A study found that both tamoxifen and Evista (chemical name: raloxifene) lower the risk of invasive and non-invasive breast cancer in women at high risk for breast cancer. These results were reported at the 2010 American Association for Cancer Research annual meeting.
Tamoxifen and Evista are hormonal therapy medicines called SERMs (selective estrogen receptor modulators). SERMs block the action of estrogen in breast and certain other cells by sitting in the cells' estrogen receptors. SERMs don't affect all estrogen receptors the same way because they're selective (as the name says). In bone cells, SERMs interact with the receptors the way estrogen does and strengthen bones. In breast cells, SERMs block the receptors' interaction with estrogen and limit cell growth.
Evista is used to:
- strengthen bones in women with osteoporosis
- reduce the risk of breast cancer in postmenopausal women at high risk
- reduce the risk of breast cancer in postmenopausal women with osteoporosis
Tamoxifen is used to:
- reduce the risk of breast cancer in women at high risk
- reduce the risk of hormone-receptor-positive breast cancer coming back (recurrence)
- treat advanced-stage hormone-receptor-positive breast cancer
Tamoxifen also can boost bone health in women getting it to treat breast cancer.
The results are from a very large study called STAR (Study of Tamoxifen and Raloxifene). Nearly 20,000 postmenopausal women at high risk for breast cancer were split into two groups. Half the women took tamoxifen to lower their risk of breast cancer and the other half took Evista.
STAR results reported after 4 years of follow-up showed that both tamoxifen and Evista reduced the risk of invasive breast cancer by 50% compared to no treatment. Both tamoxifen and Evista also lowered the risk of non-invasive breast cancer, though Evista seemed to be less effective than tamoxifen.
The results are from nearly 7 years of follow-up. Both tamoxifen and Evista are still reducing the risk of invasive and non-invasive breast cancer. But there were some new results. Women treated with Evista were:
- 24% more likely to be diagnosed with invasive breast cancer
- 22% more likely to be diagnosed with non-invasive cancer
compared to women treated with tamoxifen.
This means that after a longer follow-up time, tamoxifen reduced the risk of both invasive and non-invasive breast cancer a bit better than Evista in high-risk women.
Although tamoxifen was better at reducing breast cancer risk, there were advantages to taking Evista. Women treated with Evista were:
- 81% less likely to be diagnosed with uterine hyperplasia; hyperplasia is an abnormal overgrowth of the lining of the uterus that can lead to uterine cancer
- 45% less likely to be diagnosed with invasive uterine cancer
- 55% less likely to have a hysterectomy (which might be because of hyperplasia or uterine cancer)
compared to women taking tamoxifen.
Possible side effects of both tamoxifen and Evista include:
- hot flashes
- joint pain
- leg cramps
- flu-like symptoms
- blood clots deep in the legs
- a blood clot that travels to the lungs (called a pulmonary embolism)
Developing a blood clot or having a stroke -- called a thromboembolic event -- as a side effect of tamoxifen or Evista can be serious and life-threatening. In STAR, thromboembolic events were 25% less likely in women treated with Evista compared to women who got tamoxifen.
Women in STAR who took Evista were more likely to stick with their treatment -- probably because they had fewer serious or bothersome side effects compared to tamoxifen:
- 27.4% of women taking Evista stopped treatment dropped out of the study
- 38.9% of women taking tamoxifen stopped treatment and dropped out of the study
If you're a postmenopausal woman with a higher-than-average risk of breast cancer, you already may be taking medicine to help keep your risk as low as it can be. If not, you might want to ask your doctor if taking a SERM -- tamoxifen or Evista -- makes sense for you. Besides lowering your breast cancer risk, these medicines can help strengthen your bones. As STAR has shown, each medicine has benefits and risks. If taking a SERM makes sense for you, talk to your doctor about these benefits and risks of each. Together, you can make the best choice for your unique situation.
You can learn more about tamoxifen and Evista in the SERM pages of the Breastcancer.org Hormonal Therapy section.