Patient Summary: The study of tamoxifen and raloxifene (STAR): Initial findings from the NSABP P-2 breast cancer prevention study
The STAR trial included post-menopausal women with a high risk of developing breast cancer (Gail model risk 1.66%). Women were randomized to receive tamoxifen 20mg daily for 5 years or raloxifene 60mg daily for 5 years.
Tamoxifen and raloxifene were found to be equally effective in reducing the rate of invasive breast cancer (163 cases of invasive breast cancer in the tamoxifen group versus 168 in the raloxifene group), compared to the predicted rate of invasive cancers with no treatment of 312 cases. Tamoxifen did decrease the rate of non-invasive breast cancers more than raloxifene (57 cases in the Tam group vs. 81 cases in the Ral group).
There were fewer blood clots in the group receiving raloxifene. Although not statistically significant, there were 40% fewer endometrial cancers in the raloxifene arm (36 cases in the Tam group, 23 in the Ral group). There were also fewer cases of cataracts in the raloxifene arm. There were no significant differences in any other invasive cancers, cardiac events, osteoporotic fractures, or deaths.
In postmenopausal women at high risk for developing breast cancer, raloxifene and tamoxifen are equally effective at reducing the incidence of invasive breast cancer, but tamoxifen was more effective at reducing the incidence of non-invasive breast cancer. In deciding which agent to choose for preventing breast cancer in high-risk postmenopausal women, these factors can be considered:
- Prior hysterectomy (risk of endometrial cancer)
- Acceptance of risk of non-invasive breast cancer
- Risk of thromboembolic events (blood clots) (the study patients were highly selected to have low risk)
- Side-effect profiles of tamoxifen and raloxifene