Initial results from the Study of Tamoxifen and Raloxifene (STAR) trial show that the anti-osteoporosis drug raloxifene (Evista) is as effective as tamoxifen (Nolvadex) in reducing the risk of breast cancer in postmenopausal women at increased risk for the disease, without some of the serious side effects known to occur with tamoxifen.
More than 19,700 postmenopausal women at increased risk for invasive breast cancer were randomly allocated to 60 mg raloxifene or 20 mg tamoxifen daily for five years. Their average age was 58 years and 93.5% were white.
After an average of nearly four years of follow-up, the numbers of invasive breast cancers were statistically equivalent in raloxifene- and tamoxifen-treated women. Among those in the raloxifene arm, 167 developed invasive breast cancer compared to 163 in the tamoxifen arm.
In terms of non-invasive in situ breast cancers, there were 57 in the tamoxifen arm compared with 81 in the raloxifene arm, a difference that was "just statistically significant with approximately 40% more in situ cancers occurring in the raloxifene group".
There was a "large difference" in the number of invasive uterine cancers -- a preset trial outcome measure -- with 36 invasive uterine cancers in the tamoxifen arm compared with only 23 in the raloxifene arm -- a 38% reduction in the incidence of invasive uterine cancers among women taking raloxifene.
Overall, there was no significant difference between raloxifene and tamoxifen in the event rates for ischemic heart disease or strokes. However, there were far fewer pulmonary emboli in the raloxifene arm compared with the tamoxifen arm (35 versus 54) -- a 36% risk reduction with raloxifene. There were also fewer deep vein thromboses in the raloxifene arm -- 65 versus 87 in the tamoxifen arm -- a risk reduction of 26%.
There was no difference between the two treatment arms in terms of bone fractures, another specified outcome. As expected, women taking tamoxifen reported more menopausal symptoms such as hot flashes, night sweats, vaginal discharge and bleeding, compared with women taking raloxifene.