Table 3.
Multivariable adjusted hazard ratios (HR) and 95% confidence intervals (CI) for ER+, ER‒, PR+, PR‒ breast cancer according to different measures of smoking exposures, the Multiethnic Cohort study, 1993–2013a
| Smoking exposure | ER-positive (n = 3095) |
ER-negative (n = 659) |
P heterogeneity b | PR-positive (n = 2502) |
PR-negative (n = 1063) |
P heterogeneity b | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Cases | HR (95% CI) | Cases | HR (95% CI) | Cases | HR (95% CI) | Cases | HR (95% CI) | |||
| Common reference group | ||||||||||
| Never smokers | 1695 | 1.00 (ref) | 358 | 1.00 (ref) | 1366 | 1.00 (ref) | 581 | 1.00 (ref) | ||
| Smoking status | ||||||||||
| Former | 1020 | 1.09 (1.00–1.18) | 206 | 1.06 (0.89–1.27) | 838 | 1.11 (1.02–1.21) | 329 | 1.04 (0.91–1.20) | ||
| Current | 380 | 1.06 (0.94–1.19) | 95 | 1.13 (0.89–1.43) | 0.65 | 298 | 1.03 (0.90–1.17) | 153 | 1.19 (0.99–1.43) | 0.42 |
| Ever | 1400 | 1.08 (1.00–1.16) | 301 | 1.08 (0.92–1.27) | 0.97 | 1136 | 1.09 (1.00–1.18) | 482 | 1.08 (0.96–1.23) | 0.86 |
| Ever smokers | ||||||||||
| Smoking duration, years | ||||||||||
| ≤20 | 627 | 1.04 (0.95–1.14) | 130 | 1.01 (0.82–1.24) | 509 | 1.05 (0.94–1.16) | 212 | 1.03 (0.87–1.21) | ||
| 21–30 | 337 | 1.19 (1.06–1.35) | 77 | 1.27 (0.99–1.64) | 283 | 1.24 (1.09–1.41) | 113 | 1.18 (0.96–1.45) | ||
| ≥31 | 415 | 1.10 (0.98–1.23) | 88 | 1.09 (0.86–1.39) | 328 | 1.08 (0.95–1.22) | 147 | 1.14 (0.94–1.37) | ||
| Ptrend | 0.01 | 0.20 | 0.78 | 0.02 | 0.09 | 0.84 | ||||
| Number of cigarettes | ||||||||||
| ≤10/day | 712 | 1.10 (1.00–1.20) | 144 | 0.99 (0.82–1.21) | 568 | 1.10 (0.99–1.21) | 238 | 1.04 (0.89–1.21) | ||
| 11–20/day | 437 | 1.07 (0.96–1.19) | 105 | 1.23 (0.98–1.54) | 353 | 1.07 (0.95–1.20) | 169 | 1.22 (1.02–1.45) | ||
| ≥21/day | 237 | 1.10 (0.95–1.26) | 46 | 1.11 (0.81–1.53) | 204 | 1.15 (0.99–1.34) | 66 | 0.96 (0.74–1.25) | ||
| Ptrend | 0.07 | 0.16 | 0.68 | 0.04 | 0.28 | 0.69 | ||||
| Pack–years | ||||||||||
| ≤10 | 553 | 1.06 (0.96–1.17) | 109 | 0.96 (0.78–1.20) | 439 | 1.05 (0.94–1.17) | 188 | 1.04 (0.88–1.23) | ||
| 11–20 | 447 | 1.12 (1.00–1.24) | 98 | 1.13 (0.90–1.42) | 371 | 1.15 (1.02–1.29) | 149 | 1.08 (0.90–1.30) | ||
| ≥21 | 373 | 1.12 (1.00–1.26) | 82 | 1.23 (0.96–1.58) | 304 | 1.13 (0.99–1.28) | 129 | 1.18 (0.97–1.44) | ||
| Ptrend | 0.01 | 0.09 | 0.62 | 0.01 | 0.10 | 0.95 | ||||
| Age at smoking initiation, years | ||||||||||
| ≥25 | 806 | 1.02 (0.93–1.11) | 191 | 1.12 (0.93–1.34) | 647 | 1.02 (0.93–1.12) | 298 | 1.08 (0.94–1.25) | ||
| 20–24 | 307 | 1.23 (1.09–1.40) | 52 | 0.98 (0.73–1.32) | 258 | 1.27 (1.11–1.46) | 81 | 0.97 (0.76–1.23) | ||
| <20 | 261 | 1.23 (1.07–1.41) | 51 | 1.14 (0.83–1.54) | 211 | 1.21 (1.04–1.41) | 90 | 1.27 (1.01–1.61) | ||
| Ptrend | <0.001 | 0.42 | 0.29 | <0.001 | 0.11 | 0.49 | ||||
| Smoking initiation in relation to first childbirth for parous women | ||||||||||
| Neverc | 1459 | 1.00 (ref) | 324 | 1.00 (ref) | 1172 | 1.00 (ref) | 517 | 1.00 (ref) | ||
| During/after | 810 | 1.03 (0.94–1.12) | 182 | 0.99 (0.82–1.20) | 658 | 1.04 (0.94–1.15) | 283 | 0.99 (0.85–1.15) | ||
| ≤5 years before | 155 | 1.05 (0.89–1.24) | 32 | 1.01 (0.70–1.47) | 133 | 1.10 (0.91–1.32) | 45 | 0.90 (0.66–1.23) | ||
| >5 years before | 191 | 1.37 (1.17–1.61) | 39 | 1.44 (1.02–2.04) | 149 | 1.33 (1.11–1.59) | 73 | 1.60 (1.23–2.08) | ||
| Ptrend | 0.001 | 0.15 | 0.60 | 0.004 | 0.03 | 0.95 | ||||
aAfter excluding 466 (11.0 %) cases with missing data on both ER and PR status. Adjusted for age at cohort entry, race/ethnicity, body mass index, family history of breast cancer, age at first birth, number of children, age at menarche, age at and type of menopause, hormone replacement therapy, alcohol intake and education.
b P for heterogeneity between receptor status in a competing risk model.
cParous never smokers as reference group.