News Note: Long-term Results from Study of Tamoxifen and Raloxifene Shows Lower Toxicities of Raloxifene

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  • Posted: April 19, 2010
NCI Press Office


Initial results in 2006 of the NCI-sponsored Study of Tamoxifen and Raloxifene (STAR) showed that a common osteoporosis drug, raloxifene, prevented breast cancer to the same degree, but with fewer serious side-effects, than the drug tamoxifen that had been in use many years for breast cancer prevention as well as treatment. Differences seen in the initial study results between the two drugs dictated longer-term follow-up to clarify their relative merits in regard to a host of benefits and risks, but particularly in regard to prevention of noninvasive breast cancer, the most common form of the disease. The initial study results looked at about four years of drug use vs. this latest analysis, which looks at a bit less than seven years of use.

The longer-term results show that raloxifene retained 76 percent of the effectiveness of tamoxifen in preventing invasive disease and grew closer to tamoxifen in preventing noninvasive disease, while remaining far less toxic – in particular, there was significantly less endometrial cancer with raloxifene use. Tamoxifen continues to show better abilities to prevent invasive and noninvasive breast cancer. For a detailed Q&A on the STAR results and the latest study analysis, please go to