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IMRT The latest technology in treatment for cancer takes radiation therapy to its extreme with pinpoint accuracy By Bill Kettler Mail Tribune Rich Birkmeyer lies quietly on the treatment table while two medical technologists focus laser beams on the side of his head. Where the shafts of red light converge, pulses of radiation will bombard a tumor in Birkmeyer's brain. The Grants Pass man is one of the first Southern Oregon patients to benefit from a new computer-driven procedure that delivers more radiation to tumors while reducing damage to adjacent healthy tissues. "Part of the tumor had grown onto a vein," Birkmeyer said after a recent treatment with "intensity modulated radiation therapy" (known as IMRT in the acronym-soaked medical subculture). "They couldn't remove that. Eventually it would keep growing and block the vein." Birkmeyer has been treated at Providence Cancer Center, the first Rogue Valley cancer center to install IMRT computers and software. Providence has treated Birkmeyer and a handful of other patients since acquiring the equipment late in 2001. Rogue Valley Medical Center plans to have the capability to offer similar treatments by as early as fall 2002, said Paul Jahnke, of Asante Health System, RVMC's parent organization. The procedure will be most useful for treating tumors such as Birkmeyer's, where minimizing damage to adjacent tissue is critical, said Dr. Craig Haveman, medical director of Providence's radiation oncology department. "You've got an important structure there," Haveman said. "You can't take a little bit (of healthy tissue) here and a little bit there. If you take a little bit there, maybe the patient can't move his left arm." Haveman said the treatment also will be used for cancers of the throat, mouth, prostate and breast. To understand how the new technology works, it helps to know how radiation treatment used to happen. Until about 1995, doctors could only attack a tumor with radiation delivered equally across a square pattern, or "field" shaped with heavy metal blocks. The radiation beam damaged healthy cells around the tumor as well as cancer cells. "For years when we used radiation treatment, we'd identify a problem and point radiation beams at it and hope we didn't injure things that were in the way," Haveman said. Radiation machines with movable heads allowed physicians to treat tumors from several different directions. Assaulting a tumor from several fields reduced the overall side effects because each field was exposed to a relatively small amount of radiation. Treatments improved when scientists developed radiation machines with movable metal "leaves" that could slide back and forth to block radiation at the edges of each treatment field. Attacking a tumor from several angles with irregularly shaped radiation beams further reduced side effects, but healthy cells could still be damaged in an area of 5 millimeters (less than one-quarter inch) around the tumor. Doctors used to design the radiation-treatment fields themselves, based on images of the tumor. Calculating the fields "by hand" became overwhelming when improved technology such as CT scanning gave doctors more precise tumor images. "There's no way for the mind to shape the fields," said Suzanne Schultz, Providence's medical physicist. As computers became faster and more powerful, programs were developed that could calculate the best way to deliver the radiation. Providence's newest computer software links the computer that designs the radiation treatments directly with computer-generated three-dimensional images of the tumors and the machine that delivers the radiation. "The computer defines the field using parameters and guidelines we give it," Schultz said. "We don't come up with the shapes anymore." "The computer picks the shape and direction of the radiation fields," Haveman said. "That reduces the side effects. If we reduce the side effects, we can give more radiation (to the tumor)." Providence invested about $280,000 for IMRT equipment, in addition to the $2.5 million it spent over the past few years to build its Medford cancer center. About 20 percent of cancer patients may eventually use the procedure, said Jim Beers, Providence's director of cancer services. The new treatment adds about $10,000 to the $25,000 cost of a typical course of radiation therapy. Several security measures prevent the computers from delivering an inappropriate radiation dose. Technologists simulate the treatments before they are delivered, and each patient's individual treatment plan is saved in the computer. The computer will not allow radiation to be delivered until the technologists verify that the patient's treatment parameters are the ones being delivered. Haveman said the new technology may mark the ultimate refinement of radiation therapy as a cancer treatment. "It's probably as far as we're going to be able to go with radiation treatments (in treating cancer). In terms of what we can do (with radiation), this is the pinnacle. "The next step has to go beyond using radiation therapy." Reach reporter Bill Kettler at 776-4492, or e-mail [email protected] Mail Tribune Home | Ottaway Newspapers, Inc. | Dow Jones & Co., Inc. | Privacy | Contact Us Copyright � 2001 Mail Tribune, Inc.