Cancer of unknown primary

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Hormonal therapy for cancer of unknown primary

A few people with cancer of unknown primary (CUP) may have hormonal therapy. It is a treatment that adds, blocks or removes hormones. Hormones are substances that control some body functions, including the activity and growth of cells. Changing the levels of or blocking certain hormones can slow the growth and spread of cancer cells. Drugs, surgery or radiation therapy can be used to change hormone levels or block their effects.

You may be offered hormonal therapy if your doctors think your type of CUP will respond to it. Hormonal therapy may be used to:

  • treat the cancer
  • relieve pain or control the symptoms of advanced cancer (called palliative therapy)

Your healthcare team will consider your personal needs to plan your hormonal therapy. You may also receive other treatments.

Hormonal therapy by type of CUP

You may be offered hormonal therapy if your doctors think the CUP started in the breast or prostate.

Hormonal therapy for CUP that may have started in the breast

Hormonal therapy may be offered to women who have CUP in lymph nodes under the arm and doctors think that the breast is the primary site. The hormonal therapy drugs used are the same as those given for breast cancer and may include:

  • tamoxifen (Nolvadex, Tamofen)
  • anastrozole (Arimidex)
  • letrozole (Femara)
  • exemestane (Aromasin)
  • goserelin (Zoladex)

Find out more about hormonal therapy for breast cancer.

Hormonal therapy for CUP that may have started in the prostate

The prostate may be the primary site in men who have CUP in a bone or a high prostate-specific antigen (PSA) level. The hormonal therapy drugs used are the same as those given for prostate cancer and may include:

  • leuprolide (Lupron, Lupron Depot, Eligard)
  • goserelin (Zoladex)
  • flutamide (Euflex)
  • bicalutamide (Casodex)

Find out more about hormonal therapy for prostate cancer.

Side effects

Side effects can happen with any type of treatment for CUP, but everyone’s experience is different. Some people have many side effects. Other people have few or none at all.

Side effects of hormonal therapy will depend mainly on the type of drug, the dose and your overall health. Some common side effects of hormonal therapy drugs used for CUP are:

Tell your healthcare team if you have these side effects or others you think might be from hormonal therapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them. They can also provide more information about sexuality and cancer.

Information about specific cancer drugs

Details on specific drugs change quite regularly. Find out more about sources of drug information and where to get details on specific drugs.

Questions to ask about hormonal therapy

Find out more about hormonal therapy and side effects of hormonal therapy. To make the decisions that are right for you, ask your healthcare team questions about hormonal therapy.

prostate-specific antigen (PSA)

A protein made by the prostate that is normally found in the semen and blood. Higher amounts of PSA may be found in the blood of men who have prostate cancer, benign prostatic hyperplasia (BPH) or inflammation of the prostate.

PSA can be used as a tumour marker. It is used to monitor a man’s response to treatment for prostate cancer, or to see if prostate cancer has come back (recurred) after treatment.

tumour flare reaction

A sudden, temporary worsening of tumour-related symptoms following the start of treatment.

Also called tumour flare, flare reaction or flare response.


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