Table 3.
Adjusted Cox models* examining the associations of smoking with breast cancer recurrence and mortality in a pooled cohort of US breast cancer survivors (n = 9755)
| Smoking status | No. | Breast cancer recurrence | Breast cancer mortality | All-cause mortality | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Event | HR (95% CI) | P† | Event | HR (95% CI) | P† | Event | HR (95% CI) | P† | ||
| Never smokers | 4812 | 824 | Referent | 499 | Referent | 780 | Referent | |||
| Former smokers | ||||||||||
| <20 pack-years | 2744 | 453 | 0.98 (0.87 to 1.11) | .78 | 259 | 0.99 (0.85 to 1.15) | .88 | 410 | 0.97 (0.86 to 1.09) | .58 |
| 20–34.9 pack-years | 808 | 156 | 1.22 (1.01 to 1.48) | .04 | 93 | 1.14 (0.91 to 1.43) | .26 | 177 | 1.26 (1.07 to 1.48) | .01 |
| ≥35 pack-years | 785 | 155 | 1.37 (1.13 to 1.66) | .001 | 111 | 1.54 (1.24 to 1.91) | <.001 | 227 | 1.68 (1.44 to 1.96) | <.001 |
| Current smokers‡ | 710 | 139 | 1.41 (1.16 to 1.71) | <.001 | 97 | 1.61 (1.28 to 2.03) | <.001 | 209 | 2.17 (1.85 to 2.54) | <.001 |
| P trend | <.001 | <.001 | <.001 | |||||||
* Hazard ratios (HRs) were from delayed-entry Cox regression models with study as a stratification variable and adjusted for age at diagnosis, cancer stage, tumor grade, race/ethnicity, education, and obesity. CI = confidence interval; SD = standard deviation.
† P values (two-sided) were from the Wald test within Cox proportional hazards regression.
‡ Current smokers had smoked for a mean of 39 (standard deviation = 25) pack-years.