Cochrane: aromatase inhibitors top tamoxifen for breast cancer prevention

  • Mocellin S & al.
  • Cochrane Database Syst Rev
  • 29 Apr 2019

  • curated by Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • A network meta-analysis by the Cochrane Collaborative finds that aromatase inhibitors (AIs; such as exemestane and anastrozole) appear to be superior to tamoxifen for prevention of primary breast cancer in women with above-average lifetime risk (>17%).

Why this matters

  • AIs may be a better option for breast cancer prevention than tamoxifen.
  • Although AIs have musculoskeletal and other toxicities, they are not associated with risks for endometrial cancer or thromboembolism.

Study design

  • Search of Cochrane Breast Cancer Specialized Register, CENTRAL, MEDLINE, among others.
  • Meta-analysis of a single agent vs placebo of 6 randomized controlled trials (n=50,927); network meta-analysis for indirect comparison of AIs vs tamoxifen.

Key results

  • Tamoxifen vs placebo
    • 32% risk reduction (risk ratio [RR], 0.68; 95% CI, 0.62-0.76).
    • Higher risk for endometrial cancer (RR, 2.26; 95% CI, 1.52-3.38) and thromboembolism (RR, 2.10; 95% CI, 1.14-3.89).
  • AIs vs placebo
    • 53% risk reduction (risk ratio [RR], 0.47; 95% CI, 0.35-0.63).
    • Potential for endocrine (hot flashes), diarrhea, and musculoskeletal (e.g., arthralgias) events.
  • AIs vs tamoxifen
    • 33% risk reduction (33 vs 49 per 1000 incident breast cancers; RR, 0.67; 95% CI, 0.46-0.98) with low certainty of evidence.

Limitations

  • No studies made direct comparison of AIs vs tamoxifen.