Table 4 Breastfeeding and breast cancer risk by ER/PR status
Study | Subgroups by MP status | Exposure categories (n) | Highest/Lowest exposure category | RR (95% CI) for highest vs. lowest category | |
|---|---|---|---|---|---|
ER+PR+ | ER-PR- | ||||
Population-based case-control studies | |||||
[11] | All women | 2 | Ever/Never | 0.7 (0.5–1.0) | 0.8 (0.5–1.1) |
Pre-MP | 2 | Ever/Never | 0.7 (0.4–1.1) | 0.7 (0.4–1.1) | |
Post-MP | 2 | Ever/Never | 0.8 (0.5–1.2) | 1.1 (0.6–1.8) | |
[12] | Young | 3 | >12 months/Never | 0.80 (0.58–1.12) | 0.75 (0.50–1.12) |
[13] | All women | 3 | >6 months/Never or nulliparous | 1.05 (0.79–1.39) | 1.01 (0.69–1.48) |
Pre-MP | 3 | >6 months/Never or nulliparous | 1.41 (0.96–2.08) | 0.86 (0.53–1.39) | |
Post-MP | 3 | >6 months/Never or nulliparous | 0.92 (0.73–1.16) | 1.09 (0.77–1.52) | |
[7] | All women | 4 | >6 months/Never | 0.76 (0.65–0.89) | 0.68 (0.55–0.83) |
[8] | Young | 4 | >6 months/Never | 0.51 (0.31–0.84) | 0.57 (0.33–1.00) |
Summary RRs for population-based case-control studies | 0.78 (0.64–0.94) | 0.74 (0.61–0.89) | |||
P for homogeneity between ER+PR+ and ER-PR- cancer | p = 0.80 | ||||
Hospital-based case-control studies | |||||
[15] | All women | Per 3 months↑ | 3 months' increase | 1.02 (0.95–1.09) | 0.98 (0.90–1.07) |
[16] | 40–80 | 3 | ≥12 months/Never | 1.25 (0.67–2.50) | 0.91 (0.48–1.67) |
Summary RRs for hospital-based case-control studies | 1.02 (0.92–1.14) | 0.98 (0.88–1.09) | |||
Summary RRs by MP status | Pre-MP/Young | 0.83 (0.61–1.14) | 0.73 (0.53–1.00) | ||
Post-MP | 0.89 (0.62–1.27) | 1.09 (0.77–1.56) | |||
Summary RRs for all studies | 0.95 (0.87–1.05) | 0.91 (0.83–1.00) | |||
P for homogeneity between ER+PR+ and ER-PR- cancer | p = 0.38 | ||||