Extended aromatase inhibitor therapy reduces breast cancer recurrence in postmenopausal women

1. Invasive breast cancer recurrence was significantly reduced with extended aromatase inhibitor therapy.

2. No significant reduction was noted for breast cancer-specific mortality.

Evidence Rating Level: 1 (Excellent)

Study Rundown: In postmenopausal women with estrogen receptor–positive breast cancer, 5 years of tamoxifen significantly reduces long-term recurrence and mortality. Aromatase inhibitors (AIs) have shown additional efficacy in some studies. Continuing endocrine therapy beyond 5 years may further lower recurrence risk, but the benefits and risks remain unclear. This meta-analysis aimed to evaluate the effects of extended AI therapy in women who were recurrence-free after at least 5 years of prior endocrine treatment. The primary outcome was recurrence of invasive breast cancer, while the key secondary outcome was breast cancer–specific mortality. According to study results, extended AI therapy markedly reduced recurrence rates but increased the risk of bone fractures. Although this study was well done, it was limited by substantial non-adherence to allocated treatment, which may have underestimated the true benefit.

Click to read the study in The Lancet

Relevant Reading: Duration of Adjuvant Aromatase-Inhibitor Therapy in Postmenopausal Breast Cancer

In-depth [systematic review and meta-analysis]: Between Dec 15, 1995, and May 21, 2014, 25100 patients were assessed for eligibility. Included were postmenopausal patients, had estrogen receptor–positive breast cancer and ≥ 5 years of tamoxifen therapy. Altogether, 22,031 patients were included in the final analysis. The primary outcome of invasive breast cancer recurrence was reduced by 29% (relative risk [RR] 0.71, 95% confidence interval [CI] 0.61-0.81, p<0.0001) with extended AI therapy compared to no further treatment. The secondary outcome of breast cancer mortality was reduced non-significantly (RR 0.90, 95% CI 0.70-1.15, p = 0.40), while extended AI therapy increased the risk of bone fractures (RR 1.35, 95% CI 1.13-1.61, p = 0.0009). Findings from this study suggest that continuing AI therapy for an additional 5 years lowers recurrence risk but carries an increased risk of fractures.

Image: PD

©2025 2 Minute Medicine, Inc. All rights reserved. No works may be reproduced without expressed written consent from 2 Minute Medicine, Inc. Inquire about licensing here. No article should be construed as medical advice and is not intended as such by the authors or by 2 Minute Medicine, Inc.