Examining the Association Between Socioeconomic Status and Invasive Colorectal Cancer Incidence and Mortality in California

Abstract

Background Colorectal cancer (CRC) incidence and mortality rates vary across race/ethnicity. Socioeconomic status (SES) also influences CRC rates; however, these associations might be inconsistent across racial/ethnic groups and tumor subsite. We examined associations between area-level SES and CRC incidence and mortality in a population-based registry study of non-Hispanic Whites, African Americans, Hispanics, and Asians/Pacific Islanders from California. Methods Data on 52,608 incident CRC cases (1998–2002) and 14,515 CRC deaths (1999–2001) aged ≥50 years were obtained from the California Cancer Registry. Based on 2000 U.S. Census data, each cancer case and death was assigned a multidimensional census tract-level SES index. SES-specific quintiles of CRC incidence and mortality rates, incidence rate ratios (IRR) and mortality rate ratios, and 95% confidence intervals (CI) were estimated. Analyses were stratified by anatomical site, including left- versus right-sided tumors, race/ethnicity, and stage of disease. Results Overall CRC incidence and SES did not show a clear association, yet patterns of associations varied across tumor subsite and race/ethnicity. Positive associations between SES and CRC incidence were found in Hispanics [SES Q5 v. Q1: IRR = 1.54, CI = 1.39–1.69], irrespective of the subsite. For Whites [SES Q5 v. Q1: IRR = 0.80, CI = 0.77–0.83], and African Americans [SES Q5 v. Q1: IRR = 0.83, CI = 0.70–0.97] inverse associations were observed, predominantly for left-sided tumors. Mortality rates declined with increasing SES in Whites, whereas in Hispanics mortality rates significantly increased with SES. Conclusions Our findings show that SES differences in CRC incidence and mortality vary considerably across anatomical subsite and race/ethnicity. Impact Studies combining area- and individual-level SES information are warranted.

Correction of misclassification bias induced by the residential mobility in studies examining the link between socioeconomic environment and cancer incidence

“…In aggregated studies measuring the link between socioeconomic status and cancer incidence, biased relative risks may result from measuring the social environment of individuals at the time of diagnosis and disregarding that environment in the past [4][5][6][7][8]. To investigate this type of bias, we adopted the methodology proposed by Veierod and Laake [16] and used census data to estimate the probabilities of misclassification.…”

“…The main limitation with such an approach is that in the vast majority of studies based on cancer registries, the address used to assess the patient's environment is that at the time of diagnosis; patients may have lived in another or several other places in the years before the diagnosis was made [4][5][6][7][8]. Indeed, the social environment considered in those studies is that at the time of cancer diagnosis.…”

Associations of Census-Tract Poverty with Subsite-Specific Colorectal Cancer Incidence Rates and Stage of Disease at Diagnosis in the United States

“…This inconsistency may be due to the different study time periods, the use of a different SES measure or regional differences in the API study populations in regard to ethnicity, nativity, primary language spoken, SES, and level of acculturation, which may influence attitudes toward preventive screening and affect CRC risk [12]. The API subgroups included in both studies were extremely different.…”

Randomized trial to increase colorectal cancer screening in an ethnically diverse sample of first‐degree relatives

“…Incidence rates are highest among African Americans followed by American Indians/Alaskan Natives, Whites, Latinos and Asians 3 . Outcomes such as age and stage at diagnosis, survival, and mortality tend to be poorer among minorities 4 , and are partially attributable to differences in socioeconomic factors 5 . However, the literature consistently documents the persistence of racial disparities in CRC outcomes even after controlling for socioeconomic factors and access 6 .…”