THURSDAY, Dec. 7, 2017 (HealthDay News) -- For women with hormone-receptor positive early breast cancer, comparable benefit is seen with receiving the aromatase inhibitor anastrozole for two years and five years after an initial five years of adjuvant endocrine therapy, according to a study presented at the annual San Antonio Breast Cancer Symposium, held from Dec. 5 to 9 in Texas.
Michael Gnant, M.D., 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 two or five years of additional anastrozole as extended adjuvant therapy, after five years of adjuvant endocrine therapy. Patients were followed for a median of 105.9 months after randomization.
The researchers recorded 757 disease-free survival (DFS) events as of June 30, 2016; 22 percent each in the two-year and five-year groups. No significant difference was seen in DFS (hazard ratio, 0.997; 95 percent 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 two-year and five-year arms, 81.2 and 80.1 percent of patients were still taking the study drug at two years, respectively; 65.6 percent of patients were still on assigned medication at five years in the five-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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