Table 2.
Associations of Socioeconomic and Reproductive Factors With the Prevalence of ER/PR-Negative Breast Cancer (n = 746), Breast Cancer Care in Chicago, 2005–2008
| Characteristic | No. of Cases of Breast Cancera | % of Cases ER/PR-Negative | P Value |
|---|---|---|---|
| Race/ethnicity | 0.004 | ||
| Non-Hispanic white | 300 | 12 | |
| Non-Hispanic black | 303 | 28 | |
| Hispanic | 143 | 20 | |
| Age at diagnosis, years | |||
| <50 | 230 | 23 | |
| 50–59 | 228 | 19 | |
| 60–79 | 288 | 19 | |
| Educational level, years | 0.001 | ||
| <12 | 127 | 29 | |
| 12 | 158 | 23 | |
| >12 | 459 | 17 | |
| Annual income, dollars | <0.0001 | ||
| <20,000 | 190 | 29 | |
| 20,000–75,000 | 346 | 20 | |
| >75,000 | 193 | 11 | |
| Concentrated affluence | 0.11 | ||
| <1 SD below mean | 47 | 19 | |
| Within 1 SD of mean | 547 | 22 | |
| >1 SD above mean | 151 | 14 | |
| Concentrated disadvantage | 0.004 | ||
| <1 SD below mean | 111 | 11 | |
| Within 1 SD of mean | 494 | 20 | |
| >1 SD above mean | 140 | 26 | |
| Parity | 0.007 | ||
| Parous | 585 | 22 | |
| Nulliparous | 161 | 12 | |
| No. of live births | 0.02 | ||
| 0 | 161 | 12 | |
| 1 | 119 | 24 | |
| 2 | 187 | 20 | |
| >3 | 279 | 23 | |
| Age at first birth, years | 0.007b | ||
| 13–19 | 192 | 29 | |
| 20–29 | 292 | 20 | |
| 30–49 | 100 | 14 | |
| Nulliparous | 161 | 12 | |
| Breastfeeding | 0.09b | ||
| No (nulliparous) | 161 | 12 | |
| No (parous) | 279 | 25 | |
| Yes | 305 | 19 | |
| Duration of oral contraceptive use, years | 0.07 | ||
| 0 | 311 | 17 | |
| 1–5 | 225 | 21 | |
| 6–10 | 110 | 22 | |
| >10 | 100 | 25 | |
| Hormone replacement therapy | 0.61 | ||
| No (premenopausal) | 152 | 20 | |
| No | 408 | 21 | |
| Yes | 186 | 18 | |
| Body mass indexc | 0.02 | ||
| Underweight or normal weight | 231 | 16 | |
| Overweight | 229 | 18 | |
| Obese | 283 | 24 | |
| Family history of breast cancerd | 0.61 | ||
| None | 580 | 21 | |
| Weak | 114 | 18 | |
| Strong | 45 | 20 |
Abbreviations: ER, estrogen receptor; PR, progesterone receptor; SD, standard deviation.
a Due to missing data, not all numbers in the groups in this table add up to the total sample size of 746.
b P value for a comparison that excluded nulliparous women.
c Body mass index was calculated as weight (kg)/height (m)2, where underweight/normal was defined as ≤24.9, overweight as 25.0–29.9, and obese as ≥30.0.
d Family history of breast cancer was defined as weak when the patient had 1 affected relative diagnosed on or after age 50 years or strong when the patient had multiple affected relatives or at least 1 relative diagnosed before age 50 years).