Mapping cancer mortality-to-incidence ratios to illustrate racial and sex disparities in a high-risk population

Abstract

Background: Comparisons of incidence and mortality rates are the metrics used most commonly to define cancer-related racial disparities. In the US, and particularly in South Carolina, these largely disfavor African Americans (AAs). Computed from readily available data sources, the mortality-to-incidence rate ratio (MIR) provides a population-based indicator of survival.

Methods: South Carolina Central Cancer Registry incidence data and Vital Registry death data were used to construct MIRs. ArcGIS 9.2 mapping software was used to map cancer MIRs by sex and race for 8 Health Regions within South Carolina for all cancers combined and for breast, cervical, colorectal, lung, oral, and prostate cancers.

Results: Racial differences in cancer MIRs were observed for both sexes for all cancers combined and for most individual sites. The largest racial differences were observed for female breast, prostate, and oral cancers, and AAs had MIRs nearly twice those of European Americans (EAs).

Conclusions: Comparing and mapping race- and sex-specific cancer MIRs provides a powerful way to observe the scope of the cancer problem. By using these methods, in the current study, AAs had much higher cancer MIRs compared with EAs for most cancer sites in nearly all regions of South Carolina. Future work must be directed at explaining and addressing the underlying differences in cancer outcomes by region and race. MIR mapping allows for pinpointing areas where future research has the greatest likelihood of identifying the causes of large, persistent, cancer-related disparities. Other regions with access to high-quality data may find it useful to compare MIRs and conduct MIR mapping.

FIGURE 1

Population centers shown in geographic context. AA indicates African American.

FIGURE 2

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for all cancers combined in (A) males and (B) females. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 3

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for colorectal cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 4

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for oral cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 5

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for female breast cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 6

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for cervical cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 7

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for prostate cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.

FIGURE 8

Mortality-to-incidence (M:I) rate ratios by South Carolina Department of Health and Environmental Control (SC DHEC) Health Region for lung cancer. CDC indicates Centers for Disease Control and Prevention; ACS, American Cancer Society; PHSIS, Public Health Statistics and Information Services; C.M.M., Center for Medicare and Medicaid Services.