New drugs may rival tamoxifen
Tamoxifen has long been the standard treatment for post-menopausal women after breast cancer surgery, but the drawbacks are considerable: It provides benefits for only five years, sometimes stops working earlier and boosts risks of endometrial cancer and stroke.
A new class of drugs may become a better option.
Three studies in the past year have shown that drugs called aromatase inhibitors are better at preventing cancer recurrences. The most recent evidence suggests more women stay cancer-free by switching from tamoxifen (Nolvadex) to exemestane (Aromasin).
In the March 11 issue of the New England Journal of Medicine, researchers reported that among 4,700 women from 37 countries, those who switched from tamoxifen to exemestane after two to three years lowered by 32% their risk of developing another tumor in either breast or other organs, compared with those who stuck with tamoxifen for five years. Exemestane also had fewer side effects, although like all aromatase inhibitors, it might worsen osteoporosis.
Tamoxifen blocks estrogen’s ability to latch on to cells, but resistance to its effects can develop quickly. Aromatase inhibitors, developed as an alternative, block estrogen production in the adrenal glands.
Tamoxifen treatment remains the recommendation of the American Society of Clinical Oncology for post-menopausal women who don’t have a history of blood clots or risk of uterine cancer. But the aromatase inhibitor anastrozole (Arimidex) was shown in a study last December to prevent more recurrences than tamoxifen.
Since that time, many oncologists have been prescribing anastrozole for newly diagnosed patients.
Dr. Christy A. Russell, co-director of the Lee Breast Center at USC Norris Cancer Center in Los Angeles, said she hasn’t started any post-menopausal patients on tamoxifen since the anastrozole study results were released.
For those patients already taking tamoxifen, Russell and many of her colleagues were guided by an October study showing that letrozole (Femara) could keep cancer at bay after five years of tamoxifen use. But they remained concerned by the number of women relapsing on tamoxifen.
Russell said the latest findings are demonstrating that tamoxifen users can make an earlier switch to exemestane.
