Predictors for occlusion of cerebral AVMs following radiation therapy : Radiation dose and prior embolization, but not Spetzler-Martin grade

Association of the combined stereotactic radiosurgery and embolization strategy and long-term outcomes in brain arteriovenous malformations with a volume >10 ml: A nationwide multicenter observational prospective cohort study

BACKGROUND

To assess the long-term outcome of large brain arteriovenous malformations (AVMs) (volume > 10 ml) underwent combined embolization and stereotactic radiosurgery (E+SRS) versus SRS alone.

METHODS

Patients were recruited from a nationwide multicenter prospective collaboration registry (MATCH study, August 2011-August 2021) and categorized into E+SRS and SRS alone cohorts. Propensity score-matched survival analysis was employed to control for potential confounding variables. The primary outcome was a composite event of non-fatal hemorrhagic stroke or death. Secondary outcomes were favorable patient outcomes, AVM obliteration, favorable neurological outcomes, seizure, worsened mRS score, radiation-induced changes (RIC), and embolization complications. Furthermore, the efficacy of distinct embolization strategies was evaluated. Hazard ratios (HRs) were computed utilizing Cox proportional hazard models.

RESULTS

Among 1063 AVMs who underwent SRS with or without prior embolization, 176 patients met the enrollment criteria. Following propensity score matching, the final analysis encompassed 98 patients (49 pairs). Median (interquartile range) follow-up duration for primary outcomes spanned 5.4 (2.7-8.4) years. Overall, the E+SRS strategy demonstrated a trend toward reduced incidence of primary outcomes compared to the SRS alone strategy (1.44 vs 2.37 per 100 patient-years; HR, 0.58 [95 % CI, 0.17-1.93]). Regardless of embolization degree or strategy, stratified analyses further consistently revealed a similar trend, albeit without achieving statistical significance. Secondary outcomes generally exhibited equivalence, but the combined approach showed potential superiority in most measures.

CONCLUSIONS

This study suggests a trend toward lower long-term non-fatal hemorrhagic stroke or death risks with the E+SRS strategy when compared to SRS alone in large AVMs (volume > 10 ml).

Embolization Prior to Radiosurgery in Treatment of Arteriovenous Malformations: Defining Radiosurgery Target Dose with Nidal Volume Reduction

INTRODUCTION

Arteriovenous malformations (AVMs) can be treated with observation, surgery, embolization, stereotactic radiosurgery (SRS), or a combination of therapies. SRS has been used for AVMs that pose a high risk of surgery, such as in deep or eloquent anatomic locations. Smaller AVMs, <3 cm, have been shown to have higher rates of complete obliteration after SRS. For AVMs that are a larger size, embolization prior to SRS has been used to reduce the size of the AVM nidus. In this study we analyzed embolization prior to SRS to reduce nidal volume and describe imaging techniques to target for SRS post embolization.

METHODS

We retrospectively reviewed all patients at a single academic institution treated with embolization prior to SRS for treatment of AVMs. We then used contrast enhanced magnetic resonance imaging (MRI) to contour AVM volumes based on pre-embolization imaging and compared to post-embolization imaging. Planned AVM volume prior to embolization was then compared to actual treated AVM volume.

RESULTS

We identified 11 patients treated with embolization prior to SRS from 2011-2023. Median AVM nidal volume prior to embolization was 7.69 mL and post embolization was 3.61 ML (P < 0.01). There was a 45.5% obliteration rate at follow up in our series, with 2 minor complications related to radiosurgery.

CONCLUSIONS

In our cohort, embolization prior to SRS resulted in a statistically significant reduction in AVM nidal volume. Therefore, embolization prior to SRS can result in dose reduction at time of SRS treatment allowing for decreased risk of SRS complications without higher embolization complication rates.

Association of the combined stereotactic radiosurgery and embolization strategy and long-term outcomes in brain arteriovenous malformations with a volume ≤10 mL: a nationwide multicenter observational prospective cohort study

BACKGROUND

To compare the long-term outcomes of stereotactic radiosurgery (SRS) with or without prior embolization in brain arteriovenous malformations (AVMs) (volume ≤10 mL) for which SRS is indicated.

