Extended Aromatase Inhibitor Therapy After Sequential Endocrine Therapy

Key Points

  • A nonsignificant improvement in disease-free survival with extended aromatase inhibitor treatment was observed among all patients with hormone receptor–positive early breast cancer.
  • Extended aromatase inhibitor treatment appeared to benefit higher-risk subgroups.

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.

 

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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