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Cancer in Iowa: Iowa is changing the way it looks for cancer clusters
Community cluster probes ‘have not been successful,’ a study notes
- The Iowa Cancer Registry has investigated 150 cases of suspected cancer clusters since 1994.
- Only one investigation, near Wellman, resulted in a confirmed cluster finding.
- Researchers now want to reverse the process by identifying locations with known contamination and studying cancer rates nearby.
- The CDC has new cancer cluster guidelines that recommend tracking communities to see if disease develops over time.
This story is part of a four-part series on cancer in Iowa that began last Sunday, March 24, and concludes today. Find all of the stories at thegazette.com/cancer-in-iowa.
HUDSON — Thirteen teachers with breast cancer from a small Northeast Iowa school district seemed more than unlucky. It seemed suspicious.
As Diane Anderson, a retired junior high English teacher at the Hudson Community School District, was doing chemotherapy to fight triple negative metaplastic breast cancer in 2021, she talked with a former colleague who also had breast cancer. They started counting up current and former Hudson staff with breast cancer and eventually reached 13.
“I know cancer is common, unfortunately,” said Anderson, 68, of Cedar Falls. “But this is a really small district. I was teaching with a staff of about 65 people. It kind of started scaring me.”
Anderson asked the Iowa Cancer Registry at the University of Iowa to investigate whether the Hudson school district was a cancer cluster — defined as a greater-than-expected number of cancer cases among a group of people in a defined geographic area, like a neighborhood, town or workplace over a period of time.
The Hudson probe is one of 150 cluster investigations the Registry has done since 1994. Only one of those investigations ended with a confirmed cancer cluster and, in that case, researchers couldn’t find anything in the environment that caused the cancer.
That doesn’t necessarily mean toxic exposures didn’t cause cancer, but “to have a true finding, you'd have to rule out the role of chance,” said Charles Lynch, who led the Registry from 1990 to 2020, before he retired. “With small numbers, you'd need to have huge differences between the target area and your control area. The likelihood of that happening was very rare.”
“Instead of relying on concerned citizens to come to us, can we start to systematically look for potential clusters of cancer beyond what we would expect and then work with different groups to say ‘Is there something in that community?’,”
The Cancer Registry is expanding the way staff investigate whether the environment — air, water, chemicals in a workplace — might be causing cancer. In a reversal of the traditional process, public health researchers will start with a location with known contamination and see if people are sick nearby.
“Instead of relying on concerned citizens to come to us, can we start to systematically look for potential clusters of cancer beyond what we would expect and then work with different groups to say ‘Is there something in that community?’,” said Mary Charlton, a UI epidemiology professor and Registry director.
A confirmed cluster
Travis Juilfs was a high school senior at Mid-Prairie High School when he started getting headaches.
“In 1996 — 18, young and dumb — my focus was ‘How quickly can I get back on the football team?’” said Juilfs, 45, who now lives in Texas. ”I'm not sure at that age you understand your mortality.“
Doctors at the UI Hospitals and Clinics determined Juilfs had a brain tumor, pilocytic astrocytoma, that was cancerous, but not malignant. Still, the tumor had to come out and brain surgery is no small procedure — especially for a teenager.
“In 1996 — 18, young and dumb — my focus was ‘How quickly can I get back on the football team? I'm not sure at that age you understand your mortality.”
“Once the realization hit I wasn't going to be playing football, I wouldn’t be allowed to wrestle, even though I wasn't at risk for having to go through the treatment, it was pretty earth shattering at that point,” he said.
Juilfs was one of at least 10 people living in rural southeast Iowa, between Wellman and Kalona, diagnosed with brain tumors in the mid-1990s. The list also included a 16-year-old boy, a 28-year-old farmer, a 50-year-old prison worker and a 66-year old farm wife, according to a 1998 Gazette story.
This grouping of similar cases in a small geographic area is Iowa’s only confirmed cancer cluster in 30 years of investigations.
Lynch and former State Epidemiologist Patricia Quinlisk called in the U.S. Centers for Disease Control and Prevention (CDC) to help survey the people near Wellman who had cancer. They also recruited dozens of others in the community to complete surveys as a control group.
The goal was to figure out if there were common exposures or other environmental risks nearby.
“We looked at pretty much everything that was suspected at that time concerning causation of brain cancer,” Lynch said, including radiation exposure and chemicals in drinking water. They never identified a cause of the tumors.
Are traditional cancer cluster investigations worthwhile?
The lack of answers in the Wellman probe mirror national findings about traditional cancer cluster investigations.
