The American Cancer Society says that in order to meet the definition of a cancer cluster, occurrences must be the same type, in the same area, with the same cause, and affecting a number of people that's "greater than expected" when a baseline for occurrences is established.
“Nearly 4 out of 10 people in the United States will develop cancer during their lifetimes," the society said on its cancer clusters webpage. "So, it’s not uncommon for several people in a relatively small area to develop cancer around the same time."
The unstated numbers that matter here are many, how many people were thoroughly investigated here, was it the entire staff of the hospital (as many as a thousand, perhaps)? When X many people are thoroughly scanned how common is it for five people to have benign cancers that aren't doing anything, aren't growing, are just there?
If (for example) twenty percent of the time 500 people were scanned, five at least had benign brain cancers, would this report be unusual or suspicious in itself?
That seems circular, like it's not a cancer cluster until we find out that it's a cancer cluster, or it's not a cancer cluster because we didn't determine a common cause, so don't worry too much about there maybe being a common cause that would make it count as a cancer cluster.
This underlines how stats are no substitute for reasoning about mechanisms.
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The article closes with that note.
The unstated numbers that matter here are many, how many people were thoroughly investigated here, was it the entire staff of the hospital (as many as a thousand, perhaps)? When X many people are thoroughly scanned how common is it for five people to have benign cancers that aren't doing anything, aren't growing, are just there?If (for example) twenty percent of the time 500 people were scanned, five at least had benign brain cancers, would this report be unusual or suspicious in itself?
Right but five people all getting brain cancer is certainly more suspicious than five people getting any cancer.
That seems circular, like it's not a cancer cluster until we find out that it's a cancer cluster, or it's not a cancer cluster because we didn't determine a common cause, so don't worry too much about there maybe being a common cause that would make it count as a cancer cluster.
This underlines how stats are no substitute for reasoning about mechanisms.
You know, if a bunch of nurses got their heads exposed to a radiation burst in an event, would they all get the same type of cancer? Probably not.
It seems unlikely all 5 would only have their heads exposed. It seems it would be more likely they might develop various other cancers.