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

Radiotherapy treatment is directed at specific parts of the body and may be used when the lymphoma cells are contained in one or two areas of lymph nodes in the same part of the body (stage 1 or 2). It is often given along with chemotherapy.

The treatment is normally given as a series of short daily sessions. The treatments are usually given daily, Monday to Friday, with a rest at the weekend. The number of treatments will depend on the type and stage of the lymphoma, but the whole course of treatment will usually last a few weeks.

Each treatment takes from 10 to 15 minutes. Your doctor will discuss the treatment and possible side effects with you.

Radiotherapy has to be carefully planned to make sure that it is as effective as possible. On your first visit to the radiotherapy department, you will be asked to have a CT scan or lie under a machine called a simulator, which takes x-rays of the area to be treated. The treatment is planned by a clinical oncologist (a cancer specialist). Planning is a very important part of radiotherapy and may take a few visits.

The radiographer, who gives you your treatment, will draw marks on your skin to help position you accurately and to show where the rays are to be directed. These marks must stay throughout your treatment. Permanent marks (like tiny tattoos) may be used. These are tiny, and will only be done with your permission. Some people need to have a mould made of the area being treated – this is to help you keep still during the treatment.

At the beginning of your treatment you will be given advice on how to look after your skin in the area being treated. Perfumed soaps, creams or deodorants may irritate the skin and should not be used during the treatment.

Before each session of radiotherapy, the radiographer will position you carefully on the couch, and make sure you are comfortable. During your treatment, which only takes a few minutes, you will be left alone in the room but you will be able to talk to the radiographer who will be watching you.

Radiotherapy is not painful but you do have to lie still for a few minutes while the treatment is being given.

Radiotherapy will nearly always make people tired. Other side effects you have will depend on the part of your body being treated.

• treatment to the abdomen can cause stomach upsets such as feeling sick (nausea), vomiting or diarrhoea.
• treatment to the head can make your hair fall out in the treated area.
• radiotherapy to the neck can make your mouth or throat sore and you may notice that some foods taste different from normal.

The side effects can be mild or more troublesome, depending on the part of the body being treated and the radiotherapy dose. Your radiotherapist will be able to advise you about what to expect and your doctor can prescribe medicines to help with side effects such as sickness or diarrhoea. Our section on eating problems has helpful tips on coping with eating problems caused by treatment.

Radiotherapy can have long-term (permanent) side effects. These are rare and, again, will vary depending on the part of the body treated. You can ask your specialist about possible long-term side effects.

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