This story was updated because an earlier version included inaccuracies.
People who live in Urbandale’s ZIP code 50323 have a breast cancer rate more than two times higher than Iowans who live in Fort Dodge’s ZIP code 50501.
That’s according to age-adjusted data from a new University of Iowa mapping tool that lets residents see how cancer patterns differ from one part of a city or region to another.
Cancer data available to Iowans has long been reported at the county level, so entire metro areas and rural communities were folded into a single county average. But the new tool, called Cancer Analytics & Maps for Small Areas, or CAMSA, uses statistical models rather than exact case counts to estimate rates at the ZIP-code level instead of relying only on typical county averages.
With county data, smaller communities get “aggregated” into broader numbers, and in rural places, public reporting can disappear entirely, said Jacob Oleson, a University of Iowa biostatistician who worked on the modeling.
“That means people in rural areas don’t get to see what their rates actually are,” Oleson said.
Caglar Koylu, a University of Iowa associate professor who worked on the mapping and visualization, said the underlying issue has been that confidentiality rules mask or withhold numbers when an area records fewer than 15 cases.
The model is designed to work around privacy limits while still providing a usable estimate and not revealing individual diagnoses.
“It never shows what the true rate is, but it estimates it based on the available data in that region and around that region to give a value that should be reasonably close without identifying individuals,” Koylu said.
The effort comes as Iowa ranks second nationally in age-adjusted cancer incidence and is one of only two states where new diagnoses are still rising. State researchers estimated about 2,582 more adult cancer cases occurred in 2022 than would be expected if Iowa followed national averages.
CAMSA reveals some stark differences in some cases. For colorectal cancer, for example, the age-adjusted rate in one Sioux City ZIP code, 51106, is about 50% higher than in Iowa City ZIP code 52245.
Does cancer look the same everywhere in Iowa?
Both researchers said the tool shows cancer is not evenly distributed across the state and does not follow a single pattern.
“When you switch the cancer, the geographic pattern changes, which tells us that each cancer has its own drivers behind the scenes,” Oleson said.
Colorectal cancer clusters more heavily in northwestern Iowa and around the Des Moines metro, showing higher rates and risk probabilities.
Breast cancer shows a different scenario, with higher concentrations of cases and increased risk appearing more often around Iowa’s larger metropolitan areas than in most rural ZIP codes.
“For breast cancer specifically, you see the oranges, the larger age-adjusted rates, are in the cities,” Oleson said. “Part of that comes from the known risk factor that women who have children later in life have a higher risk of breast cancer.”
Cervical cancer shifts the picture again, with more cases and increased risk appearing mainly in southern and southwestern Iowa.
Oleson said the reasons behind those patterns are not yet clear.
“We don’t know the answer to that. We see cervical cancer is higher in the south, but it is also a much less prevalent cancer, and we would need to look at what drivers might be in those regions,” he said.
Separate statewide research led by the University of Iowa College of Public Health and the Iowa Department of Health and Human Services showed that Iowa’s most common cancers were breast, prostate, melanoma, lung and colorectal.
That analysis found the state’s elevated ranking is largely driven by early-stage diagnoses in most categories, while lung cancer shows comparatively higher late-stage incidence.
How do ZIP codes differ from each other?
Switching from counties to ZIP codes shows differences within the same city, not just across the state, the researchers said.
“There are multiple ZIP codes within each city, and we can see that rates can change drastically from one city ZIP code to the next,” Oleson said.
Within Des Moines, the contrast is especially visible: 50310 on the city’s northwest side ranks as the seventh-lowest colorectal cancer incidence ZIP code in Iowa, while 50309 in the downtown core ranks 32nd out of more than 1,000 statewide ZIP codes.
Effectively, downtown’s age-adjusted rate of colorectal cancer is about 30% higher than northwest Des Moines.
Similar disparities also apply outside metro areas. Koylu said the added detail can make it easier to notice localized cancer concentrations, including areas near bodies of water, plants or factories.
County-level analyses from the Iowa Department of Health and Human Services and University of Iowa researchers had already underscored the uneven distribution across the state, with 13 counties posting higher-than-expected overall adult cancer incidence.
Those same preliminary findings tie some regional differences to behavioral and environmental factors, including higher smoking and binge-drinking rates, obesity, and low vegetable consumption.
Officials also reported that several higher-incidence counties could not be fully explained by demographics or lifestyle patterns, indicating other local influences, such as environmental conditions, may also contribute.
Oleson said the detail from the CAMSA map could be key to understanding those factors.
Both researchers said the map is meant to show location patterns, not causes.
“There is no why of the drivers behind the work shown here, but we can use the information to start asking that question,” Oleson said.
Koylu described the project as a public platform rather than a conclusion.
He said the map can guide decisions about where to focus resources, noting the tool is already being used by cancer registries in Kentucky and New Mexico. He said he hopes to see it adopted nationwide.
Where colorectal and breast cancer rates are highest and lowest in Iowa
For colorectal cancer, CAMSA shows the lowest estimated incidence rates clustered largely in eastern and central Iowa, with several mid-size cities and suburbs appearing near the bottom of the statewide list. The estimated rates are about 35 to 38 cases per 100,000 people.
Lowest modeled colorectal cancer incidence ZIP codes:
Several northwest Iowa communities and fast-growing metro suburbs appear more frequently, with multiple Sioux City ZIP codes landing in the top tier. The estimated rates are about 55 to 51 cases per 100,000 people.
Highest modeled colorectal cancer incidence ZIP codes:
For female breast cancer, the lowest modeled incidence rates are concentrated mostly in smaller southwest and northwest Iowa communities, many of them rural or lower-density ZIP codes. Estimated rates are about 93 to 101 cases per 100,000 people.
Lowest modeled female breast cancer incidence ZIP codes:
The highest modeled female breast cancer rates, by contrast, are dominated by suburban ZIP codes in the Des Moines and Iowa City metro areas, with several of the state’s fastest-growing communities appearing near the top. Estimated rates are about 219 to 278 cases per 100,000 people.
Highest modeled female breast cancer incidence ZIP codes:
Nick El Hajj is a reporter at the Register. He can be reached at nelhajj@gannett.com. Follow him on X at @nick_el_hajj.
An earlier version of this article incorrectly described modeled “risk probability” values as differences in cancer risk between ZIP codes, when in fact the CAMSA tool uses those values to reflect the probability that a ZIP code’s rate is higher than the state average.
This article originally appeared on Des Moines Register: New Iowa tool maps cancer rates by ZIP code, revealing hidden patterns
Reporting by Nick El Hajj, Des Moines Register / Des Moines Register
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