Table 4.
Smoking and breast cancer risk by tumor subtype in premenopausal women
| n controls | ER+ | ER− | ER−, PR−, HER2− | ||||
|---|---|---|---|---|---|---|---|
| n cases | OR (95% CI)a | n cases | OR (95% CI)a | n cases | OR (95% CI)a | ||
| Never smokers | 3532 | 641 | 1.00 (ref) | 384 | 1.00 (ref) | 175 | 1.00 (ref) |
| Smoking status | |||||||
| Former | 875 | 128 | 0.75 (0.60–0.95) | 95 | 0.94 (0.72–1.23) | 44 | 0.94 (0.64–1.38) |
| Current | 992 | 165 | 0.87 (0.70–1.08) | 89 | 0.69 (0.52–0.91) | 51 | 0.82 (0.57–1.20) |
| Former/current smokers | |||||||
| Age at smoking initiation (years) | |||||||
| ≥21 | 514 | 74 | 0.77 (0.58–1.02) | 49 | 0.79 (0.56–1.12) | 23 | 0.83 (0.50–1.37) |
| 18–20 | 559 | 77 | 0.74 (0.56–0.98) | 47 | 0.69 (0.48–0.97) | 27 | 0.87 (0.55–1.39) |
| 15–17 | 531 | 97 | 0.92 (0.70–1.19) | 64 | 0.98 (0.71–1.35) | 33 | 0.96 (0.62–1.50) |
| ≤14 | 240 | 44 | 0.87 (0.60–1.26) | 23 | 0.78 (0.48–1.26) | 12 | 0.80 (0.41–1.56) |
| P for trendb | 0.16 | 0.38 | 0.79 | ||||
| Cigarettes per day | |||||||
| <5 | 558 | 75 | 0.78 (0.59–1.04) | 38 | 0.82 (0.56–1.18) | 21 | 1.11 (0.66–1.84) |
| 5–14 | 796 | 117 | 0.71 (0.56–0.90) | 81 | 0.79 (0.59–1.05) | 44 | 0.88 (0.59–1.30) |
| 15–24 | 369 | 76 | 0.99 (0.74–1.33) | 53 | 0.87 (0.61–1.23) | 26 | 0.80 (0.49–1.32) |
| ≥25 | 125 | 23 | 1.09 (0.67–1.78) | 11 | 0.66 (0.33–1.32) | 4 | 0.47 (0.16–1.43) |
| P for trendb | 0.16 | 0.72 | 0.16 | ||||
| Smoking duration (years) | |||||||
| <10 | 582 | 85 | 0.83 (0.63–1.07) | 58 | 0.76 (0.55–1.05) | 36 | 1.04 (0.68–1.59) |
| 10–19 | 624 | 87 | 0.80 (0.62–1.04) | 63 | 0.91 (0.67–1.25) | 26 | 0.77 (0.48–1.24) |
| ≥20 | 625 | 119 | 0.82 (0.64–1.05) | 62 | 0.77 (0.56–1.07) | 32 | 0.80 (0.51–1.25) |
| P for trendb | 0.95 | 0.97 | 0.47 | ||||
| Pack-years | |||||||
| <10 | 1180 | 170 | 0.76 (0.62–0.93) | 110 | 0.78 (0.61–1.00) | 64 | 0.96 (0.68–1.35) |
| 10–19 | 431 | 74 | 0.83 (0.62–1.11) | 59 | 0.98 (0.70–1.37) | 24 | 0.80 (0.49–1.32) |
| ≥20 | 214 | 45 | 1.13 (0.78–1.64) | 13 | 0.55 (0.30–1.01) | 6 | 0.50 (0.20–1.22) |
| P for trendb | 0.068 | 0.60 | 0.11 | ||||
| Year smoked before first birthc | |||||||
| Never smokers | 2472 | 487 | 1.00 (ref) | 308 | 1.00 (ref) | 143 | 1.00 (ref) |
| Smoked after only | 404 | 64 | 0.69 (0.50–0.96) | 51 | 0.73 (0.50–1.06) | 26 | 0.79 (0.47–1.33) |
| 1–5 | 491 | 69 | 0.75 (0.55–1.02) | 60 | 0.99 (0.71–1.40) | 31 | 1.00 (0.62–1.60) |
| 6–9 | 231 | 41 | 0.86 (0.59–1.27) | 26 | 0.98 (0.61–1.57) | 10 | 0.68 (0.33–1.42) |
| ≥10 | 332 | 58 | 0.84 (0.60–1.19) | 19 | 0.58 (0.34–0.99) | 13 | 0.97 (0.49–1.92) |
| P for trendb | 0.087 | 0.31 | 0.48 | ||||
aAdjusted for age, study, time period, geographic region, education, age at menarche, age at first birth, parity, oral contraceptive use, estrogen only use, estrogen and progesterone use, body mass index, family history of breast cancer and alcohol consumption.
bExcluding never smokers.
cAmong parous women.