Effect Modification of the Association Between Race and Stage at Colorectal Cancer Diagnosis by Socioeconomic Status.

OBJECTIVES

To compare risks of distant-stage colorectal cancer (CRC) diagnosis between whites and American Indian/Alaska Natives (AI/ANs) and to explore effect modification by area-based socioeconomic status (SES).

DESIGN

Retrospective cohort study using data from the Oklahoma Central Cancer Registry.

SETTING

Oklahoma.

PARTICIPANTS

White and AI/AN cases of CRC diagnosed in Oklahoma between 2001 and 2008 (N = 8 438). A subanalysis was performed on the cohort of those aged 50 years and older (N = 7 728).

MAIN OUTCOME MEASURE

Risk of distant-stage CRC diagnosis stratified by SES score.

RESULTS

Race and SES were independently associated with distant-stage diagnosis. In SES-stratified analyses, AI/ANs in the 2 lowest SES groups experienced increased risks in the overall cohort and among those aged 50 years and older. In multivariable models, risks remained significant among those aged 50 years and older in the lowest SES groups (Adjusted risk ratio SES score of 2: 1.31, 95% confidence interval: 1.06-1.63 and adjusted risk ratio SES score of 1: 1.21, 95% confidence interval: 1.01-1.44).

CONCLUSION

Socioeconomic status is an effect modifier in the association between race/ethnicity and stage at CRC diagnosis. Disparities in stage at CRC diagnosis exist between AI/ANs and whites with lower estimated SES. Efforts are needed to increase CRC screening among lower SES AI/ANs.