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Hyperthermia - Cancer therapy hots up

Forget surgery: in a few years’ time, cancerous tumours might be kept in check with hyperthermia, a new treatment using heat. Successfully trialled on brain and prostate cancer patients, it could spare many people the surgeon’s knife, but also make existing chemotherapy drugs more effective.

The first step of the treatment is to precisely locate the tumour and inject it with tiny packets of magnetic nanoparticles. ‘If you’ve got a well defined tumour somewhere, you can simply squirt them into it,’ comments Kevin O’Grady, Professor of Experimental Physics at the University of York.

Hyperthermia relies on the properties of iron oxide nanoparticles, which are ferromagnetic. ‘If you magnetise a ferromagnet, when you turn the magnetic field off, you retain a fraction of the magnetisation,’ explains O’Grady. This principle is at play for instance when you magnetise a steel needle using a magnet (try it yourself here).

If you want to change the direction in which a ferromagnet is magnetised, you need to apply another magnetic field in the opposite direction. Energy is however lost during this process. ‘Every time you remagnetise a ferromagnet, you waste a certain amount of energy from your magnetic field,’ comments O’Grady. And this energy is lost as heat.

‘All energy in the universe eventually degrades to become heat,’ he adds. ‘If you rub your finger against your desk rapidly, your finger gets warm. What you’re doing is converting mechanical energy into heat energy.’

Turning up the heat

How does this relate back to cancer treatment? Just like any cell in the human body, tumour cells aren’t fond of high temperatures. Injecting a tumour with magnetic nanoparticles and then exposing the patient to an alternating magnetic field produces heat. This warms only the areas immediately around the nanoparticles, killing tumour cells without hurting the healthy tissue.

‘Of course the nanoparticles are quite small and each generates an unmeasurably tiny amount of heat. But if you’ve got tens of billions of them, you can start to make the tumour warm up, and when you get the tumour above 45C, the cells die,’ explains O’Grady.

The body’s immune system then takes care of flushing out the nanoparticles. Although synthesised in the lab, such nanoparticles are widespread in nature. ‘Every shovelful of soil you turn over in your garden has iron nanoparticles in it,’ says O’Grady.

Iron oxide nanoparticles

Although enthusiastic about hyperthermia, O’Grady is realistic about its potential. ‘This is not a cure for cancer,’ he says, ‘it’s a way of managing tumour size. You’d never be able to completely eliminate a tumour – you’d be burning into good cells.’

For conditions such as prostate cancer, hyperthermia could however avoid repeated, invasive surgery, vastly improving patients’ quality of life. And it doesn’t end there.

Targeting chemotherapy

‘Another application of hyperthermic heating is to increase the efficacy of the chemotherapy,’ adds O’Grady. Chemotherapy is as destructive to healthy tissue as it is to tumours, causing many unpleasant side effects. Chemotherapy drugs are however activated by heat, meaning they can be targeted with the help of hyperthermia. ‘If you warm up the tumour, then as the drugs pass around in the blood, they’ll do much more damage on the warm tissue than they will on the cold,’ explains O’Grady.

O’Grady is confident that it won’t be long before hyperthermia is used in major hospitals worldwide. ‘Given the relative simplicity of the technology, I’d suggest that it might be quite common in 5 years,‘ he says.

This rapid progress has in fact come as a shock to many experts, as O’Grady explains: ‘What has surprised me and I think everyone else is that the hyperthermic heating of tumours has now been demonstrated and is going through procedures for actual use in people. I thought it was never going to work!’

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