Table 4.
Ever oral contraceptive use in relation to ER+PR+ and ER-PR- cancer according to categories of breast cancer risk factors
| ER+PR+ |
ER−PR− |
|||||
|---|---|---|---|---|---|---|
| Risk factor | OC use ever/never (no. cases) | IRR* 95% CI | P* | OC use ever/never (no. cases) | IRR 95% CI | P** |
| Age <50 | 144/23 | 1.28 (0.82–2.00) | 0.07 | 119/14 | 1.80 (1.03–3.15) | 0.87 |
| 50+ | 140/70 | 1.04 (0.77–1.41) | 114/32 | 1.59 (1.05–2.41) | ||
| Premenopausal | 130/19 | 1.36 (0.84–2.21) | 0.14 | 106/15 | 1.49 (0.86–2.57) | 0.75 |
| Postmenopausal | 112/27 | 0.95 (0.69–1.31) | 90/27 | 1.66 (1.05–2.62) | ||
| BMI at age 18<20 | 134/43 | 0.89 (0.61–1.29) | 0.55 | 116/25 | 1.43 (0.91–2.25) | 0.42 |
| 20+ | 146/57 | 1.10 (0.79–1.54) | 116/21 | 1.85 (1.14–3.01) | ||
| BMI current <25 | 69/19 | 0.94 (0.55–1.61) | 0.35 | 62/11 | 1.53 (0.78–2.98) | 0.97 |
| 25+ | 214/83 | 1.13 (0.85–1.49) | 171/35 | 1.67 (1.14–2.44) | ||
| Age menarche <12 | 77/28 | 1.05 (0.65–1.69) | 0.90 | 77/18 | 1.41 (0.82–2.44) | 0.41 |
| 12+ | 206/74 | 1.10 (0.82–1.47) | 156/28 | 1.79 (1.18–2.73) | ||
| Age 1st birth <20 | 62/29 | 0.99 (0.61–1.61) | 0.44 | 57/14 | 1.56 (0.84–2.90) | 0.25 |
| 20+ | 150/47 | 1.02 (0.71–1.46) | 140/18 | 2.18 (1.31–3.62) | ||
| Parity 0 | 72/24 | 1.54 (0.91–2.61) | 0.33 | 34/14 | 1.00 (0.50–1.98) | 0.06 |
| 1+ | 212/78 | 0.99 (0.75–1.32) | 198/32 | 1.92 (1.30–2.83) | ||
| Female.hormone use never | 184/51 | 1.19 (0.85–1.66) | 0.29 | 165/24 | 2.05 (1.32–3.19) | 0.12 |
| ever | 98/49 | 1.04 (0.69–1.45) | 68/21 | 1.26 (0.74–2.14 | ||
| Family history No | 229/85 | 1.39 (0.77–2.54) | 0.24 | 194/39 | 2.15 (0.93–4.98) | 0.55 |
| Yes | 55/17 | 1.04 (0.79–1.37) | 39/7 | 1.59 (1.10–2.28) | ||
| Cigarette smoking never | 170/54 | 1.23 (0.88–1.72) | 0.59 | 141/26 | 1.53 (0.99–2.35) | 0.75 |
| ever | 114/47 | 1.01 (0.69–1.47) | 92/20 | 1.83 (1.09–3.08) | ||
| Alcohol drinks/wk <1 | 207/78 | 1.08 (0.81–1.43) | 0.82 | 169/38 | 1.42 (0.98–2.05) | 0.49 |
| 1+ | 77/24 | 1.16 (0.69–1.94) | 64/8 | 2.81 (1.29–6.09) | ||
| Vigorous exercise No | 159/59 | 1.25 (0.90–1.74) | 0.24 | 131/30 | 1.59 (1.05–2.42) | 0.72 |
| Yes | 122/41 | 0.89 (0.61–1.31) | 101/15 | 1.82 (1.04–3.21) | ||
| Education years <16 | 143/49 | 1.39 (0.97–1.99) | 0.15 | 139/29 | 1.77 (1.16–2.70) | 0.44 |
| 16+ | 141/53 | 0.87 (0.62–1.23) | 102/17 | 1.55 (1.07–2.31) | ||
*
Never use of oral contraceptives is the reference category; IRRs adjusted for age, age at menarche, BMI at age 18, family history of breast cancer, education, parity, age at first birth, menopausal status, age at menopause, menopausal hormone use, vigorous activity, alcohol intake.
**
P value for interaction