Some studies have results that are fairly straightforward to understand and act upon. Others need a little more time to digest. Monday’s news about the ability of raloxifene to prevent breast cancer falls into the latter category.

The Study of Tamoxifen and Raloxifene (STAR) compared the gold standard for the prevention of breast cancer (tamoxifen) to a drug that has already been approved to treat and prevent osteoporosis (raloxifene). The study lasted four years and looked at more than 19,000 post-menopausal women who were also at high risk of developing breast cancer. Both drugs work by targeting estrogen receptors throughout the body

Initial results from the head-to-head comparison determined that raloxifene is just as effective as tamoxifen at preventing breast cancer. However, raloxifene offered some clear advantages: women who took the drug were somewhat less likely to develop uterine cancer, blood clots and cataracts.

What it Means: These results are going to require closer analysis. Already it's clear there are several important caveats to keep in mind. Previous studies have shown that tamoxifen reduces a woman’s risk of developing both ductal carcinoma in situ (DCIS), which can develop into invasive breast cancer, and lobular carcinoma in situ (LCIS), which recent research suggests may not be as harmless as was once thought. The results from the STAR study showed that raloxifene offered no such benefit.

Also, we’re talking about small improvements in absolute risk. For example, giving either raloxifene or tamoxifen to 1,000 women for five years would prevent about 20 breast cancers. Researchers have to make sure they understand the risks and benefits more thoroughly before making any broad recommendations.

The results are also preliminary and have not yet been published in a peer-reviewed medical journal. More information will be presented in June at the annual meeting of the American Society for Clinical Oncology. There is still much work that needs to be done to sort out what the results of the STAR trial might mean for individual patients.

From the Archive:
02/18/2002: Estrogen: A Villain and Possible Savior
10/20/2003: Cancer Fighter