Thermal treatments of cancer are remarkably effective

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Even as some scientists are seeking to understand how cancer works, in order to treat it more effectively, others prefer a more robust approach. They are exploring ways of killing cancer cells by heating them up without damaging surrounding healthy tissue. Although various such treatments have been tried in the past, advances in medicalimaging technology (which allow surgeons to see inside a body without opening it up) and improvements in the treatments themselves, mean that such treatments are receiving more and more attention.

At the end of 2003, Martin Mack of the Goethe University in Frankfurt told a meeting of the Radiological Society of North America, in Chicago, of his success in using lasers to treat secondary liver cancers. These secondaries were the results of cells from primary colorectal or breast cancers breaking off and lodging in the livers of the patients in question-1,400 of them. Such secondaries are hard to treat by traditional methods.

Dr Mack used magnetic-resonance imaging (MRI) to guide a fibre-optic probe through a patient's skin to the tumour. When the end of the probe was next to a tumour, he fired a laser beam through the optical fibre and blasted the cancer cells with it. He found that up to and including five years after the treatment, more patients who had had this treatment survived, than did those who had had traditional surgery.

Earlier last year Antonio Giorgio, and his colleagues at the Cotugno Hospital for Infectious Diseases in Naples, published a paper in the American Journal of Roentgenology describing their success in using radio waves, rather than laser light, to treat hepatocellular carcinoma, another form of liver cancer and one that is among the deadliest in the world. Such radio waves act like the microwaves in an oven, heating organic matter up to the point where, if it was not dead already, it soon will be. But unlike Dr Mack, who used MRI, Dr Giorgio employed an ultrasonic scanner to help him guide the device which generated the radio waves to its target. Ultrasound machines are a lot cheaper than MRI ma-chines, and also smaller. This technique is thus more attractive.

Indeed, ultrasound is being used not only for imaging, but also as a source of heat itself. This, potentially, is cheaper still, and it has the additional advantage of being noninvasive. That is because, like light waves, sound waves can be focused. The ultrasound generator used in this technique can focus its energy into a space about the size of a grain of rice. Thus concentrated, it shakes cells so violently that they heat up.

But in front of the focus, and behind it, the energy density is lower, and little or no damage is done. David Cun-ningham and Gail ter Haar have used this technique to treat liver cancer at the Royal Marsden Hospital in London, while other groups in America, China and Japan, are using high-intensity sound to kill cancers in the prostate gland, uterus and brain. Hot stuff indeed.

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