Relationship between menopausal hormone therapy and incidence risk of breast cancer: systematic review and meta-analysis.
Qing Wu, Liwen Shen, Shengtao Hu et al.
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In 30 seconds
This systematic review and meta-analysis assessed the association between menopausal hormone therapy (MHT) and breast cancer incidence across 34 studies. Overall, MHT was associated with a modest increase in risk (OR = 1.15, 95% CI: 1.09-1.22), with substantial heterogeneity (I ² = 92.4%). The association was concentrated in estrogen-progestin therapy (EPT; OR = 1.44, 95% CI: 1.26-1.64); estrogen-only therapy (ET) showed no overall association (OR = 1.00, 95% CI: 0.91-1.10). Findings varied by hormone type, study design, and region.
Key findings
- Across 34 studies, MHT was associated with breast cancer risk overall (OR = 1.15, 95% CI: 1.09-1.22; I ² = 92.4%).
- EPT was associated with increased risk (OR = 1.44, 95% CI: 1.26-1.64), whereas ET showed no overall association (OR = 1.00, 95% CI: 0.91-1.10).
- For ET, randomized controlled trials suggested a protective association (OR = 0.78, 95% CI: 0.70-0.87), unlike observational studies, which were neutral.
- Hormone type, use status, and region modified the association (P for interaction < 0.001); substantial heterogeneity remained overall.
Why it matters
The pooled findings indicate that breast cancer risk estimates for MHT differ by regimen and are not interchangeable across estrogen-only and estrogen-progestin therapy. The contrast between randomized and observational ET findings, alongside marked geographical heterogeneity, underscores the importance of considering study design and context when interpreting evidence about MHT and breast cancer.
What to keep in mind
The overall association was highly heterogeneous (I ² = 92.4%), limiting the uniformity of the pooled estimate.