METHODS

Patients were recruited from a nationwide multicenter prospective collaboration registry (the MATCH study) between August 2011 and August 2021, and categorized into combined embolization and SRS (E+SRS) and SRS alone cohorts. We performed propensity score-matched survival analysis to compare the long-term risk of non-fatal hemorrhagic stroke and death (primary outcomes). The long-term obliteration rate, favorable neurological outcomes, seizure, worsened mRS score, radiation-induced changes, and embolization complications were also evaluated (secondary outcomes). Hazard ratios (HRs) were calculated using Cox proportional hazards models.

RESULTS

After study exclusions and propensity score matching, 486 patients (243 pairs) were included. The median (IQR) follow-up duration for the primary outcomes was 5.7 (3.1-8.2) years. Overall, E+SRS and SRS alone were similar in preventing long-term non-fatal hemorrhagic stroke and death (0.68 vs 0.45 per 100 patient-years; HR=1.46 (95% CI 0.56 to 3.84)), as well as in facilitating AVM obliteration (10.02 vs 9.48 per 100 patient-years; HR=1.10 (95% CI 0.87 to 1.38)). However, the E+SRS strategy was significantly inferior to the SRS alone strategy in terms of neurological deterioration (worsened mRS score: 16.0% vs 9.1%; HR=2.00 (95% CI 1.18 to 3.38)).

CONCLUSIONS

In this observational prospective cohort study, the combined strategy of E+SRS does not show substantial advantages over SRS alone. The findings do not support pre-SRS embolization for AVMs with a volume ≤10 mL.

Non-Oncological Radiotherapy: A Review of Modern Approaches

Despite being usually delivered in oncological patients, radiotherapy can be used as a successful treatment for several non-malignant disorders. Even though this use of radiotherapy has been scarcely investigated since the 1950s, more recent interest has actually shed the light on this approach. Thus, the aim of this narrative review is to analyze the applications of non-oncological radiotherapy in different disorders. Key references were derived from a PubMed query. Hand searching and clinicaltrials.gov were also used. This review contains a narrative report and a critical discussion of non-oncological radiotherapy approaches. In conclusion, non-oncological radiotherapy is a safe and efficacious approach to treat several disorders that needs to be further investigated and used in clinical practice.

Predictive Factors for AVM Obliteration after Stereotactic Radiosurgery: A Single Center Study

BACKGROUND

SRS is particularly useful for deep AVMs in eloquent territory with a high associated surgical risk. Prior studies have demonstrated high rates of AVM obliteration with SRS typically ranging 60-80% in a latency period of 2-4 years for complete obliteration. Studies have identified several factors associated with successful obliteration of the AVM nidus, however, these present inconsistent and conflicting data.

OBJECTIVE

To present a single center study examining factors associated with successful obliteration of AVMs treated with SRS.

METHODS

We performed a retrospective review of 210 consecutive patients undergoing SRS for brain AVMs between 2010 and 2019 at our institution. Chi square and logistic regression analyses were utilized to identify patient and AVM factors associated with successful obliteration.

RESULTS

Younger age (p=0.034) and prior embolization (p=0.012) were associated with complete obliteration. Figure 2 demonstrates survival curves for those with complete obliteration comparing those with prior embolization (n = 6) to those without prior embolization (n = 182). The presence of coronary artery disease (CAD) was associated with incomplete obliteration (p=0.04). There were no AVM characteristics statistically associated with complete obliteration although superficial venous drainage (p=0.08) and frontal location (p=0.06) trended towards significance.

CONCLUSIONS

Successful obliteration of the AVM nidus was significantly associated with younger age and prior embolization. The presence of coronary artery disease negatively affected obliteration rates. These results add to the mixed results seen in the literature and emphasize the need for continued studies to delineate more specific patient and AVM factors that contribute to successful obliteration.

