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Cancer Resources > Cancer News > Cancer News from Reuters > Reuters Cancer News > 2008 > December
Letrozole better than tamoxifen after surgery in women with early breast cancer
Jill Stein
Last Updated: 2008-12-11 15:04:15 -0400 (Reuters Health)
SAN ANTONIO (Reuters Health) - The aromatase inhibitor letrozole is more effective than tamoxifen as initial adjuvant hormonal therapy in postmenopausal women with hormone-sensitive, early-stage breast cancer, researchers announced here at the 2008 San Antonio Breast Cancer Symposium.
The results, from an updated analysis of the Breast International Group (BIG) 1-98 study, showed that women who received letrozole for five years after surgery had a 13% lower risk of death than women treated with tamoxifen (p = 0.08).
"Importantly, the findings offer first-time evidence of a superior survival benefit with an aromatase inhibitor over tamoxifen when used as monotherapy immediately after breast cancer surgery," said co-investigator Dr. Henning T. Mouridsen, professor of oncology at Copenhagen University, Denmark, who reported the results on behalf of the BIG 1-98 Collaborative and the International Breast Cancer Study Group.
The survival benefit of letrozole in the adjuvant setting, he added, is primarily a function of the reduction in risk of recurrent and distant metastases.
The phase 3 trial included 8,010 postmenopausal women who had completed surgery for estrogen receptor-positive invasive breast cancer and who had no evidence of metastasis.
Patients were randomized to receive tamoxifen only for 5 years, letrozole only for 5 years, tamoxifen for 2 years followed by letrozole for 3 years, or letrozole for 2 years followed by tamoxifen for 3 years.
Results reported in 2005 showed that letrozole-treated patients had significantly fewer recurrences and fewer distant metastases than tamoxifen-treated patients. Afterwards, the tamoxifen monotherapy arm was unblinded, and roughly 25% of patients in this cohort selectively crossed over to letrozole treatment.
An analysis of the 4,922 patients assigned to the letrozole monotherapy or tamoxifen monotherapy arms of the trial at a median of 76 months showed that women receiving letrozole monotherapy had a 13% lower risk of death even if they had been initially treated with tamoxifen monotherapy and then switched to letrozole monotherapy.
When the analysis excluded patients after they had crossed over to letrozole, the reduction in mortality risk was 19%.
The trial found that a strategy involving sequencing hormonal therapy after surgery is not superior to letrozole alone. The 5-year survival rates were 87.9% in women receiving letrozole only, 86.2% in women receiving 2 years of tamoxifen followed by 3 years of letrozole, and 87.6% in women receiving 2 years of letrozole followed by 3 years of tamoxifen.
Study co-investigator Dr. Beat Thurlimann, head of the Breast Cancer Division at Kantonsspital Hospital in St. Gallen, Switzerland, told Reuters Health that a significant proportion of breast cancer patients are likely to benefit from these findings.
"About two-thirds of all breast cancer patients between 25 and 99 years old are postmenopausal at the time they are diagnosed with breast cancer," he said. "Of these patients, three quarters have tumors expressing some degree of endocrine sensitivity and are therefore candidates for letrozole monotherapy."
Furthermore, "What we now know is that letrozole monotherapy suggests improved overall survival compared to tamoxifen and that it should be given upfront," he said.
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