Radiotherapy to the pelvis for rectal tumours

This information is about radiotherapy to the pelvis for tumours of the rectum. It describes all possible treatments, and some may not apply to you. The clinical team will discuss your treatment with you and explain anything you do not understand.

Please share this information with your family and friends.  They can have a role in helping you. It’s important that they feel well-informed and understand what is happening.

If you would like more detailed information about your own treatment, please ask the staff. There are also films about radiotherapy available to watch at home on The Christie website.

The Christie gives radiotherapy treatment at our main Withington site and at the radiotherapy centres at Oldham and Salford. However, if you are having chemotherapy with radiotherapy, this is only given at the main Withington site.

You may have heard about radiotherapy from people you know or from the patients at The Christie. Remember that their information may not apply to you.

When is radiotherapy offered and what are the benefits?

Each patient has their treatment planned individually, and your doctor at The Christie will discuss with you the type and length of treatment that is recommended for you.

Agreeing to treatment

Consent to treatment

We will ask you to sign a consent form agreeing to accept the treatment that you are being offered. The basis of the agreement is that you have had The Christie’s written description of the proposed treatment and that you have been given an opportunity to discuss any concerns.

You are entitled to request a second opinion from another doctor who specialises in treating this cancer. You can ask your own consultant or your GP to refer you.

Your consent may be withdrawn at any time before or during treatment. Should you decide to withdraw your consent, a member of your treating team will discuss the possible consequences with you.

Radiation can be harmful to the unborn child. It is important to let the radiographers know if you have missed a period or suspect that you might be pregnant before you are exposed to any radiation.

When will radiotherapy begin?

You will be cared for by a team including consultants, registrars, radiographers and nurses. The team also have colorectal radiographers who are dedicated to caring for patients with rectal cancer.

In choosing your treatment, your clinical oncologist at The Christie has carefully considered the nature of your illness, and your particular needs with regard to your treatment plan. During your initial radiotherapy planning appointment, the radiographers will be able to tell you exactly when you will start your treatment. As everybody’s treatment varies, the amount of time needed to plan the treatment varies. You may have between one and 25 treatments (occasionally additional treatments are given).

Planning the treatment

To help with the planning of your treatment, you will have a CT scan.

The scans which are undertaken to plan your radiotherapy are solely aimed to give enough information to plan the radiotherapy accurately. These scans are not diagnostic and therefore do not give sufficient information to assess the status of your cancer or any other abnormalities.

You may be asked to drink a special contrast drink before your scan which helps to get clearer pictures and improves the planning of your treatment. You may also be given an injection of contrast. The appointment letter for your scan will include a leaflet explaining in more detail what will happen.

During your planning session, the radiographers will draw some marks on your chest with a skin pen. These marks do wash off and so some permanent marks, like tiny black freckles, will need to be made. These will help the radiographers set you up in the correct position for treatment every day. The radiographers will ask you to lie on your back, but if this is not possible, please discuss this with the radiographers.

What happens during treatment?

On the day of your first treatment, you will come to the radiotherapy department. If you are an inpatient, a radiotherapy care assistant may collect you from your ward and escort you to the department.

On the treatment unit, you will meet a radiotherapy support worker. They help patients plan their appointments for the treatment. The radiographers will have the details of your treatment which the doctor has carefully planned. They will explain to you exactly what will happen.

The Christie is a training centre, so you may meet students in the radiotherapy department who may be involved in the delivery of your treatment. If you have any objections, let the radiographers know.

The radiographers will discuss the treatment and how to minimise side effects. They will also check whether you are still happy to go ahead with your treatment. This is the ideal opportunity to ask any questions you may have.

The radiographers will take you into the treatment room and ask you to loosen your clothing around your pelvis so that they can see the marks made during treatment planning. They will help you on to the treatment bed. The radiographers will then adjust the bed and your position so that you are in the correct position for the treatment.

They will try to make you as comfortable as possible as you will be asked to keep still for the duration of the treatment.

