No cancer cluster in county, but CDC urges long-term analysis

A federal review of the number and causes of childhood cancer cases in Johnson County in recent years has confirmed that no cancer cluster exists.

The Centers for Disease Control and Prevention said that the evidence so far does not support further investigation into a suspected cancer cluster, but is suggesting that the Indiana State Department of Health take further steps if the contamination investigations underway find evidence the public has been exposed to chemical contaminants that are potential risk factors for pediatric cancer.

The cancer cluster study review and findings by the National Center for Environmental Health, a division of the U.S. Department of Health and Human Services, was initiated this summer. The review was requested by the Indiana State Department of Health due to the ongoing concern from residents about a higher-than-normal number of childhood cancers in Johnson County since 2010, according to a letter from Erik R. Svendsen, director of the Division of Environmental Health Science and Practice for the National Center for Environmental Health.

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The issue of whether Johnson County has a cancer cluster has been raised for years. If It Was Your Child formed in 2015 after a group of area parents whose children had been diagnosed with cancer vowed to find causes for the county’s high incidences of childhood cancers. The latest National Cancer Institute data shows that the age-adjusted cancer incidence rate for children under 20 in Johnson County is 22.2, is higher than the state average of 17.3.

Since 2010, the county has reported 48 cases of childhood cancer. Of that number, 28 cases of blood cancers such as leukemia and lymphoma have been reported.

The state updated its cancer cluster study in June 2017 with data from 2000 to 2015, the most recent available, and found no evidence of a cancer cluster, according to a state department of health report. The number of childhood cancer cases was 123 during that 15-year period, compared to an expected number of 113, which was not statistically significant, the report said. The state continues to monitor the data, the report said.

If It Was Your Child has been advocating for Johnson County to be declared a cancer cluster. The group also wants the CDC’s guidelines to be updated as to what determines whether a cancer cluster exists, such as considering similar cancers together.

The Indiana Department of Environmental Management and the U.S. Environmental Protection Agency are conducting multiple investigations at sites across Franklin. Higher-than-allowed levels of contaminants have been found in the sewer backfill, or dirt and gravel along buried sewer pipes, leading from the former Amphenol facility in Franklin.

The CDC is recommending that if the contamination investigations find “evidence of community exposure to chemical contaminants that are potential risk factors for pediatric cancer, that ISDH compare incidence data for those specific pediatric cancer types,” according to the letter sent to Dr. Melissa Collier, chief medical officer of the Indiana State Department of Health on Nov. 16.

The agency is recommending that the state consider using more specific geographic boundaries that more closely align with known or likely routes of exposure to contaminants. The state should also review longer term historical trends in pediatric cancer incidence rates to determine whether local and state cancer rates are increasing or decreasing over time.

A third recommendation from the CDC is for the state department of health to continue to monitor the Indiana cancer registry data for new cases of pediatric cancer among Johnson County residents and update the incidence rates with new data as it becomes available, the letter said.

In 2015, the Indiana State Department of Health conducted two investigations into potential cancer clusters in Johnson County. The first was a normal review that the department conducts for all counties, and the second was requested by the county health department due to concerns from citizens, including those who formed If It Was Your Child.

That review found that the number, type and location of childhood cancer cases here do not meet the guidelines for a cancer cluster, which is defined as having a more than expected number of cancer cases for a certain population.

The state updated its findings in a 2017 report.

The federal agency reviewed both the findings by the state department of health, and the approach the state investigation took, the letter said.

The agency defines a cancer cluster as “a greater than expected number of cancer cases that occurs within a group of people in a geographic area over a defined period of time.”

That means that the cancer cases have to be linked by more than being a childhood case or a common childhood cancer, the letter said, because “different cancer types included in these categories are not known to be related to one another and are unlikely to share a common, environmental etiology,” the letter said.