Effect of treatment period on outcomes after stereotactic radiosurgery for brain arteriovenous malformations: an international multicenter study

Biologically Effective Dose and Prediction of Obliteration of Arteriovenous Malformations in Pediatric Patients Treated by Gamma Knife Radiosurgery

BACKGROUND AND OBJECTIVES

Stereotactic radiosurgery (SRS) represents an effective treatment for pediatric arteriovenous malformations (AVMs). Biological effective dose (BED) has shown promising results in 2 previous studies as a predictive variable for outcomes in adults, but its role has never been studied in pediatric outcomes.

METHODS

Retrospective data for patients 18 years or younger treated with a single-session SRS for AVMs were collected from 1989 to 2019. BED calculations were performed using an α/β ratio of 2.47. Kaplan-Meier analysis was used to evaluate obliteration, new hemorrhage, and radiation-induced changes (RIC). Cox-regression analysis was used for obliteration prediction using 2 models (margin dose vs BED).

RESULTS

One hundred ninety-seven patients (median age = 13.1 years, IQR = 5.2) were included; 72.6% (143/197) of them presented initially with spontaneous hemorrhage. A median margin dose of 22 Gy (IQR = 4.0) with a median BED of 183.2 Gy (IQR = 70.54) was used to treat AVM with a median volume of 2.8 cm 3 (IQR = 2.9). After SRS, obliteration was confirmed in 115/197 patients (58.4%) using magnetic resonance imaging and angiography at a median follow-up of 2.85 years (IQR = 2.26). The cumulative obliteration probability was 43.6% (95% CI = 36.1-50.3), 60.5% (95% CI+ = 2.2-67.4), and 66.0% (95% CI = 56.0-73.7) at 3, 5, and 10 years, respectively. In Cox multivariate analysis, a BED >180 Gy (hazard ratio [HR] = 2.11, 95% CI = 1.30-3.40, P = .002) in model 1 and a margin dose >20 Gy (HR = 1.90, 95% CI = 1.15-3.13, P = .019) in model 2 were associated with obliteration. An AVM nidus volume >4 cm 3 was associated with lower obliteration rates in both models. The probability of symptomatic RIC at 10 years was 8.6% (95% CI = 3.5-13.4). Neither BED nor margin dose was associated with RIC occurrence, with the only predictive factor being deep AVM location (HR = 3, 95% CI = 1-9.1, P = .048).

CONCLUSION

This study confirms BED as a predictor for pediatric AVM obliteration. Optimization of BED in pediatric AVM SRS planning may improve cumulative obliteration rates.

Frameless versus frame-based stereotactic radiosurgery for intracranial arteriovenous malformations: A propensity-matched analysis

Objective

The frameless linear accelerator (LINAC) based stereotactic radiosurgery (SRS) has been evolving with a reduction in patient discomfort. However, there was limited evidence comparing frame-based and frameless SRS for intracranial arteriovenous malformations (AVM). We aimed to compare the treatment outcomes between frame-based and frameless LINAC SRS.

Materials and Methods

This retrospective cohort compared the outcomes of frame-based LINAC SRS (1998-2009) with frameless LINAC SRS (2010-2020). The primary outcome was the obliteration rate. The other outcomes included the neurological, radiological, and functional outcomes after SRS. A matched cohort was identified by propensity scores for further comparisons.

Results

A total of 65 patients were included with a mean follow-up time of 13.2 years (158.5 months). There were 40 patients in the frame-based group and 25 patients in the frameless group. The overall obliteration rate was comparable (Frame-based 82.5% vs Frameless 80.0%, p = 0.310) and not significantly different over time (log-rank p = 0.536). The crude post-SRS hemorrhage rate was 1.5% and the incidence was 0.3 per 100 person-years. There were 67.7% of patients with AVM obliteration without new persistent neurological deficits at the last visit and 56.9% of patients with AVM obliteration without any deficits (transient or persistent) during the entire follow-up period. Four patients (8.0%) developed late onset persistent adverse radiation effects (more than 96 months after SRS) among 50 patients with more than 8-year surveillance. In the propensity-matched cohort of 42 patients, there was no significant difference in AVM obliteration (Frame-based vs Frameless, log-rank p = 0.984).

