Breast cancer

What is overdiagnosis?

Overdiagnosis. What does overdiagnosis actually mean?

Is it like misdiagnosis? Not really. Misdiagnosis is a wrong diagnosis: For instance, if someone is diagnosed with cancer but they actually have a benign cyst.

Overdiagnosis is in fact a correct diagnosis. But the medical condition that was diagnosed would never have caused any symptoms or problems. In other words, this kind of diagnosis is unnecessary.

Take Mr. Williams, for example. He gets prostate cancer at the age of 65, but doesn't have any symptoms because the tumor hardly grows. He dies of a heart attack at the age of 77, without ever knowing that he had cancer.

If he had been screened for prostate cancer when he was 65, he would have been diagnosed with cancer – and possibly had surgery, radiotherapy and years of emotional stress. But he wouldn't have lived longer as a result.

That's what's meant by overdiagnosis. And the treatment that follows is called "overtreatment” – because it wouldn't have been necessary either. But how can that be? Isn't cancer always dangerous? Nowadays we know that different kinds of cancer behave differently – but no one can predict whether or how a tumor will progress. All tumors start off small and go unnoticed at first. Some grow faster and become life-threatening. Discovering this kind of tumor at an early stage can save lives. Others don’t grow, or hardly grow, and don’t cause any problems. If these tumors are discovered through screening, it’s considered to be overdiagnosis.

So what does that mean? That you should stop going to the doctor? That screening is pointless or you shouldn't have treatment?

No, of course not. But it's a good idea to find out about the pros and cons of a screening test before doing it.

Let's take a look at another example: Breast cancer.

If 1,000 women between the ages of 50 and 69 have mammograms every two years, 2 to 6 deaths from breast cancer are prevented – thanks to screening. But screening also leads to overdiagnosis in 9 to 12 of the women – which often leads to unnecessary and stressful treatments.

In other words, screening can improve the chances of recovery. But it can also be harmful if it leads to the discovery of cancer that would never have caused any problems. So what can you do? Choose the option that best suits you:

Would you rather have regular screening tests, even if that means risking overdiagnosis, with all the physical and psychological consequences?

Or would you prefer to avoid unnecessary diagnoses and treatments? Even if that means that a serious illness might only be discovered at a later stage, when treatment may be less effective?

Many people find it hard to make this kind of decision.

It's important to carefully consider the pros and cons. Talk things over with the people you are close to, and don't hesitate to ask other doctors about the potential advantages and disadvantages of the screening test.

Created on April 20, 2017
Next planned update: 2020

Authors/Publishers:

Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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