The radiotherapy machines are quite large and you may find them a little frightening to begin with, but there is no need to worry – the treatment is painless. Although the machines may come quite close to you, they will not actually touch you.

Each session may take about 15 minutes, but the actual treatment only lasts a few minutes. The radiographers operate the machines from outside the room. When all the adjustments have been made and you are in exactly the right position, the radiographers will make sure you are all right and then leave the room to switch the machine on.

There is nothing to feel and nothing to see. The machines make a buzzing noise when they are giving treatment.

During your treatment, the radiographers will need to take images of the area you are having treated. This will be done at the same time as your treatment, and you probably will not notice that the images have been taken. Some machines can complete a scan of the treatment area. These images are purely to check that you are in the correct position and not to check how the tumour is responding to treatment.

Please do not feel abandoned. A closed-circuit television on the control desk gives the radiographers a clear view of you and they will be watching you all the time. If you feel you need to cough or sneeze, the radiographers will tell you beforehand how to let them know this. They will switch off the machine and come in immediately.

Once your treatment has finished, the radiographers will help you off the bed and arrange your next visit. You are then able to return home or to your ward.

It is very important that you do not miss treatment days as this may make your treatment less effective. If you feel you are unable to attend for any reason, please telephone the staff on your treatment machine or contact The Christie Hotline to discuss the problem.

Some questions you may have

Radiation used in medical treatment is given in controlled, carefully measured doses. The aim is to include all tissues that could possibly contain cancer cells while minimising the dose to the normal tissue.

No. Patients treated by X-rays do not become radioactive. The radiation does not stay in your body after treatment, so you cannot do anyone else any harm. It is safe for you to mix with other people including children and pregnant women and to have visitors if you are on the wards.

Not usually. The treatment may make you feel more tired than normal. Please tell your treatment team about any existing medical conditions and continue with any medication you may be taking. Ask your Christie doctor if you are worried about any other health problems.

If you are having treatment as an outpatient, the radiographers will give you an appointment time for the first treatment when you attend for your planning session. After that, you can arrange with your treating team the time that suits you and the machine.

Please try and be as flexible as possible and give priority to your treatment sessions over other general appointments. The time you prefer may not be available at the start of your treatment because of the large numbers of patients on the unit.

If you need a specific time, please give the radiographers at least 48 hours’ notice. The time we give you may vary half an hour either way each day due to emergencies. You may be given your appointment times for the whole of your treatment on your first visit or alternatively appointment times will be given on each visit for the following day.

Once a week, you will meet your consultant or one of their team. You do not need an appointment for this. We will take you to the clinic before or after your radiotherapy. We will give you a morning or afternoon appointment to fit in with your consultant’s clinic.

If you are an inpatient, the treating team will send a care assistant for you when they have a free slot. If you are going away for the weekend, please let the staff know and they will do their best to treat you before lunch.

You will usually have your treatment as an outpatient. Some people continue to work during part of their treatment. However, after daily travel and treatment, you may feel tired and need to rest.

Your doctor will have discussed with you the need for travelling daily for your treatment as an outpatient. However, if you become unwell during your treatment, we will usually admit you as an inpatient to support you through your radiotherapy.

You will not have to stay in bed so bring suitable day wear such as tops and skirts or trousers. Treatment usually takes up only a small part of the day and, if you are well enough, you may be able to go out – check with the ward staff first.

Many patients can bring themselves or can ask a friend or relative to help them out. If you think you may need ambulance transport, please discuss this with a radiotherapy support worker or radiographer on your first visit to the radiotherapy department.

Transport can be arranged subject to eligibility criteria based on medical need. There also needs to be a medical need for you to bring an escort on hospital transport. There can be delays for some time either side of your appointment because of the high demand for transport. Please take this into account when you are deciding whether to use transport or not.

Hospital transport is provided by North West Ambulance Service and West Midlands Ambulance Service. Contact the transport liaison office at The Christie directly on 0161 446 8114 or 8143 for advice and bookings. Patients attending The Christie at Salford can contact 0161 918 7800 and patients attending The Christie at Oldham can contact 0161 918 7700 for advice about transport.

