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Fighting Cancer with Radioactive Glass Microspheres

        Glass microspheres are proving an effective way of safely delivering large doses of radiation to cancerous tumors -- researchers see multiple medical possibilities.
        A promising new cancer treatment, in which radioactive glass microspheres are injected directly into diseased areas, will begin clinical trials in the United States by the end of this year, according to The American Ceramic Society, a professional organization whose members were instrumental in the treatment's development.
        The therapy, already in use in Canada, is being named by the society as one the greatest medical advances in its 100-year history. Currently the treatment is finding success in fighting liver cancer, but may also be used for other cancers, such as brain tumors, where surgery or traditional radiation treatments present extraordinary risks.
        The society, which represents more than 10,000 members in 80 countries, is publicizing news of the treatment -- which as of yet has received little public notice -- as part of its efforts to help boost awareness of National Engineers Week and emphasize the crucial role engineers play in a broad range of lifesaving activities. Ceramic engineering uses high-temperature processing to convert processed and raw materials, typically clay or sand, into inorganic, nonmetallic solids such as brick, glass, electronic components, nuclear fuel, abrasives, engine components and common household items like tableware. National Engineers Week, February 21-27, 1999, is co-chaired this year by the society, known by the acronym ACerS, and Eastman Chemical Company.
        While any cancer treatment is difficult, fighting liver cancer presents particularly onerous challenges. It is almost always fatal, with typical life (more) expectancy after diagnosis often measured in weeks. Surgery is rarely used because of the tendency of the disease to form multiple tumors scattered throughout the organ. Powerful chemotherapy drugs may provide temporary relief, but usually must be discontinued before all malignant cells are killed, allowing the disease to flare back up. Because the liver is large and lies deep inside the body, doses of external beam radiation strong enough to reach the liver can excessively damage healthy tissue around the organ. Smaller doses minimize collateral damage, but still have negative side effects and usually don't kill all malignant cells.
        According to Delbert Day, Curators' Professor of Ceramic Engineering at the Materials Research Center at the University of Missouri-Rolla and co-developer of the treatment, irradiating the liver in place with a weaker radiation delivered only to the organ means less damage to surrounding tissues. External beam radiation, for example, requires about ten treatments over a 30-day period to deliver a total dose of 2,000 to 2,500 rads. Unfortunately, this dose is too small to be completely effective, but any larger amount would cause too much damage to healthy tissue. By contrast, radioactive microspheres injected into the liver safely deliver an average dose of 15,000 rads in one treatment with minimal damage to healthy surrounding tissue.
        Best of all, says Day, there are very few side effects. The single injection of microspheres into the bloodstream takes about one minute. Delivery is through a catheter inserted into a major artery. The patient is observed for a few hours after injection and, if no complications develop, can go home the same day and resume normal activity. Most patients rarely suffer side effects, though a few may have a low grade fever that lasts for 24 hours. The liver, which continues to function normally, remains radioactive for about four weeks, but the radiation is too weak to escape from the body. After the radioactivity in the microspheres disappears, they remain harmlessly in the liver.
        The glass microspheres are incredibly small, about one-third the diameter of a strand of hair. Yet, the five-to-ten million used in each injection are still too large to pass through the liver, which acts as a filter to prevent them from traveling into other parts of the body.
        Though most people don't associate glass with ceramics, it is actually a subset of ceramics. Like ceramics, glass is inorganic, non-metallic material and uses some of the same raw materials as ceramics. Unlike ceramics, however, glass is amorphous, that is, without long-range crystalline order, a feature that makes glass clear.
        The microsphere treatment is now in the experimental stage in the United States, but a decision to allow broadened use is expected from the Food and Drug Administration in 1999.
        ACerS also notes that glass microspheres show strong potential for other successful medical applications, such as injecting radioactive microspheres directly into the joints of patients suffering from rheumatoid arthritis for the purpose of reducing inflammation and pain.
        Yet another possible use is for hollow, non-radioactive glass microspheres injected into bones afflicted with osteoporosis. In this treatment, the spheres provide a protective "framework" within which osteoblasts -- the producers of new bone -- may form. Currently, freeze-dried bone material from cadavers is used for such implants, but fears of contamination and diminished patient confidence has inhibited widespread acceptance.
        A related process, already cleared for orthopedic use by the FDA, places a paste-like filling of bioactive glass into cranial fractures. The technique has been successful for grafting facial bones, replacing bones in the middle ear and repairing periodontal defects. It's currently in trials for fixing fractures of long bones, such as the femur, spinal fusion and joint replacement.
        Stephen Freiman, President of The American Ceramic Society, says advancements such as radioactive microspheres and bioactive glasses typify the behind-the-scenes support engineers provide far outside the realm in which most people think they operate. "Artificial heart valves, MRIs, drug delivery systems, diagnostic equipment -- all these things are the work and genius of engineers," says Freiman. "We're at the very foundation of modern medicine."