Incidence Data for Locally Advanced and Stage IV Breast Cancer in California, by SES, age, and Race/ethnicity.

Data from the California Cancer Registry between 1988–1999 echo the findings in the US at large, but add more detail about Hispanics and Asian/Pacific Islanders.

Breast cancer falls disproportionately among different groups and ages, however. While it accounts for only 9 percent of invasive cancers in whites, it accounts for nearly a quarter of invasive cancers diagnosed in very young black women, aged 20–29. By age 30–39, breast cancer accounts for nearly half of diagnosed cancers in black women. While breast cancer is largely a disease of older women, with a median age of 63, for women younger than 50, breast cancer accounts for nearly 40 percent of all invasive cancers and is the principle cause of cancer death.

Table 1 displays breast cancer incidence per 100,000 people by age, demonstrating the dramatic increase in numbers of cases in older women, at a rate nearly ten times higher that in younger women, with a disproportionately high incidence in older white women.

Race/Ethnicity Under 50 Years of Age Over 50 Years of Age
All Races Combined
40.1
363.0
White
43.5
412.7
Black
41.8
317.9
Hispanic
30.8
221.9
Asian/Pacific Islander
38.1
220.3

Table 1. Female Breast Cancer Age-adjusted Incidence per 100,000 Population by Race/Ethnicity, California, 1995–199918

From 1988–1999, 258,849 women in California were diagnosed with breast cancer at a combined, age-adjusted rate of 128.8 per 100,000 population. The rate of breast cancer diagnosed at a distant stage was highest among blacks (7.5) and lowest among Asian/Pacific Islanders (3.0). The highest rate of unstaged breast cancer was also among black women (5.2). Asian/Pacific Island women were far more likely than black or Hispanic women to be diagnosed at an early stage.

The California Cancer Registry assesses socio-economic status (SES) not from individual data, but by place of residence, according to census block groups, each representing about 1,000 individuals. A statistically significant association exists between stage at diagnosis and SES as determined in this fashion. Those living in more affluent neighborhoods tended to be diagnosed at an earlier stage, while those living in poorer areas, were more likely to be diagnosed at a later stage. “Black women living in the most affluent areas were 60 percent more likely to be diagnosed at an early stage than those living in the poorest areas.” Interestingly, the association of SES as predictor of later stage diagnosis was most pronounced in black and Hispanic women and less so, though still statistically significant, for white and Asian/Pacific Islanders.19

An analysis of California Cancer Registry data from November 2002, based on follow-up through 2000 using SEER 1990 life tables20, confirms that in California both race/ethnicity and socio-economic status (SES) have an impact on survival from breast cancer.

Without regard to race, relative survival (excluding death from other causes) improved dramatically as SES increased. As Figure 5 shows, the five-year relative survival was 76.6 percent for the lowest socio-economic group, and 90.1 percent for the highest socio-economic group. As already discussed, a breakdown by race/ethnicity shows similar disparities in five-year relative survival, with 86.8 percent in white women and a low 73 percent in black women. Hispanic women had a five-year relative survival of 81.3 percent, while the figure for Asians was 85.6 percent.

Figure 5

Figure 5. Five-year Relative Breast Cancer Survival in California by Socio-economic Status

 

  SES1 SES2 SES3 SES4 SES5
White
79.3%
83.5%
85.6%
85.7%
90.7%
Black
68.3
74.1
76.0
76.8
78.0
Hispanic
76.9
79.7
82.7
85.4
86.8
Asian
80.1
81.5
85.1
87.5
88.7

Table 2 illustrates what happens to five-year relative survival when the two variables of race/ethnicity and SES are combined.

An examination of the interaction of the two variables of race/ethnicity and socio-economic status shows poorer fiveyear survival for black women at all socio-economic levels, as well as poorer survival for white, Hispanic, and Asian women by socio-economic level. It is interesting to note that within each racial/ethnic group, the variable of SES can accurately predict for five-year survival, as is visually evident in the bar chart in Figure 6. This clearly shows that class may well be as important an issue—or even more important—as race. In fact, these figures are so compelling that some believe that race/ethnicity is actually a proxy for socio-economic status.

Figure 6