Parity and breast cancer risk stratified by hormone receptor expression
| First author (reference) . | Country (study) . | Cases (n) . | Births (n)* . | Risk estimate (95% CI)† . | . | |
|---|---|---|---|---|---|---|
| ER+ | ER− | |||||
| Wohlfahrt (22) | Denmark (DBCG) | 6,044 | 1+ | 0.8 (0.7-0.8) | 0.9 (0.8-1.0) | |
| Hildreth (42) | United States | 148 | 1+ | 0.6 (0.3-1.1) | 2.5 (0.8-10.0) | |
| Cooper (36) | Australia | 380 | 1 | 1.4 (0.7-2.7) | 1.3 (0.5-3.4) | |
| 2 | 0.8 (0.5-1.4) | 0.8 (0.4-1.9) | ||||
| 3+ | 0.8 (0.5-1.4) | 1.0 (0.4-2.3) | ||||
| Hislop (37) | Canada (BC) | 512 | 1-2 | 0.8 (0.6-1.0)‡ | 0.9 (0.6-1.4)‡ | |
| 3+ | 0.7 (0.6-1.0)‡ | 1.3 (0.9-2.0)‡ | ||||
| McTiernan (39) | United States (CASH-WA) | 240 | 1-2 | 0.8 | 1.9 | |
| 3+ | 0.6 (0.3-1.5) | 1.4 (0.6-3.6) | ||||
| Stanford (38) | United States (CASH-GA) | 458 | 1-2 | 1.0 (0.6-1.6)‡ | 0.9 (0.6-1.5)‡ | |
| 3-4 | 0.7 (0.4-1.2)‡ | 0.8 (0.5-1.3)‡ | ||||
| 5+ | 0.5 (0.2-1.0)‡ | 1.0 (0.5-1.9)‡ | ||||
| Kreiger (35) | Canada (ON) | 528 | 1-3 | 0.7 (0.5-0.9) | 0.9 (0.5-1.6) | |
| 4+ | 0.7 (0.4-1.1) | 1.4 (0.6-3.0) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 1.0 (0.8-1.1) | 0.9 (0.8-1.2) | |
| PR+ | PR− | |||||
| Kreiger (35) | Canada (ON) | 528 | 1-3 | 0.6 (0.4-0.9) | 0.9 (0.6-1.5) | |
| 4+ | 0.5 (0.3-0.8) | 1.6 (0.9-3.1) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 0.9 (0.7-1.1) | 1.0 (0.9-1.2) | |
| ER+/PR+ | ER−/PR− | |||||
| McCredie (23) | Melbourne (Australia) | 618 | 1 | 1.1 (0.7-1.7) | 1.3 (0.8-2.3) | |
| 2 | 1.0 (0.7-1.5) | 1.0 (0.6-1.7) | ||||
| 3+ | 1.0 (0.5-1.2) | 0.8 (0.4-1.3) | ||||
| Cotterchio (24) | Canada (ON) | 3,276 | Premenopause | |||
| 1 | 0.6 (0.4-1.1) | 1.0 (0.5-2.0) | ||||
| 2 | 0.7 (0.4-1.0) | 1.1 (0.6-2.0) | ||||
| 3+ | 0.4 (0.3-0.8) | 0.9 (0.5-1.8) | ||||
| Postmenopause | ||||||
| 1 | 1.0 (0.7-1.4) | 0.9 (0.6-1.6) | ||||
| 2 | 0.8 (0.6-1.2) | 0.7 (0.5-1.2) | ||||
| 3+ | 0.7 (0.5-1.0) | 0.7 (0.5-1.1) | ||||
| Britton (29) | United States (WISH) | 1,212 | 1+ | 0.8 (0.6-1.1) | 0.8 (0.5-1.2) | |
| Potter (17) | United States (IWHS) | 610 | 1-2 | 0.8 (0.5-1.1) | 2.1 (0.6-6.9) | |
| 3+ | 0.8 (0.5-1.1) | 2.2 (0.7-7.2) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 1.0 (0.8-1.2) | 1.0 (0.8-1.2) | |
| First author (reference) . | Country (study) . | Cases (n) . | Births (n)* . | Risk estimate (95% CI)† . | . | |
|---|---|---|---|---|---|---|
