EMBARGOED FOR RELEASE ON APRIL 11, 9:45 A.M. MST
Research Analyzes the Risks and Outcomes of Repeat Stereotactic Radiosurgery in Patients with Arteriovenous Malformations
Newswise — DENVER (April 11, 2011) − An arteriovenous malformation (AVM) is a tangle of abnormal and poorly formed blood vessels (arteries and veins), with an innate propensity to bleed. An AVM can occur anywhere in the body, but brain and spinal AVMs present substantial risks when they bleed. Because the brain and its blood vessels are formed together during embryological development, abnormal blood vessel formation is often associated with abnormal brain tissue. Consequently, AVMs are usually associated with a focal abnormality of brain tissue, allowing them to be removed without damage to normal brain tissue.
AVMs affect an estimated one in 100,000 people, with two-thirds of cases occurring in people ages 40 and younger. Every year, about four out of every 100 people with an AVM experience a hemorrhage. Each hemorrhage poses a 15-20 percent risk of death or stroke, 30 percent neurological morbidity, and 10 percent mortality. Stereotactic radiosurgery precisely focuses radiation directly at the AVM causing the vessels to slowly block off over several years, thereby greatly decreasing the risk of intracranial bleeding in the majority of patients.
Researchers at the University of Pittsburgh School of Medicine assessed the risks and efficacy of repeat stereotactic radiosurgery in patients with AVMs. The results of this study, Repeat Stereotactic Radiosurgery for Arteriovenous Malformations, will be presented by Hideyuki Kano, MD, PhD, 4:31-4:45 pm, Monday, April 11, during the 79th Annual Scientific Meeting of the American Association of Neurological Surgeons in Denver. Co-authors are Douglas Kondziolka, MD, MSc, John C. Flickinger, MD, Huai che Yang, MD, Thomas J. Flannery, MD, PhD, Nasir R. Awan, FCPS, Ajay Niranjan, MCh, MBA, Josef Novotny Jr., PhD, and L. Dade Lunsford, MD, FACS.
Between 1987 and 2006, Gamma Knife® SRS was performed on 996 patients with AVMs. During this time period, repeat SRS was performed on 105 patients who had incompletely obliterated AVMs. Of the 105 patients, there were 53 males and 52 females. Their median age was 31 years (range, 2-66 years) at time of the initial SRS treatment.
Repeat SRS was performed at a median of 40.9 months after initial SRS treatment (range, 27.5-139 months). The median AVM target volume at initial SRS was 6.4 cc (range, 0.2-26.3cc) but was reduced to 2.3cc (range, 0.1-18.2cc) at the time of the second procedure. The median margin dose at both initial SRS and repeat SRS was 18 Gy. The following results were noted:
•The actuarial rate of total obliteration by angiography or MRI after repeat SRS was 35 percent, 68 percent, 77 percent, and 80 percent at 3, 4, 5, and 10 years, respectively. •The median time to complete angiographic or MRI obliteration after repeat SRS was 39 months. •Factors associated with a higher rate of AVM obliteration were smaller residual AVM target volume (p=0.038), and > 50 percent of volume reduction after the initial procedure (p=0.014). •Seven patients (7 percent) had a hemorrhage in the interval between initial SRS and repeat SRS. •Seventeen patients (16 percent) had a hemorrhage after repeat SRS and six patients died. •The cumulative actuarial rates of new AVM hemorrhage after repeat SRS were 1.9 percent, 8.1 percent, 10.1 percent, 10.1 percent and 22.4 percent at 1, 2, 3, 5, and 10 years, respectively. That translates to annual hemorrhage rates of 4.05 percent and 1.79 percent for developing new post-repeat-SRS bleeds a year for years 0-2 and 2-10 following repeat SRS.
“Repeat SRS for incomplete obliterated AVMs significantly improves the eventual obliteration rate of AVMs that are not occluded after the first procedure. The risk of delayed hemorrhage and death are reduced over time, but persist if the AVM fails to obliterate despite this additional management. Our research shows that repeat SRS is most effective in patients with smaller residual AVM volumes after the first procedure and those who have not experienced a prior hemorrhage,” said Dr. Kano.
Founded in 1931 as the Harvey Cushing Society, the American Association of Neurological Surgeons (AANS) is a scientific and educational association with more than 8,000 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public. All active members of the AANS are certified by the American Board of Neurological Surgery, the Royal College of Physicians and Surgeons (Neurosurgery) of Canada or the Mexican Council of Neurological Surgery, AC. Neurological surgery is the medical specialty concerned with the prevention, diagnosis, treatment and rehabilitation of disorders that affect the entire nervous system, including the spinal column, spinal cord, brain and peripheral nerves.
Disclosure: The work described in this report was funded by an outcomes research grant to Dr. Kano from AB Elekta, Stockholm, Sweden.
Drs. Lunsford, Kondziolka, Niranjan, and Novotny are consultants for AB Elekta and Dr. Lunsford is a stockholder.
Media Representatives: If you would like to cover the meeting or interview a neurosurgeon − either on-site or via telephone − please contact the AANS Communications Department at (847) 378-0517 or call the Annual Meeting Press Room beginning Monday, April 11 at (303) 228-8431.
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