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Continued Raloxifene Use Further Reduces Breast Cancer Risk

NEW YORK (Reuters Health) Nov 30 - Findings from a follow-up study indicate that taking raloxifene for longer than 4 years provides reductions in the risk of invasive breast cancer beyond that already found in previous studies of 4 years' treatment.

In the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, treatment with raloxifene for 4 years was shown to reduce the risk of invasive breast cancer in postmenopausal women with osteoporosis. In the new study, termed the Continuing Outcomes Relevant to Evista (CORE) trial, the risk continued to drop over 4 additional years of treatment.

CORE involved 5213 women who participated in MORE and were randomized to receive either raloxifene or placebo, according to the report in the December 1st issue of the Journal of the National Cancer Institute.

Women treated with raloxifene in MORE were given a dose of 60 or 120 mg/day, but in CORE they all received 60 mg/day, lead author Dr. Silvana Martino, from the Cancer Institute Medical Group in Santa Monica, California, and colleagues write.

In CORE, treatment with raloxifene was associated with a 59% and 66% drop in the 4-year rate of overall and ER-positive invasive breast cancer, respectively. In contrast, raloxifene therapy seemed to have no effect on rates of ER-negative breast cancer.

For the combined 8-year study period, raloxifene therapy cut the rate of overall and ER-positive invasive breast cancer by 66% and 76%, respectively.

However, raloxifene therapy was tied to an elevated risk of thromboembolism. Throughout the 8-year period, the rate of this outcome among raloxifene users was about double that seen in controls.

In a related editorial, Dr. Powel Brown and colleagues, from Baylor College of Medicine in Houston, comment that based on the results from MORE and CORE, "raloxifene is a reasonable choice to treat osteoporosis and also to reduce the risk of breast cancer" in postmenopausal women with osteoporosis.

Further studies, however, are needed to determine if the drug is also useful for women without osteoporosis, but at increased risk for breast cancer, the editorialists add.

J Natl Cancer Inst 2004;96:1731-1733,1751-1761.