Table 3.
BC risk associated with number of childbirths and breastfeeding period according to HR status among BC cases and population-based matched controls in the Korea Breast Cancer Study, 2004 to 2012
| Total women |
Premenopausal women |
Postmenopausal women |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | Luminal A | Luminal B | HER2-enriched | Triple-negative | |
| No. of childbirths | ||||||||||||
| 0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| 1 | 0.72 (0.58, 0.88)1 | 0.87 (0.55, 1.25)1 | 1.43 (0.83, 2.38)1 | 1.19 (0.78, 1.82)1 | 1.01 (0.72, 1.39)2 | 0.83 (0.49, 1.39)2 | 1.77 (0.81, 4.00)2 | 1.69 (0.90, 3.13)2 | 0.56 (0.37,0.83)3 | 0.85 (0.42, 1.72)3 | 1.06 (0.52, 2.17)3 | 0.80 (0.44, 1.45)3 |
| 2 | 0.45 (0.40, 0.51)1 | 0.80 (0.63, 1.03)1 | 1.23 (0.88, 1.74)1 | 0.96 (0.75, 1.25)1 | 0.63 (0.50, 0.79)2 | 0.88 (0.65, 1.17)2 | 1.38 (0.84, 2.36)2 | 1.41 (0.94, 2.09)2 | 0.36 (0.27, 0.47)3 | 0.74 (0.48, 1.16)3 | 1.04 (0.66, 1.65)3 | 0.64 (0.44, 0.91)3 |
| 3+ | 0.34 (0.30, 0.38)1 | 0.74 (0.61, 0.91)1 | 1.10 (0.83, 1.48)1 | 0.92 (0.73, 1.15)1 | 0.55 (0.46, 0.66)2 | 0.89 (0.72, 1.08)2 | 1.13 (1.08, 1.68)2 | 1.68 (1.21, 2.28)2 | 0.26 (0.20, 0.33)3 | 0.65 (0.44, 0.99)3 | 1.03 (0.68, 1.59)3 | 0.56 (0.40, 0.78)3 |
| Breastfeeding duration (mo) | ||||||||||||
| 0 | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) | 1.00 (reference) |
| 1-12 | 0.73 (0.68, 0.79) | 0.80 (0.68, 0.92) | 0.84 (0.70, 0.99) | 0.71 (0.62, 0.83) | 0.67 (0.61, 0.74)4 | 0.69 (0.57, 0.83)4 | 0.68 (0.53, 0.87)2 | 0.61 (0.51, 0.75)4 | 0.87 (0.76, 0.99)4 | 1.00 (0.78, 1.28)4 | 1.00 (0.79, 1.27)4 | 0.88 (0.70, 1.11)4 |
| 13-24 | 0.51 (0.45, 0.55) | 0.63 (0.53, 0.74) | 0.50 (0.42, 0.61) | 0.52 (0.44, 0.61) | 0.51 (0.45, 0.57) | 0.65 (0.51, 0.87) | 0.50 (0.37, 0.67) | 0.45 (0.36, 0.57) | 0.50 (0.44, 0.57) | 0.60 (0.46, 0.77) | 0.48 (0.37, 0.63) | 0.59 (0.47, 0.75) |
| 25+ | 0.39 (0.36, 0.43) | 0.42 (0.34, 0.51) | 0.40 (0.32, 0.50) | 0.37 (0.31, 0.45) | 0.45 (0.38, 0.53) | 0.44 (0.31, 0.63) | 0.68 (0.44, 1.03) | 0.39 (0.27, 0.55) | 0.38 (0.33, 0.43) | 0.43 (0.33, 0.58) | 0.35 (0.27, 0.47) | 0.41 (0.32, 0.53) |
Values are presented as OR (95% CI).
The OR (95% CI) in all women was estimated in conditional logistic regression stratified by age and enrollment year and adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and breastfeeding duration in the analyses of parity and number of childbirths; or adjusted for family history of BC, age at menarche, age at first full-term pregnancy, duration of oral contraceptive use, BMI, and number of childbirths in the analyses of breastfeeding and its duration.
HR, hormone receptor; BC, breast cancer; OR, odds ratio; CI, confidence interval; BMI, body mass index.
p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among total women =0.035 for [childbirths=1]; 0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among premenopausal women : 0.021 for [childbirths=1]; 0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
p-value for the heterogeneity of four ORs (95% CIs) from 4 pathological subtypes among postmenopausal women: 0.401 for [childbirths=1]; <0.001 for [childbirths=2]; <0.001 for [childbirths=3+].
p-value for the heterogeneity of eight ORs (95% CIs) from 8 subgroups classified by pathological subtypes and menopausal status: <0.001 for [breastfeeding period =1-12 months].