Next up on the cancer continuum: Overdiagnosis

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Here's a 1938 ad by the American Society for the Control of Cancer, issued a year after the formation of the National Cancer Institute. And another further down by the same organization, which would eventually become the American Cancer Society. They promoted early detection as the sine qua non of cancer survivorship, a motif that played steady for decades and decades.

1938 ad

And it makes sense doesn't it. Most cancers are progressive; the sooner you detect it, well … as Fred Sanford would say, the sooner you can go get your bud nipper and nip it in the bud.

NOT SO FAST

Now, a pair of researchers have published some explosive findings in the Journal of the National Cancer Institute: according to their data, one in four breast cancers detected by mammograms, and three of five prostate cancers found using prostate-specific antigen (PSA) tests contribute to the phenomenon of overdiagnosis in cancer [1].

curable

What does that mean? Overdiagnosis means that these discovered cancers would not cause any symptoms in the patient, or cause any illness, or death—they would either come on and fade out, or come on and stick around, going nowhere and never inflicting more than a sneeze on their host.

The consequence is hideous: these otherwise harmless cancers, when detected by the PSA test, or mammogram, no doubt sent untold thousands into unnecessary surgery, chemotherapy, radiation and other therapies, likely killing some and significantly shortening the lives of others.

And it wasn't just the breast or the prostate, but lungs too: they argue that x-rays used in a trial for lung cancer screening led to overdiagnosis in one of every two cases.

The problem is, how do you discern a tumor on a deadly course from one hitching an innocent ride? That has yet to be determined. So does the ultimate answer to overdiagnosis.

THE PSA MISTAKE

Richard Ablin, the man credited with discovering the prostate-specific antigen (PSA) that is used to detect prostate cancer in men, recently wrote an op-ed piece for the New York Times called "The Great Prostate Mistake". In it he writes "American men have a 16 percent lifetime chance of receiving a diagnosis of prostate cancer, but only a 3 percent chance of dying from it … men lucky enough to reach old age are much more likely to die with prostate cancer than to die of it."

That almost sounds bittersweet. Fortunately Albin brutally sums it all up in what feels like an oratorical peroration:

  • "I never dreamed that my discovery four decades ago would lead to such a profit-driven public health disaster. The medical community must confront reality and stop the inappropriate use of P.S.A. screening. Doing so would save billions of dollars and rescue millions of men from unnecessary, debilitating treatments."

WHAT NOW

What's a patient to do? Who the hell knows. It would seem that misdiagnosis plagues the field of lymphoma far more often than overdiagnosis, but I don't know if that's true or not.

And in the great cancer continuum, even if it were true and accepted today, there's a decent chance it'll be proven wrong tomorrow. Scientists have yet to isolate the precise mechanism that triggers most cancers inside a cell, so theories persist.

I'm not a scientist but this is actually why I like science; it's a field that's forever self-correcting. It's your job as a scientist to question everything that came before you, it's your job either to prove your colleagues right or prove them wrong. Thus it's also your job to admit when you were wrong, which is probably the hardest part of the job.

So is the call for early detection another blunder in the cancer continuum? Well no, for many people it's a lifesaver. For others, a disaster.

Just a few decades ago the notion of overdiagnosis was probably unheard-of, or laughable; and now it can be fatal. Typical cancer.

By Ross Bonander

[1] H. Welch, W. Black. "Overdiagnosis in Cancer." Advance Access published on May 5, 2010, DOI 10.1093/jnci/djq099. J. Natl. Cancer Inst. 102: 605-613.

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