Table 4a.
(2007–11) Relative risks (RRs) with 95% confidence intervals for overall and ER±/HER2± first primary invasive breast cancers diagnosed in 2007 or later by reproductive variables among nulliparous and parous women born in 1935 or later
| Exposure | Overall | ER+/HER2– | ER+/HER2+ | ER–/HER2+ | ER–/HER2– |
|---|---|---|---|---|---|
| Number of cases | n = 17 564 | n = 11 446 | n = 1321 | n = 882 | n = 1611 |
| Parity | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) |
| Nulliparous | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) |
| Parous | 0.94 (0.89, 0.98) | 0.92 (0.87, 0.98) | 1.02 (0.86, 1.02) | 1.03 (0.83, 1.27) | 1.16 (0.99, 1.36) |
| p-heterogeneity | 0.006 | 0.008 | 0.98 | 0.76 | 0.09 |
| Parous cases (n = 15 597) | |||||
| Number of cases | n = 15 597 | n = 10 193 | n = 1166 | n = 785 | n = 1439 |
| Number of live births | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) |
| 1 | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) |
| 2 | 0.97 (0.93, 1.02) | 0.95 (0.90, 1.00) | 1.02 (0.88, 1.20) | 1.08 (0.88, 1.32) | 1.10 (0.95, 1.27) |
| 3 | 0.93 (0.89, 0.98) | 0.92 (0.86, 0.98) | 0.97 (0.80, 1.17) | 1.14 (0.90, 1.44) | 0.99 (0.83, 1.18) |
| 4+ | 0.79 (0.73, 0.85) | 0.76 (0.69, 0.84) | 0.50 (0.35, 0.71) | 1.06 (0.75, 1.48) | 1.07 (0.84, 1.37) |
| p-trend | <0.001 | <0.001 | 0.006 | 0.43 | 0.97 |
| p-heterogeneity | <0.001 | <0.001 | <0.001 | 0.66 | 0.27 |
| AFLB (years) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) |
| 12–19 | 1.02 (0.97, 1.07) | 1.01 (0.95, 1.07) | 0.87 (0.72, 1.06) | 0.89 (0.71, 1.12) | 1.20 (1.02, 1.40) |
| 20–24 | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) |
| 25–29 | 1.07 (1.03, 1.12) | 1.02 (1.02, 1.13) | 1.18 (1.03, 1.36) | 1.06 (0.89, 1.25) | 1.04 (0.96, 1.38) |
| 30–34 | 1.24 (1.17, 1.31) | 1.29 (1.20, 1.38) | 1.19 (0.97, 1.45) | 1.09 (0.85, 1.40) | 1.15 (1.01, 1.40) |
| 35+ | 1.16 (1.05, 1.27) | 1.22 (1.09, 1.37) | 1.17 (0.85. 1.61) | 1.03 (0.67, 1.59) | 1.10 (0.81, 1.50) |
| p-trend | <0.001 | <0.001 | 0.002 | 0.18 | 0.59 |
| p-heterogeneity | <0.001 | <0.001 | 0.024 | 0.68 | 0.12 |
| Nulliparous cases (n = 1967) and uniparous cases (n = 3011) | |||||
| Number of cases | n = 4978 | n = 3251 | n = 385 | n = 235 | n = 434 |
| AFLB (years) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) | RR (95% CI) |
| 12–19 | 0.93 (0.81, 1.06) | 0.91 (0.77, 1.08) | 0.85 (0.49, 1.47) | 1.36 (0.79, 2.35) | 0.99 (0.60, 1.64) |
| 20–24 | 0.93 (0.86, 1.01) | 0.91 (0.83, 1.01) | 1.20 (0.90, 1.59) | 0.90 (0.62, 1.32) | 0.98 (0.73, 1.31) |
| 25–29 | 0.99 (0.92, 1.08) | 1.03 (0.94, 1.13) | 1.07 (0.81, 1.41) | 0.97 (0.68, 1.38) | 1.11 (0.86, 1.45) |
| 30–34 | 1.15 (1.05, 1.25) | 1.18 (1.06, 1.32) | 0.96 (0.69, 1.35) | 0.94 (0.62, 1.43) | 1.32 (1.00, 1.75) |
| 35+ | 1.05 (0.93, 1.17) | 1.10 (0.95, 1.26) | 1.05 (0.70, 1.59) | 0.87 (0.49, 1.52) | 1.05 (0.71, 1.55) |
| Nulliparous | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) | 1.0 (reference) |
| p-trend | 0.14 | 0.18 | 0.57 | 0.77 | 0.80 |
| p-heterogeneity | <0.001 | 0.001 | 0.72 | 0.85 | 0.11 |
Cases with unknown ER/HER2 status (n = 2304) were excluded from the ER/HER2 specific analyses. AFLB, age at first live birth.