Questions you may want to ask your clinical team

  • What type and extent (stage) of disease do I have?
  • Why are you recommending radiotherapy for me?
  • What might be the benefits and side effects?
  • Is there any alternative treatment, and, if not, why is this?
  • What will the radiotherapy involve and how many times will I have to visit the hospital?
  • Will there be any lasting effects from treatment?

Chemotherapy as well as radiotherapy

Some people who are having a course of radiotherapy will also have chemotherapy. You will be given outpatient chemotherapy unless your doctor feels it is necessary to admit you. Your treating team will give you further information about the potential side effects of chemotherapy treatment.

Further treatment

For people having radiotherapy before surgery, Christie staff will liaise with the surgical team to ensure that your operation/re-assessment fits in with the treatment you are having at this hospital.

Sometimes further chemotherapy is offered after radiotherapy, this will be discussed with you beforehand.

Side effects

Side effects happen because as well as destroying cancer cells, radiotherapy can also damage healthy cells nearby. When planning treatment, the clinical team choose the dose that will give the best chance of destroying the cancer cells and reducing the symptoms – with the smallest possible effect on healthy tissue.

It seems that some patients are more sensitive to radiation than others and are more likely to experience side effects. At present, it is not possible to identify these patients before treatment starts. Also, in some patients the tumour itself can cause damage to the surrounding tissue and structures.

There are short-term (acute) and long-term (late) side effects with the treatments.

Acute side effects will generally develop during the second half of the course of treatment usually after 7 to 14 days, and last up to 12 weeks after the treatment ends. They are usually temporary and vary in severity from person to person. Some patients may develop minimal side effects and others may have more. If you have any questions about side effects, please ask any member of the team treating you.

  • Diarrhoea is a common symptom. If this occurs, a low fibre diet may help reduce symptoms. Anti-diarrhoea medication may also be helpful, like Imodium or Loperamide, you can discuss this with your treating team.
  • Symptoms similar to cystitis such as increased frequency and burning or difficulty when passing urine. We recommend that you take plenty of fluids, 2 to 3 litres per day but avoid drinking lots of alcohol, tea and coffee. Simple pain relief like paracetamol may help if you have pain when you pass urine.
  • Tiredness varies greatly from person to person. Gentle exercise and rest when feeling tired may be beneficial.
  • You may feel sick with treatment, and this is more common if you are having chemotherapy. Anti-sickness tablets may be beneficial. Please discuss this with your treating team.
  • Most radiotherapy treatments to the pelvis do not cause sore skin. We will advise you at the start of treatment if your treatment is likely to do so, and what you can do to help yourself. If you have a low rectal cancer, it is likely that you will have some skin soreness. You may find a daily moisturiser to the outside skin may be beneficial.


Your bowels may become disturbed due to your treatment. For most patients, this is in the form of diarrhoea but occasionally it can be constipation. Diarrhoea can start after about 2 weeks of treatment and last for several weeks after treatment ends. With diarrhoea, patients often get increased ‘wind’, severe urgency, intermittent abdominal gripes/cramps, abdominal bloating and may pass mucus. If diarrhoea becomes a persistent problem, please discuss this with the radiotherapy staff.

The bowel symptoms vary greatly between patients. Most people start to see some improvement 2 to 3 weeks after treatment has finished. Some patients are virtually back to normal within 6 weeks, for others they remain unsettled for several months and for some they may never return to what was normal for them.

What you can do to help

It is important that you continue to eat nourishing food during and after treatment. Ask the nursing or radiotherapy staff for a copy of ‘Eating – Help Yourself’ which contains dietary information about coping with eating problems such as loss of appetite or weight loss. If you have diabetes you can ask for a copy of ‘Eating well with diabetes’.

