Will Afinitor Work 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 (chemical name: letrozole) or Arimidex (chemical name: anastrozole) and has stopped responding to those treatments. Afinitor has to be given in combination with Aromasin (chemical name: exemestane).

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.”

Different labs have different cutoff points for calling the cancer either “hormone-receptor-positive” or “hormone-receptor-negative.” For example, if less than 10% of your cells — or fewer than 1 in 10 — stain positive, one lab might call this a negative result. Another lab might consider this positive, even though it is a low result. Research studies have shown that even cancers with low numbers of hormone receptors may respond to hormonal therapy.

A score of “0” generally means that hormonal therapy will not be helpful in treating the breast cancer. When the score is 0, the cancer is called hormone-receptor-negative.

Sometimes, a report will come back from the laboratory saying that the hormone status is “unknown.” If you receive a result of “unknown,” ask your doctor what this means, and ask what further steps should be taken to determine your hormone receptor status.

Talk with your doctor to make sure that your test is done by a laboratory with a great deal of experience in hormone receptor testing. The more tests the lab does, the more accurate your results are likely to be. If you receive a negative test result, ask for a complete explanation as to why the cancer is considered hormone-receptor-negative. Talk to your doctor about the criteria that were used to determine the negative status and whether the results should be looked at again.

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