Conclusion

Frameless and frame-based LINAC SRS have comparable efficacy in intracranial AVM obliteration. A longer follow-up duration may further characterize the rate of late adverse radiation effects in frameless SRS.

Stereotactic radiosurgery for intermediate- and high-grade arteriovenous malformations: outcomes stratified by the supplemented Spetzler-Martin grading system

OBJECTIVE

The supplemented Spetzler-Martin (Supp-SM) grading system was developed to improve the predictive accuracy of surgical risk for patients with brain arteriovenous malformations (AVMs). The aim of this study was to apply the Supp-SM grading system to patients having stereotactic radiosurgery (SRS) for Spetzler-Martin (SM) intermediate- (grade III) or high-grade (grade IV-V) AVMs to enable comparison with published microsurgical series.

METHODS

In 219 patients who underwent SRS during the period from 1990 to 2016, the Supp-SM grade was calculated for SM grade III (n = 154) or SM grade IV-V (n = 65) AVMs. The Supp-SM grades in these patients were 4 (n = 14, 6%), 5 (n = 36, 16%), 6 (n = 67, 31%), 7 (n = 76, 35%), and 8-9 (n = 26, 12%). Sixty patients (27%) had deep AVMs (basal ganglia, thalamus, or brainstem). Thirty-nine patients (18%) had volume-staged SRS; 41 patients (19%) underwent repeat SRS. The median follow-up period was 69 months for SM grade III AVMs and 113 months for SM grade IV-V AVMs.

RESULTS

AVM obliteration was confirmed in 163 patients (74%) at a median of 38 months after initial SRS. The obliteration rates at 4 and 8 years were 59% and 76%, respectively. Thirty-one patients (14%) had post-SRS deficits from hemorrhage (n = 7, 3%) or radiation injury (n = 24, 11%). Six patients (3%) died after SRS (hemorrhage, n = 5; radiation injury, n = 1). The rates of neurological decline or death at 4 and 8 years were 11% and 18%, respectively. Factors predictive of nonobliteration were deep location (HR 0.57, 95% CI 0.39-0.82, p = 0.003) and increasing AVM volume (HR 0.96, 95% CI 0.93-0.99, p = 0.002). Increasing AVM volume was the only factor associated with neurological decline (HR 1.05, 95% CI 1.02-1.08, p = 0.002). The Supp-SM grading score did not correlate with either obliteration (HR 0.94, 95% CI 0.82-1.09, p = 0.43) or neurological decline (HR 1.15, 95% CI 0.84-1.56, p = 0.38).

CONCLUSIONS

The Supp-SM grading system was not predictive of outcomes after SRS of intermediate- or high-grade AVM. In a cohort that included a high percentage (47%) of "inoperable" AVMs according to Supp-SM grade (≥ 7), most patients had obliteration after SRS, although there was a high risk of neurological decline.

The factors associated with obliteration following stereotactic radiosurgery in patients with brain arteriovenous malformations: a meta-analysis

BACKGROUND

Various factors have been reported to affect the obliteration of brain arteriovenous malformations (AVM) following stereotactic radiosurgery (SRS). This meta-analysis was conducted to identify the factors potentially associated with AVM obliteration after SRS.

METHODS

We comprehensively searched databases and included studies that evaluated predictors of AVM obliteration after SRS using Cox proportional hazard regression analysis. Hazard ratios (HRs) with 95% confidence intervals (CIs) were utilized as effect estimates.

RESULTS

Twelve studies, involving 4415 AVM cases, were included. According to combined estimates on univariate (UV) and multivariate (MV) analysis, age, gender and prior haemorrhage did not affect the closure probability. The following factors showed a significant and independent association with increased AVM obliteration: smaller AVMs maximal diameter (MV, HR: 1.32), smaller AVM volume (MV, HR: 1.05), AVM volume <10-15 cc (MV, HR: 1.55), higher margin dose (MV, HR: 1.05), margin dose ≥17-18 Gy (MV, HR: 3.71) and early treatment period (MV, HR: 1.78). Previous embolization and deep-seated AVM were independently negative predictors of obliteration whereas deep venous drainage was a positive predictor. Prior surgery, compactness of nidus, lower grading scores and higher SRS maximum dose were associated factors subject to confounding factors.

