The technique involves a high-intensity ultrasound beam about 10,000 times more powerful than that used to show pregnant women the developing foetus in the womb.
The beam is focused on a point inside the body where it "cooks" malignant tissue without harming neighbouring healthy tissue. A shot lasting one or two seconds raises the temperature to more than 55C, high enough to destroy the cells in the target area.
The technique is also being developed for the treatment of soldiers wounded in battle. Four in 10 battlefield deaths are caused by internal bleeding. A device that could "spot weld" damaged blood vessels in the field would save many lives.
Researchers at the Royal Marsden Hospital in London have used the technique experimentally on 23 patients with prostate, kidney and liver cancers. The treatment required no anaesthetic and caused nothing more than a slight tingling in the prostate gland, which the men involved described as "not unpleasant".
The patients all had advanced disease and the experiment was carried out only to see how well the treatment was tolerated.
Robert Shearer, medical director of the Royal Marsden and a consultant urologist who was involved in the trial, said: "It does seem to produce destruction of malignant tissue with minimal side-effects."
The technique, known as High Intensity Focused Ultrasound, uses transducers to produce the powerful energies required. The beam can be focused to a depth of 15 centimetres. It is so precise it is sharper than a scalpel.
Mr Shearer said the device, described in The Lancet, could be in use within two or three years to treat patients with advanced cancer which had spread to other organs, but it would need to be evaluatedcarefully to see if it extended survival.
"It is absolutely fascinating. It may be used for tissue destruction of metastatic disease [cancer which has spread]. But it may have an even more important role on the battlefield," he said.
American researchers funded by the military are hoping to develop a portable ultrasound device to locate and treat internal haemorrhages. A team at the University of Washington in Seattle has experimented on pigs' livers, creating a wall of cauterised tissue that allowed a thick lobe to be cut away with minimal bleeding.
Mr Shearer said: "The aim is to develop a device to stabilise a patient where they were injured and then get them back to a medical centre where they could be tidied up."