Table 1.
Distribution of study variables by socioeconomic status (SES), breast cancer diagnosed in 1998-2002
| Percentage of area-based SES group | ||||||
|---|---|---|---|---|---|---|
| Number of cases | Highest SES | Upper middle | Lower middle | Lowest SES | p-value | |
| Age at diagnosis (year) | <0.0001 | |||||
| 15-44 | 15520 | 14.4 | 14.0 | 12.4 | 14.4 | |
| 45-54 | 26545 | 25.2 | 23.3 | 22.3 | 23.6 | |
| 55-64 | 25545 | 23.3 | 23.2 | 21.9 | 22.5 | |
| 65-74 | 22462 | 18.6 | 19.7 | 21.1 | 20.3 | |
| 75+ | 22471 | 18.4 | 19.8 | 22.3 | 19.2 | |
| Year of diagnosis | <0.0001 | |||||
| 1998 | 22134 | 19.4 | 18.4 | 21.4 | 19.4 | |
| 1999 | 22487 | 19.5 | 18.7 | 21.3 | 20.1 | |
| 2000 | 22385 | 20.2 | 21.0 | 18.6 | 20.0 | |
| 2001 | 22791 | 20.3 | 20.9 | 19.6 | 20.2 | |
| 2002 | 22746 | 20.6 | 21.0 | 19.1 | 20.3 | |
| Race | <0.0001 | |||||
| White | 92717 | 90.8 | 79.7 | 85.4 | 74.4 | |
| Black | 9831 | 4.3 | 7.2 | 6.3 | 16.1 | |
| Other | 9995 | 4.9 | 13.1 | 8.3 | 9.5 | |
| Rural/urban residence | <0.0001 | |||||
| Rural | 9819 | 2.7 | 4.0 | 23.1 | 4.0 | |
| Urban | 102724 | 97.3 | 96.0 | 76.9 | 96.0 | |
| AJCC† stage | <0.0001 | |||||
| I | 50608 | 46.7 | 45.7 | 46.6 | 41.4 | |
| II | 41646 | 36.2 | 37.1 | 35.1 | 39.5 | |
| III | 7188 | 5.7 | 5.8 | 5.5 | 8.3 | |
| IV | 4770 | 3.8 | 4.1 | 4.3 | 4.7 | |
| Unknown | 8331 | 7.6 | 7.3 | 8.5 | 6.2 | |
| Number of positive lymph nodes | <0.0001 | |||||
| None | 60700 | 64.9 | 64.0 | 65.4 | 60.2 | |
| 1-3 | 21948 | 22.8 | 23.2 | 21.9 | 23.9 | |
| ≥ 4 | 12896 | 12.3 | 12.8 | 12.7 | 16.0 | |
| First course treatment received | ||||||
| Surgery | 106076 | 95.3 | 94.5 | 93.6 | 93.8 | <0.0001 |
| Radiation | 58144 | 57.3 | 55.1 | 47.8 | 47.7 | <0.0001 |
† AJCC: American Joint Committee on Cancer.