'No Rationale' for Extended Anastrozole Tx in HR+ Early Breast CA, Study Finds

No significant difference in DFS for women receiving anastrozole for two, five years after endocrine tx
No significant difference in DFS for women receiving anastrozole for two, five years after endocrine tx

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.

The study was funded by AstraZeneca, which manufactures anastrozole.

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