Background: African-Americans are more likely than Caucasians to be diagnosed at an advanced stage of colorectal, lung, breast, cervical, and prostate cancers. This study explores if racial differences in stage at diagnosis can be explained by socioeconomic status (SES) differences. Previous studies investigating this association have used aggregate SES indicators from census tract of residence; we used census block-group data, representing a smaller, potentially more homogenous group.
Methods: We included all African-American and Caucasian invasive cancers of the colon and rectum, lung and bronchus, female breast, cervix uteri, and prostate that were diagnosed between January 1, 1988 and December 31, 1992 in the Detroit area. Stage of disease at diagnosis was grouped as local or non-local. An SES value was calculated for each case using aggregate 1990 US Census data for education, poverty status, and occupation specific to each case's census block-group. Logistic regression analysis was used to model the probability of non-local stage using SES, race, age group, and sex as covariates.
Results: SES was an independent predictor of stage at diagnosis for each cancer site, with cases from the highest SES block-group more likely to present with local stage disease than those from the lowest SES group. Race independently predicted stage only for breast and prostate cancers; African-Americans presented with more advanced stage than Caucasians.
Conclusions: Based on census block-group aggregate data, SES is an important predictor of stage at diagnosis, most likely accounting for much of the disparity in stage between African-Americans and Caucasians for colorectal, lung, and cervical cancers. Biological factors may play a role in racial disparities for breast and prostate cancer stage at diagnosis.