Tjan-Heijnen VCG, et al. - Researchers began the DATA study to clarify the effect of extended adjuvant aromatase inhibition in hormone receptor-positive breast cancer after sequential endocrine therapy of tamoxifen followed by an aromatase inhibitor for a 5-year treatment period. As per findings, the use of extended adjuvant aromatase inhibition after 5 years of sequential endocrine therapy was not recommended in all postmenopausal women with hormone receptor-positive breast cancer.

Methods

• In 79 hospitals in the Netherlands, DATA was performed.
• DATA was a prospective, randomised, open-label, multicentre, phase 3 study.
• Postmenopausal women with hormone receptor-positive early breast cancer with no signs of disease recurrence after 2–3 years of adjuvant tamoxifen were randomly assigned to either 3 or 6 years of anastrozole treatment (1 mg orally once a day) in a 1:1 ratio.
• For the randomisation procedure, TENALEA (Trans European Network for Clinical Trials Services) was used.
• For this study, stratification factors were nodal status, hormone receptor status, HER2 status, and tamoxifen treatment duration.
• Disease-free survival starting beyond 3 years after randomisation was the primary study endpoint.

Results

• From June 28, 2006, to Aug 10, 2009, 1912 patients were screened; 955 of these were assigned to the 3-year group and 957 to the 6-year anastrozole treatment group.
• For this study, 1860 patients were eligible (931 in the 6-year group and 929 in the 3-year group).
• 1660 patients were disease free 3 years after randomisation.
• In the 6-year group, the 5-year adapted disease-free survival was 83.1% (95% CI 80.0–86.3) and in the 3-year group, it was 79.4% (76.1–82.8) (hazard ratio [HR] 0·79 [95% CI 0.62–1.02]; p=0.066).
• Patients in the 6-year treatment group, compared to those in the 3-year treatment group, indicated more adverse events, including all-grade arthralgia or myalgia (478 [58%] of 827 in the 6-year treatment group vs438 [53%] of 833 in the 3-year treatment group) and osteopenia or osteoporosis (173 [21%] vs 137 [16%]).