CONCLUSION

Multiple factors associated with obliteration should be taken into consideration for selection of candidates with AVMs for SRS. AVM volume and radiation dose are the most prominent factor in assessing obliteration after SRS. Age, gender and prior haemorrhage may not affect the consideration of SRS treatment. Cautious use of SRS is needed for previously embolized AVM patients.

Long-term outcomes of 170 brain arteriovenous malformations treated by frameless image-guided robotic stereotactic radiosurgery: Ramathibodi hospital experience

This study was conducted to report long-term outcomes of the frameless robotic stereotactic radiosurgery (SRS) for brain arteriovenous malformation (AVM) at Ramathibodi Hospital.Retrospective data of patients with brain AVM (bAVM), who underwent CyberKnife SRS (CKSRS) at Ramathibodi Hospital from 2009 to 2014, were examined. Exclusion criteria were insufficient follow-up time (<36 months) or incomplete information. Patients' demographics, clinical presentation, treatment parameters, and results were analyzed. Excellent outcome was defined as AVM obliteration without a new neurological deficit. Risk factors for achieving excellent outcome were assessed.From a total of 277 CKSRS treatments for bAVM during the 6 years, 170 AVMs in 166 patients met the inclusion criteria. One hundred and thirty-nine cases (81.76%) presented with hemorrhages from ruptured bAVMs. Almost two-thirds underwent embolization before radiosurgery. With the median AVM volume of 4.17 mL, three-quarters of the cohort had single-fraction CKSRS, utilizing the median prescribed dose of 15 Gray (Gy). In the multisession group (25.29%), the median prescribed dose and the AVM volume were 27.5 Gy and 22.3 mL, respectively. An overall excellent outcome, at a median follow-up period of 72.45 months, was observed in 99 cases (58.24%). Seven AVMs (4.12%) ruptured after CKSRS but 1 patient suffered a new neurological deficit. Two patients (1.18%) were classified into the poor outcome category but there were no deaths. Negative factors for excellent outcome, by multivariate regression analysis, were the male sex and multisession SRS delivery, but not age, history of AVM rupture, previous embolization, or AVM volume.Despite relatively larger bAVM and utilizing a lower prescribed radiation dose, the excellent outcome was within the reported range from previous literature. This study offers one of the longest follow-ups and the largest cohorts from the frameless image-guided robotic SRS community.

Outcomes of Cushing's disease following Gamma Knife radiosurgery: effect of a center's growing experience and era of treatment

OBJECTIVE

Stereotactic radiosurgery (SRS) is used for the management of residual or recurrent Cushing's disease (CD). Increasing experience and technological advancements of Gamma Knife radiosurgery (GKRS) systems can impact the outcomes of CD patients. The authors evaluated the association of their center's growing experience and the era in which GKRS was performed with treatment success and adverse events in patients with CD.

METHODS

The authors studied consecutive patients with CD treated with GKRS at the University of Virginia since installation of the first Gamma Knife system in March 1989 through August 2019. They compared endocrine remission and complication rates between patients treated before 2000 (early cohort) and those who were treated in 2000 and later (contemporary cohort).

RESULTS

One hundred thirty-four patients with CD underwent GKRS during the study period: 55 patients (41%) comprised the early cohort, and 79 patients (59%) comprised the contemporary cohort. The contemporary cohort, compared with the early cohort, had a significantly greater treatment volume, radiation prescription dose, maximal dose to the optic chiasm, and number of isocenters, and they more often had cavernous sinus involvement. Endocrine remission rates were higher in the contemporary cohort when compared with the early cohort (82% vs 66%, respectively; p = 0.01). In a Cox regression analysis adjusted for demographic, clinical, and SRS characteristics, the contemporary GKRS cohort had a higher probability of endocrine remission than the early cohort (HR 1.987, 95% CI 1.234-3.199; p = 0.005). The tumor control rate, incidence of cranial nerve neuropathy, and new anterior pituitary deficiency were similar between the two groups.

