Predicting risk for cancer years before the event

There is a lot of media hype about a paper just published in the online journal EBioScience. The paper suggests that it may, perhaps, be able to project risk for diagnosis of cancer (prostate cancer specifically included) as much as 13 years before the actual event.

According to this report in Genetic Engineering and Biotechnology News, the original article states that ability to project risk for a diagnosis of cancer may be dependent on critical shortening of blood cell telomere length. This may contribute to cancer initiation which then, in turn, activates telomere maintenance mechanisms to compensate and further promote cancer. Here is a link to the full text of the paper on the ScienceDirect web site

What we actually have here is an early stage hypothesis … that it is possible that there is some meaningful association between blood telemere length (BTL) and risk for diagnosis with at least some types of prostate cancer. And that it may be possible to develop a useful test to predict risk for some cancers based on BTL and other factors. However, we are going to need some answers to some important questions before we start to believe “all the news” about this finding that is “fit to print” (or put out over the Net). For example:

  • What is the positive predictive value of this finding? (How many people would a test of BTL tell us are going to get cancer who really do?)
  • What is the negative predictive value of this finding? (How many people would a test of BTL tell us are going to get cancer who then don’t?)
  • Are there specific cancers for which this test really is highly accurate — and others for which it is far less accurate?
  • In the case of prostate cancer particularly, what do we mean by “a diagnosis”? In other words, if this test were to tell you that you were at high risk for a really indolent form of prostate cancer, do you really want to know this?

This is another case of a scientific finding that is certainly interesting but doesn’t warrant the types of heading we are seeing in much of the media.

Here, for example, is a link one of the earlier media reports (which appeared in the Calgary Herald), and which begins:

A test that can predict with 100 per cent accuracy whether someone will develop cancer up to 13 years in the future has been devised by scientists.

It is very clear to anyone with even a limited degree of scientific training that this is absolutely not what Hou and his colleagues are saying in the published article. Alas, much media coverage of science and medicine is still in the Dark Ages when it comes to communicating actual facts!

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