Overdiagnosis is still ruffling feathers

3 minute read

Some doctors are still struggling to get their heads around the concept of overdiagnosis, writes Dr Kerri Parnell


The first time I published an article about the “overdiagnosis” of breast cancer, I came in for a bit of flak. Some doctors equated the term with “misdiagnosis”, and thought we were talking about medical error – diagnosing a condition when there was none to be found.

Of course, the basic tenet of what we now know as overdiagnosis – that some cancers won’t ever go on to do harm – was an unfamiliar and counterintuitive concept in the mid 2000s.

Until then, it had been an accepted and sacred truth that early detection saved lives, so the idea that by picking up potentially fatal diseases we could be harming our patients was understandably hard to get our heads around.

Maybe it was in the name; the term “overdiagnosis” can easily sound like we’re being chastised for doing something wrong. However, it wasn’t medical acumen under scrutiny, rather the unintended consequences of mammographic screening programs in asymptomatic women.

Ten or more years later, when entire conferences are now dedicated to overdiagnosis, the concept can still ruffle feathers, as the response to a recent epidemiological study of mammography shows.

The NEJM study  attempted to estimate the rate of overdiagnosis, and showed that since the introduction of routine screening, women were more likely to have breast cancer that was overdiagnosed than to have earlier detection of a tumour that was destined to become large.

Put simply, a large proportion of screening-detected breast cancers in asymptomatic women will, if left untreated, not go on to do harm.

Understandably, such a finding is anathema to those patients, patient advocates, politicians and even some in the profession, who remain convinced their own lives, or those of their loved ones, were saved by a mammogram.

And it’s true breast-cancer mortality has fallen by roughly 30% since 1990, which according to Dr David Gorski, US cancer surgeon and academic, reflects a key controversy in the field.

“The controversy is not over whether breast cancer mortality is declining. It is,” Dr Gorski says. “The controversy is over what’s the cause: screening, better treatment, or some combination of the two.”

Either way, for affected women and their clinicians, there’s no choice. Until we have tests that can tell the dangerous cancers from those that are biologically self-limiting, we have to treat them all as if they’ll progress.

So while advocates of screening argue its critics are killing women, sceptics of screening claim it’s useless.

Let’s hope researchers are close to discovering that test.

Dr Kerri Parnell is the Editor-In-Chief of The Medical Republic – kerri@medicalrepublic.com.au 

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