Effects of individual-level socioeconomic factors on racial disparities in cancer treatment and survival: findings from the National Longitudinal Mortality Study, 1979-2003.

BACKGROUND: This is the first study to use the linked National Longitudinal Mortality Study and Surveillance, Epidemiology, and End Results (SEER) data to determine the effects of individual-level socioeconomic factors (health insurance, education, income, and poverty status) on racial disparities in receiving treatment and in survival.

METHODS: This study included 13,234 cases diagnosed with the 8 most common types of cancer (female breast, colorectal, prostate, lung and bronchus, uterine cervix, ovarian, melanoma, and urinary bladder) at age ≥ 25 years, identified from the National Longitudinal Mortality Study-SEER data during 1973 to 2003. Kaplan-Meier methods and Cox regression models were used for survival analysis.

RESULTS: Three-year all-cause observed survival for cases diagnosed with local-stage cancers of the 8 leading tumors combined was ≥ 82% regardless of race/ethnicity. More favorable survival was associated with higher socioeconomic status. Compared with whites, blacks were less likely to receive first-course cancer-directed surgery, perhaps reflecting a less favorable stage distribution at diagnosis. Hazard ratio (HR) for cancer-specific mortality was significantly higher among blacks compared with whites (HR, 1.2; 95% confidence interval [CI], 1.1-1.3) after adjusting for age, sex, and tumor stage, but not after further controlling for socioeconomic factors and treatment (HR, 1.0; 95% CI, 0.9-1.1). HRs for all-cause mortality among patients with breast cancer and for cancer-specific mortality in patients with prostate cancer were significantly higher for blacks compared with whites after adjusting for socioeconomic factors, treatment, and patient and tumor characteristics.

CONCLUSIONS: Favorable survival was associated with higher socioeconomic status. Racial disparities in survival persisted after adjusting for individual-level socioeconomic factors and treatment for patients with breast and prostate cancer.