Cancer of unknown primary (CUP) treatment

When doctors think that someone may have cancer, they do tests to try and find the primary site (where the cancer started). If the primary site cannot be found, this is called cancer of unknown primary (CUP).

In people with CUP, cancer has already spread from 1 part of the body to another. In many cases, this means the cancer is already advanced. It is not usually possible to cure cancer that is advanced and has spread to other parts of the body. But even if the cancer cannot be cured, it may be possible to control it for some time.

Before explaining your treatment options, your doctor will consider:

• where the secondary cancer is
• how active treatment such as chemotherapy or radiotherapy might help
• how you might cope with any side effects
• any risks of treatment
• whether less invasive treatments to control your symptoms would help you.

Making decisions about your treatment can be difficult. You may need to discuss whether you wish to have treatment with your doctor. If you choose not to have active treatment, you can have supportive (palliative) care to control any symptoms.

Active treatment for CUP aims to:

• control the cancer
• help you live longer
• relieve your symptoms
• improve your quality of life.

The main treatment for CUP is chemotherapy. This is because chemotherapy goes into the bloodstream and can reach most parts of the body. Radiotherapy, hormonal therapy, targeted therapy and sometimes surgery may also be used. You may be asked to take part in a clinical trial to try newer treatments.

If you have CUP, you might find it hard to accept that even after testing, doctors still do not know what the primary cancer is. Or you might feel relieved that the tests are over, and treatment can now start. Everyone is different.

In some cases, doctors may have a good idea where the cancer started. This is based on:

• where the secondary cancer is
• your symptoms
• the type of cancer cell
• your test results.

In this situation, doctors may plan treatment for the most likely type of cancer.

For example, if you have a raised PSA level and adenocarcinoma (a type of cancer cell) in the bones, you may be treated with hormonal therapy for prostate cancer. This is because PSA is a protein produced in the prostate gland, and it is common for prostate cancer to spread to the bones.

Supportive or palliative care is an important part of treatment if you have CUP. This is when medicines are used only to control your symptoms. It is sometimes given alongside chemotherapy or radiotherapy treatment.

The aim of palliative care is to give you the best possible quality of life. Palliative care is often given alongside treatment such as chemotherapy or radiotherapy.

When cancer is very advanced, the disadvantages of treatment, such as side effects, may outweigh the possible benefits of treating the cancer. If you are too unwell to have treatment, your doctor may suggest you have palliative care on its own, instead of treating the cancer.

In certain situations, treatment may give you a better outcome even if the primary cancer cannot be found. If the secondary cancer is only in a very small area of the body, such as the lymph nodes, it is usually close to the primary cancer. Your cancer doctor or specialist nurse can explain the aim of your treatment. Here are some examples of this:

Radiotherapy uses high-energy x-rays to destroy cancer cells while doing as little harm as possible to normal cells. Doctors can give radiotherapy to try to shrink and control the cancer, and stop it from growing any further. It may also be given to try and improve any symptoms (palliative radiotherapy).

Radiotherapy may be given on its own or together with other treatments, such as surgery. You will usually have this type of radiotherapy over a few weeks.

Radiotherapy is directed at specific parts of the body. There are 2 ways of giving radiotherapy:

• external beam radiotherapy is given from outside the body by a radiotherapy machine
• internal radiotherapy uses a radioactive material placed inside the body.

People with CUP may have external radiotherapy to help control the cancer and improve symptoms. Internal radiotherapy is not commonly used to treat CUP.

If it is an option for you, your cancer doctor will explain more about radiotherapy.

If the cancer has spread to more than 1 place in the body, you may have radiotherapy to help improve symptoms. For example, radiotherapy can help relieve pain caused by cancer in the bones. This is called palliative radiotherapy. It is usually given as a shorter course of treatment and has fewer side effects. Palliative radiotherapy can be used to treat:

• pain – by shrinking the cancer and relieving the pressure that is causing pain
• breathlessness – if the cancer is affecting the lungs
• difficulty swallowing – by shrinking a cancer that is pressing on the gullet (oesophagus)
• bleeding – radiotherapy may help to stop or reduce any bleeding that might be caused by a cancer in the bowel, cervix or womb
• brain swelling – if you have a secondary cancer in the brain, radiotherapy can reduce swelling and help to improve symptoms.

The side effects of palliative radiotherapy are usually mild.

If you are having radiotherapy to control the cancer, the side effects will depend on the dose and the area being treated.

You usually have side effects for a few weeks after treatment finishes. They usually become slightly worse before they get better, but will improve over time.

Tell your cancer doctor, specialist nurse or radiographer about any side effects you have. They may be able to help reduce them.

Targeted therapy uses drugs to find and attack cancer cells. There are many different types of targeted therapy. Each type targets something in or around the cancer cell that is helping it grow and survive. Targeted therapies may be given as tablets or capsules, or by injection under the skin (subcutaneously) or drip into a vein in the arm (intravenous infusion).

Targeted therapy is not often used to treat CUP. Some clinical trials have shown that they may be useful. But we need to know more about them before they can be used as a treatment.