The U.S. Food and Drug Administration (FDA) has approved Afinitor® (everolimus) for use in combination with Aromasin® (exemestane) to treat postmenopausal women with advanced hormone-receptor positive, HER2-negative breast cancer. The combination is intended for use in women who experience recurrence or progression of cancer after treatment with Femara® (letrozole) or Arimidex® (anastrozole).
Each year roughly 200,000 U.S. women are diagnosed with breast cancer. Many of these breast cancers are hormone receptor-positive, meaning that exposure to estrogen and/or progesterone can cause them to grow.
Treatment of hormone receptor-positive breast cancer often includes hormonal therapies such as tamoxifen or an aromatase inhibitor. Tamoxifen acts by blocking estrogen receptors, and aromatase inhibitors—such as Femara and Arimidex—suppress the production of estrogen in postmenopausal women. Many women with advanced breast cancer become resistant to hormonal therapy, and treatment options for these women remain limited.
Afinitor is an oral medication that works by inhibiting a protein known as mTOR. The mTOR protein plays an important role in regulating cancer cell division and blood vessel growth. Currently, Afinitor is used for the treatment of selected patients with kidney cancer, pancreatic neuroendocrine tumors, and subependymal giant cell astrocytoma (SEGA).
The approval was based on the results of a multi-center, randomized, double-blind study that included 724 women with estrogen receptor-positive, HER2-negative, advanced breast cancer with recurrence or progression following treatment with Femara or Arimidex. Patients were randomly assigned to receive Afinitor plus Aromasin (485 patients) or placebo plus Aromasin (239 patients). Patients received treatment until their cancer progressed or until side effects became unacceptable.
The primary endpoint of the study was progression-free survival (PFS)—or the length of time a patient lived before their cancer progressed. The median PFS was 7.8 months in the Afinitor/Aromasin group, compared to 3.2 months in the placebo/Aromasin group. The objective response rate was 12.6 percent in the Afinitor group and 1.7 percent in the placebo group.
The most common side effects observed in the Afinitor group were mouth ulcers, infections, rash, fatigue, diarrhea, and decreased appetite. Older patients appeared to experience a higher rate of serious side effects than their younger counterparts.
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