Recap of Three Adjuvant Hormonal Therapy Studies

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By Sharon Giordano, Associate Professor, Department of Breast Medical Oncology


Results from several important studies on adjuvant hormonal therapy for breast cancer were presented Thursday at the CTRC-AACR San Antonio Breast Cancer Symposium.

The TEAM study compared the outcomes of over 9,000 post-menopausal women with hormone receptor positive breast cancer who were randomized to either a) five years of exemestane or b) tamoxifen for 2½-3 years followed by exemestane for a total of five years of treatment. With a follow-up of just over five years, the survival of both groups of women was virtually identical, although side effects were a little different. These results show that either up-front treatment with an aromatase inhibitor or a switching strategy results in equivalent outcomes.

Another study of aromatase inhibitors also was presented Thursday morning. The IES study compared the outcomes of postmenopausal women who were treated with 2-3 years of tamoxifen and then were randomized to either finish a total of five years of tamoxifen or switch to exemestane for the last 2-3 years. In contrast to the previous study, the women who switched to an aromatase inhibitor had superior disease free and overall study. However, this analysis excluded some of the women who were originally enrolled in the study but were later found to have hormone receptor negative breast cancer. Despite this limitation, the study shows that post-menopausal women who start on tamoxifen have better outcomes if they switch to an aromatase inhibitor after 2-3 years. 

A third study of aromatase inhibitors also had some very interesting findings. Dr. Goss presented a sub-analysis of the previously reported MA.17 study. The original study had compared the outcomes of women who were treated with five years of tamoxifen and then were randomized to either letrozole or placebo for five additional years. At the time of randomization, all women were required to be post-menopausal.

The original trial showed improved outcomes for the women who received letrozole. The analysis evaluated whether women who were pre-menopausal at cancer diagnosis but who went through menopause during the years of tamoxifen treatment benefited from letrozole. The findings were striking -- the women who became post-menopausal during treatment with tamoxifen had a large benefit of subsequent treatment with letrozole. These findings are very relevant as many women undergo menopause as a result of cancer treatment, and information about the effectiveness of aromatase inhibitors in this group has been limited. 

Now doctors and patients can feel more confident about the activity of aromatase inhibitors in this population of women. 


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