Oct. 12, 2004 Emory University's Winship Cancer Institute is the first site in the world to offer a new, extremely precise, image-guided radiation treatment system for brain tumors, offering patients an alternative to surgical removal of tumors. The Trilogy system, created by Varian Medical Systems, delivers higher doses of targeted radiation to smaller areas with more precision over a shorter period of time. It allows doctors to customize the treatment plan for each patient.
The Trilogy can deliver several types of radiation to the head depending on the needs of the patient. For a small brain tumor, doctors use stereotactic radiosurgery, which delivers a single high-dose of radiation in one treatment. For larger tumors, doctors use stereotactic radiotherapy, delivering radiation in multiple treatments. The Trilogy can also be used for traditional radiation therapy, which is delivered in daily small doses over a period of weeks. In all cases, treatment involves the use of focused external beams of radiation delivered to a specific area of the brain to treat arteriovenous malformations (AVMs) or tumors. Patients are placed in a mask or a frame to completely restrict the head's movement, permitting the most precise and accurate treatment. Each treatment takes 30 to 45 minutes.
"Stereotactic radiosurgery has been a non-surgical alternative for certain types of brain tumors for many years," says Nelson Oyesiku, MD, PhD, FACS, professor of neurosurgery, Emory University School of Medicine. "It may be used as a primary treatment for inoperable brain tumors or in combination with other treatments with recurrent or malignant tumors. This new Trilogy system allows for the most precise targeting of tumors or brain abnormalities, targeting the area within 0.4 of a millimeter, compared with the next best machine which targets within 0.75 of a millimeter." One might describe 0.4 of a millimeter as similar to the width of a pencil line drawn on a piece of paper.
The new machine comes equipped with a robotic medical linear accelerator, which rotates around the patient to deliver radiation treatments from nearly any angle. It also includes a device to shape the radiation beam to match the three-dimensional shape of the tumor. A new On-Board Imager device provides fast, real-time tumor tracking and automated patient positioning. This allows doctors to see and track the tumor at the moment of treatment. The machine can also deliver higher doses of radiation to smaller areas.
"In many cases, this new system allows patients to undergo a same-day, outpatient procedure, rather than a trip to the operating room," says Ian Crocker, MD, FACR, professor of radiation oncology at Emory. "It's a quick treatment and it's extremely accurate in targeting the tumor, and only the tumor, without affecting surrounding healthy brain tissue."
Stereotactic radiosurgery works by damaging the DNA in tumor cells. In some cases, it causes complete disappearance of the tumor, where in other cases, it may prevent further growth of the tumor. For fast-growing malignant and metastatic tumors, results may be seen as soon as a month. With slow-growing tumors, these changes may appear over months to a year or two. Besides benign and malignant tumors, radiosurgery can be used to treat AVMs, which are tangles of abnormal blood vessels in the brain that are prone to bleed.
The most common side-effect of stereotactic radiosurgery is swelling at the sites of the frame placement, where screws attach to the skull. This swelling will resolve in a week or two. Because the amount of radiation to normal brain tissue is very small, side-effects are infrequent. In rare cases, however, serious long-term side-effects could occur.
"The benefits of stereotactic approaches are most appropriate with smaller lesions or tumors," says Dr. Oyesiku. "This new technology is bringing new hope to patients with certain forms of brain cancer."
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