Originally published as JCO Early Release 10.1200/JCO.2006.08.8054 on June 11 2007

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Improved Overall Survival in Postmenopausal Women With Early Breast Cancer After Anastrozole Initiated After Treatment With Tamoxifen Compared With Continued Tamoxifen: The ARNO 95 Study

Manfred Kaufmann, Walter Jonat, Jörn Hilfrich, Holger Eidtmann, Günther Gademann, Ivan Zuna, Gunter von Minckwitz

From the J.W. Goethe-University of Frankfurt, Frankfurt am Main; University of Kiel, Kiel; Henriettenstift, Hannover; University of Magdeburg, Magdeburg; and the Institute of Statistics SKM, Wiesbaden, Germany

Address reprint requests to Manfred Kaufmann, MD, Department of Obstetrics and Gynaecology, Johann Wolfgang Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany; e-mail: m.kaufmann{at}em.uni-frankfurt.de

Purpose: In postmenopausal women with estrogen receptor–positive early breast cancer, surgery is usually followed by a 5-year course of tamoxifen. This report presents results of a prospective, open-label, randomized study, designed to evaluate the benefits of switching to anastrozole after 2 years of tamoxifen treatment, compared with continuing on tamoxifen for 5 years.

Patients and Methods: After receiving tamoxifen treatment for 2 years, eligible patients (n = 979) were randomly assigned to switch to anastrozole (1 mg/d) or continue tamoxifen (20 or 30 mg/d) for an additional 3 years. Patients were monitored every 6 months during years 1 to 3 and annually thereafter. The primary efficacy variable was disease-free survival, including local or distant recurrence, new contralateral breast cancer, or death. Secondary variables were overall survival and assessment of safety.

Results: Switching to anastrozole resulted in a significant reduction in the risk of disease recurrence (hazard ratio [HR], 0.66; 95% CI, 0.44 to 1.00; P = .049), and improved overall survival (HR, 0.53; 95% CI, 0.28 to 0.99; P = .045) compared with continuing on tamoxifen. Fewer patients who switched to anastrozole reported serious adverse events (22.7% v 30.8%) compared with those who continued on tamoxifen, mainly due to more patients in the tamoxifen group with endometrial events. The overall safety profile for anastrozole was consistent with previous reports and no new safety issues were identified.

Conclusion: Postmenopausal women who have taken tamoxifen for 2 years as adjuvant therapy are less likely to experience a recurrence of breast cancer and have improved overall survival if they switch to anastrozole compared with continuing to receive tamoxifen.

published online ahead of print at www.jco.org on June 11, 2007.

Supported by grants from AstraZeneca, Germany.

Presented in part in abstract format at the 42nd Annual Meeting of the American Society of Clinical Oncology, Atlanta, GA, June 2-6, 2006.

This trial is registered with ClinicalTrials.gov, No. NCT00287534.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

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