985 - How to Investigate a Cancer Cluster

Dec 10, 2025

Guest

Megan Latshaw

Guest

Suzanne Condon

Suzanne Condon, an environmental health expert and former associate commissioner at Massachusetts’ health department, and Megan Latshaw, a professor at Johns Hopkins, dive into the intricate world of cancer cluster investigations. They discuss the alarming case of Woburn, where contaminated water likely led to a spike in leukemia. The guests explain how unusual cancer patterns are detected, the importance of community involvement, and the challenges faced in pinpointing causes. They emphasize a proactive approach to health investigations despite the complexity of cancer causation.

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INSIGHT

Definition Matters: Clusters Versus Patterns

A cancer cluster is more cases of the same cancer in a place over time compared to expectation.
'Unusual patterns' broaden this to group cancers with shared causes rather than one type.

ADVICE

Start By Calculating Expected Cases

Calculate a standardized incidence ratio using cancer registry data to see if observed cases exceed expectations.
Use that finding to trigger deeper follow-up when excess cases appear.

ANECDOTE

Woburn Clinicians First Raised Alarm

In Woburn, clinicians flagged an unusually high number of childhood leukemia cases before the registry existed.
Community concern focused quickly on contaminated drinking water from local wells.

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About this episode:

In 1979, the town of Woburn, MA, raised the alarm as unusual numbers of children fell ill with leukemia. An investigation determined that this cancer cluster was likely caused by contaminated drinking water from two of the town's wells. In this episode: Suzanne Condon, who served as the associate commissioner of the Massachusetts Department of Health at the time, and Megan Latshaw, an expert in disease clusters, explain what the Woburn investigation highlights about unusual patterns of cancer and how they are studied.

Guests:

Suzanne Condon, MSM, is an environmental health expert who served as the associate commissioner of the Massachusetts Department of Health from 1980 to 2015.

Megan Latshaw, PhD, MHS, is a professor in Environmental Health and Engineering at the Johns Hopkins Bloomberg School of Public Health. She is also the co-instructor of an online course on disease clusters.

Host:

Dr. Josh Sharfstein is distinguished professor of the practice in Health Policy and Management, a pediatrician, and former secretary of Maryland's Health Department.

Show links and related content:

How The Post found growing rates of cancer in America's Corn Belt—Washington Post
Disease Clusters—Coursera
LEUKEMIA STRIKES A SMALL TOWN—New York Times
Childhood Leukemia in Woburn, Massachusetts—Public Health Reports

Transcript information:

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