Extended Aromatase Inhibitor Therapy After Sequential Endocrine Therapy
In the Dutch phase III DATA trial reported in The Lancet Oncology by Tjan-Heinjen et al, a nonsignificant disease-free survival advantage was found for 6 vs 3 years of adjuvant aromatase inhibitor therapy after 2 to 3 years of tamoxifen in hormone receptor–positive early breast cancer. Extended aromatase inhibitor treatment appeared to benefit subgroups of higher-risk patients.
Study Details
In the open-label trial, 1,860 eligible postmenopausal women from 79 sites in the Netherlands with no signs of disease recurrence after 2 to 3 years of adjuvant tamoxifen were randomized between June 2006 and August 2009 to receive 3 (n = 929) or 6 years (n = 931) of anastrozole treatment at 1 mg once daily. Randomization was stratified by nodal status, hormone receptor status, HER2 status, and tamoxifen treatment duration. The primary endpoint of the current analysis was disease-free survival starting beyond 3 years after randomization (adapted disease-free survival).
Disease-Free Survival
Of the 1,860 patients, 1,660 were disease free 3 years after randomization. The 5-year adapted disease-free survival was 83.1% in the 6-year group vs 79.4% in the 3-year group (hazard ratio [HR] = 0.79, P = .066). Patients in the 6-year treatment group had a higher incidence of adverse events, including any-grade arthralgia or myalgia (58% vs 53%) and osteopenia or osteoporosis (21% vs 16%).
The 5-year adapted disease-free survival was 84.8% in the 6-year group vs 78.8% in the 3-year group among patients with both estrogen receptor– and progesterone receptor–positive disease (n = 1,260; HR = 0.70, 95% confidence interval = 0.53–0.92). In a post hoc analysis, 5-year adapted disease-free survival was 84.4% vs 76.2% in patients with both estrogen receptor– and progesterone receptor–positive and node-positive disease (n = 849; HR = 0.64, P = .0075) and 82.7% vs 69.2% among those also having a larger tumor size (≥ T2, n = 429; HR = 0.53, P = .0031).
The investigators concluded: “We cannot recommend the use of extended adjuvant aromatase inhibition after 5 years of sequential endocrine therapy in all postmenopausal women with hormone receptor-positive breast cancer.”
The study was funded by AstraZeneca.
Vivianne C. G. Tjan-Heijnen, MD, of Maastricht University Medical Center, is the corresponding author of The Lancet Oncology article.
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