According to an article recently published in the journal Cancer, combined results from two clinical trials provide further confirmation that postmenopausal women with hormone-positive early breast cancer have improved survival when they switch from tamoxifen (Nolvadex®) to an aromatase agent.
The majority of breast cancers are estrogen receptor-positive (ER-positive), often referred to as hormone positive. This means that the cancer is stimulated to grow by the female hormones estrogen and/or progesterone. Depriving hormone-positive breast cancers of estrogen can slow the growth of these cancers. Patients with hormone-positive breast cancer are often treated with therapy referred to as hormone therapy.
For many years tamoxifen, acts by blocking estrogen receptors, has been a mainstay of hormonal therapy for breast cancer. More recently, however, drugs known as aromatase inhibitors, which interfere with the production of estrogen, have produced superior results to tamoxifen alone in the treatment of ER-positive, postmenopausal breast cancer. Currently available aromatase inhibitors include Arimidex® (anastrozole), Aromasin® (exemestane), and Femara® (letrozole).
When considering how best to use aromatase inhibitors in the treatment of postmenopausal breast cancer, researchers have considered several possibilities: 1) as extended hormonal therapy; 2) after completion of tamoxifen treatment; 3) women could be switched to aromatase inhibitors after a brief (two- to three-year) period of tamoxifen therapy; 4) aromatase inhibitors could be used in place of tamoxifen as initial hormone therapy.
Although it’s still uncertain which of these approaches is best, each of them appears to produce better outcomes than use of tamoxifen alone. The primary benefit observed thus far is a reduction in the risk of cancer recurrence. Researchers continue to evaluate which order and/or schedule will provide optimal outcomes for patients with breast cancer; their focus is on survival.
Researchers from Italy recently conducted two clinical trials evaluating a switch from tamoxifen to an aromatase inhibitor after two to three years. These trials included 828 postmenopausal women with hormone-positive breast cancer who were initially treated with tamoxifen for two to three years. One group of women then switched to treatment with an aromatase agent (anastrozole or aminoglutethimide) or continued treatment with tamoxifen for an additional two to three years.
At a median follow-up of 78 months, it was apparent that patients who switched to an aromatase agent had a 39% reduced risk of death compared to those who continued treatment with tamoxifen.
The researchers concluded that among postmenopausal, hormone-positive women with early breast cancer “switching to an aromatase inhibitor after 2 or 3 years of tamoxifen therapy significantly improves survival compared with continuing 2 or 3 years of additional tamoxifen treatment.”
Postmenopausal women with hormone-positive breast cancer may wish to speak with their physician regarding their individual risks and benefits of treatment with either tamoxifen or an aromatase inhibitor.
Reference: Boccardo F, Rubagotti A, Aldrighetti D, et al. Switching to an aromatase inhibitor provides mortality benefit in early breast carcinoma. Cancer. 2007; 109: 1060–1067.