X-ray source could lead to improved therapy

An experimental form of radiation therapy could become an effective technique in hospitals if improvements now being tested prove viable. The technique is microbeam radiation therapy, and it has been studied for more than a decade in the laboratory.

The technique has traditionally required a high-intensity synchrotron x-ray source, such as the superconducting wiggler at Brookhaven Laboratory's National Synchrotron Light Source in Upton, NY. The wiggler produces parallel and extraordinarily thin (25- to 90-micrometer) x-rays instead of the broad beams used in conventional radiation treatment. In preclinical studies these thin beams deposit high radiation doses in cancers, while subjecting adjacent normal tissue to little collateral damage.

Research now indicates that special x-ray tubes, compatible with hospital use, might produce the same effect using thicker microbeams. Researchers from Brookhaven, Stony Brook University, the IRCCS Neuromed Medical Center in Italy, and Georgetown University have found that after seven months, animals exposed to beams as thick as 0.68 millimeters show no or little damage to the nervous system, according to an online report in this week's Proceedings of the National Academy of Sciences. The findings demonstrate the ability of these beams to spare healthy tissue. Additional tests indicate that high doses can be delivered to a specific target in the brains of rats - enough to destroy a tumor.

"This form of microbeam radiation therapy could improve the treatment of many forms of cancer now treated with radiation, because it can deliver a more lethal dose to the tumor while minimizing damage to surrounding healthy tissue," said Dr. Eliot Rosen, a radiation oncologist at Lombardi Comprehensive Cancer Center at Georgetown University. "It may also extend the use of radiation to cases where it is now used only judiciously, such as brain cancer in patients under three years of age, because of the high sensitivity of young brain tissue to radiation."

The technique may also have applications in treating a wide range of benign and malignant brain tumors and other functional brain disorders, such as epilepsy and Parkinson's disease, the authors said. This potential is highly speculative, however, as neither the original nor the improved radiation technique has been tested in humans.