Original article
Racial differences in colorectal cancer mortality: The importance of stage and socioeconomic status

https://doi.org/10.1016/S0895-4356(00)00316-4Get rights and content

Abstract

This investigation studies racial and socioeconomic differences in mortality from colorectal cancer, and how they vary by stage and age at diagnosis. Cox proportional hazards models were used to estimate the hazard ratio of dying from colorectal cancer, controlling for tumor characteristics and sociodemographic factors. Black adults had a greater risk of death from colorectal cancer, especially in early stages. The gender gap in mortality is wider among blacks than whites. Differences in tumor characteristics and socioeconomic factors each accounted for approximately one third of the excess risk of death among blacks. Effects of socioeconomic factors and race varied significantly by age. Higher stage-specific mortality rates and more advanced stage at diagnosis both contribute to the higher case-fatality rates from colorectal cancer among black adults, only some of which is due to socioeconomic differences. Socioeconomic and racial factors have their most significant effects in different age groups.

Introduction

Colorectal cancer is the second leading cause of death in the United States, accounting for more than 57,000 deaths in 1996 [1]. There are notable racial differences in both the incidence of and mortality from the disease [2]. According to recent data from the Surveillance, Epidemiology and End Results Program (SEER), the incidence rate is 13% higher for black males than for white males, and 27% higher among black females than among white females [3]. Despite a decreasing incidence and morbidity of colorectal cancer among whites since the 1980s, the rates for blacks have remained stable or even increased 2, 4.

Racial differences in mortality are even greater than those in incidence, with 27% and 38% higher age-adjusted death rates for black males and females compared with white males and females, respectively [5]. The higher mortality rate from colorectal cancer among black adults may be partially due to an advanced stage at diagnosis. A study of colorectal cancer in New York City revealed that although low socioeconomic status explained some of the excessive rates of late-stage diagnosis among blacks, black race remained an independent predictor of late-stage diagnosis [6]. The National Cancer Institute Black/White Cancer Survival Study (B/WCSS) [7] has detailed mortality differences between races for the period 1985 to 1986, prior to the widespread use of adjuvant chemotherapy. In our analysis, we present a more recent examination of racial differences in mortality when adjuvant chemotherapy was a much more common treatment modality [8].

We use survival models to estimate the effects of race and socioeconomic factors on colorectal cancer mortality for subjects from 1987 through 1993. We also investigate the extent to which stage at diagnosis affects the associations of race, gender, age, and socioeconomic factors with mortality, taking advantage of the large sample size to conduct stage-specific analyses without an appreciable loss of statistical power. We use data from the Pennsylvania State Tumor Registry and the 1990 U.S. Census of the Population to measure tumor-specific variables and socioeconomic factors.

Section snippets

Data

The data source for this study is the Expanded Cancer Incidence File from the Pennsylvania State Tumor Registry [9]. This file contains basic descriptors of tumor and demographic information for each diagnosed case, and is also linked to the state's death certificates to obtain the cause and date of death. The tumor registry is population based, and all Pennsylvania hospitals are required to report their incident cases to the registry. Additionally, there is a reciprocal agreement between

Results

Table 1 shows the distribution of cases by race and gender among the sociodemographic and tumor characteristics of each group. Age at diagnosis within each gender is greater for white than for black cases, with a mean difference of 2 years among males and 3 years among females (P < .0001). By every measure, black subjects were, on average, from communities with lower socioeconomic status than their white counterparts.

There are also racial differences in the stage at diagnosis and other tumor

Discussion

Analysis of data from a large population-based cancer registry in Pennsylvania reveals that black adults, especially men, have markedly higher fatality rates from colorectal cancer than do their white counterparts. Our findings reveal that racial discrepancies in mortality from colorectal cancer are due to both differences in the stage at presentation and in stage-specific mortality rates. We also show that the effect of socioeconomic status mediates some of this excess mortality. While earlier

Acknowledgements

Special thanks to Dona Schneider for supplying us with the census data and to Paul Speer and Mark Ontkush for the use of their programs enabling us to generate summary measures by minor civil division. Thanks to Gene Weinberg and the Pennsylvania Department of Health for making the Expanded Tumor Registry Data available for our analysis. Thanks to George Rhoads and Kitaw Demissee for their critical reading of the manuscript and to Susan Marcella for final editing assistance. Stephen Marcella

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