The study reviewed here 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:
Tamoxifen is used to:
Tamoxifen also can boost bone health in women getting it to treat breast cancer.
The results reported here are from a very large study called STAR (Study of Tamoxifen and Raloxifene). Nearly 20,000 post-menopausal 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 reviewed here 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:
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:
compared to women taking tamoxifen.
Possible side effects of both tamoxifen and Evista include:
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:
If you're a post-menopausal 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.
WASHINGTON (MedPage Today) -- Women at high risk for breast cancer benefited from treatment with tamoxifen or raloxifene (Evista), according to long-term data from a large, randomized clinical trial.
After a median follow-up of almost seven years, tamoxifen edged ahead of raloxifene for prevention of invasive breast cancers, which were 24% more common in the raloxifene group, investigators reported here at the American Association for Cancer Research meeting.
The two agents demonstrated similar effectiveness for preventing noninvasive breast cancer.
Raloxifene had a significant advantage in toxicity and tolerability, including substantial reductions in the risk of endometrial cancer, uterine hyperplasia, and thromboembolic events.
The difference translated into a higher rate of nonadherence in the tamoxifen group, D. Lawrence Wickerham, MD, National Surgical Adjuvant Breast and Bowel Project in Pittsburgh, said at an AACR press briefing.
"These data are good news for postmenopausal women who want to reduce their risk of breast cancer," he declared. "I see women each week in a high-risk clinic, and I end up telling one or two of them, all too often, that they have a breast cancer. I'd love for that part of my job to go away. These data are a step in that direction."
The Study of Tamoxifen and Raloxifene (STAR) involved 19,747 healthy, high-risk postmenopausal women randomized to tamoxifen or raloxifene for five years.
After 47 months of follow-up, both groups had about a 50% reduction in breast cancer incidence compared with historical data on untreated women (JAMA 2006; 295: 2727-41).
At that point, raloxifene and tamoxifen appeared equally effective against invasive cancer, but raloxifene was somewhat less effective for preventing noninvasive cancer. Analyses of toxicity and adverse effects favored raloxifene.
The updated analysis, after a median follow-up of 81 months, showed that patients in the raloxifene group had a 1.24 relative risk of invasive breast cancer compared with the tamoxifen group (95% CI 1.05 to 1.47), an increase from the 47-month analysis.
Raloxifene-treated patients had a relative risk of 1.22 for noninvasive breast cancer versus tamoxifen, a narrowing of the difference from the earlier analysis (95% CI 0.95 to 1.59).
In an article published simultaneously in Cancer Prevention Research, Wickerham and colleagues put the results into context.
They noted that tamoxifen reduced the risk of breast cancer by 50% compared with untreated women in the Breast Cancer Prevention Trial (J Natl Cancer Inst 1998; 90: 1371-88).
The 1.24 relative risk of invasive cancer with raloxifene versus tamoxifen meant that raloxifene was 76% as effective as tamoxifen, which translated into a 38% reduction in the risk of invasive breast cancer, compared with untreated women.
Comparing toxicity between treatment groups yielded several significant differences in favor of raloxifene:
Mortality did not differ significantly between treatment groups (236 deaths in the tamoxifen arm, 202 with raloxifene) but trended in favor of raloxifene (RR 0.84, 95% CI 0.70 to 1.02).
More patients dropped out of the tamoxifen group than the raloxifene group (38.9% versus 27.4%).
At the AACR press briefing, Gabriel Hortobagyi, MD, of the M.D. Anderson Cancer Center in Houston, said the updated STAR results reinforce an existing large body of evidence showing that selective estrogen receptor modulators, such as tamoxifen and raloxifene, prevent breast cancer in high-risk women.
With the efficacy proven, the emphasis should shift toward increasing the use of the agents.
"We need to reassess why we are not using these drugs more broadly and why we are not prepared to reduce the risk of breast cancer by about 50% in high-risk women," said Hortobagyi.
Wickerham disclosed relationships with AstraZeneca and Eli Lilly.
Primary source: American Association for Cancer Research Source reference: Wickerham, DL "Update of the NSABP Study of Tamoxifen and Raloxifene (STAR) P-2 trial: Preventing breast cancer" AACR 2010.
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