External radiotherapy for nasopharyngeal cancer

External beam radiotherapy uses high energy x-rays to kill the cancer cells. The rays come from a machine into your body. The machine is called a linear accelerator (LINAC). It is similar to having an x-ray, but the radiation is stronger. This treatment directs a high dose of radiation to the area of the tumour.

External radiotherapy is normally given as a series of short treatment sessions known as fractions. You have the treatment in the hospital radiotherapy department. You go to the hospital for treatment once a day, from Monday to Friday, with a break at the weekends. The length of the course of treatment varies, depending on the type and size of the cancer and the aim of the treatment. But the treatment usually continues for between 4 and 7 weeks.

Your doctor chooses the type of radiotherapy and the machine for your treatment according to the type of cancer you have and its position in the body.

Your doctor will make sure that the treatment covers the whole area of the cancer, and about one centimetre all round it. This is to make sure they don’t miss any stray cancer cells. Doctors call these stray cells microscopic spread. A scan is unable to pick them up because they are so small. But if they are left, they could cause your cancer to come back.

3D conformal radiotherapy (3D CRT) uses special computers to see the tumour in three dimensions (3D) – width, height and depth using CT scan or MRI scan. This allows doctors to plan the radiotherapy treatment in 3D. The radiotherapy machine can deliver radiation beams that are matched very precisely (conform) to the shape of the tumour. This helps to avoid healthy tissue as far as possible. There is more information about conformal radiotherapy in our question and answer section.

An advanced form of conformal radiotherapy is intensity modulated radiotherapy (IMRT), which doctors are increasingly using. IMRT uses a machine linked to a computer. The machine moves around you as it gives the radiotherapy from different angles. While it is moving it is shaping and aiming the radiation beams at the tumour. The strength of the beams are adjusted to avoid normal tissue. IMRT may be particularly useful if the cancer has spread into the parapharyngeal space. This is the fatty space on either side of the nasopharynx. There is information about IMRT on the nasopharyngeal cancer research page.

If you have radiotherapy to any area of your face and neck, you will usually need to wear a treatment mask, also called a cast, mould or shell. This keeps your head and neck very still during your treatment. Keeping your head very still helps to make sure that the radiation only goes to the exact area that needs treating. The mask will fit over your lower jaw and neck. The radiographer attaches it to the radiotherapy couch each time you’re treated.

You have your mask made during your first planning appointment. Before you have anything done, the staff will explain what is going to happen. The mould room technician will make your mask individually for you in the mould room. It should feel comfortable and secure when you wear it. Having the mask made won't hurt. But it may feel a bit strange to have someone working so near to your face.

You may have a dental impression made with gel. The technician will put the gel into your mouth and take an impression of your teeth. This takes between 5 and 10 minutes. The technician will also make an impression of your lower jaw and neck. The whole visit takes about 30 minutes.

Masks are made from either a thin sheet of clear plastic or various materials that mould to shape easily when they are heated up. The technician will cut holes in the mask for your nose and mouth so that you can breathe comfortably. You can read detailed information about how masks are made in the radiotherapy section.

Radiotherapy treatment is carefully planned. You may need to have a CT scan as part of your radiotherapy planning. This is so the radiotherapy specialist can see the tumour from all sides (3D, 3 dimensionally). During your planning appointment, you lie under a large machine called a simulator. Using the information from the CT scan or X-rays the simulator works out exactly where to give the treatment in order to

• Include the whole of the tumour
• Include a small border of healthy tissue all around the tumour to include any cancer cells very close to it
• Avoid as much surrounding healthy body tissue as possible

Each treatment only takes a few minutes. The radiographer will help position you on the couch and make sure your mask feels comfortable. You will be left alone for the minute or two the machine is switched on. The staff will be able to see and hear you through a CCTV link, so you can call if you need them. The treatment does not hurt – you won’t be able to feel it at all. You must lie very still for the few minutes it takes to treat you.

Having external radiotherapy does not make you radioactive. It’s perfectly safe to be with other people, including children, throughout your treatment course.

In our main radiotherapy section there is general information about radiotherapy, including sections about

• What radiotherapy involves
• How your radiotherapy treatment is planned