HealthDay News — For women with hormone-receptor positive early breast cancer, comparable benefit is seen with receiving the aromatase inhibitor anastrozole for 2 years and 5 years after an initial 5 years of adjuvant endocrine therapy, according to a study presented at the annual San Antonio Breast Cancer Symposium, held from December 5 to 9 in Texas.

Michael Gnant, MD, from the Medical University of Vienna, and colleagues randomized 3,484 women with postmenopausal stage I to III hormone-receptor positive early breast cancer to receive 2 or 5 years of additional anastrozole as extended adjuvant therapy, after 5 years of adjuvant endocrine therapy. Patients were followed for a median of 105.9 months after randomization. 

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The researchers recorded 757 disease-free survival (DFS) events as of June 30, 2016; 22% each in the 2-year and 5-year groups. No significant difference was seen in DFS (hazard ratio, 0.997; 95% confidence interval, 0.86 to 1.15; P=0.982), or in overall survival, time to secondary carcinoma, and time to contralateral breast cancer. In the 2-year and 5-year arms, 81.2 and 80.1% of patients were still taking the study drug at 2 years, respectively; 65.6% of patients were still on assigned medication at 5 years in the 5-year arm.

“There is simply no rationale to keep most patients on extended aromatase inhibitor for longer than two years,” Gnant said in a statement.

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The study was funded by AstraZeneca, which manufactures anastrozole.

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