Something peculiar is happening in the United States – thyroid cancer rates are soaring. The disease is almost three times more prevalent than it was 30 years ago, making it the fastest-increasing cancer in the US. Treatment requires the removal of all or part of the gland. The operation is difficult. The thyroid sits in the neck, just in front of the windpipe, and inadvertent damage to important structures, including the nerves that control the vocal cords, is not uncommon.
Still, if you’ve got cancer and a delicate operation is required to cure it, then an operation is what you’re going to want, regardless of the risks. And you won’t mind lifelong treatment with thyroid hormone replacement afterwards, either.
Thankful survivors have joined a campaign called “Light of Life” to raise awareness of the disease. A purple scarf is their symbol, in much the same way that British breast cancer charities have adopted the pink ribbon. Advertisements urge people to “check your neck” or, more precisely, to ask a doctor to check it for you.
Yet over the past 30 years, death rates from thyroid cancer have remained resolutely unchanged: no more Americans will die from the disease this year than succumbed to it in 1983. One possible explanation is that US doctors are getting better at treating it, saving ever more lives among the escalating numbers of affected people. That would be good if it were true but the reality is very different. The burgeoning incidence of thyroid cancer is an artefact of medical technology and many patients are being subjected to unnecessary treatment.
To understand this, you need to know about Vomit – or “victims of medical imaging technology”. The acronym was coined in 2003 by Richard Hayward, a consultant neurosurgeon at Great Ormond Street Hospital in London. Vomit suggests that the more successful we become at imaging the body, the more abnormalities we will find that we don’t know how to interpret. Take a random sample of healthy New Statesman readers and put them through a CT scanner, for example, and around 25 per cent of you would prove to have a lump in an organ somewhere.
US doctors, with ready access to expensive technology and a morbid fear of litigation should they “miss” something, rely heavily on imaging. Chest CT scans, routinely used to assess lung symptoms, take in the thyroid gland, as do MRI scans performed to investigate neck pain. Around 16 per cent of these scans turn up incidental lumps in the thyroid, most of which are too small to feel on examination.
Having raised an alarm, something more invasive – a biopsy – follows. Tissue from the thyroid lump is examined under the microscope by a pathologist and that’s where the problem is compounded. Pathologists are good at recognising thyroid cancer – they’ve spent their careers analysing samples obtained from aggressive tumours that have presented clinically as enlarging masses. And the tissue from the incidental lumps is often indistinguishable from clinically important cancers, setting in train the full curative machine. Most of the operations are unnecessary, however. A Japanese study, published in 2010, followed 340 such patients who volunteered for surveillance rather than surgery. Only a tiny minority had any tumour growth and some lumps even regressed during the six years of follow-up. No one came to any harm.
Cancer, long the feared foe, is evidently more nuanced than we have appreciated. For every tumour capable of causing disease or death, many more lie dormant – or are dealt with by our immune systems – and never progress. Using powerful imaging technologies developed in recent decades, we can now detect these indolent cancers but we have no way of predicting which can be left alone safely.
The problem is not unique to the thyroid gland, nor to the US. It is now accepted that for every life saved by the UK national breast screening programme, another three women are diagnosed and aggressively treated for a screen-detected cancer that would never have caused disease. And each year, thousands of men are diagnosed with prostate cancer that won’t ever pose them a problem.
It’s a horrible dilemma for patients caught up in the process: cancer provokes inevitable fear. Even given the option of surveillance, most people will choose radical treatment, with all the attendant side effects and risks. Until we can reliably predict the behaviour of the cancers we are detecting by screening or by accident, doctors are arguably causing as much – or even more – harm than good.
Over-diagnosis of cancer is one of the conundrums that have inspired the “Too Much Medicine” campaign, an international medical movement concerned with the damage modern medicine is inflicting, albeit with the best of intentions. It is likely to be an important influence in the coming years and is something to which this column will no doubt return.
Next week: the trials of a country vet
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