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25 September 2011

Aromatase inhibitor letrozole guards against breast cancer relapse for up to eight years

Results from the longest-running trial comparing tamoxifen with the aromatase inhibitor letrozole show unequivocally that letrozole has withstood the test of time and continues to prevent breast cancer recurrences and reduce the risk of death in post-menopausal women with hormone receptor-positive early breast cancer.
Professor Richard Gelber told delegates at the 2011 European Multidisciplinary Cancer Congress , in Stockholm today (Monday 26 September) that a 12-year update of results from the Breast International Group (BIG) 1-98 trial showed that if women with early breast cancer (cancer that has not spread from the breast) were given letrozole after surgery for at least five years, they continued to do better and have fewer recurrences of the disease than those who were given tamoxifen.
"Over a median of eight years of follow-up, women who were assigned to receive five years of letrozole after surgery had an 18% reduced risk of relapse and a 21% reduced risk of death compared with those assigned to receive tamoxifen," said Prof Gelber, Director of the International Breast Cancer Study Group (IBCSG) Statistical and Data Management Center at the Dana-Farber Cancer Institute, Boston, MA, USA.
"The current 12-year update is the longest follow-up to date and includes much more information than we had after ten years. For instance, there have been 32% more relapses and 39% more deaths since the ten-year update, which increases substantially the reliability of the results and provides reassurance regarding the long-term value of letrozole. This additional follow-up and accumulation of information on relapses and deaths show that the overall survival advantage for adjuvant letrozole compared to tamoxifen continues to be statistically significant."
Adjuvant therapy (treatment that is given after surgery), using drugs that target hormones such as oestrogen, is given to patients with early breast cancer who have hormone receptor-positive tumours. These tumours occur in approximately 75% of breast cancer cases. Tamoxifen has been the "gold standard" hormone treatment for women with early, oestrogen-receptor-positive breast cancer and works by blocking the growth-promoting action of oestrogen on the cancer cells. Aromatase inhibitors, such as letrozole, are newer and alter the function of aromatase, an enzyme involved in oestrogen production. They can be used in sequence with, or as an alternative to tamoxifen for post-menopausal women.
In the BIG 1-98 trial, researchers enrolled 8,010 patients to receive letrozole and tamoxifen either alone or in sequence, with a total of 4,922 patients included in the monotherapy arms of the study.
Efficacy analyses comparing the treatment groups were conducted every two years following the initial report of results, because the patients had a long-term risk of recurrence. This 12-year update shows that, among all 8,010 patients, there were 2,074 relapses and 1,284 deaths, compared with 1,569 relapses and 923 deaths at the ten-year update.
"The data also show that the sequential use of letrozole and tamoxifen (two years of one agent followed by three years of the other) provided similar outcomes compared with five years of letrozole alone for patients who are not at high risk for recurrence," said Prof Gelber.

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