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Trial Comparisons Show Equal Progression-Free Survival in Breast Cancer for Patients on Aromatase Inhibitors: Presented at SABCS

By Ed Susman

SAN ANTONIO, TX -- December 18, 2006 -- An analysis of 2 major clinical trials indicates that 5 years of aromatase inhibitor therapy shows similar progression-free survival if a breast cancer patient is on anastrozole (Arimidex) or letrozole (Femara), researchers said at the 29^th Annual San Antonio Breast Cancer Symposium (SABCS).

Luc Vakaet, MD, professor of medicine, department of radiotherapy, University of Ghent, Ghent, Belgium, said there were few differences in outcomes between the 2 studies -- Arimidex, Tamoxifen Alone or in Combination (ATAC), and Breast International Group (BIG) 1-98 Study.

In both trials, women with breast cancer were offered treatment with an aromatase inhibitor or tamoxifen in long-term adjuvant use as a protective agent.

Dr. Vakaet said that outcome comparisons are difficult due to differences in the definitions used and in patient populations. "Differences in patient population between the trials included follow-up time -- 33.3 months in ATAC and 28.5 months in BIG; the proportion of node-positive patients -- 35% in ATAC and 41% in BIG; and hormone receptor positivity -- 84% in ATAC and 99.8% in BIG," Dr. Vakaet said in his poster presentation on December 15^th.

In his analysis, Dr. Vakaet noted that the 2 trials showed similar results in progression-free survival among patients who were on aromatase inhibitors. In both studies the risk of progression was reduced significantly.

Letrozole showed a significant reduction in the risk of distant recurrence and death following a cancer event compared with tamoxifen.

Anastrozole showed a significant reduction in contralateral invasive breast cancer compared with tamoxifen.

Further follow-up will be required to determine if the early reduction in cancer-related deaths in the BIG 1-98 trial will result in overall survival benefit, Dr. Vakaet said.

Dr. Vakaet suggested that a formal individual analysis of the patients in the studies be undertaken. "Some of the results of ATAC and BIG are still emergent," he said.

"This is particularly true of deaths unrelated to cancer," he added. "In the latest update of ATAC, at a median 68 months of follow-up, the beneficial effect of anastrozole in significantly reducing deaths after a breast cancer event was counterbalanced by an equal number of deaths unrelated to cancer, leading to identical survival in both arms of the study after a median 5 years of follow up."


[Presentation title: Comparative Results of Two Adjuvant Trials Comparing 5 Years of an Aromatase Inhibitor (AI) With 5 Years of Tamoxifen (TAM) in Postmenopausal Women With Early Breast Cancer (EBC). Abstract 2084]

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