| ER+ | ER− | |||||
| Wohlfahrt (22) | Denmark (DBCG) | 6,044 | 1+ | 0.8 (0.7-0.8) | 0.9 (0.8-1.0) | |
| Hildreth (42) | United States | 148 | 1+ | 0.6 (0.3-1.1) | 2.5 (0.8-10.0) | |
| Cooper (36) | Australia | 380 | 1 | 1.4 (0.7-2.7) | 1.3 (0.5-3.4) | |
| 2 | 0.8 (0.5-1.4) | 0.8 (0.4-1.9) | ||||
| 3+ | 0.8 (0.5-1.4) | 1.0 (0.4-2.3) | ||||
| Hislop (37) | Canada (BC) | 512 | 1-2 | 0.8 (0.6-1.0)‡ | 0.9 (0.6-1.4)‡ | |
| 3+ | 0.7 (0.6-1.0)‡ | 1.3 (0.9-2.0)‡ | ||||
| McTiernan (39) | United States (CASH-WA) | 240 | 1-2 | 0.8 | 1.9 | |
| 3+ | 0.6 (0.3-1.5) | 1.4 (0.6-3.6) | ||||
| Stanford (38) | United States (CASH-GA) | 458 | 1-2 | 1.0 (0.6-1.6)‡ | 0.9 (0.6-1.5)‡ | |
| 3-4 | 0.7 (0.4-1.2)‡ | 0.8 (0.5-1.3)‡ | ||||
| 5+ | 0.5 (0.2-1.0)‡ | 1.0 (0.5-1.9)‡ | ||||
| Kreiger (35) | Canada (ON) | 528 | 1-3 | 0.7 (0.5-0.9) | 0.9 (0.5-1.6) | |
| 4+ | 0.7 (0.4-1.1) | 1.4 (0.6-3.0) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 1.0 (0.8-1.1) | 0.9 (0.8-1.2) | |
| PR+ | PR− | |||||
| Kreiger (35) | Canada (ON) | 528 | 1-3 | 0.6 (0.4-0.9) | 0.9 (0.6-1.5) | |
| 4+ | 0.5 (0.3-0.8) | 1.6 (0.9-3.1) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 0.9 (0.7-1.1) | 1.0 (0.9-1.2) | |
| ER+/PR+ | ER−/PR− | |||||
| McCredie (23) | Melbourne (Australia) | 618 | 1 | 1.1 (0.7-1.7) | 1.3 (0.8-2.3) | |
| 2 | 1.0 (0.7-1.5) | 1.0 (0.6-1.7) | ||||
| 3+ | 1.0 (0.5-1.2) | 0.8 (0.4-1.3) | ||||
| Cotterchio (24) | Canada (ON) | 3,276 | Premenopause | |||
| 1 | 0.6 (0.4-1.1) | 1.0 (0.5-2.0) | ||||
| 2 | 0.7 (0.4-1.0) | 1.1 (0.6-2.0) | ||||
| 3+ | 0.4 (0.3-0.8) | 0.9 (0.5-1.8) | ||||
| Postmenopause | ||||||
| 1 | 1.0 (0.7-1.4) | 0.9 (0.6-1.6) | ||||
| 2 | 0.8 (0.6-1.2) | 0.7 (0.5-1.2) | ||||
| 3+ | 0.7 (0.5-1.0) | 0.7 (0.5-1.1) | ||||
| Britton (29) | United States (WISH) | 1,212 | 1+ | 0.8 (0.6-1.1) | 0.8 (0.5-1.2) | |
| Potter (17) | United States (IWHS) | 610 | 1-2 | 0.8 (0.5-1.1) | 2.1 (0.6-6.9) | |
| 3+ | 0.8 (0.5-1.1) | 2.2 (0.7-7.2) | ||||
| Yoo (41) | Japan | 455 | Per 1 child | 1.0 (0.8-1.2) | 1.0 (0.8-1.2) | |
NOTE: Adjustment for other reproductive variables was sometimes unclear. Hildreth et al., McTiernan et al., and Yoo et al. adjusted for age at first birth and breast-feeding, assigning nulliparous women a value of zero in the model.
Reference group is nulliparous women.
ORs were the reported risk estimates for case-control studies and RRs for cohort designs.
Age-adjusted only.