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.

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.

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 can stop the hormone estrogen from being made or can 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 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.
• Darolutamide.
• Abiraterone acetate.

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.
• 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 doctor about any side effects you have. There are often ways to ease them or keep them from getting worse.

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

Talk with your care team about what symptoms to watch for and when to call them. Know how to get help when your doctor'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 care team to manage your side effects.