Table 3.
Association Between Duration of Cigarette Smoking, Amount of Cigarette Smoking, and Years Since Quit Before Diagnosis and Death As a Result of Breast Cancer and All Causes
| Cigarette Smoking Variable Before Diagnosis | No. (%) of Patients (N = 20,691) | Cause of Death | |||
|---|---|---|---|---|---|
| Breast Cancer | All Causes | ||||
| No. of Deaths (n = 2,894) | HR* (95% CI) | No. of Deaths (n = 6,778) | HR* (95% CI) | ||
| Duration of smoking, years | |||||
| Never smoker | 10,399 (50) | 1,448 | 1 (Reference) | 3,234 | 1 (Reference) |
| Former smoker | |||||
| < 15 | 2,376 (11) | 275 | 0.92 (0.81 to 1.05) | 480 | 0.95 (0.86 to 1.04) |
| 15 to < 30 | 2,132 (10) | 238 | 0.82 (0.71 to 0.94) | 562 | 0.95 (0.87 to 1.04) |
| ≥ 30 | 1,725 (8) | 242 | 1.10 (0.95 to 1.27) | 868 | 1.39 (1.29 to 1.50) |
| Recent smoker | |||||
| < 15 | 187 (1) | 41 | 1.36 (0.99 to 1.88) | 54 | 1.36 (1.03 to 1.79) |
| 15 to < 30 | 1,104 (5) | 188 | 1.07 (0.91 to 1.26) | 273 | 1.21 (1.06 to 1.39) |
| ≥ 30 | 2,768 (13) | 462 | 1.32 (1.18 to 1.47) | 1,307 | 1.81 (1.69 to 1.94) |
| Amount of smoking, pack-years | |||||
| Never smoker | 10,399 (50) | 1,448 | 1 (Reference) | 3,234 | 1 (Reference) |
| Former smoker | |||||
| < 15 | 3,448 (17) | 406 | 0.91 (0.82 to 1.02) | 858 | 0.98 (0.90 to 1.05) |
| 15 to < 30 | 1,314 (6) | 153 | 0.87 (0.73 to 1.03) | 400 | 1.07 (0.96 to 1.19) |
| ≥ 30 | 1,471 (7) | 196 | 1.05 (0.90 to 1.23) | 652 | 1.41 (1.29 to 1.54) |
| Recent smoker | |||||
| < 15 | 768 (4) | 130 | 1.12 (0.93 to 1.35) | 218 | 1.21 (1.05 to 1.40) |
| 15 to < 30 | 1,126 (5) | 180 | 1.10 (0.94 to 1.29) | 379 | 1.49 (1.33 to 1.66) |
| ≥ 30 | 2,165 (11) | 381 | 1.39 (1.23 to 1.56) | 1,037 | 1.92 (1.78 to 2.06) |
| Years since quit | |||||
| Never smoker | 10,399 (50) | 1,448 | 1 (Reference) | 3,234 | 1 (Reference) |
| ≥ 25 | 1,660 (8) | 175 | 0.93 (0.79 to 1.09) | 459 | 0.97 (0.87 to 1.07) |
| 15 to < 25 | 1,713 (8) | 189 | 0.84 (0.72 to 0.98) | 457 | 1.00 (0.90 to 1.10) |
| 10 to < 15 | 939 (5) | 104 | 0.82 (0.67 to 1.00) | 272 | 1.05 (0.92 to 1.19) |
| 5 to < 10 | 1,122 (5) | 152 | 0.97 (0.82 to 1.15) | 392 | 1.26 (1.13 to 1.40) |
| < 5 | 799 (4) | 135 | 1.20 (1.00 to 1.44) | 330 | 1.52 (1.35 to 1.71) |
| Recent smoker | 4,059 (20) | 691 | 1.25 (1.13 to 1.38) | 1,634 | 1.68 (1.58 to 1.80) |
Abbreviation: HR, hazard ratio.
*
HR stratified by age at diagnosis, study phase, state of residence, and stage at diagnosis and adjusted for education, body mass index, parous status, age at first birth, menopausal status, use of postmenopausal hormone therapy, mammography history, alcohol consumption, and first-degree family history of breast cancer.