Stereotactic Radiosurgery With vs. Without Prior Embolization for Brain Arteriovenous Malformations: A Propensity Score Matching Analysis

Objective: Whether partial embolization could facilitate the post-stereotactic radiosurgery (SRS) obliteration for brain arteriovenous malformations (bAVMs) remains controversial. We performed this study to compare the outcomes of SRS with and without prior embolization for bAVMs.

Methods: We retrospectively reviewed the Beijing Tiantan AVMs prospective registration research database from September 2011 to October 2014. Patients were categorized into two groups, combined upfront embolization and SRS (Em+SRS group) and SRS alone (SRS group), and we performed a propensity score matching analysis based on pre-embolization baseline characteristics; the matched groups each comprised 76 patients.

Results: The obliteration rate was similar between SRS and Em+SRS (44.7 vs. 31.6%; OR, 1.754; 95% CI, 0.905–3.401; p = 0.096). However, the SRS group was superior to the Em+SRS group in terms of cumulative obliteration rate at a follow-up of 5 years (HR,1.778; 95% CI, 1.017–3.110; p = 0.033). The secondary outcomes, including functional state, post-SRS hemorrhage, all-cause mortality, and edema or cyst formation were similar between the matched cohorts. In the ruptured subgroup, the SRS group could achieve higher obliteration rate than Em+SRS group (56.5 vs. 31.9%; OR, 2.773; 95% CI, 1.190–6.464; p = 0.018). The cumulative obliteration rate at 5 years was also higher in the SRS group (64.5 vs. 41.3%; HR, 2.012; 95% CI, 1.037–3.903; p = 0.038), and the secondary outcomes were also similar between the matched cohorts.

Conclusion: Although there was no significant difference in the overall obliteration rate between the two strategies, this study suggested that pre-SRS embolization may have a negative effect on post-SRS obliteration. Furthermore, the obliteration rates of the SRS only strategy was significantly higher than that of the Em+SRS strategy in the ruptured cohort, while no such phenomenon was found in the unruptured cohort.

Radiotherapy of non-tumoral refractory neurological pathologies

Intracranial radiotherapy has been improved, primarily because of the development of stereotactic approaches. While intracranial stereotactic body radiotherapy is mainly indicated for treatment of benign or malignant tumors, this procedure is also effective in the management of other neurological pathologies; it is delivered using GammaKnife® and linear accelerators. Thus, brain arteriovenous malformations in patients who are likely to experience permanent neurological sequelae can be managed by single session intracranial stereotactic body radiotherapy, or radiosurgery, in specific situations, with an advantageous benefit/risk ratio. Radiosurgery can be recommended for patients with disabling symptoms, which are poorly controlled by medication, such as trigeminal neuralgia, and tremors, whether they are essential or secondary to Parkinson's disease. This literature review aims at defining the place of intracranial stereotactic body radiotherapy in the management of patients suffering from non-tumoral refractory neurological pathologies. It is clear that the multidisciplinary collaboration of experienced teams from Neurosurgery, Neurology, Neuroradiology, Radiation Oncology and Medical Physics is needed for the procedures using high precision radiotherapy techniques, which deliver high doses to locations near functional brain areas.

Spontaneous Occlusion of a Complex Brain Arteriovenous Malformation Following Partial Embolization

BACKGROUND

Curative embolization for cerebral arteriovenous malformation (AVM) cannot always be achieved. Rather, embolization plays a role in AVM treatment as an adjuvant therapy before radiosurgery and microsurgery. Curative embolization for large, complex AVMs is not commonly seen.

CASE DESCRIPTION

A man in his 30s with an unruptured left cerebral AVM underwent radiosurgery in 2014 and was lost to follow-up. He presented with intracerebral hemorrhage in 2019, and diagnostic cerebral angiography demonstrated a large, complex AVM. The patient was scheduled for 2-stage embolization in preparation for microsurgical resection. Initial embolization targeted and occluded 20% of the AVM nidus involving primarily the anteroinferior portion. A cerebral angiogram obtained 5 weeks following initial embolization revealed spontaneous occlusion of the remaining AVM.