While you have diarrhoea you may find that your symptoms are eased by following a lower fibre diet. See The Christie booklet ‘Eating well when following a low fibre diet’. Fibre is the part of food that passes through your gut undigested.  It is contained in whole grains, pulses, vegetables and fruit. To reduce fibre, we suggest you:

  • Replace wholemeal, multigrained or seeded bread with white bread.
  • Replace wholewheat cereals, oat based cereals, porridge and muesli with Rice Krispies, Cornflakes or Special K.
  • Replace wholemeal biscuits with biscuits made from white flour such as Rich Tea, Marie biscuits, shortbread or custard creams.
  • Avoid nuts and pulses (baked beans, kidney beans, peas and lentils).
  • Take only small amounts of fruit and vegetables and avoid eating their skins, pips and seeds.

Whilst following a lower dietary fibre diet, you will need to take a complete multi-vitamin and mineral supplement daily until you return to your full diet. These are available from your local chemist.

It is important to drink enough to replace fluid that is being lost. Aim for 2 litres a day to prevent dehydration. Fluids can include milk, milkshakes, soup, fruit juice, squash, fruit tea, herbal tea as well as tea, coffee and water.

At this time, you may find it easier to graze through the day, eating small amounts but at frequent intervals.

When you have no more diarrhoea, slowly start re-introducing the foods that you have been avoiding. By adding in one new fibre-containing food each day, you will find the foods your body can tolerate without the symptoms returning. Keep reintroducing new foods one at a time until you have returned to your normal diet.

There are patient information sheets available about dietary advice for reducing bowel gas during radiotherapy and dietary advice for reducing diarrhoea during radiotherapy. Please ask your radiographer if you need a printed copy.


In a small number of cases, radiotherapy can irritate the bladder and give symptoms similar to cystitis such as increased frequency and burning or difficulty when passing urine. We recommend that you drink plenty of fluids, preferably aiming for 2 litres a day.

It is best to avoid drinking lots of tea and coffee and avoid alcohol. Bladder problems gradually get better, and most people are back to normal 6 weeks after treatment.

Fatigue (tiredness)

You may feel tired during treatment so rest is important, although a small amount of exercise each day has been found to be beneficial in reducing fatigue. This is explained further in the DVD/booklet ‘Be Active, Stay Active: a guide to exercising during and after cancer treatment’ which is available from the information centre.

Tiredness often affects people after treatment ends, so you may need help with housework and shopping. Please ask any member of the team treating you if you would like to see a social worker who can advise on help available.

Radiotherapy treatment can be a demanding treatment. If you are feeling low or are not coping, let the nurses, doctors or radiographers treating you know so they can discuss with you what might help.


Very occasionally, you may feel sick during your radiotherapy treatments, your taste changes or you go off your food. This is more likely to happen if you are having chemotherapy. Let the clinical team looking after you know because they can suggest things that may help.

Skin/pubic hair

Some radiotherapy treatments to the pelvis may cause sore skin. This is dependent on the location of your cancer and length of your treatment.

If you have a low rectal tumour, (closer to the exit or anus) it is likely that you will have some skin soreness. Your skin may become red, painful and break down. We will advise you at the start of treatment if this is likely, and what you can do to help yourself.

You may find that moisturising your skin in the pelvis may help with this side effect. Any moisturiser can be used. If you do have pain or skin breakdown, you may be given different creams and pain relief to help.

Some patients find that their pubic hair falls out during or shortly after treatment, this usually grows back but it may be thinner.

Sexual relations

It is important for men and women to take contraceptive precautions whilst having radiotherapy. However, a course of radiotherapy is the equivalent of a major operation; it may be some months before you feel interested in the physical aspect of your relationship. However, if this is a concern to you, please let your treating team know so they can discuss with you what might help.

There are some late side effects of radiotherapy that your doctor will discuss with you. These may occur months or years after your treatment and happen only in a very few cases.

For anyone having radiotherapy to the rectum, there is a small risk of developing these long-term effects. The risk is higher for people having a long course of radiotherapy. These late effects may be managed with life-style advice and medication.


Scarring may result in feeling the urge to go more often or you may feel you have less control (incontinence). Some people may need to wear pads.

