Effects of socioeconomic status and treatment disparities in colorectal cancer survival

Background: Poor survival among colorectal cancer (CRC) cases has been associated with African-American race and low socioeconomic status (SES). However, it is not known whether the observed poor survival of African-American CRC cases is due to SES itself and/or treatment disparities. We set out to determine this using data from the large, population-based California Cancer Registry database. Methods: A case-only analysis of CRC was conducted including all age groups using California Cancer Registry data from 1994 to 2003, including descriptive analysis of relevant clinical variables, race, and SES. CRC-specific survival univariate analyses were conducted using the Kaplan-Meier method. Multivariate survival analyses were done using Cox proportional hazards ratios (HR). Results: Incident cases of colon (90,273) and rectal (37,532) cancer were analyzed, including 91,739 (71.8%) non-Hispanic Whites, 8,535 (6.7%) African-Americans, 14,943 (11.7%) Hispanics, 3,564 (2.8%) Chinese, and 7,950 (6.2%) non-Chinese Asians. African-Ameri cans had a greater proportion of metastatic stage at presentation (P < 0.0001) and decreased CRC-specific survival (P < 0.0001 for colon and rectal cancer). After adjustment for age, sex, histology, site within the colon, and stage, African-Americans [colon: HR, 1.19; 95% confidence interval (95% CI), 1.14-1.25; rectum: HR, 1.27; 95% Cl, 1.17-1.38] had an increased risk of death compared with Caucasians. However, after further adjustment for SES and treatment, the risk of death for African-Americans compared with Caucasians was substantially diminished (colon: HR, 1.08; 95% CI, 1.03-1.13; rectum: HR, 1.11; 95% CI, 1.02-1.20). Conclusion: Among CRC cases, disparities in treatment and SES largely explain the observed decreased survival of African-Americans, underscoring the importance of health disparity research in this disease.