Arimidex ‘Highly Effective’ at Reducing Long-term Breast Cancer Rates in At-risk Women, Study Finds

Arimidex ‘Highly Effective’ at Reducing Long-term Breast Cancer Rates in At-risk Women, Study Finds
Postmenopausal women at increased risk of breast cancer are half as likely to develop the cancer after a five-year treatment with Arimidex (anastrozole), compared to a placebo, and this reduced likelihood holds for up to seven years after stopping the therapy, a long-term follow-up study has found. The findings suggest that Arimidex is a better preventive treatment for postmenopausal women than tamoxifen — which reduces cancer rates by 29% — and could replace it as the standard approach for this indication. The study, “Use of anastrozole for breast cancer prevention (IBIS-II): long-term results of a randomised controlled trial,” was published in The Lancet and simultaneously presented at the 2019 San Antonio Breast Cancer Symposium, in Texas. Because exposure to estrogen in postmenopausal women increases the risk of breast cancer, those at high risk are often offered preventive treatments that delay or prevent cancer from developing.  Preventive therapies such as tamoxifen — a hormone therapy that blocks the action of estrogen by binding to the estrogen receptor — have been shown to reduce about one-third of breast cancers in long-term studies. Arimidex, by AstraZeneca, is also a hormonal therapy, but prevents the effects of estrogen in a different way. It is an aromatase inhibitor that blocks the production of estrogen by inhibiting aromatase, an enzyme necessary for this process.  In 2013, researchers in the U.K. showed that five-year treatment with Arimidex reduced the incidence of all breast cancers by 53% compared to a placebo. The Phase 3 clinical trial — called International Breast Cancer Intervention Study II (IBIS-II) (NCT00078832) — included 3,864 postmenopausal women from 40 to 70 years old. After five years, 40 women
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