Radiotherapy for cancer of unknown primary (CUP)

Radiotherapy uses high energy waves (radiation) to treat cancer. Your doctor may recommend this type of treatment in certain situations for cancer of unknown primary (CUP). Radiotherapy can be external or internal treatment. How you have the treatment depends on the part of your body being treated and whether the treatment is designed to help with symptoms or to try to cure the cancer. Your doctor carefully works out the total radiation dose. 

External radiotherapy beams pass through some body tissues and cause damage to body cells. But the radiotherapy tends to cause much more damage to cancer cells than it does to normal cells. So the cancer cells die but the healthy cells can recover. Internal radiotherapy is a mildly radioactive liquid that collects in the areas of cancer. 

For external radiotherapy, the total treatment dose is usually divided up into a series of smaller daily treatments called fractions. Most often, you have these daily treatments from Monday to Friday, with a break at the weekend. With external radiotherapy, you may have the treatment as a single dose, but it is more usual to have a course of treatments spread over out over days or weeks. Usually you have radiotherapy as an outpatient, but for some types of treatment you may have to stay in hospital for a few days. Below is a picture of a radiotherapy machine.

Internal radiotherapy for CUP is most often used to treat a cancer that has spread quite widely through the bones. You usually have this treatment as an injection. There is detailed information about internal radiotherapy in the main radiotherapy section.

Radiotherapy may be able to help if you have

• Breathing problems
• Bleeding
• Bone problems
• Swelling in an arm or leg

Breathing problems

Radiotherapy may be able to help if you have wheezing or breathlessness due to cancer cells in your lungs. 

Bleeding

Cancers can sometimes cause bleeding. This happens in some cancers that affect the skin. It can also happen with cancers in the back passage (rectum). Sometimes cancer cells in the lung can make you bring up small amounts of blood when you cough. You may hear this called haemoptysis (pronounced heem-op-tih-sis). Radiotherapy can sometimes reduce or stop the bleeding.

Bone problems

If your cancer was found because you had 1 or 2 secondary tumours in your bones, you are likely to be offered radiotherapy to the affected bones. This treatment is likely to work well. The radiotherapy kills off the cancer cells in the affected bone and so shrinks the cancer. This helps to relieve pain. Once the cancer has been shrunk, the bone starts to heal itself by laying down more calcium and building itself back up again. This strengthens the bone.

For widespread cancer in the bone, specialists will sometimes suggest internal radiotherapy using a radioactive injection of strontium. The strontium in the injection travels through the body and is taken up by the bones. It can treat bone cancer throughout the whole body, whereas external radiotherapy is usually targeted at a particular bone or area of bones.

Swelling in an arm or leg

Fluid circulates around the body in the network of blood vessels and in the lymphatic system. Cancer can block the normal drainage routes and cause swelling. This swelling is called lymphoedema (lim-fo-dee-ma). It can happen either because a tumour puts pressure on blood vessels and lymphatic vessels. Or because cancer is growing in a lymph node (or group of lymph nodes). The lymph nodes normally filter the fluid that drains from body tissues. Cancer growing in a lymph node blocks this drainage route.

Radiotherapy may help to reduce swelling in either of these situations. How much it helps may depend on the primary type of cancer. Radiotherapy works better for some types of cancer than others.

Apart from causing general tiredness, external radiotherapy causes side effects only in the part of the body that is being treated. For example, radiotherapy to the neck can cause a sore throat and painful swallowing, whereas radiotherapy to the tummy (abdomen) tends to make you feel sick. These side effects tend to come on as you go through your course of treatment. If you have a short course of treatment of only a few days, you may have very few side effects. The side effects will gradually go in the days after your treatment has finished. There is information about side effects according to the part of the body being treated in the main radiotherapy section.

Internal radiotherapy tends to cause very few side effects but you may feel tired for a few days after the treatment. 

The main radiotherapy section has lots more information. You can go to sections about

• What radiotherapy is
• How radiotherapy is planned
• Possible side effects for different parts of the body
• Radiotherapy for symptoms

If you would like more information about anything to do with radiotherapy, contact our cancer information nurses. They will be happy to help.