CONCLUSIONS

Technological advancements over the years and growing center experience were important factors for improved endocrine remission rates in patients with CD. Technological aspects and results of contemporary Gamma Knife systems should be considered when counseling patients, planning treatment, and reporting treatment results. Studies exploring the learning curve for GKRS are warranted.

Does the Diffuseness of the Nidus Affect the Outcome of Stereotactic Radiosurgery in Patients with Unruptured Cerebral Arteriovenous Malformations?

BACKGROUND

We proposed an algorithm to automate the components within the identification of components within the nidus of cerebral arteriovenous malformations (AVMs) which may be used to analyze the relationship between its diffuseness and treatment outcomes following stereotactic radiosurgery (SRS).

OBJECTIVES

to determine the impact of the diffuseness of the AVM nidus on SRS outcomes.

METHODS

This study conducted regular follow-ups of 209 patients with unruptured AVMs who underwent SRS. The diffuseness of the AVM nidus was estimated by quantifying the proportions of vascular nidal component, brain parenchyma, and cerebrospinal fluid in T2-weighted MRIs. We used Cox regression analysis to characterize the association between nidal diffuseness and treatment outcomes in terms of obliteration rate and radiation-induced change (RICs) rate following SRS.

RESULTS

The median AVM volume was 20.7 cm3. The median duration of imaging follow-up was 51 months after SRS. The overall AVM obliteration rate was 68.4%. RICs were identified in 156 of the 209 patients (74.6%). The median proportions of the nidus of AVM and brain parenchyma components within the prescription isodose range were 30.2 and 52.2%, respectively. Cox regression multivariate analysis revealed that the only factor associated with AVM obliteration rate after SRS was AVM volume. However, a larger AVM volume (>20 mL) and a larger proportion of brain parenchyma (>50%) within the prescription isodose range were both correlated with a higher RIC rate following SRS.

CONCLUSIONS

The diffuseness of the nidus indeed appears to affect the RIC rate following SRS in patients with unruptured AVMs.

Stereotactic Radiosurgery for Cavernous Sinus Versus Noncavernous Sinus Dural Arteriovenous Fistulas: Outcomes and Outcome Predictors

BACKGROUND

Dural arteriovenous fistulas (DAVFs) can be categorized based on location.

OBJECTIVE

To compare stereotactic radiosurgery (SRS) outcomes between cavernous sinus (CS) and non-CS DAVFs and to identify respective outcome predictors.

METHODS

This is a retrospective study of DAVFs treated with SRS between 1988 and 2016 at 10 institutions. Patients' variables, DAVF characters, and SRS parameters were included for analyses. Favorable clinical outcome was defined as angiography-confirmed obliteration without radiological radiation-induced changes (RIC) or post-SRS hemorrhage. Other outcomes were DAVFs obliteration and adverse events (including RIC, symptomatic RIC, and post-SRS hemorrhage).

RESULTS

The overall study cohort comprised 131 patients, including 20 patients with CS DAVFs (15%) and 111 patients with non-CS DAVFs (85%). Rates of favorable clinical outcome were comparable between the 2 groups (45% vs 37%, P = .824). Obliteration rate after SRS was higher in the CS DAVFs group, even adjusted for baseline difference (OR = 4.189, P = .044). Predictors of favorable clinical outcome included higher maximum dose (P = .014) for CS DAVFs. Symptomatic improvement was associated with obliteration in non-CS DAVFs (P = .005), but symptoms improved regardless of whether obliteration was confirmed in CS DAVFs. Non-CS DAVFs patients with adverse events after SRS were more likely to be male (P = .020), multiple arterial feeding fistulas (P = .018), and lower maximum dose (P = .041).

CONCLUSION

After SRS, CS DAVFs are more likely to obliterate than non-CS ones. Because these 2 groups have different total predictors for clinical and radiologic outcomes after SRS, they should be considered as different entities.

