Does hemorrhagic presentation in cerebral arteriovenous malformations affect obliteration rate after gamma knife radiosurgery?

Linear accelerator stereotactic radiosurgery in the management of intracranial arteriovenous malformations: long-term outcome

BACKGROUND

Arteriovenous malformation (AVM) is one of the cerebrovascular diseases that bear a high risk of hemorrhage. The treatment modalities include microsurgical resection, endovascular embolization, stereotactic radiosurgery, or combinations that vary widely. Several large series have been reported, while data from Asian populations were few. The aim of this study was to examine the efficacy of linear accelerator stereotactic radiosurgery (LINAC SRS) for the treatment of intracranial AVMs, to evaluate the hemorrhage rate and to analyze associated factors.

METHODS

One hundred and sixteen patients with AVM were treated with LINAC SRS in a single institute between September 1994 and May 2005 and were retrospectively evaluated. The demographics of patients, clinical characteristics of AVM, the treatment modalities, and the parameters of the LINAC SRS were analyzed. Delayed toxicity and hemorrhage rate after treatment were also evaluated. The AVM obliteration and bleed rates were calculated using the Kaplan-Meier method and Cox regression analyses.

RESULTS

The efficacy rate with total obliteration after treatment was 81.9% (95 of 116 patients). The median interval to achieve total obliteration was 49 months. Microsurgical resection combined with SRS for residual AVMs achieved better obliteration rates compared to SRS alone (statistically significant, p = 0.001), while no significant difference was found between the embolization group and the group with no prior treatment (p = 0.895). The Spetzler-Martin grade of AVM is a relative factor of obliteration, higher grades resulting in a worse outcome (p = 0.009). Obliteration was significantly influenced by AVM volume in univariate analysis (p = 0.034), and volume <5 cm(3) contributed to improved obliteration (p = 0.01). There was no statistically significant difference in the hemorrhagic rate and the complication rate between ruptured and unruptured AVMs, while the unruptured group had a higher obliteration rate (p = 0.024). The annual hemorrhage rate after LINAC SRS treatment was 1.9%. The bleeding rate was 3.3% in the first year after radiosurgery, 2.1% in the second year, 1.9% between the second and fifth year, and 1.5% between the fifth and tenth year. Patients with hemorrhagic events before radiosurgery appeared to have a higher rebleeding risk during the latency period. Twenty-three patients (19.8%) had late adverse effects with regard to posttreatment radiological follow-up, but only 1 (0.8%) had newly developed neurological deficits.

CONCLUSION

LINAC SRS achieved a high obliteration rate and reduced the risk of hemorrhage effectively in ruptured and unruptured intracranial AVMs. Prior microsurgical resection provided better outcome, while embolization showed no benefit. Adverse effects after treatment are acceptable and require long-term follow-up.

Proposal for a new prognostic score for linac-based radiosurgery in cerebral arteriovenous malformations

PURPOSE

We evaluate patient-, angioma-, and treatment-specific factors for successful obliteration of cerebral arteriovenous malformations (AVM) to develop a new appropriate score to predict patient outcome after linac-based radiosurgery (RS).

METHODS AND MATERIALS

This analysis in based on 293 patients with cerebral AVM. Mean age at treatment was 38.8 years (4-73 years). AVM classification according Spetzler-Martin was 55 patients Grade I (20.5%), 114 Grade II (42.5%), 79 Grade III (29.5%), 19 Grade IV (7.1%), and 1 Grade V (0.4%). Median maximum AVM diameter was 3.0 cm (range, 0.3-10 cm). Median dose prescribed to the 80% isodose was 18 Gy (range, 12-22 Gy). Eighty-five patients (29.1%) had prior partial embolization; 141 patients (51.9%) experienced intracranial hemorrhage before RS. Median follow-up was 4.2 years.

RESULTS

Age at treatment, maximum diameter, nidus volume, and applied dose were significant factors for successful obliteration. Under presumption of proportional hazard in the dose range between 12 and 22 Gy/80% isodose, an increase of obliteration rate of approximately 25% per Gy was seen. On the basis of multivariate analysis, a prediction score was calculated including AVM maximum diameter and age at treatment. The prediction error up to the time point 8 years was 0.173 for the Heidelberg score compared with the Kaplan-Meier value of 0.192. An increase of the score of 1 point results in a decrease of obliteration chance by a factor of 0.447.

CONCLUSION

The proposed score is linac-based radiosurgery-specific and easy to handle to predict patient outcome. Further validation on an independent patient cohort is necessary.

Linac stereotactic radiosurgery for the treatment of small arteriovenous malformations: lower doses can be equally effective

OBJECTIVE

The purpose of this study was to examine the efficacy and toxicity of treating small arteriovenous malformations (AVMs) (≤3 cm in diameter) with a median marginal applied dose of 14 Gy.

METHODS

Two hundred and thirteen patients diagnosed with AVMs were treated between January 1991 and December 2005. Seventy-three percent of the patients had hemorrhaged prior to treatment, 13% had had previous surgery and 19.2% had had previous embolization. The median follow-up duration was 48.1 months.

RESULTS

The Kaplan-Meier analysis estimated that the 36-month obliteration rate was 65.5% for patients undergoing their first stereotactic radiosurgery (SRS) and 68.3% for those undergoing repeated SRS. The Kaplan-Meier analysis estimated the 60-month AVMs obliteration rate for the entire cohort to be 82.4%. The median time to AVM obliteration was 40 ± 2.8 months. We found a statistically significant relationship between the time of obliteration and the following factors: site of the AVMs (sites other than brainstem), a higher prescribed dose and a positive history of previous hemorrhage. Thirteen patients (7.6%) experienced toxicities.

CONCLUSIONS

SRS was an effective and safe treatment for AVMs ≤3 cm in diameter, with acceptable toxicity.

The radiosurgical treatment of arteriovenous malformations: obliteration, morbidities, and performance status

OBJECTIVE

This study examined the single-center treatment outcomes of arteriovenous malformations (AVMs) of the brain using stereotactic radiosurgery, with regard to obliteration, predictive factors, morbidities, and patient performance status.

PATIENTS AND METHODS

127 patients were treated between 1990 and 2008 by use of linear accelerator or Gamma Knife. Their median age was 37 years, the median AVM volume was 7.3 cc (range, 0.014-113.13 cc), and the median follow-up duration was 42 months (range, 6-209 months). Forty-two percent of patients presented with intracranial hemorrhage, 31% received embolization, and 8% underwent prior resection. Thirty-one percent of patients received more than one round of radiosurgery.

RESULTS

64% of patients had complete obliteration confirmed by magnetic resonance imaging or angiography. Positive predictors of obliteration included pretreatment hemorrhage (p = 0.042), smaller AVM volume (odds ratio = 1.25; 95% CI, 1.03-1.52), and larger marginal dose (odds ratio = 0.292; 95% CI, 0.100-0.820), whereas embolization (p < 0.001) was a negative predictor . The annual risk of hemorrhage after radiosurgery was 2.2%, and the risk of death as a result of hemorrhage was 0.6-1.3%. Eleven percent of patients reported new or worsened neurologic symptoms. Radiosurgery was effective in treating AVM-related headaches (p < 0.001) but did not improve the performance status of patients.

CONCLUSIONS

Stereotactic radiosurgery is an effective tool in the treatment of AVMs and amelioration of AVM-related headaches, but it did not affect the patients' performance status. Factors affecting obliteration include prior hemorrhage, marginal dose, prior embolization, and AVM volume. Risk of hemorrhage persists in the latency period after radiosurgery, and it remains finite even after complete obliteration.