Cauterising tumours with radio waves may provide a less invasive alternative to surgery for liver cancer and many other types of tumour, say two cancer specialists. Surgery to remove a tumour can prevent cancer spreading throughout the body. But in some cases, doctors decide not to operate, perhaps because the tumour is too close to an artery or because the patient is too weak to survive the operation. Sometimes chemotherapy can be used to kill the tumour cells. But these drugs kill healthy cells, too, and can make the patient feel very ill.
So radiologist John McGahan and oncologist Philip Schneider of the University of California at Davis are developing another alternative treatment, which is known as radio-frequency ablation. It involves heating the diseased cells with a fine electrode, and is similar to the traditional technique for cauterising blood vessels. "Essentially, we are hard-boiling the tissue," says Schneider. To treat liver cancers, the researchersinsert a flexible catheter through a patient's abdomen, using an ultrasound scan to guide it into position against the tumour. They then run a cluster of eight to ten wires through the catheter. When the wires reach the end of the tube, they fan out and penetrate the tumour.
A very high-frequency current in the wires causes nearby atoms to vibrate, heating the tissue from within just as a microwave cooker heats food. It takes ten minutes to kill all the cells in a region measuring 3 to 5 centimetres across. The technique can be used to destroy up to five liver tumours in a single session. Patients receiving this treatment can leave hospital much sooner than those who undergo conventional surgery. However, radio-frequency ablation does have serious side effects. The liver contains many biochemically active substances that leak into the body from the dead cells. As a result, patients may become feverish or nauseous. "They feel like they have the flu," says McGahan. And if the treatment damages nerves near the liver's surface, patients may feel chest or abdominal pain for up to a week.
The California team have so far tested their treatment on a dozen patients. Nine of the twelve have been free of cancer for more than a year. Left untreated, liver cancer is invariably fatal. Schneider expects that several more years of evaluation will be needed before the procedure becomes common. McGahan says radio-frequency ablation could treat benign tumours as well as cancer. For example, he recently removed a painful bone tumour from a girl's leg by inserting the wire through a small hole in her femur.
Param Sharma, an electrophysiologist at the University of Arizona, says radio-frequency ablation is already widely used to treat certain heart arrhythmias by destroying wayward pacemaker cells. He says there is no reason it couldn't be used for other tissue-killing procedures as well. "You can make a lesion any-where."
Author: Jonathan Knight, San Francisco
New Scientist issue 10th October 1998
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