Table 3.
All-cause and breast cancer-specific mortality by age at first birth and stratified by histologic subtypea
| All histologies |
Ductal subtype |
Lobular subtype |
Mixed ductal-lobular subtype |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cases | Events | HR (95% CI) | Cases | Events | HR (95% CI) | Cases | Events | HR (95% CI) | Cases | Events | HR (95% CI) | |
| Age at first birth | Breast cancer-specific mortality | |||||||||||
| Nulliparous | 445 | 1.09 (0.95 – 1.25) | 2463 | 366 | 1.10 (0.95 – 1.28) | 235 | 42 | 0.89 (0.55 – 1.44) | 108 | 10 | 1.03 (0.32 – 3.30) | |
| <20 | 3041 | 405 | 1 | 2439 | 342 | 1 | 226 | 35 | 1 | 110 | 8 | 1 |
| 20-24 | 8891 | 1219 | 1.00 (0.90 – 1.12) | 7068 | 1008 | 1.01 (0.89 – 1.14) | 769 | 104 | 0.71 (0.47 – 1.07) | 312 | 36 | 1.74 (0.68 – 4.45) |
| 25-29 | 5064 | 652 | 0.93 (0.82 – 1.05) | 3970 | 532 | 0.94 (0.82 – 1.08) | 475 | 63 | 0.63 (0.40 – 0.98) | 220 | 19 | 1.24 (0.43 – 3.58) |
| 30+ | 2260 | 335 | 1.11 (0.96 – 1.29) | 1756 | 268 | 1.11 (0.94 – 1.30) | 249 | 41 | 1.05 (0.65 – 1.70) | 99 | 15 | 2.39 (0.80 – 7.12) |
| PTrend | 0.66 | 0.65 | 0.87 | 0.41 | ||||||||
| Age at first birth | All-cause mortality | |||||||||||
| Nulliparous | 3046 | 910 | 1.02 (0.92 – 1.12) | 2463 | 737 | 1.05 (0.94 – 1.17) | 235 | 80 | 0.98 (0.69 – 1.38) | 108 | 22 | 1.31 (0.65 – 2.66) |
| <20 | 3041 | 848 | 1 | 2439 | 681 | 1 | 226 | 66 | 1 | 110 | 20 | 1 |
| 20-24 | 8891 | 2503 | 0.93 (0.86 – 1.00) | 7068 | 2053 | 0.97 (0.89 – 1.06) | 769 | 214 | 0.78 (0.58 – 1.04) | 312 | 63 | 1.00 (0.56 – 1.78) |
| 25-29 | 5064 | 1455 | 0.87 (0.80 – 0.95) | 3970 | 1170 | 0.91 (0.82 – 1.00) | 475 | 141 | 0.76 (0.56 – 1.04) | 220 | 36 | 0.94 (0.50 – 1.77) |
| 30+ | 2260 | 702 | 1.01 (0.91 – 1.12) | 1756 | 548 | 1.02 (0.91 – 1.14) | 249 | 80 | 0.97 (0.69 – 1.37) | 99 | 25 | 1.51 (0.76 – 3.03) |
| PTrend | 0.44 | 0.51 | 0.96 | 0.37 | ||||||||
HR indicates hazard rate ratio; CI confidence interval
a
Proportional hazards models were stratified by state of residence, year of interview and age at diagnosis and adjusted for menopausal status, BMI, hormone replacement therapy use, smoking status, mammography, time from date of diagnosis to interview and stage of disease at diagnosis.