Bentley JR, Delfino RJ, Taylor TH, Howe S, Anton-Culver H.
Differences in breast cancer stage at diagnosis between non-Hispanic white and Hispanic populations, San Diego County 1988-1993.
Breast Cancer Res Treat 1988;50(1):1-9.

Survival after diagnosis with breast cancer is shorter for Hispanic than for non-Hispanic white women. It is possible that this pattern is due to differences between these two ethnic groups in the stage of diagnosis. The later stage of diagnosis of Hispanic women indicates a failure in existing screening programs for this population, and economic and cultural factors play an important role in defining barriers to screening. This study examined differences in incidence of breast cancer for non-Hispanic white and Hispanic women in order to assess whether living in lower income census tracts explains stage at diagnosis differences between these two ethnic groups.

Data for this study were drawn from a population-based breast cancer incidence registry (the San Diego County/Imperial Organization for Cancer Control) for the five-year period from 1988 to 1993.

Non-Hispanic whites had a higher age-adjusted incidence rate for breast cancer compared with Hispanics (131.3/100,000 versus 73.9/100,000). This was true for both early-stage disease and late-stage disease, as well as for each of three age groups (younger than 50 year, 50 to 64 years, 65 years and older). Hispanic women were diagnosed at significantly younger ages than non-Hispanic white women (mean age for early stage was 68.2 years for Hispanic and 64.0 years for non-Hispanic white women; mean age for late stage was 53.9 years for Hispanic and 61.9 years for non-Hispanic white women). The authors note that this age pattern is "likely explained by the higher proportion of younger Hispanic women in the population at risk as compared with whites."

Both ethnic groups had a higher incidence rate for early- compared with late-stage disease. The ratio of incidence rates (early to late) was significantly higher for non-Hispanic whites, indicating that non-Hispanic whites were more likely than Hispanics to be diagnosed at early-stages than late-stages of disease. This was particularly true in the youngest age category (younger than 50 years). In this age category, Hispanic women had nearly an equal chance of being diagnosed at early- or late-stage cancer. The authors suggest several possible explanations for these findings – Hispanic women under 50 years may be significantly less likely to have ever had a mammogram than Hispanic women over 50 year; Hispanic women with a breast tumor might have higher proliferation rates and larger tumors that could become evident at a younger age than non-Hispanic white women; and once a suspicious lesion is diagnosed; and Hispanics may be less likely to seek definitive treatment secondary to economic or cultural barriers.

The incidence of early stage breast cancer for non-Hispanic whites increased significantly as income level rose (from 75.3 to 99.0/100000). For Hispanics, the incidence only increased slightly as income level rose (41.5 to 53.6/100000). The incidence of late stage cancer only increased slightly as income level rose. The ratio of early to late stage incidence rates was highest for non-Hispanic white women in the highest income level (IRR=2.26; 59% confidence interval, 2.10 to 2.46). The authors suggest that the lack of a similar finding for Hispanics could be "because, within the Hispanic population, barriers to mammography screening cut across class lines." However they note that the upper tertile of income for Hispanic women was low (compared with that of non-Hispanic white women) and "may not have included enough cases with very high incomes to demonstrate an income differential for stage at diagnosis."

The authors conclude that screening practices targeting Hispanics should include commencing mammography for screening at 40 years of age for Hispanics and that additional efforts to promote mammography screening in low-income women are also needed. They add that, "research is needed to determine whether breast cancer in younger Hispanic women is biologically more aggressive than non-Hispanic white women, and earlier screening can impact overall survival rates among Hispanics."