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Duration of Adjuvant Aromatase-Inhibitor Therapy in Postmenopausal Breast Cancer
Michael Gnant1, Florian Fitzal1, Gabriel Rinnerthaler1
1From the Comprehensive Cancer Center (M.G., C.F.S., C.D., F.F., K.W., S.K.-S.), the Department of General Surgery (F.F., K.W., S.K.-S.), the Department of Internal Medicine I, Division of Oncology (G.G.S., R.B.), and the Department of Obstetrics and Gynecology (C.F.S., C.D.), Medical University of Vienna, Austrian Breast and Colorectal Cancer Study Group (M.G., R.J., L.S., C.F.), Breast Care Center, Hanusch Hospital (U.W.), the Department of Gynecology, Hospital Hietzing, and Karl Landsteiner Institute for Gynecological Oncology and Senology (P.S.), Vienna, the Department of Internal Medicine III and Salzburg Cancer Research Institute-Center for Clinical Cancer and Immunology Trials, Paracelsus Medical University Salzburg, Salzburg (G.R., S.G.-R., S.P.G., R.G.), the Departments of Oncology (M.B., C.S.) and Gynecology (V.B.-R.), Medical University Graz, Graz, the Department of Surgery, Ordensklinikum Linz, Linz (D.H.), the Department of Internal Medicine IV, Klinikum Wels-Grieskirchen, Wels (J.T.), the Department of Gynecology, Medical University Innsbruck, Innsbruck (D.E., C.B.), Doctor's Office Manfreda, Klagenfurt (D.M.), the Department of Surgery, Hospital Wolfsberg, Wolfsberg (E.M.-Z.), the Department of Internal Medicine, Hospital Vöcklabruck, Vöcklabruck (F.H.), the Department of Surgery, General Hospital Baden, Baden (H.T.), and the Breast Center, Doctor's Office Wette, Sankt Veit an der Glan (V.W.) - all in Austria; and the Breast Unit, University Hospital Helios, University Witten Herdecke, Wuppertal, Germany (V.B.-R.).
Background:
For postmenopausal women with hormone-receptor-positive breast cancer, the most effective duration for adjuvant therapy with an aromatase inhibitor remains unclear.
Methods:
In this prospective, phase 3 trial, we randomly assigned postmenopausal women with hormone-receptor-positive breast cancer who had received 5 years of adjuvant endocrine therapy to receive the aromatase inhibitor anastrozole for an additional 2 years (2-year group, receiving a total of 7 years) or an additional 5 years (5-year group, receiving a total of 10 years). The primary end point was disease-free survival. The primary analysis included all the patients who were still participating in the trial and who had no recurrence 2 years after randomization (i.e., when treatment in the 2-year group had ended). Secondary end points were overall survival, contralateral breast cancer, second primary cancer, and clinical bone fracture.
Results:
Among the 3484 women who were enrolled in the trial, 3208 remained in the trial without disease progression after the first 2 years of extended anastrozole treatment following randomization. Among these women, disease progression or death occurred in 335 women in each treatment group in the primary-analysis set at 8 years (hazard ratio, 0.99; 95% confidence interval [CI], 0.85 to 1.15; P = 0.90). No between-group differences occurred in most secondary end points, and subgroup analyses did not indicate differences in any particular subgroup. The risk of clinical bone fracture was higher in the 5-year group than in the 2-year group (hazard ratio, 1.35; 95% CI, 1.00 to 1.84).
Conclusions:
In postmenopausal women with hormone-receptor-positive breast cancer who had received 5 years of adjuvant endocrine therapy, extending hormone therapy by 5 years provided no benefit over a 2-year extension but was associated with a greater risk of bone fracture. (Funded by AstraZeneca and the Austrian Breast and Colorectal Cancer Study Group; ABCSG-16/SALSA ClinicalTrials.gov number, NCT00295620.).
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