Afinitor (chemical name: everolimus) is used in combination with Aromasin (chemical name: exemestane) to treat advanced-stage, hormone-receptor-positive, HER2-negative breast cancer in postmenopausal women that has already been treated with Femara (chemical name: letrozole) or Arimidex (chemical name: anastrozole).

Afinitor is a pill taken by mouth.

Learn more about:

  • How Afinitor works
  • Is Afinitor right for you?
  • What to expect when taking Afinitor
  • Paying for Afinitor
  • Afinitor side effects


How Afinitor works

Afinitor is an mTOR (mammalian target of rapamycin) inhibitor. mTOR is a kinase, a type of protein in the body. Kinases help all cells — both healthy and cancer cells — get the energy they need. When kinases don’t act normally or are overactive, they help certain breast cancers grow. mTOR inhibitors work by interfering with the mTOR kinase and stopping cancer cells from getting the energy they need to grow.

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Is Afinitor right for you?

Afinitor can work in postmenopausal women diagnosed with advanced-stage, hormone-receptor-positive, HER2-negative breast cancer that has already been treated with Femara or Arimidex and has stopped responding to those treatments. Afinitor has to be given in combination with Aromasin.

Advanced-stage cancer refers to locally advanced or metastatic cancer. Locally advanced breast cancer is cancer that has spread beyond the breast to the chest wall below the breast or the skin on top of the breast. Metastatic breast cancer is advanced-stage cancer that has spread to parts of the body away from the breast, such as the bones or liver.

Aromasin, Femara, and Arimidex are all aromatase inhibitors, a type of hormonal therapy. Aromatase inhibitors stop the production of estrogen in postmenopausal women. Aromatase inhibitors work by blocking the enzyme aromatase, which turns androgen hormones into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells.

To find out if a cancer is hormone-receptor-positive, most testing labs use a special staining process that makes the hormone receptors show up in a tissue sample. The test is called an immunohistochemical staining assay, or ImmunoHistoChemistry (IHC). Not all labs use the same method for analyzing the results of the test, and they do not have to report the results in exactly the same way. So you may see any of the following on your pathology report:

  • A percentage that tells you how many cells out of 100 stain positive for hormone receptors. You will see a number between 0% (none have receptors) and 100% (all have receptors).
  • An Allred score between 0 and 8. This scoring system is named for the doctor who developed it. The system looks at what percentage of cells test positive for hormone receptors, along with how well the receptors show up after staining (this is called “intensity”). This information is then combined to score the sample on a scale from 0 to 8. The higher the score, the more receptors were found and the easier they were to see in the sample.
  • The word “positive” or “negative.”

Learn more about how to read hormone receptor test results.

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What to expect when taking Afinitor

Afinitor is prescribed with Aromasin, an aromatase inhibitor. Both medicines are pills taken by mouth. You take the pills at the same time every day, with or without food.
You keep taking Afinitor with Aromasin as long as you are getting benefits from the medicines.

Women who are pregnant or are planning to get pregnant should not take Afinitor. Doctors don’t know if Afinitor will harm your unborn baby. It’s important that you don’t get pregnant while you’re getting Afinitor; you must use effective birth control while you’re taking it and for 8 more weeks after you stop taking it.

Also, women who are breastfeeding or plan to breastfeed shouldn’t take Afinitor. Together you and your doctor will decide if you should take Afinitor or breastfeed. You shouldn’t do both.

Visit Treatment for Breast Cancer During Pregnancy for more information.

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Paying for Afinitor

If your doctor prescribes Afinitor and you have any problems getting it covered by insurance or don’t have insurance, an Afinitor co-pay card can help lower your costs for the medicine. Sponsored by Novartis, the company that makes Afinitor, the co-pay card allows you to pay only $25 per month for Afinitor. The co-pay card also helps cover the cost of generic Aromasin while you’re taking Afinitor.

If you’re not eligible for a co-pay card, Novartis also offers the Patient Assistance NOW Oncology program that may be able to help you find another support or reimbursement program. You also can call the Novartis Oncology Reimbursement Hotline at 1-800-282-7630.

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Afinitor side effects

The most common side effects of Afinitor are:

  • mouth sores
  • infection
  • rash
  • fatigue
  • diarrhea
  • decreased appetite

Afinitor also may cause serious side effects, including:

Lung and breathing problems: In some women, Afinitor may cause severe lung and breathing problems that can dramatically compromise their health. Tell your doctor right away if you develop a cough, have trouble breathing or feel short of breath, or have chest pain.

Infections: Afinitor may make some women more likely to develop an infection such as pneumonia or a fungal or viral infection. Afinitor may reactivate hepatitis B in some people who’ve had that disease in the past. Tell your doctor right away if you have a temperature higher than 100.5, chills, or don’t feel well.

Kidney failure: Afinitor may cause kidney failure in some women. Your doctor will order tests to monitor your kidney function before, during, and after you’re taking Afinitor. If you’ve had kidney or liver problems in the past or have been diagnosed with diabetes, it’s important to tell your doctor before you start taking Afinitor.

Because Afinitor is likely to be given with Aromasin, it’s important to know that bone thinning and weakening and a higher-than-average risk of broken bones can be side effects of Aromasin.

Other common side effects of Aromasin are:

  • bone and joint pain
  • hot flashes
  • fatigue
  • headache
  • insomnia
  • increased sweating

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  1. Afinitor (everolimus) prescribing information. Novartis. East Hanover, NJ. 2018. Available at (PDF)