The Chest Radiograph: Low Reward, High Risk, Extreme Uncertainty

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 - Saurabh Jha, MBBS, MRCS
Saurabh Jha, MBBS, MRCS

A radiologist considers the disconnect between evidence-based medicine and the courtroom.

In a recent verdict, a jury in Massachusetts awarded $16.7 million 1 in damages to the daughter of a Boston woman who died from lung cancer at 47. Her cancer was missed on a chest x-ray. The verdict recalls the words of John Bradford, burned at the stake in the 16th century as a heretic: “There, but for the grace of God, go I.”

Many radiologists will sympathize with both the patient, who died prematurely, and the radiologist, who missed a 15-mm nodule on the patient’s chest x-ray when she presented with cough to the emergency department. The damages are instructive of the degree of tension between the Affordable Care Act’s push for both resource stewardship and patient-centeredness; but the verdict mostly speaks of the ineffectualness of evidence-based medicine (EBM) in court.

EBM tells us that had the patient’s cancer been detected thirteen months before it actually was, it would have made little difference to her survival. Statistically speaking, that is the prevailing wisdom.

Researchers from Mayo Clinic 2, Rochester, Minnesota, examining the impact of frequent chest x-rays in screening for lung cancer in a large number of smokers, found that the intensively screened group knew about their cancers earlier, had more cancers removed, but did not live longer as a result. This is known as lead-time bias: Early detection means more time knowing that one has the cancer, not more time one is actually alive. Had the nodule been seen on the patient’s initial chest x-ray, she would probably, not certainly, not have survived much beyond 47.

Lead-time bias is a basic concept in epidemiology and biostatistics. Physicians have it drilled into them. Recognition of this artifact curbs therapeutic and screening optimism.

Blind to lead-time bias

Why does lead-time bias not cross the courtroom door? Plaintiffs’ lawyers need raise only the possibility that early detection could have cured the cancer to prevail in a suit. Though cure in this case was statistically improbable, it was certainly not impossible: Statistics predict, they don’t prophesize.

Evidence-based medicine speaks of the probable. Plural of possibility is not evidence, but possibility beats probability in court. A defense attorney for medical malpractice once confided to me that the last thing he wanted was to call the plaintiff a statistic, a guaranteed turnoff for the jury.

Physicians are increasingly asked to be mindful of the population, not just the individual patient. The explicit message from policymakers is that we must be sensitive to limited resources. We are chastised for overutilization of imaging, yet it’s hard to see how excess utilization can be curbed unless courts respect evidence-based medicine.

It’s at times like this that meaningful tort reform appears painfully conspicuous by its absence from the Affordable Care Act. The damages in this case are particularly ironic given the intensity of the scrutiny on overdiagnosis and the recent lack-of-confidence vote in low-dose CT lung cancer screening by the Medicare Evidence Development & Coverage Advisory Committee. Policymakers are sending a schizoid message: Picking up cancer doesn’t save lives, but missing cancer costs lives.

A miss is a miss

One might suppose that had the radiologist picked up the lung nodule, the lawsuit would never have occurred, that a miss is a miss, regardless of the outcome. That, too, is not so simple. Perceptual errors are common 3 in interpreting chest x-rays. Researchers have found that a large number of cancers can be seen, in hindsight4, on chest x-rays, so much so that an appeals court once proffered that a perceptual error is not necessarily negligence5.

The late outstanding chest radiologist Wallace T. Miller, Sr, MD, once cautioned, “The first 10,000 chest x-rays are easy.”  Puzzled then, I understand now what he meant having interpreted well over 10,000 chest x-rays. I am more aware of what I might miss than before, and this has created an odd combination of expertise and insecurity.

When the insecurity gets the better of me, I imagine shadows on x-rays and recommend CT scans to “rule out a mass.” Sometimes I catch a cancer. More often than not, I raise false alarms, inconveniencing patients and wasting resources.

Options traders can avoid trades that are low on the upside and high on the downside. Radiologists do not have that luxury. Paid barely $10 for a chest x-ray, which