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Diagnosing Cancer - turtles, birds or rabbits?

Diagnosing cancer – turtles, birds or rabbits?


In an article entitled “Overkill” in the 11 May 2015 issue of the New Yorker Atul Gawande describes how an avalanche of unnecessary medical care is harming patients physically and financially, and asks what can we do about it.1 Atul Gawande, a surgeon and public health researcher, has been a New Yorker staff writer since 1998. He was in New Zealand at the Auckland Writers’ Festival in May this year talking about his latest book, Being Mortal.
In his lengthy article, Atul Gawande refers to the latest book by H. Gilbert Welch, a Dartmouth Medical School professor, who is also an expert on overdiagnosis. In his book Less Medicine, More Health,2 Welch explains the phenomenon in this unique and unforgettable way:
“We’ve assumed that cancers are all like rabbits that you want to catch before they escape the barnyard pen. But some are more like birds—the most aggressive cancers have already taken flight before you can discover them, which is why some people still die from cancer, despite early detection. And lots are more like turtles. They aren’t going anywhere. Removing them won’t make any difference.
We’ve learned these lessons the hard way. Over the past two decades, we’ve tripled the number of thyroid cancers we detect and remove in the United States, but we haven’t reduced the death rate at all. In South Korea, widespread ultrasound screening has led to a fifteen-fold increase in detection of small thyroid cancers. Thyroid cancer is now the No. 1 cancer diagnosed and treated in that country. But, as Welch points out, the death rate hasn’t dropped one iota there, either. (Meanwhile, the number of people with permanent complications from thyroid surgery has skyrocketed.) It’s all over-diagnosis. We’re just catching turtles.
Every cancer has a different ratio of rabbits, turtles, and birds, which makes the story enormously complicated. A recent review concludes that, depending on the organ involved, anywhere from fifteen to seventy-five per cent of cancers found are indolent tumors—turtles—that have stopped growing or are growing too slowly to be life-threatening. Cervical and colon cancers are rarely indolent; screening and early treatment have been associated with a notable reduction in deaths from those cancers. Prostate and breast cancers are more like thyroid cancers. Imaging tends to uncover a substantial reservoir of indolent disease and relatively few rabbit-like cancers that are life-threatening but treatable.
We now have a vast and costly health-care industry devoted to finding and responding to turtles. Our ever more sensitive technologies turn up more and more abnormalities—cancers, clogged arteries, damaged-looking knees and backs—that aren’t actually causing problems and never will. And then we doctors try to fix them, even though the result is often more harm than good.
The forces that have led to a global epidemic of over-testing, over-diagnosis, and over-treatment are easy to grasp. Doctors get paid for doing more, not less. We’re more afraid of doing too little than of doing too much. And patients often feel the same way. They’re likely to be grateful for the extra test done in the name of “being thorough” – and then for the procedure to address what’s found.”1
The story of one of Atul Gawande’s patients, Mrs E provides a telling and very insightful example of the human cost of all this testing.
Mrs E, a woman in her fifties, had had surgery for a thyroid lump. The biopsy revealed that the lump was benign. But the pathologist examining the specimen found a pinpoint “microcarcinoma” next to it. It was just five millimetres in size. Some experts argue that we should stop calling these microcarcinomas “cancers” as they are very unlikely to turn into dangerous cancers.  
The surgeon told Mrs E about the tiny cancer that had been found and ordered regular ultrasounds every few months to monitor her thyroid. When another five millimeter nodule was found he recommended removing the rest of her thyroid. When the surgeon had to cancel the planned surgery Mrs E was referred to Atul Gawande. He advised her that she really didn’t need surgery and the operation posed a greater risk of causing harm – vocal-cord paralysis and life-threatening bleeding – than any microcarcinoma she had. Removing her thyroid would also result in the need to take a daily hormone-replacement pill for the rest of her life. She would be better off being monitored with regular scans.
But Mrs E was too fearful of the tiny “cancers” she was told she had, and opted for surgery. “Given that the surgery posed a greater likelihood of harm than of benefit, some people would argue that I shouldn’t have done it,” Atul Gawande writes.

“I took her thyroid out because the idea of tracking a cancer over time filled her with dread, as it does many people. A decade from now, that may change. The idea that we are overdiagnosing and overtreating many diseases, including cancer, will surely become less contentious. That will make it easier to calm people’s worries. But the worries cannot be dismissed. Right now, even doctors are still coming to terms with the evidence.”
Mrs E had post-surgery complications. Two hours after the operation she began to bleed and had to be rushed back into the operating room to find and fix the cause of the bleeding. While she suffered no permanent harm and made a full recovery, she had to take a pill for the rest of her life.  
She was also extremely grateful. “She thanked me profusely for relieving her anxiety. I couldn’t help reflect on how that anxiety had been created. The medical system had done what it so often does: perform tests, unnecessarily, to reveal problems that aren’t quite problems to then be fixed, unnecessarily, at great expense and no little risk.”
However, these issues are now starting to be addressed. The third international conference on preventing overdiagnosis will take place in Washington in September 2015.3

  1. http://www.newyorker.com/magazine/2015/05/11/overkill-atul-gawande

  2. H. Gilbert Welch. Less Medicine, More Health. Beacon Press 2015.

  3. http://www.preventingoverdiagnosis.net/?p=830

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