A very intelligent NYT OpEd about CT screening for lung CA (by Steven Woloshin, Lisa Schwartz and H. Gilbert Welch -- physician researchers at the Department of Veterans Affairs and faculty members at Dartmouth Medical School.):
The less familiar, but more worrisome, harm comes from overdiagnosis and overtreatment. In the largest study to date, Japanese researchers using CT scans found almost 10 times the amount of lung cancer they had detected in a similar group of patients using X-rays. Amazingly, with CT screening, almost as many nonsmokers were found to have lung cancer as smokers.Ahh, those young whippersnappers don't seem to remember one of the most disastrous errors in imaging screening -- neonatal retinoblastoma.
Given that smokers are 15 times as likely to die from lung cancer, the CT scans had to be finding abnormalities that were technically cancer (based on their microscopic appearance), but that did not behave in the way most people think of cancer behaving - as a progressive disease that ultimately kills. So here's the problem. Because we can't distinguish a progressive cancer from a nonprogressive cancer on the CT scan, we tend to treat everybody who tests positive. Obviously, the patients with indolent cancers cannot benefit from treatment; they can only experience its side effects. Treatment - usually surgery, but sometimes chemotherapy or radiation therapy - is painful and risky. Some 5 percent of patients older than 65 die following partial lung removal, and nearly 14 percent die with complete removal.
I'm not sure, however, that I remember the story correctly -- a quick PubMed search did not immediately validate my recollection. Either I'm mis-remembering or we're sweeping another of our mistakes under the carpet.
What I remember is that sometime when CT was new we started diagnosing a LOT of retinoblastoma. Many infant eyes were removed, with congratulations all around at disaster averted. The only question was -- why the sudden upsurge in this terrible malignancy? Ahh. That was the catch. It turned out the newfangled scans were detecting a lesion that looked like retinoblastoma, but actually spontaneously regressed (maybe we call this retinocytoma now?). In retrospect almost all of those eyes could have been retained. (I don't recall if any infants lost both eyes.)
Maybe my memory is completely faulty. I'd love to see comments if anyone else remembers this. If so, it's a story that bears repeating.