Women, who are taking tamoxifen as adjuvant treatment of breast cancer, would benefit from switching to aromasin (exemestane) after 2 to 3 years of starting tamoxifen according to a new study. This data comes from Intergroup Exemestane Study (IES) which showed that this switch would result in 17 percent improved survival and 25 percent improvement in breast cancer recurrence compared to women who continue with tamoxifen for 5 years.

This study is notable because this is the first time any hormonal treatment has shown improved overall survival over tamoxifen in the adjuvant treatment of breast cancer. These new findings are based on nearly 5 years of follow-up after initiation of the IES trial. This was a large randomized double blind multinational clinical trial of post-menopausal woman with early stage breast cancer. A total of 2352 women switched from tamoxifen to aromasin after 2 to 3 years while a total of 2372 women continued on tamoxifen for 5 years. This study was conducted under the leadership of Professor Charles Coombes who is the director of cancer medicine at Imperial College, London.

Earlier results of the IES trial has shown that switching to aromasin after 2 to 3 years of tamoxifen results 35 percent decrease in breast cancer recurrence in postmenopausal women who have hormone receptor positive breast cancer. Based on this study this drug was approved by US FDA and European regulatory agencies for therapy of early breast cancer. Improvement in overall survival was not seen at that time.

There was no significant differences between in the toxicity profile between the two groups of women who took aromasin and those women who continued on tamoxifen. Most common side effects (switching to aromasin Vs tamoxifen alone) were hot flushes (21.2% vs 19.9), fatigue (16.1% vs 14.7%), arthralgia (14.6% vs. 8.6%), headache (13.1% vs. 10.8%), insomnia (12.4% vs. 8.9%), and increased sweating (11.8% vs. 10.4%).

Aromasin is NOT to be used in premneopausal women or pregnant women, nursing women or women who are allergic to this drug. Aromasin was approved in the United States for therapy of postmenopausal women with estrogen-receptor positive early breast cancer following two-to-three years of tamoxifen, for a combined total of five consecutive years of treatment. It also is approved for use in Canada, Europe, Japan and South America.

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