Raloxifene (Evista®) Reduces Incidence of Invasive Breast Cancer
Researchers from the U.S. and UK have reported that raloxifene (Evista®) reduces the incidence of invasive breast cancer by 66% among postmenopausal women with osteoporosis.[1] These results confirm earlier findings and were reported at the 19th European Society of Medical Oncology Congress held in Vienna, Austria, October 29 to November 2, 2004.
Raloxifene is a selective estrogen receptor modulator (SERM) that has been approved by the FDA for the treatment of osteoporosis in postmenopausal women. A study of raloxifene for the treatment of osteoporosis in postmenopausal women, called The Multiple Outcomes of Raloxifene Evaluation (MORE) study, produced secondary findings indicating that, compared to placebo, 4 years of raloxifene treatment reduced invasive breast cancer by 72% in postmenopausal women with osteoporosis.[2]
The clinical trial presented at ESMO 2004 was an extension of the MORE trial called Continuing Outcomes Relevant to Evista® (CORE) and its primary objective was to evaluate the effect of raloxifene on the incidence of invasive breast cancer in order to confirm the initial findings of the MORE study.
There were 7,705 postmenopausal women with osteoporosis who enrolled in the first trial and 4,011 chose to continue. The patients who received placebo in the initial trial continued on placebo and the patients who received raloxifene initially continued on a 60 mg dose.
The results of the follow-up study and the combined results of the two studies confirm the initial finding that raloxifene reduced the risk of invasive breast cancer. Results from the CORE trial alone showed a 59% reduction in invasive breast cancer among women who received raloxifene compared to those who received placebo. Over the total 8 years of raloxifene treatment (MORE study plus CORE study), patients who received raloxifene experienced a 66% reduction in the incidence of invasive breast cancer.
Raloxifene appeared to reduce the risk of invasive breast cancer regardless of whether women had received prior hormonal therapy. There was no significant difference in the reduction of invasive breast cancer compared to placebo between women who had received prior hormonal therapy (occurrence of invasive breast cancer reduced by 71%) and those who had not received prior hormonal therapy (64%).
Patients who received raloxifene were twice as likely to experience a venous thromboembolism (blood clot) compared to patients who received placebo. However, vaginal bleeding and endometrial cancer were not increased compared to placebo. Hot flushes and leg cramps were more frequent among patients who received raloxifene versus placebo in the first 4 years of treatment, but not in years 5-8.
Comments: This very large prevention trial suggests that roloxifene can reduce the incidence of breast cancer in post-menopausal women without an increase in uterine cancer. However, it remains to be determined what groups of post-menopausal women should receive such preventive treatment.
References:
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[1] Purdie D, Caluey J, Disch D, et al. Effect of raloxifene on incidence of invasive breast cancer in postmenopausal women having a history of prior hormone therapy use: Results of the CORE trial. Proceedings from the 29th ESMO Congress, Vienna Austria, 10.29-11.2.2004; (Abstract #4).
[2] ME Lippman, KA Krueger, S Eckert, et al. Exposure: Effect on Breast Cancer Incidence and Interaction with Raloxifene Therapy in the Multiple Outcomes of Raloxifene Evaluation Study Participants. Journal of Clinical Oncology . 2001;19(12):3111-3116.
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