How can you have an overdiagnosis of cancer? Either it's there, or it's not.

"How can you have an overdiagnosis of #cancer?  Either it's there, or it's not." – @susila55

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Rates of new diagnosis and death for five types of cancer in the US, 1975-2005. Adapted from Welch and Black, in Preventing overdiagnosis: how to stop harming the healthy. BMJ 2012; 344:e3502

In response to tweets about a potential for overdiagnosis in thyroid cancer cases, a twitter user, Susan Burke Mangano (@susila55), asked this question.

There have been many articles lately on overdiagnosis of almost all kinds of cancer. Our twitter discussion was mainly around thyroid cancer (with Dr Gilbert Welch leading in publications eg. Current Thyroid Cancer Trends in the United States).

Whether breast or prostate, thyroid or renal, the conclusions are generally the same: we are diagnosing more and more cancer, but it is not affecting mortality rates.

How? What?

"There is an ongoing epidemic of thyroid cancer in the United States. The epidemiology of the increased incidence, however, suggests that it is not an epidemic of disease but rather an epidemic of diagnosis." – Welch et al.

I'm not going to explain it here myself since it has already been done well in many places, the most straightforward of which is this video/article combo, by the Wall Street Journal.

I highly recommend you take a look.

Read Some Cancer Experts See 'Overdiagnosis,' Question Emphasis on Early Detection in the Wall Street Journal.

 

* As they have just locked this article (you need a WSJ subscription or institutional access eg. university library account), I will include a few pertinent quotes here:

 

While it's clear that early-stage cancers are more treatable than late-stage ones, some leading cancer experts say that zealous screening and advanced diagnostic tools are finding ever-smaller abnormalities in prostate, breast, thyroid and other tissues. Many are being labeled cancer or precancer and treated aggressively, even though they may never have caused harm . . .
"We're not finding enough of the really lethal cancers, and we're finding too many of the slow-moving ones that probably don't need to be found," says Laura Esserman, a breast-cancer surgeon at the University of California, San Francisco. . . .
"Unfortunately, when patients hear the word cancer, most assume they have a disease that will progress, metastasize and cause death," the group wrote in the journal Lancet Oncology in May. "Many physicians think so as well, and act or advise their patients accordingly." . . .
Overdiagnosis--the detection of tumors that aren't likely to cause harm--is now a hot topic in other cancers as well. A growing volume of studies estimate that as many as 30% of invasive breast cancers, 18% of lung cancers and 90% of papillary thyroid cancers may not pose a lethal threat. . . .
"Everyone says they'd be willing to be overtreated if it means not dying--but that's a big fallacy," says Dr. Esserman. "By treating 1,000 people who have low-risk disease, we're not going to save the one person with aggressive disease." . . .
Says Dr. Esserman: "We need to start testing some of these ideas, rather than just fighting over them. People are afraid to do less. We want to figure out how to do less safely."
- Melinda Beck, WSJ