Table 3.
Multivariable Cox Proportional Hazards Model According to Stage and BC Subtypes Among 6,827 Patients With Stage I to III BC Diagnosed Between 1997 and 2011 and Treated With Adjuvant Chemotherapy
| TTC (days) | OS |
RFS |
DRFS |
||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | HR | 95% CI | P | |
| All | |||||||||
| 31-60 v ≤ 30 | 1.05 | 0.94 to 1.18 | .39 | 1.04 | 0.94 to 1.14 | .44 | 1.04 | 0.94 to 1.15 | .49 |
| ≥ 61 v ≤ 30 | 1.19 | 1.02 to 1.38 | .03 | 1.10 | 0.97 to 1.25 | .15 | 1.13 | 0.99 to 1.29 | .07 |
| Stage I | |||||||||
| 31-60 v ≤ 30 | 0.85 | 0.64 to 1.12 | .25 | 0.89 | 0.71 to 1.12 | .33 | 0.88 | 0.69 to 1.13 | .31 |
| ≥ 61 v ≤ 30 | 0.80 | 0.54 to 1.18 | .26 | 0.82 | 0.6 to 1.12 | .20 | 0.81 | 0.57 to 1.14 | .22 |
| Stage II | |||||||||
| 31-60 v ≤ 30 | 1.13 | 0.97 to 1.31 | .12 | 1.16 | 1.02 to 1.31 | .02 | 1.18 | 1.03 to 1.34 | .02 |
| ≥ 61 v ≤ 30 | 1.17 | 0.96 to 1.42 | .12 | 1.16 | 0.99 to 1.36 | .07 | 1.20 | 1.02 to 1.43 | .03 |
| Stage III | |||||||||
| 31-60 v ≤ 30 | 1.14 | 0.88 to 1.48 | .33 | 0.99 | 0.8 to 1.23 | .95 | 0.96 | 0.77 to 1.2 | .7 |
| ≥ 61 v ≤ 30 | 1.76 | 1.26 to 2.46 | < .001 | 1.34 | 1.01 to 1.76 | .04 | 1.36 | 1.02 to 1.8 | .03 |
| Hormone receptor–positive | |||||||||
| 31-60 v ≤ 30 | 1.14 | 0.95 to 1.36 | .16 | 1.15 | 1.00 to 1.32 | .04 | 1.18 | 1.02 to 1.36 | .03 |
| ≥ 61 v ≤ 30 | 1.29 | 1.02 to 1.64 | .03 | 1.14 | 0.94 to 1.37 | .19 | 1.17 | 0.96 to 1.42 | .12 |
| HER2-positive | |||||||||
| 31-60 v ≤ 30 | 0.92 | 0.69 to 1.22 | .54 | 0.82 | 0.64 to 1.04 | .1 | 0.85 | 0.66 to 1.09 | .21 |
| ≥ 61 v ≤ 30 | 1.16 | 0.82 to 0.63 | .41 | 1.02 | 0.76 to 1.38 | .87 | 1.04 | 0.76 to 1.41 | .82 |
| Triple negative | |||||||||
| 31-60 v ≤ 30 | 1.74 | 1.32 to 2.29 | < .001 | 1.21 | 0.96 to 1.54 | .11 | 1.23 | 0.95 to 1.59 | .11 |
| ≥ 61 v ≤ 30 | 1.54 | 1.09 to 2.18 | .02 | 1.24 | 0.91 to 1.68 | .18 | 1.36 | 0.99 to 1.89 | .06 |
NOTE. Variables in the model include age, race/ethnicity, axillary node involvement, tumor size, tumor grade, surgery, lymphovascular invasion, and No. of comorbidities (0, 1-2, 3-4, 5+). Among patients with triple-negative BC, type of chemotherapy was included as a different covariate. Among HER2-positive patients, the use of trastuzumab was included as an additional covariate.
Abbreviations: BC, breast cancer; DRFS, distant relapse-free survival; HER2, human epidermal growth factor receptor 2; HR, hazard ratio; OS, overall survival; RFS, relapse-free survival; TTC, time to initiation of adjuvant chemotherapy.