Breask Cancer Risk

Raloxifene cuts breast cancer risk: 8-year data reported at ASCO

(Reuters Health) New long-term data provide more evidence that the incidence of invasive breast cancer, especially estrogen-receptor positive invasive breast cancer, is significantly reduced in postmenopausal women with osteoporosis who are treated with raloxifene (Evista, Eli Lilly).

Dr. Silvana Martino from the Cancer Institute Medical Group in Santa Monica, California presented the results from the Continuing Outcomes Relevant to Evista (CORE) trial, a 4-year double-blind placebo-controlled follow-up to the Multiple Outcomes of Raloxifene (MORE) trial, at the annual meeting of the American Society of Clinical Oncology.

In the 7705-patient MORE trial, 4 years of daily treatment with raloxifene was associated with a 72% reduction in the risk of invasive breast cancer among postmenopausal women with osteoporosis compared with placebo. (See Reuters Health report Feb. 13, 2001).

With this "exciting" result, Dr. Martino said, the decision was made to continue raloxifene in as many women as possible for an additional 4 years and the CORE trial was born. In CORE, 3,510 women continued on raloxifene (60 mg/d) while 1,703 took placebo.

According to Dr. Martino, a 59% reduction in risk of invasive breast cancer was noted in women treated with raloxifene compared to placebo in years 4 to 8 as part of the CORE trial, with a hazard ratio of 0.41.

"For the entire 8-year period, the reduction in risk with raloxifene is 66%," Dr. Martino reported. Raloxifene was especially effective in reducing the risk of estrogen-receptor positive tumors, with a hazard ratio of 0.34.

"Whether one looks at the MORE trial, the CORE trial or the two combined, the same biology is observed and, yes, this agent does have the ability to reduce the risk and the incidence of breast cancer," Dr. Martino said.

Importantly, she added, during the second four years, "no new toxicities" were identified. A "serious but rare" problem noted in the MORE trial - venous thromboembolism - continued in the CORE trial. "Women treated with raloxifene throughout the entire 8 year period continued to have twice as many of these events as the women given placebo," Dr. Martino said. Long term use of raloxifene did not increase the risk of uterine cancer.

While it remains premature to recommend raloxifene for chemoprevention, this study adds to the evidence suggesting that selective estrogen receptor modulators (SERMs) can have a significant effect on breast cancer risk, Dr. Martino concluded.

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