Cancer of unknown primary treatment

The aim of treatment for CUP is to try to control the cancer, treat the symptoms and improve or maintain your quality of life.

How is CUP treated?

When cancer of unknown primary (CUP) is diagnosed, you might find it hard to accept that even with tests, the 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.

When CUP is diagnosed, cancer has already spread from one 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 if the cancer cannot be cured, it may be possible to control it for some time.

The aim of treatment for CUP is to try to:

  • control the cancer
  • help you live longer
  • treat your symptoms.

Your cancer doctor will consider the following things before explaining your treatment options:

  • where the secondary cancer(s) is
  • how you might benefit from treatment
  • how you might cope with any side effects.

Treatment for certain types

In some cases, the doctors may have a strong indication of where the cancer started. This is based on:

  • knowing where the secondary cancer is
  • your symptoms
  • test results.

In this situation, your doctors may plan treatment that is often used for that type of cancer.

For example, if you have a raised PSA level and adenocarcinoma 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.

Palliative care

The aim of palliative care is to control symptoms to improve or maintain your quality of life. Palliative support 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. Some people may be too unwell to have treatment. In this situation, your cancer doctor may suggest you have palliative care on its own, instead of treating the cancer.

Treating small secondary

Even when the primary cancer cannot be found, you may have a much better outcome with treatment. But this is only in certain situations. It is usually when the secondary cancer is only in a very small area of the body. In this situation, the secondary cancer is usually close to where the primary cancer might be, such as in the lymph nodes.

Here are some examples of this:

  • Squamous cell lymph nodes in your neck

    this may mean the primary cancer is in the head and neck area. You will be referred to a head and neck specialist team for assessment. You may have surgery to remove the lymph nodes or have radiotherapy. Or you may have both. You might also have chemotherapy.

  • Adenocarcinoma in lymph nodes in one armpit

    this may mean the primary cancer is in the breast tissue. You will be referred to a specialist breast cancer team for assessment. You may have surgery or radiotherapy to the lymph nodes, then chemotherapy and hormonal therapy.

  • Squamous cell lymph nodes in the groin

    this may mean the cancer started in the groin area or in the back passage. You will be referred to a specialist surgeon to have the nodes removed, which may be followed by radiotherapy.

Your cancer doctor or specialist nurse can explain what the aim of your treatment is.

We understand that having treatment can be a difficult time for people. We're here to support you. If you want to talk, you can:

Chemotherapy for CUP

Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. It is the most commonly used treatment for CUP. This is because chemotherapy goes into the bloodstream. This means it can reach most parts of the body.

Even though doctors do not know the primary type of cancer, tests may have shown which type of cancer is most likely. This means they can choose the chemotherapy that works best for that cancer type. For example, if the primary cancer is most likely breast cancer, you will have chemotherapy that is usually used to treat breast cancer.

The aim of chemotherapy is to shrink the cancer and relieve symptoms. You may have a chemotherapy drug on its own, or you may have a combination of drugs. Some people may have chemotherapy and radiotherapy together.

We have more information about chemotherapy and possible side effects of chemotherapy.

Radiotherapy for CUP

Radiotherapy uses high-energy 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 is sometimes given to try and cure CUP. This might be if the cancer is in one area of lymph nodes, such as the neck, armpit or groin. It 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 two ways of giving radiotherapy:

  • internal radiotherapy is when a radioactive material is placed inside the body. Internal radiotherapy is not commonly used to treat CUP. Your cancer doctor will explain more about internal radiotherapy if it is an option for you.

Palliative radiotherapy

If the cancer has spread to more than one place in the body, you may have radiotherapy to help improve symptoms. For example, radiotherapy can help improve symptoms such as 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 the following symptoms:

  • Pain

    radiotherapy shrinks the cancer and relieves the pressure that is causing the pain.

  • Breathlessness

    radiotherapy may relieve breathlessness if the cancer is affecting the lungs.

  • Difficulty swallowing

    radiotherapy can help with swallowing difficulties 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

    radiotherapy can be used to treat a secondary cancer in the brain. It reduces swelling and can help to improve symptoms.

Side effects

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. We have more information about possible side effects of radiotherapy.

Hormonal therapy for CUP

Sometimes hormonal therapies are used to treat CUP.

Your cancer doctor might suggest hormonal therapy if tests show that the cancer has hormone receptors. If the cancer has hormone receptors, it means some hormones produced naturally by the body may encourage the cancer to grow. For example, oestrogen is a hormone that can encourage breast cancer cells to grow.

Hormonal therapies reduce the amount of hormones in the body, or stop hormones attaching to the cancer cells. Hormonal therapies are used to treat CUP when the most likely primary cancer is breast or prostate cancer. But they may also be used to treat cancer of the womb or kidney. They are usually given as tablets or injections.

The side effects depend on the individual drug. They can include:

  • tiredness
  • headaches
  • feeling sick
  • muscle or joint aches.

There are different types of hormonal therapies. Your specialist may try a different type if the first one does not work for you.

We have more information about individual hormonal therapies.

Targeted therapy for CUP

Targeted therapies are drugs that affect how cancer cells grow. There are different types of targeted therapies. They work slightly differently. Targeted therapies may be given as tablets or by injection or drip into a vein in the arm (intravenous infusion).

Targeted therapies are 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.

Surgery for CUP

Surgery is not often used to treat CUP. But you may have an operation to remove a secondary cancer if:

  • there is a single tumour that can be easily removed
  • lymph nodes with cancer in them are close together and in a single area, such as the armpit
  • symptoms can be improved by removing the cancer, for example if the cancer is causing pain.

After surgery, you may have another treatment, such as radiotherapy or chemotherapy. This is to treat any cancer cells that may be left behind.

Even if the cancer is in a single area, you may not be well enough to have surgery. In this situation your CUP specialist will talk to you about what other treatments might be suitable.