Cancer clusters the very idea sounds scary. But writing in Slate, science journalist George Johnson writes that there s very little evidence that they exist at all. Time after time, the clusters have turned out to be statistical illusions artifacts of chance.
The two that probably aren t, Johnson writes, are the Woburn, Mass., cluster made famous in A Civil Action, and a cluster in Toms River, N.J.: the subject of a new book by Dan Fagin, Toms River: A Story of Science and Salvation.
We re not talking about thousands of cancer cases unleashed in a town by industrial poisons. Or hundreds. Cancer clusters occur on a far smaller scale, Johnson writes. In the central part of Toms River, there were 14 childhood cancers during those years when between nine and 10 would have been expected. But however closely you analyzed the cases, it was extremely difficult and maybe impossible to distinguish the blips in the data from what could have occurred by chance. For the children and their parents these were not blips but tragedies. They naturally wanted an explanation. Something or someone to blame.
But was it, really? It s not clear, and we ll probably never know.
The article got a fascinating comment by How Risky Is It Really? author David Ropeik, who writes, I was an environmental reporter in Boston and covered the Woburn case from the very outset, before the phrase 'cancer cluster' even entered the wider public discussion. My expertise now is in the psychology of risk perception. We see the evidence through subjective emotional lenses, even when it is bright and clear, all the more so when it is cloudy and uncertain. As Dan has so well captured, and the Woburn experience did as well (although Harr's Civil Action really didn't), tragedy is a powerful lens.
He concluded with these evocative insights: The tools of statistics, so powerful when applied to large populations, break down with small numbers. As so often in life, we re left wondering how to distinguish between randomness and patterns too subtle to see.
ACSH s Dr. Elizabeth Whelan says that the article is fascinating, but notes the idea of cancer clusters shouldn t be dismissed entirely. For example, she adds, In a sense smokers with lung cancer represent a cancer cluster one that led to our understanding of the causal link between cigarette smoking and lung cancer.