Urbanization and Breast Cancer Incidence in North Carolina, 1995–1999
Introduction
Female breast cancer incidence rates have been reported to be higher in urban areas compared with rural areas in the United States since 1955. Past studies have found urban elevations with relative risks ranging from 1.06 to 1.83 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16. Only one estimate showed higher rates in rural areas, among African-Americans only (6). The urban excess has also been observed among males with breast cancer (17) and among females in Canada (18), European countries 17, 19, 20, 21, 22, 23, 24, Costa Rica (25), and Japan (17).
Higher rates in urban areas such as Long Island, New York, have been used as a justification for studying environmental pollution as a cause of breast cancer (26). Higher urban incidence may be the result of exposures, behaviors, or reproductive patterns more common in urban areas that elevate risk. However, higher rates in urban areas could arise from differential ascertainment due to higher rates of detection in urban areas, and consequently, higher reported incidence.
Quality of reporting has been considered as an explanation for the urban excess of breast cancer in six studies 1, 2, 3, 10, 11, 12. Most found that quality in rural areas was poorer by their indicator (percent of incident cases found by review of death certificates) 1, 2, 3, 10, 12. One study noted a potential reporting bias by “registry hospital,” noting that larger hospitals reported more completely, but did not conclude that this bias explained the urban excess (5). In a 1995 study, American hospitals with the largest cancer caseloads were found to more completely report their cases to the Surveillance, Epidemiology, and End Results (SEER) Program than hospitals with smaller cancer caseloads. Also, the percentage of cases missed and unreported to SEER was lower for hospital cancer registries compared with case-finding by the central cancer registry for the SEER region (27).
In North Carolina, a greater proportion of urban than rural hospitals are certified by the American College of Surgeons' (ACOS) Commission on Cancer as “Approved Cancer Programs.” Such hospitals are required to have an in-house cancer registry (28). Our study was undertaken to investigate whether breast cancer incidence rates in urban areas were higher than in rural areas in North Carolina (NC), measuring urbanization using a standardized, non-dichotomous scale that accounts for adjacency with Metropolitan Areas (29). We hypothesized that the presence of a hospital approved by the ACOS' Commission on Cancer in a county would also be related to higher incidence, possibly due to greater detection, more complete case-finding, or more complete case reporting.
Section snippets
Materials and Methods
We conducted an ecologic study of female breast cancer incidence in the state of North Carolina, using county as the unit of analysis. Our study was approved by the Institutional Review Board of the School of Public Health at the University of North Carolina at Chapel Hill. We used incident case count data supplied by the North Carolina Central Cancer Registry; incident cases were North Carolina resident women with a first case of invasive or in situ breast cancer diagnosed between January 1995
Incidence Rates
For the state of North Carolina, the rate of average annual age-adjusted in situ breast cancer incidence for 1995 to 1999 was 22.5 per 100,000 for white women and 18.2 per 100,000 for non-white women. For invasive breast cancer, incidence rates were 118.2 and 104.6 for whites and non-whites, respectively. Considering rates by urbanization level, stage, and race, the highest rates among white women for in situ breast cancer were in the two most urban categories and the lowest rates were observed
Discussion
We conducted an ecologic study to determine if an urban excess of breast cancer incidence was present in North Carolina for our study years, and, if so, to consider the role of hospital characteristics as a potential explanation. We found that greater urbanization, as represented by the grouped UIC, was related to higher in situ breast cancer incidence in white and non-white women and higher invasive incidence among white women but not non-white. Both invasive and in situ breast cancer
References (45)
- et al.
Urban-rural variation in cancer incidence in Denmark 1943-1987
Eur J Cancer
(1993) - et al.
Cancer in Connecticut, 1935-1951
(1956) - et al.
Cancer Morbidity in Urban and Rural Iowa
(1956) - et al.
Cancer incidence in urban and rural areas of New York State
J Natl Cancer Inst
(1960) - et al.
Rural v. urban aspects of cancer: First-year data from the Mississippi Central Cancer Registry
Fam Community Health
(2001) - et al.
Relation between population density and cancer incidence, Illinois, 1986-1990
Am J Epidemiol
(1993) Cancer incidence and mortality in urban versus rural areas of Texas, 1980 through 1985
Tex Med
(1996)- et al.
Urban-rural differential in breast cancer incidence and mortality in Olmsted County, Minnesota, 1935-1974
Int J Epidemiol
(1980) - et al.
Cancer in Utah: Risk by religion and place of residence
J Natl Cancer Inst
(1980) - et al.
Nutrition and age at first birth in breast-cancer risk
Br J Cancer
(1980)
Population density and cancer incidence differentials in New York State, 1978-82
Cancer Causes Control
Population density as an indicator of urban-rural differences in cancer incidence, upstate New York, 1968-1972
Am J Epidemiol
Cancer incidence rates among blacks in urban and rural Georgia, 1978-82
Am J Public Health
Cancer in south Louisiana. Part III: Cancers of the breast and the reproductive system
J La State Med Soc
Evaluating local differences in breast cancer incidence rates: A census-based methodology (United States)
Cancer Causes Control
Geographic differences in invasive and in situ breast cancer incidence according to precise geographic coordinates, Connecticut, 1991-95
Int J Cancer
Cancer incidence among predominantly black, rural-poor populations in southern states
South Med J
Comparison of urban and rural incidence data
Population density as an indicator of urban-rural differences in cancer incidence, Alberta, Canada, 1969–73
Can J Public Health
Comparison of age-adjusted cancer incidence rates in Denmark and the United States
J Natl Cancer Inst
Trends in incidence of various cancers in Bulgaria, 1981-1990
Int J Epidemiol
Urban-rural differences in cancer incidence in The Netherlands 1989-1991
Int J Epidemiol
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This work was supported by UNC's Lineberger Comprehensive Cancer Center Pre-Doctoral Fellowship, and a Dissertation Completion Fellowship from the Graduate School at UNC-Chapel Hill.