Evaluation of stereotactic radiosurgery for cerebral dural arteriovenous fistulas in a multicenter international consortium

OBJECTIVE

In this multicenter study, the authors reviewed the results obtained in patients who underwent Gamma Knife radiosurgery (GKRS) for dural arteriovenous fistulas (dAVFs) and determined predictors of outcome.

METHODS

Data from a cohort of 114 patients who underwent GKRS for cerebral dAVFs were compiled from the International Gamma Knife Research Foundation. Favorable outcome was defined as dAVF obliteration and no posttreatment hemorrhage or permanent symptomatic radiation-induced complications. Patient and dAVF characteristics were assessed to determine predictors of outcome in a multivariate logistic regression analysis; dAVF-free obliteration was calculated in a competing-risk survival analysis; and Youden indices were used to determine optimal radiosurgical dose.

RESULTS

A mean margin dose of 21.8 Gy was delivered. The mean follow-up duration was 4 years (range 0.5-18 years). The overall obliteration rate was 68.4%. The postradiosurgery actuarial rates of obliteration at 3, 5, 7, and 10 years were 41.3%, 61.1%, 70.1%, and 82.0%, respectively. Post-GRKS hemorrhage occurred in 4 patients (annual risk of 0.9%). Radiation-induced imaging changes occurred in 10.4% of patients; 5.2% were symptomatic, and 3.5% had permanent deficits. Favorable outcome was achieved in 63.2% of patients. Patients with middle fossa and tentorial dAVFs (OR 2.4, p = 0.048) and those receiving a margin dose greater than 23 Gy (OR 2.6, p = 0.030) were less likely to achieve a favorable outcome. Commonly used grading scales (e.g., Borden and Cognard) were not predictive of outcome. Female sex (OR 1.7, p = 0.03), absent venous ectasia (OR 3.4, p < 0.001), and cavernous carotid location (OR 2.1, p = 0.019) were predictors of GKRS-induced dAVF obliteration.

CONCLUSIONS

GKRS for cerebral dAVFs achieved obliteration and avoided permanent complications in the majority of patients. Those with cavernous carotid location and no venous ectasia were more likely to have fistula obliteration following radiosurgery. Commonly used grading scales were not reliable predictors of outcome following radiosurgery.

Evaluation of the radiosurgical treatment of cerebral arteriovenous malformations: a retrospective single-center analysis of three decades

BACKGROUND

Gamma Knife radiosurgery (GKRS) in the treatment of arteriovenous malformations (AVMs) is still controversially discussed.

OBJECTIVE

To present long-term follow-up data on patients after Gamma Knife radiosurgery for cerebral AVMs.

METHODS

Overall, 516 patients received radiosurgery for cerebral AVMs between 1992 and 2018 at our department, of whom 265 received radiosurgery alone and 207 were treated with a combined endovascular-radiosurgical approach. Moreover, 45 patients were treated with a volume-staged approach. Two eras were analyzed, the pre-modern era between 1992 and 2002 and the modern era thereafter.

RESULTS

In GKRS-only treated patients, median time to nidus occlusion was 3.8 years. Spetzler-Ponce (SP) class was a significant predictor for time to obliteration in the whole sample. Median time to obliteration for the combined treatment group was 6.5 years. Patients in the pre-modern era had a significantly higher obliteration rate than those treated in the modern era. Overall, the calculated yearly hemorrhage risk in the observation period after first GKRS was 1.3%. Permanent post-radiosurgical complications occurred in 4.9% of cases but did not differ between the treatment groups or treatment eras. The obliteration rate was significantly lower and the hemorrhage rate was higher in volume-staged treated patients than in conventionally treated patients.

CONCLUSION

GKRS is an effective treatment option for SP class A and B cerebral AVMs. After combined endovascular-radiosurgical treatment, the outcome of selected SP class C AVMs aligns with that of SP class B lesions. Both the combined therapy and radiosurgery alone constitute sound methods for treatment of cerebral AVMs.