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Most people want to know risk of overdiagnosis, but aren’t told

An independent UK inquiry estimated that perhaps one in five of the cancers detected via breast cancer screening are overdiagnosed. Army Medicine/Flickr, CC BY-SA

An Australian survey released today has found a large majority of people report they’ve never been told by doctors about the danger of being overdiagnosed – and an equally large majority say they want to be informed.

This is the first time anywhere in the world the general community has been asked about their knowledge and views on the “modern epidemic” of overdiagnosis, which happens when someone is diagnosed with a disease that won’t actually harm them. Being overdiagnosed means you’re likely to be over-treated, and potentially suffer the harms of that treatment without getting any of its benefits.

It can occur as a result of healthy people undergoing certain cancer screening programs, for instance, and being diagnosed and treated for a cancer that would never progress to cause symptoms or early death.

Wanting to know

While there’s ongoing scientific debate about how often this happens, a large independent UK inquiry estimated that, along with saving lives of those diagnosed with harmful cancers, perhaps one in five of the cancers detected via breast cancer screening are overdiagnosed.

Overdiagnosed cancers were defined in the inquiry’s full report as those “diagnosed by screening that would not otherwise have come to attention in the woman‘s lifetime”.

For prostate cancer screening, evidence suggests as many as one in two cancers may be overdiagnosed – causing some public health authorities to recommend against screening for it at all.

Run with colleagues at Bond and Sydney universities, our national survey of 500 Australians – published today in global open-access journal PLOS ONE – specifically asked people if they’d been screened for breast or prostate cancer. And if so, whether or not they’d been informed about the risk of overdiagnosis associated with the screening.

Of the men reporting being screened for prostate cancer, 80% said they had not been told of the risk of overdiagnosis. Of women who’d been screened for breast cancer, 87% said they had not been told. Overall, only one in ten said they’d ever been informed by a doctor about overdiagnosis.

Asked whether they thought that, along with the benefits of being screened, people should also be informed about the risk of being overdiagnosed, 93% agreed.

Remarkably, at the end of the anonymous telephone survey, 80% of people agreed to share their personal details so they could participate in follow-up qualitative research on overdiagnosis. Their agreement highlights a public hunger for more information about the issue.

Expanding definitions

Another reason overdiagnosis happens is because diagnostic thresholds for some diseases are lowered so much that people with mild symptoms, or at very low risk of illness, are labelled as “diseased” – even though many will never actually be harmed by the disease.

Consider “pre-hypertension” which is said to affect a whopping one in three adults, or the continually expanding definitions of attention deficit hyperactivity disorder (ADHD).

These changes to disease definitions, which often expand the numbers of people classified as sick, are commonly made by panels of experts that include doctors who are paid to speak for or consult to drug companies. In a previous study published in PLOS Medicine, our team found around 75% of these experts have multiple relationships with a median of seven drug or device companies.

In our current survey, we asked the public what they thought about doctors who define disease also having relationships with pharmaceutical companies. This is likely the first time anywhere in the world the public has been asked about the experts who draw the line between health and illness.

Almost 80% of the survey participants thought these relationships with drug companies were inappropriate, and 90% thought the panels should have a minority of members with these conflicts of interest, or be totally free of them.

Public thinking, it seems, is very much in tune with recommendations from august bodies including the United States Institute of Medicine, which have concluded there is a need for much greater independence between influential medical panels and the pharmaceutical industry.

Better care

Like all research, our survey has limitations and we’ve spelt them out in our published article. One of them is that out of all the people contacted and eligible for the survey, just under half agreed to take part, raising the possibility of differences between our sample and the wider population.

Notwithstanding limitations, our survey adds weight to calls to better inform people about the risk of overdiagnosis, particularly those who take part in cancer screening programs. This has started to happen around the world, and is on the cards in Australia.

On the question of conflicted experts, our results suggest there might be strong public sympathy for any professional group or policymaker brave enough to try and bring more independence to the influential panels that decide who is sick and how they should be treated.

Despite the counter-intuitive and complex nature of the problem, preventing overdiagnosis is increasingly on the radar of those working for a more rational and sustainable health-care system. It may help shift resources wasted on unnecessary care to those in genuine need.

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