Post-menopausal breast cancer patients who switched from tamoxifen to Aromasin (exemestane tablets) had a significantly reduced chance of recurrence and increased disease-free survival compared to patients who remained on tamoxifen, according to new data published in the New England Journal of Medicine.
The Intergroup Exemestane Study (IES) involved over 4,700 post-menopausal women in 37 countries with breast cancer who were followed for an average of 31 months. According to a current treatment paradigm, post-menopausal women with estrogen-receptor positive breast cancer receive tamoxifen for five years after surgery to prevent recurrence.
The IES study demonstrated that patients who switched to Aromasin after two or three years of taking tamoxifen were more likely to remain cancer free than those who continued on tamoxifen. Patients receiving Aromasin experienced a 32 per cent reduction in the risk of recurrence of the disease at three years, as compared to those continuing on tamoxifen. This reduction includes fewer local and distant tumors as well as new cancer in the other breast.
"Results from this study are important since many patients taking tamoxifen alone relapse within five years of diagnosis," said Dr. Charles Coombes, lead investigator and Head of Department of Cancer Medicine, Imperial College School of Medicine in England. "This is the first large multi-center trial to challenge the current concept of five years monotherapy with endocrine agents after surgical treatment of primary breast cancer. It shows that patients switched to Aromasin experienced statistically significant clinical benefit and longer disease-free survival."
The independent group monitoring the IES study recommended releasing these findings early as a result of the strength of these data.
"These are important findings for the many women afflicted with breast cancer worldwide," said Dr. Joseph Feczko, president of Worldwide Development at Pfizer. "These data provide women with a new treatment option that can provide a real disease-free survival benefit."
In the double-blind trial, after two-to-three years of adjuvant (after surgery) tamoxifen therapy, patients were randomized to receive either Aromasin (25 mg) or to continue on tamoxifen (20 mg) daily.
"This large global study had significant results in terms of reduction in the risk of recurrence of breast cancer as well as the occurrence of new cancer in the other breast," said Dr. Stephen Jones, medical director at U.S. Oncology Research. "I believe the importance of this study is that it could alter practice. Standard practice has been to give tamoxifen for five years, however this study shows that patients will have better outcomes when they receive tamoxifen for two-to-three years then switch to exemestane." Aromasin was generally well tolerated. Continuation of tamoxifen therapy was associated with a greater incidence of endometrial cancer, blood clots, hot flashes, vaginal bleeding, and muscle cramps. Joint pain and diarrhea were reported more frequently in the Aromasin group.
The International Collaborative Cancer Group under the auspices of the Breast International Group coordinated the IES study, which was sponsored by Pfizer.
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