If you are going to have a permanent stoma, radiotherapy is less likely to have an adverse effect on your bowel function. You may be referred to a specialist if your symptoms continue despite life-style changes and medication.

Some people may have bleeding from the back passage. If you have significant rectal bleeding, you must contact your surgical team.

Rarely, radiotherapy may inflame the healthy bowel, affecting how well it works. This may need alternative nutrition or surgery to manage. Very rarely, a blockage, or narrowing of the bowel or hole may occur, even at an early stage. This could require surgery, although the possibility is low.


Scarring may result in feeling the urge to go more often or you may feel you have less control. Some people may need to wear pads. There is a small risk that you may need surgery to the bladder.

Fatigue (tiredness)

Some people find that tiredness continues for several months after their radiotherapy treatment has finished. Planning ahead can help with tiredness. If you are finding that you are still struggling with tiredness, please see the Macmillan booklet ‘Living with fatigue’.

Skin/pubic hair

As your skin heals, long term skin changes may occur due to your radiotherapy treatment. You may find that your skin feels itchy, dry or tighter due to your radiotherapy. This is usually well managed with a moisturiser. If this is of a concern to you, please speak with your GP who can prescribe different creams to try.

Your pubic hair may grow back thinner or may not grow back at all in some areas. If this is a concern to you, please speak with your GP who may be able to refer you to a specialist for support.

Bone changes

A late side effect of radiotherapy to the pelvic area is damage to the bones in the pelvic area.

Hairline cracks may occur, known as pelvic fractures. If this happens, it can cause pain and may make it difficult to walk and move around. The pain normally settles overnight and does not stop you from sleeping well.

The changes in the bone may cause a dull, constant ache, which you may worry is due to your cancer having spread to the bone. If you have dull aching in the bone that lasts for more than a few weeks, your doctors may need to do tests (a bone scan or MRI scan) to find out the cause. If the bone is weakened enough, it may break (fracture) but this is very rare. The strength of your bones can be checked using a bone density scan.

It is important to be aware of the signs of bone problems so you can let your doctor know if they occur. Radiotherapy damage to the bones is uncommon, so it is likely that if you have any symptoms, they will have another cause.

Fertility and sexual function

This treatment causes infertility which is permanent. If infertility is an issue for you or your partner, please let the clinical team know. It is important that you discuss your concerns urgently, so you can be referred to a fertility specialist prior to starting treatment.

Radiotherapy can cause long term changes to your sexual function. Your clinical team may suggest you avoid having anal sex during and after radiotherapy. If you have bowel problems or a sensitive anus after radiotherapy, you may want to wait until symptoms have settled before trying anal sex again.

Although problems in the back passage may settle down after a few months there can be some permanent damage leading to leakage and incontinence. If this is a concern for you and your partner, please let your clinical team know so that this can be discussed further with you.

For women, this treatment is very likely to induce the menopause. This usually occurs 3 to 4 months after treatment in women who are still having regular periods. We recommend that you discuss this with your GP who may advise you to start hormone placement therapy (HRT) if your symptoms are troublesome.

Radiotherapy can cause vaginal narrowing and dryness which can affect your sex life. However, advice will be given about lessening this problem. If this is a concern for you or your partner, please discuss it with your clinical team.

Some men may notice it is more difficult to achieve an erection or ejaculate following a course of radiotherapy. This is more common in men over the age of 50 and may be permanent. Treatment is available in the form of medication from your GP, or a referral to your local erectile dysfunction clinic. If this is a concern for you or your partner, please discuss it with your clinical team.

Delayed wound healing

This treatment has a small risk of delayed wound healing, so it may take you longer to heal after surgery if this is needed in the future. If this is a concern for you please discuss this with your clinical team.

Secondary cancer

This treatment has a small risk of a secondary cancer. This means that the radiotherapy treatment given for this cancer could cause another cancer in the future. This is usually a different cancer in the pelvis which occurs around 5 to 10 years after the radiotherapy treatment. If this is a concern for you, please discuss this with your clinical team.

Last updated: March 2024