Researchers focusing on various image-guided methods also evaluate quality of embolizing particles
MR-guided focused ultrasound may be a hot technique for treating uterine fibroids, but it has a major disadvantage. Patients must endure hours in an MR magnet while undergoing thermal treatment. A new rapid interleaved technique can slash the treatment time by at least 50%, a development that could make the study more practical.
High-intensity focused ultrasound uses ultrasound beams to thermally ablate vessels supplying blood to fibroids. With the current technique, ultrasound beams frequently overlap and can result in overheating an area. To safeguard against this, practitioners wait 90 seconds between sonications to allow cooling. The rapid interleaved technique involves moving each successive sonication far enough away to spread out the beams and avoid overlap. Cooling time is reduced to 45 seconds.
"Compared to the prior technique, you can either treat fibroids in 50% to 60% less time, or you can treat double the size fibroid," said Dr. George Holland, director of MRI at the Lahey Clinic in Burlington, MA.
Holland and colleagues demonstrated the rapid interleaved technique in 42 treatments in a study funded entirely by InSightec, makers of the only FDA-approved MR-guided focused ultrasound device. During a three-hour treatment with the new technique, researchers achieved 127 sonications, compared with 60 or 70 sonications with the conventional method. Patients recovered immediately or within two days post-treatment. None required narcotics or hospitalization.
As an alternative to the MR magnet, some facilities are performing high-intensity focused ultrasound with ultrasound guidance on an investigational basis. A system produced by Beijing Yuande Biomedical Engineering of China, which is not approved for commercial use in the U.S., has been installed in a number of sites. The University of Washington in Seattle recently received a unit.
Ultrasound guidance can be performed almost in real-time, measuring thermal spots and determining the need for more or less therapy, said Dr. R. Torrance Andrews, chief of vascular and interventional radiology at UW.
Meanwhile, new evidence is emerging about materials used in another increasingly popular fibroid treatment: uterine fibroid embolization. Traditionally, doctors used PVA, classic polyvinyl alcohol particles, and extensive research shows this agent is safe and effective.
But newer agents that have a spherical shape, such as Contour SE (sPVA) and Embosphere Microspheres (trisacryl gelatin microspheres), are now approved and available. Most recently, Bead Block has hit the market. Spherical agents are said to be easier to use, due to their round shape, but long-term safety and efficacy data have been lacking.
A number of studies have shown that Contour SE is less effective than other agents and more likely to lead to fibroid recurrence. The differences became evident on contrast-enhanced MRI.
"We should put all of the new products to the test. We want to treat patients with durable agents," said Dr. James Spies, a professor of radiology at Georgetown University.
At the 2006 Society of Interventional Radiology meeting, Spies presented the first long-term results in a multicenter trial of Embosphere. Researchers enrolled about 100 patients in the study and had long-term follow-up data after three years for 64% of them. The agent proved safe and effective.
"There were good outcomes across the board. This is good news for patients," Spies said.