In a 2012 study, researchers reviewed 428 investigations of 567 cancers of concern and found only 72 (13 percent) showed an increased incidence of cancer over control groups. Three cluster investigations were linked to exposures and only one revealed a clear cause.
“It is fair to state that extensive efforts to find causes of community cancer clusters have not been successful,” the study authors noted. “There are fundamental shortcomings to our current methods of investigating community cancer clusters.”
Even though cluster probes often end without definitive results, Lynch thinks they are beneficial.
“I knew from experience that if you didn't respond to a concern like this, as time went on … people felt like you were covering up,” Lynch said.
No matter the results, the Cancer Registry puts together a report they provide to the person or group asking for the probe. Public health researchers share cancer statistics for the general population, which often are on par with cases in the alleged cluster. They also will report on how risk factors — such as smoking or obesity — can ratchet up cancer incidence and how genetics may play a role.
“We were able to discuss it with the person and give them our knowledge of cancer and that was satisfying to them,” Lynch said.
With the Hudson investigation — which ended in December 2022 without a finding of a cancer cluster — researchers were able to share statistics showing college-educated women have a higher rate of breast cancer because they wait longer, on average, to have children.
Employers often don’t want to help with workforce probes
Public health researchers investigating possible cancer clusters also can run into roadblocks, such as employers not wanting to participate in a review of potential workplace exposures.
“It's really hard to do one where you rely on personnel records,” said Michele West, an associate research scientist who has conducted cancer cluster investigations for the Cancer Registry since the 1990s. “We've tried to do others in the past and it's just been a flat out 'no'. The administration is just unwilling to release those records.”
The Hudson investigation is the first West remembers in which district leaders agreed to release limited information about current and former staff so researchers could attempt to find out about cancer diagnoses and potential exposures. But the level of detail the district provided wasn’t enough to verify specific people in the Registry.
“It was requested that we provide Social Security numbers, middle initials, home addresses, and dates of birth for more than 1,300 employees (past and present), without their consent,” Superintendent Anthony Voss said in an email to The Gazette. “We did not feel comfortable sharing all of this personal data with an outside agency.”
Anderson, who now is in remission, thinks the investigation could have gone further if the district had provided more information. But she appreciates the Registry’s work. “I'm just so thankful for Dr. West and Dr. Charlton, their communication was so good.”
New approach
Cancer researchers are looking for new ways to study environmental risks in Iowa — which has the nation’s fastest-growing cancer rate.
Camanche, a city of about 4,500 in Clinton County, last year switched to a backup well after learning the well where they had been drawing drinking water was contaminated with per- and polyfluoroalkyl substances (PFAS). These chemicals, linked to thyroid cancer, were manufactured for years at the 3M plant in Cordova, Ill., just upstream of Camanche.
The Cancer Registry is working with the UI Center for Health Effects of Environmental Contamination to develop a list of places that should be studied for greater incidence of cancer nearby.
“The best thing we can do is set up a monitoring system to start watching for signals in places like Camanche to see if they start to have higher rates or distributions of certain types of cancers,” Charlton said.
An early test of this new approach happened at the site of the former Chamberlain Manufacturing plant, a Waterloo factory where workers made ammunition in previous decades. Government tests showed heavy metals and other contaminants in the soil.
“It was brought to my attention as a concern of an environmental exposure,” West said. Waterloo residents had “concern that they (plant owners or managers) might have buried radioactive waste, and/or been dumping waste into the river.”
Because cancer is a reportable disease, Registry officials were able to look at cancer rates in the geographic area around the Chamberlain site. They found an excess of prostate cancer in men in the target area but determined it was not a cluster linked to the former industrial site.
Sometimes cancer doesn’t show up years, or even decades, after the exposure.
The CDC put out new guidelines in 2022 for cancer cluster investigations. Now the agency recommends epidemiologists look for people with related cancers, not necessarily the exact same kind. The CDC also recommends routine monitoring of past clusters to see if new related cancers develop.
The Registry now puts some cluster sites on a schedule to look at newly reported cancers in the future.
Support Iowans fighting cancer
Diane Anderson, a Cedar Falls breast cancer survivor, started the Accessing Cancer Treatment (ACT) Fund, which helps under-resourced Iowans access early cancer screenings and cancer treatment at service providers in Eastern Iowa. The fund can help with copays, transportation or other costs that might keep a patient from seeking care.
You can donate online or by mailing a check to 114 E. Fourth St., Suite, 300, Waterloo, Iowa, 50703. Please include ACT in the memo line.
Comments: (319) 339-3157; erin.jordan@thegazette.com
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