Table 1.
Characteristics of patients with contralateral breast cancer and control patients*
| Controls | Patients with contralateral breast cancer |
|
|---|---|---|
| n=661 | n=352 | |
| n (%) | n ( %) | |
| Demographic characteristics | ||
| Age at first breast cancer diagnosis, years | ||
| 40–49 | 120 (18.2) | 69 (19.6) |
| 50–59 | 174 (26.3) | 89 (25.3) |
| 60–69 | 206 (31.2) | 108 (30.7) |
| 70–79 | 161 (24.4) | 86 (24.4) |
| Reference age, years | ||
| 40–49 | 59 ( 8.9) | 33 ( 9.4) |
| 50–59 | 129 (19.5) | 66 (18.8) |
| 60–69 | 211 (31.9) | 111 (31.5) |
| 70–79 | 199 (30.1) | 103 (29.3) |
| 80–89 | 63 ( 9.5) | 39 (11.1) |
| Year of first breast cancer diagnosis | ||
| 1990–1993 | 241 (36.5) | 131 (37.2) |
| 1994–1997 | 220 (33.3) | 115 (32.7) |
| 1998–2001 | 147 (22.2) | 79 (22.4) |
| 2002–2005 | 53 ( 8.0) | 27 ( 7.7) |
| Race/ethnicity | ||
| Non-Hispanic white | 606 (92.0) | 322 (92.0) |
| Asian/Pacific Islander | 16 ( 2.4) | 9 ( 2.6) |
| African American | 24 ( 3.6) | 11 ( 3.1) |
| Native American | 10 ( 1.5) | 5 ( 1.4) |
| Hispanic white | 3 ( 0.5) | 3 ( 0.9) |
| Missing | 2 | 2 |
| Education | ||
| High school or less | 173 (33.7) | 78 (31.5) |
| High school or some college | 169 (32.9) | 102 (41.1) |
| College graduates or higher | 172 (33.5) | 68 (27.4) |
| Missing | 147 | 104 |
| Treatments for first breast cancer | ||
| Received radiation therapy | ||
| No | 229 (34.6) | 127 (36.1) |
| Yes | 432 (65.4) | 225 (63.9) |
| Received chemotherapy | ||
| No | 488 (73.8) | 264 (75.0) |
| Yes | 173 (26.2) | 88 (25.0) |
| Received hormonal therapy, years | ||
| None | 183 (27.7) | 130 (36.9) |
| <1 | 100 (15.1) | 56 (15.9) |
| 1–4 | 195 (29.5) | 87 (24.7) |
| ≥5 | 183 (27.7) | 79 (22.4) |
| Tumor characteristics of first breast cancer | ||
| AJCC stage | ||
| I | 454 (68.7) | 231 (65.6) |
| II/III | 207 (31.3) | 121 (34.4) |
| Tumor size, cm | ||
| ≤1.0 | 229 (35.6) | 111 (33.0) |
| 1.1–2.0 | 282 (43.8) | 136 (40.5) |
| >2.0 | 133 (20.7) | 89 (26.5) |
| Missing | 17 | 16 |
| Established breast cancer risk factors | ||
| First-degree family history of breast cancer | ||
| No | 463 (74.3) | 227 (70.5) |
| Yes | 160 (25.7) | 95 (29.5) |
| Missing | 38 | 30 |
| No. of full-term pregnancies | ||
| Nulliparous | 98 (15.2) | 54 (15.9) |
| 1–2 | 273 (42.5) | 149 (44.0) |
| ≥3 | 272 (42.3) | 136 (40.1) |
| Missing | 18 | 13 |
| Recency of menopausal hormone use at first breast cancer diagnosis | ||
| Never | 292 (46.9) | 166 (50.9) |
| Former | 71 (11.4) | 38 (11.7) |
| Current estrogen alone user | 138 (22.2) | 70 (21.5) |
| Current estrogen + progestin user | 122 (19.6) | 52 (16.0) |
| Missing | 38 | 26 |
| Health status and lifestyle factors | ||
| Had a diagnosis of hypertension between first breast cancer and reference date | ||
| No | 330 (50.6) | 180 (51.9) |
| Yes | 322 (49.4) | 167 (48.1) |
| Missing | 9 | 5 |
| Had a diagnosis of heart disease between first breast cancer and reference date | ||
| No | 495 (76.5) | 272 (78.8) |
| Yes | 152 (23.5) | 73 (21.2) |
| Missing | 14 | 7 |
| BMI at first breast cancer diagnosis, kg/m2 | ||
| <25 | 284 (43.8) | 125 (36.5) |
| 25–29.9 | 194 (29.9) | 112 (32.7) |
| ≥30 | 170 (26.2) | 105 (30.7) |
| Missing | 13 | 10 |
| Alcohol consumption between first breast cancer and reference date, drinks/week | ||
| None | 241 (47.2) | 113 (45.2) |
| <3 | 132 (25.8) | 71 (28.4) |
| ≥3 | 138 (27.0) | 66 (26.4) |
| Missing | 150 | 102 |
| Smoking status at reference date | ||
| Never | 269 (52.2) | 120 (47.6) |
| Former | 49 ( 9.5) | 35 (13.9) |
| Current | 197 (38.3) | 97 (38.5) |
| Missing | 146 | 100 |
*
Cases and controls were individually matched on age, year of diagnosis, county, race/ethnicity, and cancer stage. Controls also had to be alive for at least the duration between their matched cases’ first and CBC diagnoses.