Total Obliteration Rate Research Articles

Treatment selection for cerebral arteriovenous malformations: radiosurgery or microsurgery

The clinical results and patient characteristics of 318 cases of cerebral arteriovenous malformations (AVMs) were analyzed: 138 patients were treated by surgery including 98 cases of total removal and 17 cases of subtotal removal; 37 patients were treated conservatively; 139 patients were treated by gamma-knife and 6 patients were treated by linac-knife radiosurgery using stereotactic multi-converging arcs systems. Clinical data analysis was performed using the same protocol in both of the surgery and the radiosurgery groups. Operative mortality for total removal was one out of 98 cases (1%). There was one death by hemorrhage, one case of symptomatic rebleeding and two cases of asymptomatic bleeding in patients treated by radiosurgery. Thus, mortality was 1 out of 145 (0.7%). Patients with total resection of AVMs had the best clinical results in comparison with subtotal resection or with conservative treatment. Morbidity was the lowest in the patients treated by radiosurgery. However, the total obliteration rate was lower than the surgical cure rate. The decision for treatment should be based on an estimation of mortality, morbidity and cure rate for each treatment.

A CEREBRAL ARTERIOVENOUS MALFORMATION GRADING SYSTEM FOR GAMMA KNIFE RADIOSURGERY WITH THE AIM OF EARLY OBLITERATION

Bleeding in the latency period before obliteration considerably worsens the prognosis of cerebral arteriovenous malformations (AVMs). Bleeding risk should be considered and total obliteration should performed as early as possible. In this study we investigated factors related to early obliteration following Gamma Knife radiosurgery and proposed a grading system for AVMs. Forty-six patients with cerebral AVMs followed angiographically within twelve months after Gamma Knife radiosurgery were analyzed. Four factors, volume, type (categorized by our own method), location, and marginal dose were found to be correlated with early obliteration rate. We scored these factors, and categorized the scores into a grade 0 to 6 Gamma Knife Score (GKS), and evaluated the obliteration rate of each grade. The total obliteration rate in twelve months according to grade was : grades 0 and 1, 61.9% grades 2 and 3, 36.0%, grades 4 and 5, 16.7%. AVMs with a low GKS (grades 0 and 1) had a high early obliteration rate and seemed suitable for Gamma Knife radiosurgery. Since early obliteration is difficult to obtain in the high grade group, endovascular surgery should be considered to reduce the GKS before Gamma Knife radiosurgery.

State-of-the-Art Review: Gamma Knife Radio Isurgery Treatment of Cerebral AVMs

Gamma knife stereotactic radiosurgery has been shown to be a relatively safe, cost-effective, and less invasive neurosurgical intervention for the treatment of intracranial arteriovenous malformations (AVMs). Total AVM obliteration rates at 3 years postradiosurgery approach 90%, with minimal morbidity and no mortality.

Heavy-Charged-Particle Radiosurgery for Intracranial Arteriovenous Malformations

We have treated over 400 patients with symptomatic inoperable intracranial arteriovenous malformations (AVMs) with stereotactic heavy-charged-particle Bragg peak radiosurgery at the University of California at Berkeley in a collaborative program with Stanford University Medical Center and the University of California Medical Center, San Francisco. A long-term dose-searching clinical trial protocol has been developed and we have followed more than 250 patients for more than 2 years. Initially, radiation doses ranged from 45 to 35 GyE, and now doses of 25, 20, 15 and, under special circumstances, 10 GyE, depending on a number of factors, are being evaluated. The characteristics of charged-particle beams provide a relatively homogeneous dose distribution with the 90% isodose contour to the periphery of the lesion. When the entire arterial phase of the AVM core is included in the treatment field, the rates for complete obliteration 3 years after treatment are: 90-95% for volumes less than or equal to 4 cm3; 90-95% for volumes greater than 4 and less than or equal to 14 cm3; and 60-70% for volumes greater than 14 cm3. The total obliteration rate for all volumes up to 70 cm3 is approximately 80-85%. For complete radiation-induced obliteration there is a relationship of dose and volume primarily, and location secondarily. Results on relationships between dose, AVM obliteration, and complications and sequelae of the radiosurgical procedure are presented and discussed.

Radiosurgery of cerebral arteriovenous malformations with the dynamic stereotactic irradiation

From December 1986 through December 1988, 33 patients with inoperable arteriovenous malformation (AVM) were treated in our center with the dynamic stereotactic radiosurgery, which uses a standard 10 MV isocentric linear accelerator. There were 18 females and 15 males with a median age of 26 years (range: 9–69) and a median follow-up time of 16 months (range: 7–32). The arteriovenous malformation volumes treated ranged from 0.2 to 42 cm 3. The prescribed doses at the isocenter varied from 50 to 55 Gy and were given as a single fraction in the majority of the patients ( 31 33 ). Late complications consisting of intracranial bleeding and/or hemiparesis were observed in three patients. To date, 21 patients underwent repeat angiographic studies at 1 year post-treatment. A complete obliteration of the lesion was achieved in 38% of these patients. For the patients whose arteriovenous malformation nidus was covered by a minimum dose of 25 Gy, the total obliteration rate was 61.5% (8/13), whereas none of the patients who had received less than 25 Gy at the edge of the nidus obtained a total obliteration. Our preliminary analysis at I year post-radiosurgery reveals results comparable to those previously reported for other radiosurgical techniques for the same follow-up period.