Infrared light offers promise of laser-sharp cancer therapy
Technique zaps tumors with reduced risk of side effects
By Janet Raloff
Claiming scalpel-like precision, Canadian scientists have delivered lightning-fast laser pulses of infrared light to obliterate tumors in animals. Whereas 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, its creators say.
The spillover damage to healthy bystander cells triggers the nausea and other side effects associated with conventional radiation therapy, explains Nancy Ellerbroek, a clinical radiation oncologist in Manhattan Beach, Calif. So, if the new technology can treat tumors deep inside the body without exposing healthy tissue, “that would be really great,” she says.
The just-patented system under development at the University of Sherbrooke in Canada delivers 1,000 pulses of infrared light per second, each lasting only about 100 quadrillionths of a second, explains laser physicist and study coauthor Daniel Houde. 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 illustrate the laser’s accuracy, Houde’s 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.