Biology in the News Explained

More evidence that more screening = more cancer

Is prostate cancer common in families?  It has been presumed to be so based on clusters of men in families that have been diagnosed with the disease.  But in fact, it turns out that brothers of prostate cancer patients undergo more diagnostic activities – meaning it could be that they are diagnosed more simply because they are screened more.

It’s only natural – a first-degree relative gets a cancer diagnosis, and everyone in the family gets screened soon after for that cancer. It is encouraged by doctors because of the tendency for some cancers at least to have a clear genetic component. But the funny thing about prostate cancer is that similar to breast cancer, but even more so, the more you look for it the more you will find it. So a recent study tried to tease apart this cancer detection bias from a real genetic effect. Given that it is well understood now that a cancer diagnosis is a far, far different situation than having clinically significant (i.e. potentially harmful) cancer, they asked the pertinent question of whether or not prostate cancer clusters in families are due to genetics, or due to family members looking for it after a relative has been diagnosed. Apparently, in previous epidemiological studies, data simply for cancer rates have been used, without taking into account this potential bias.

It was a large study, involving over 36,000 Swedish men, but the data are significant enough to suggest they are not spurious results due simply to huge sample size. Particularly telling was the finding that the risk of a brother being diagnosed with prostate cancer was highest in the first year after the original brother’s diagnosis. The best explanation for this is that most relatives get tested soon after their relative’s diagnosis, which reinforces the strong correlation between prostate cancer testing and diagnosis. Prostate cancer diagnosis also ran more in families of higher socioeconomic status; again, almost certainly because those with more resources are more likely to be tested.

These correlations demonstrate an almost certain strong bias in epidemiological studies that declare prostate cancer to be strongly genetically determined. As the accompanying editorial states, 70% of autopsied men in their 60s who never received a prostate cancer diagnosis did have prostate cancer. This indicates two things: first, that genetics is probably not a particularly useful indicator of the risk of prostate cancer for a given individual; and second, it is clear that epidemiological analyses should be assessing the genetics of clinically significant prostate cancer, not just any prostate cancer, which is clearly a meaningless label.

Cancer developed a reputation as a unequivocal killer in the days before scans and screens, because we only became aware of the clinically significant, usually deadly, cases. Our current medical technology has outstrapped our cultural understanding of what cancer really is. A vital cultural shift, supported by more and more information but still not accepted by the general public or even most doctors, is that we need, need, need to stop considering all cancer as a death sentence unless aggressive treatment is administered immediately. It is necessary because cancer screening and treatment is reaching into all aspects of health care like, well, a cancer. Huge amounts of money and energy will continue to be wasted, and stress to be caused, if we don’t make this shift.

And yes, the shift is clearly not possible without tort reform.


One Response to “More evidence that more screening = more cancer”

  1. Jay says:

    In addition to the money and the stress, people will become ill and die from the effects of the cancer treatment. It is not always better to know, and when we know it is not always better to treat. I have lost count of the number of times I’ve had to push families to let me stop ordering mammograms on patients in their 90s with dementia, and I didn’t usually even try to talk the highly-functional 80 year old out of the studies.

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