Radiotherapy treats cancer by using high-energy rays, which destroy the cancer cells while doing as little harm as possible to normal cells.

Radiotherapy is usually given in the hospital radiotherapy department, every weekday, with a rest at the weekend. The length of your treatment will depend on the type and size of the cancer, but will normally last a few weeks. Your doctor will discuss your treatment with you beforehand.

Ewing's sarcoma responds very well to radiotherapy and this treatment is often used after chemotherapy and before surgery. If surgery is not possible – for example, if the tumour is in the spine – radiotherapy may be given instead of surgery.

Radiotherapy is not often used to treat osteosarcoma as the tumour is not very sensitive to radiation. However, if a limb has fractured and the risk of spread is increased, radiotherapy may be given after surgery to destroy any remaining cancer cells, especially in the surrounding tissues.

Radiotherapy given after surgery may help to reduce the chance of a chondrosarcoma or a spindle cell sarcoma coming back.

To make your radiotherapy as effective as possible, it must be carefully planned. On your first few visits to the radiotherapy department you will be asked to lie under a large machine called a simulator, which takes x-rays of the area to be treated. Sometimes a CT scanner can be used for the same purpose. The planning will be done by a clinical oncologist and medical physicist, and may take a few visits. Marks may be drawn on your skin to help the radiographer, who gives you your treatment, to position you accurately and to show where to direct the rays. These marks must stay visible throughout your treatment, but they can be washed off once it is over. At the beginning of your radiotherapy you will be given instructions on how to look after the skin around the area to be treated.

Before each session of radiotherapy the radiographer will position you carefully on the couch and make sure that you are comfortable. During your treatment, which takes only a few minutes, you will be left alone in the room. However, you will be able to talk to the radiographer who will be watching you carefully from the next room. Radiotherapy is not painful but you do have to lie still for a few minutes while it is being given.

Radiotherapy can cause general side effects such as feeling sick (nausea) and tiredness. These side effects can be mild or more troublesome, depending on the strength of the radiotherapy dose and the length of your treatment. The radiotherapist will be able to advise you what to expect.

Tiredness As radiotherapy can make you tired you should try and get as much rest as you can, especially if you have to travel a long way for treatment every day.

Feeling sick Nausea can usually be effectively treated by anti-sickness drugs (anti-emetics), which your doctor can prescribe. If you don’t feel like eating, you can replace meals with nutritious, high-calorie drinks. These are available from most chemists and can also be prescribed by your GP.

Hair loss Radiotherapy can make your hair fall out in the area being treated.

All these side effects should disappear gradually once your course of treatment is over, but it is important to let your doctor know if they continue.

Radiotherapy does not make you radioactive and it is perfectly safe for you to be with other people, including children, throughout your treatment.

We have a section on radiotherapy, which gives more details about this treatment and its side effects.