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No Evidence of Cancer Cluster in Poolesville by Meghan Tierney, Montgomery Gazette | Health

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No Evidence of Cancer Cluster in Poolesville by Meghan Tierney, Montgomery Gazette
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An expanded look at cancer cases in Poolesville has found no evidence of unusual patterns or frequencies.

Officials with Montgomery County's Department of Health and Human Services and the Maryland Department of Health and Mental Hygiene presented their final report from a joint investigation into a suspected cancer cluster in Poolesville at Monday night's commissioners meeting.

A cancer cluster is defined as a greater than expected number of cases of similar cancers occurring in a short period of time among people who live or work near each other.

The study began in December 2008 after county health officials were contacted by a town resident concerned about the town's water quality. The U.S. Centers for Disease Control and Prevention assisted with the study during the first six months at the departments' request.

Preliminary results based on a review of cancer cases in Maryland from 1992-2003 and presented to the town in July 2009 showed no evidence of a cancer cluster. The final report incorporates recently released Maryland Cancer Registry data from 2004-2006 and reaches the same conclusion.

"It's a much more robust, conclusive analysis," said Dr. Clifford Mitchell, the state's director of environmental health coordination.

State and county health officials expect to report back to the town in summer 2012 when cancer data from 2007-2009 is available, as recommended by the CDC, county health officer Dr. Ulder Tillman said.

The study compared cancer cases in the registry for individuals living in Poolesville or the 20837 ZIP code when they were diagnosed and found that the overall number and pattern of cancer cases within Poolesville are not significantly different from the pattern and number of cases in Montgomery County and Maryland as a whole.

The study found no obvious patterns based on age, year of diagnosis, sex, race or geographic clustering.

The study was limited by the small population of municipal and non-municipal Poolesville, about 6,000 people, and the complexities of assessing the impacts of environmental health factors.

"[T]he number of any specific type of cancer in the Poolesville population is too small to analyze or detect trends, even aggregated over a long period of time," the report states.

There were 319 cancer cases in Poolesville reported to the registry from 1992 to 2007, according to the report. The most common types of cancer in Poolesville — female breast, prostate, lung and bronchus and colon and rectum cancers — were the same as in the state as a whole.

A comparison of cancer cases in Poolesville by age group to the county and the state found no significant difference in all but one instance. There were 39 cancer cases among people ages 60 to 64 compared with the 26 cases that would be expected if Poolesville were similar to the county as a whole, a statistically significant difference.

When performing a large number of statistical tests, it is not unusual for one or two outliers to occur by chance alone, Mitchell said. Some outliers can be significant, for instance, if the number of cancer cases in children is higher than expected, he said.

"I would've been surprised if they were all the same," Mitchell said.

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