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. Afinitor also is being studied as a treatment for other cancers, including breast cancer.
In a study called BOLERO-2, women who received the hormonal therapy Aromasin (chemical name: exemestane) and Afinitor lived, on average, for a longer period of time without the cancer showing signs of progression (called progression-free survival), compared to women who received Aromasin and a placebo (a sugar pill that looked like Afinitor). The findings were presented at the September 2011 European Multidisciplinary Cancer Conference (ECCO-ESMO) annual meeting.
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.
724 women diagnosed with advanced-stage or metastatic breast cancers that were hormone-receptor-positive and HER2-negative participated in the study. 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 cancer that has spread to parts of the body away from the breast, such as the bones or liver. All the women in the study had been treated with hormonal therapy before participating in 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 Aromasin along with Afinitor. The other 33% got Aromasin and a placebo.
In July 2011 the BOLERO-2 study was stopped early because of positive results. Researchers found that the women who got Aromasin and Afinitor were, on average, less likely to have the cancer grow compared to women who got Aromasin and placebo.
The time a woman lives without the cancer growing is called progression-free survival. The BOLERO-2 analysis presented in September 2011 showed that among women who got Aromasin and Afinitor, median of progression-free survival was 10.6 months. Median means that half the women whose treatment included Afinitor lived more than 10.6 months without the cancer showing signs of progression while the other half lived less than 10.6 months without progression. Median progression-free survival for the women treated with Aromasin and placebo was only 4.1 months. It is important to know that most of the women in the study didn't show any signs that the cancer responded to either treatment plan (called overall response), but overall response was more likely in the women who got Aromasin and Afinitor compared to Aromasin and placebo. 9.5% of women who got Afinitor and Aromasin showed some response to treatment, compared to fewer than 1% of women who got Aromasin and placebo.
When the researchers stopped the study early because of the positive results, women getting placebo could switch to Afinitor if they and their doctors wanted to do so.
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 these early research results are promising, doctors will continue to review the longer term experiences of women in the BOLERO-2 study to better understand the potential benefits of Afinitor for treating advanced-stage breast cancer. It's not clear from the latest analysis whether overall survival (the time the women lived, with or without the cancer growing) was better in women who got Afinitor. The overall survival information is important because the FDA may be less willing to approve a new treatment for advanced-stage breast cancer if research shows 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. If you're willing to participate in a clinical trial, you may have even more options, possibly including an experimental treatment such as Afinitor. Talk to your doctor about clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.
And stay tuned to Breastcancer.org for more news about the BOLERO-2 study and the use of Afinitor to treat advanced breast cancer.