Useful websites


Other information

Northampton General Hospital operates a smoke-free policy. This means that smoking is not allowed anywhere on the Trust site, this includes all buildings, grounds and car parks.

Leaflets, information, advice and support on giving up smoking and on nicotine replacement therapy are available from the local Stop Smoking helpline on 0845 6013116, the free national helpline on 0300 123 1044, email: and pharmacies.

Car parking at Northampton General Hospital is extremely limited and it is essential to arrive early, allowing ample time for parking. You may find it more convenient to be dropped off and collected.

This information can be provided in other languages and formats upon request including Braille, audio cassette and CD. Please contact (01604) 544516 or the Patient Advice & Liaison Service (PALS) on (01604) 545784, email:


 This information was taken from Northampton General Hospital leaflet PC140 (Feb 2018).

© Northampton General Hospital NHS Trust 2022       Privacy Notice | Social Media | Cookie PolicyTerms of Use | Accessibility | Accessibilty Statement