Medical Device Daily Washington Editor
WASHINGTON - While bioengineering usually tends to mean the radical reshaping of living tissues and their analogues, a parallel - and equally fascinating development - is the engineering of synthetic materials with high biocompatibility, suggesting biology- and tissue-friendly uses.
One of the most fascinating of these efforts is in the development of bioceramics, including glass materials, an area focused on during a session jointly hosted early this week by The Congressional Research & Development Caucus and the Federation of Materials Societies (Washington). The session presented a brief on how these materials are being newly engineered for use in medical science, such as in the repair of bones and other human organs.
Delbert Day, CEO of MO-SCI (Rolla, Missouri), a developer of precision glass technology, led the session with a discussion on how university research on bioceramics has impacted efforts to eradicate liver cancer. He discussed the role of the company's Therasphere product - glass microspheres that encase yttrium-90 - in combating this deadly disease.
Day remarked that primary hepatocellular carcinoma (HCC), at about 18,000 cases per year in the U.S., is not as prevalent as secondary cancers of the liver that metastasize from other regions, especially the bile ducts. Secondary liver cancers occur at the rate of about 150,000 diagnoses per year. The median survival time for HCC is 18 months or less, and U.S. mortality for all liver cancers runs to 80,000 deaths per year.
Day, who conducted the first experiment on glass melting in low-gravity (near-Earth orbit) environments, observed that Theraspheres encasing yttrium-90 can attack liver cancers effectively while avoiding some of the difficulties associated with external sources of radiation, which he stated incurred the risk of damaging healthy tissue adjacent to the tumor.
The Therasphere has a diameter less than half that of the typical human hair. These spheres, which MO-SCI manufactures and sells to MDS Nordion (Ottawa, Canada), are injected into the hepatic artery which provides from 80% to 100% of the total blood supply to the liver.
The microspheres cum radiation deposit in tumor tissue at the rate of 16 to 40 times the rate of normal liver tissue because of the relatively greater blood flow to a tumor.
Day told Medical Device Daily that 60%-70% of patients displayed a "positive response" to the microspheres, meaning either a halt to tumor growth or tumor shrinkage, though he said he could not estimate survival rates for Theraspheres in this application.
"Liver cancer is the fourth leading cause of all cancer deaths," Day noted, describing the condition as "the silent death" due to lack of discernable symptoms in the early stages.
Because the disease is asymptomatic in its early stages, only 10%-18% of patients are candidates for surgery as a consequence of the advanced stage of the disease, but the difficulty of removing cancerous tissue is also a factor in the low rate of surgeries. This then provides large opportunity for use of the treatment via Theraspheres.
According to the American Cancer Society (Atlanta), "fewer than 30% of patients having surgery are able to have their cancer completely removed" and the five-year relative survival rate from liver cancer is about 7%, a number that does not include mortalities of other origins.
Erik Erbe, PhD, the chief science officer at Orthovita (Malvern, Pennsylvania), gave an overview of two of his company's flagship products, Vitoss and Cortoss, bioengineered composite materials which can be employed in spinal surgeries.
Vitoss is a material that exhibits the same kind of spongy, porous structure characteristic of some bones, allowing the mechanisms of normal bone turnover to fill in and replace this resorbable material.
Erbe said that Vitoss "is 90% air" and serves as a substitute for bone graft in a number of applications, including hip and spinal repair. This material is often employed with cultured bone marrow stromal cells to speed the replacement of diseased bone. Vitoss is made from beta-tricalcium phosphate ( -TCP) in particles roughly 100 nanometers in diameter, forming a porous, 3-D scaffold that dissolves at a rate that roughly matches the natural turnover of bone.
The spinal surgery market is a sector that promises to grow substantially as baby boomers inch up the generational ladder. According to the American Academy of Orthopedic Surgeons (Rosemont, Illinois), "281,300 primary and 18,000 revision fusion procedures were performed in 2003, representing a 130% and 170% increase, respectively, from 1990."
The Congressional R&D Caucus, according to its web site, is a bipartisan group of legislators that the 108th Congress established "at the request of Congressman Rush Holt (D-New Jersey) and Congresswoman Judy Biggert (R-Illinois)" for the purpose of raising awareness of "the national importance of research and the interdependency of research efforts across disciplines," as well as to keep other members of Congress up-to-date on issues related to such research.
The caucus' advisory committee includes the Federation of Material Societies as well as 16 other public and private sector organizations, including the American Association for the Advancement of Science and the American Chemical Society (both Washington).