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Cancer of Unknown Primary: Hormone Therapy

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What is hormone therapy?

Natural hormones made in the body can help certain kinds of cancer cells grow. Hormone therapy is used to change this. It might lower hormone levels or keep cancer cells from using them. Hormone therapy may be used to help stop a tumor from growing or shrink a tumor. It may help you live longer.


When might hormone therapy be used for cancer of unknown primary?

Tests are done on your cancer to see if hormone therapy might work. If they show that the cancer of unknown primary might be breast or prostate cancer, hormone therapy may be a choice. It's used to keep hormones from helping cancer cells to grow.

Hormone therapy can be done in different ways. For instance, surgery can be done to take out certain organs that make hormones, like the testicles. Another choice may be using radiation to damage the organs that make hormones. For instance, radiation to the ovaries can stop estrogen from being made. Medicines that change the way hormones work can also be used.


How is hormone therapy given for cancer of unknown primary?

Hormone therapy is most often given as shots or pills. Sometimes surgery or radiation is used to keep certain organs from making hormones.

Some medicines stop a woman's body from making the female hormone estrogen or keep cancer cells from using it. This may help slow the growth of breast cancer cells. These medicines include:

  • Exemestane

  • Anastrazole

  • Letrozole

  • Tamoxifen

  • Toremifene

  • Fulvestrant

  • Leuprolide

  • Goserelin

If CUP in a man might be caused by prostate cancer, medicines can be used to lower the testosterone level or keep cancer cells from using it to fuel tumor growth. These medicines include:

  • Leuprolide

  • Goserelin

  • Triptorelin

  • Flutamide

  • Bicalutamide

  • Enzalutamide

  • Apalutamide


Possible side effects from hormone therapy for cancer of unknown primary

Hormone therapy may cause side effects. These depend on the type of treatment you get or the medicines you take. Common side effects include:

  • Hot flashes

  • Vaginal dryness or discharge in women

  • Trouble thinking and remembering

  • Mood changes

  • Nausea

  • Diarrhea

  • Tiredness and fatigue

  • Muscle, bone, or joint pain and stiffness

  • Weak bones (osteoporosis)

  • Loss of interest in sex

  • Period changes in people who haven't gone through menopause yet

Tell your healthcare provider about any side effects you have. There are often ways to ease them or keep them from getting worse.


Working with your healthcare provider

It's important to know which medicines you're taking. Write down the names of your medicines. Ask your healthcare team how they work and what side effects they might cause.

Talk with your healthcare team about what symptoms to watch for and when to call them. Know how to get help when your healthcare provider's office is closed.

It may be helpful to keep a journal of your side effects. Write down physical, mental, and emotional changes. A written list will make it easier for you to remember your questions when you go to your appointments. It will also make it easier for you to work with your healthcare team to manage your side effects.

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© 2025 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.

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