While conventional radiation therapy delivers cell-killing radiation to all cells throughout a beam’s path, the new approach causes no damage to tissue surrounding a targeted tumor, so say researchers.
Canadian scientists have used fast pulses on infrared light to destroy cancerous tumours in animals. The new technique is said to be more precise than current methods. Why? While conventional radiation therapy delivers cell-killing radiation to all cells throughout a beam’s path, the new approach causes no damage to tissue surrounding a targeted tumor, so say researchers.
Using conventional radiation therapy, collateral damage to neighbouring non-cancerous cells triggers the nausea and other side effects suffered by patients, explains Nancy Ellerbroek, a clinical radiation oncologist in Manhattan Beach, California.
In her own words, it "would be really great" if this new technology can treat tumours inside the body without damaging healthy tissue.
The technique developed at the University of Sherbrooke in Canada delivers 1000 pulses of infrared light per second, each lasting about 100 quadrillionths of a second. In tiny regions of tissue — typically a volume about 100 micrometers in diameter and up to 10 centimeters long — this blast briefly creates a low-energy electron plasma called a filament, in which molecules are stripped of their outer electrons.
To demonstrate the laser’s precision, the team irradiated a clear gel that turns cloudy when exposed to enough radiation to kill human cells. Using laser pulses, the Sherbrooke scientists wrote the S from their university’s logo into the gel. No gel in front of the S turned cloudy, the researchers report online August 27 in the Proceedings of the National Academy of Sciences. When the researchers repeated the experiment with a gamma radiation beam, all gel in the path of the beam turned cloudy, up to and including the targeted region.
Functionally, the laser’s impact on affected tissue is exactly like X-rays. Both types of radiation unleash electrons that deposit lethal amounts of energy. Both also induce the production of free radicals, molecular fragments that kill cells.
The laser therapy obliterated tumors induced experimentally in mice. However, those tumors were just under the skin of the animals’ legs. Still unclear, Houde acknowledges, is how deeply filaments can be induced and still maintain their pinpoint accuracy. The goal, he says, “is to begin tests in humans within two years.”
Radiation oncologist Theodore Phillips of the University of California, San Francisco, suspects the laser technique may have limited applicability given the questions about how deeply inside the body it will work. “I suspect perhaps 1 or 2 centimeters at best,” he says. So, for the more common, deeper tumors, he says, this technique would hold little appeal.
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