Afinitor Helps Slow Growth of Certain Advanced-Stage Breast Cancers

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Afinitor (chemical name: everolimus) is a targeted therapy medicine approved by the U.S. Food and Drug Administration (FDA) to treat advanced-stage kidney cancer. It is being studied as a treatment for other cancers, including breast cancer.

In July 2011, the BOLERO-2 study, which wanted to know if Afinitor could help treat certain advanced-stage and metastatic breast cancers, was stopped early because of good results. Women who got Afinitor and the hormonal therapy Aromasin (chemical name: exemestane) were less likely to have the cancer grow during the study than women who got only Aromasin. Since then, the researchers have continued to follow the women in the study. Newer information from the same study showed that the women who got the Afinitor and Aromasin combination lived more than twice as long without the cancer growing (progression-free survival) compared to women who got only Aromasin.

The new results were presented at the 2011 San Antonio Breast Cancer Symposium.

Afinitor is an mTOR (mammalian target of rapamycin) inhibitor. mTOR is a kinase, a type of protein. 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. Afinitor is a pill taken by mouth.

More than 700 women diagnosed with hormone-receptor-positive, HER2-negative advanced-stage or metastatic breast cancer are in the BOLERO-2 study. The women diagnosed with advanced-stage cancer had locally advanced breast cancer, which 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 cancer that has spread to parts of the body away from the breast, such as the bones or liver.

The women had been treated with hormonal therapy before the study -- either Femara (chemical name letrozole) or Arimidex (chemical name: anastrazole) -- but the cancer had stopped responding to that treatment.

About 66% of the women were randomly chosen to get the Afinitor and Aromasin combination. The other 33% got Aromasin and a placebo (a sugar pill) that looked like Afinitor.

The latest information from the study showed that women who got Afinitor and Aromasin were twice as likely to show some benefit from the treatment (clinical benefit) compared to women who got only Aromasin. Clinical benefit means that the cancer showed signs of being weakened by the treatment or that it didn't grow for a period of time during treatment.

Just over 50% of the women who got Afinitor and Aromasin showed some clinical benefit compared to 25.5% of the women who got only Aromasin.

Progression free-survival was more than twice as long for women treated with Afinitor and Aromasin compared to women treated with only Aromasin (7.2 months compared to 3.2 months):

  • Among all women treated with Afinitor and Aromasin, half lived without the cancer growing for more than 7.2 months and half lived with no cancer growth for shorter periods of time.
  • Among all women treated with only Aromasin, half lived without the cancer growing for about 3.2 months and half lived with no cancer growth for shorter periods of time.

The researchers need to follow the women for more time before they can see if overall survival -- the time a woman lives with or without the cancer growing -- is better with the Afinitor and Aromasin combination. Still, these results suggest that compared to hormonal therapy alone, Afinitor and Aromasin may offer women diagnosed with locally advanced and metastatic breast cancer more time before a more aggressive treatment (chemotherapy, for example) is needed.

Besides being a pill taken by mouth, which is more convenient than an infusion or an injection (Aromasin also is a pill taken by mouth), the BOLERO-2 study found that there was only a small increase in side effects in women who got Afinitor and Aromasin compared to women who got only Aromasin.

Novartis, the company that makes Afinitor, is expected to ask the FDA to consider approving the Afinitor and Aromasin combination to treat hormone-receptor-positive, HER2-negative locally advanced and metastatic breast cancer that has already been treated with Arimidex or Femara and stopped responding to those medicines.

Doctors continue to look for new treatments for women diagnosed with locally advanced or metastatic breast cancer that has stopped responding to standard treatments. While the research results reviewed here are very promising, doctors will wait for more results to see if overall survival is better in women who got Afinitor and Aromasin. Overall survival information is important because the FDA may be less willing to approve Afinitor to treat advanced-stage breast cancer if there's no improvement in overall survival.

If you're being treated for advanced-stage breast cancer, you and your doctor may be considering a number of treatment options, especially if the cancer has stopped responding to standard treatments. Even though Afinitor is not currently approved to treat breast cancer, it's a good idea to ask your doctor if Afinitor and Aromasin might be an option to consider in your specific situation. It's also worth talking to your doctor about any clinical trials that might be a good fit for you.

Stay tuned to Breastcancer.org for more news on the BOLERO-2 study and Afinitor.

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