CONCLUSIONS

There are few reported cases of spontaneous occlusion of a large, complex AVM following embolization with previous radiation therapy. The spontaneous occlusion in this case suggests that at least some AVMs that receive embolization after radiation, rather than before, may have a potential for spontaneous, curative thrombosis.

Time course of pain response and toxicity after whole-nerve-encompassing LINAC-based stereotactic radiosurgery for trigeminal neuralgia-a prospective observational study

PURPOSE

To prospectively evaluate the time course of pain response and toxicity after linear accelerator-based whole-nerve-encompassing radiosurgery (LINAC-SRS) using a uniform treatment schedule for dosing and target volume definition in patients with refractory trigeminal neuralgia.

METHODS

From December 2012 to December 2016, 21 patients were treated using a standardized protocol. Patients received LINAC-SRS with 70 Gy to the cisternal portion while aiming for the 90% isodose to fully envelope the nerve in one cross-sectional plane. Data on pain, analgesics, and toxicity were gathered prospectively. Four time intervals (1-6, 6-12, 12-18, and 18-24 months) were defined and compared to baseline and each other.

RESULTS

The median follow-up from radiotherapy was 16 months. Freedom from pain was achieved at least once in 90.5, 81.0, and 85.7% of patients for everyday pain, rest pain, and pain peaks, respectively. At 1-6 months, pain was significantly reduced in everyday routine (mean VAS, 2.0/10 vs. 5.8/10; P = 0.004), at rest (1.5/10 vs. 4.0/10; P = 0.002), and for pain peaks (2.9/10 vs. 10/10; P < 0.001), as was the number of analgesics (mean 1.5 vs. 2.9; P < 0.001). No significant increase in pain or analgesics was observed for subsequent time intervals. At last follow-up, reduction in pain compared to baseline for everyday routine (2.1/10 vs. 5.8/10; P = 0.010) and for pain peaks (3.3/10 vs. 10/10; P < 0.001) was significant, whereas it was not for rest pain (1.8/10 vs. 3.9/10; P = 0.073). Most toxicities were related to trigeminal nerve impairment, with 42.9% reporting new-onset hypoesthesia at last follow-up.

CONCLUSION

This study provides prospective data after whole nerve encompassing LINAC-SRS for trigeminal neuralgia. No significant pain relapse was observed.

Comparison of the Long-term Efficacy and Safety of Gamma Knife Radiosurgery for Arteriovenous Malformations in Pediatric and Adult Patients

It is debated whether the efficacy and long-term safety of gamma knife radiosurgery (GKRS) for arteriovenous malformations (AVMs) differs between adult and pediatric patients. We aimed to clarify the long-term outcomes of GKRS in pediatric patients and how they compare to those in adult patients. We collected data for 736 consecutive patients with AVMs treated with GKRS between 1990 and 2014 and divided the patients into pediatric (age < 20 years, n = 144) and adult (age ≥ 20 years, n = 592) cohorts. The mean follow-up period in the pediatric cohort was 130 months. Compared to the adult patients, the pediatric patients were significantly more likely to have a history of hemorrhage (P < 0.001). The actuarial rates of post-GKRS nidus obliteration in the pediatric cohort were 36%, 60%, and 87% at 2, 3, and 6 years, respectively. Nidus obliteration occurred earlier in the pediatric cohort than in the adult cohort (P = 0.015). The actuarial rates of post-GKRS hemorrhage in the pediatric cohort were 0.7%, 2.5%, and 2.5% at 1, 5, and 10 years, respectively. Post-GKRS hemorrhage was marginally less common in the pediatric cohort than in the adult cohort (P = 0.056). Cyst formation/encapsulated hematoma were detected in seven pediatric patients (4.9%) at a median post-GKRS timepoint of 111 months, which was not significantly different from the rate in the adult cohort. Compared to adult patients, pediatric patients experience earlier therapeutic effects from GKRS for AVMs, and this improves long-term outcomes.

Effectiveness of Preradiosurgical Embolization with NBCA for Arteriovenous Malformations - Retrospective Outcome Analysis in a Japanese Registry of 73 Patients (J-REAL study)

Purpose

Recent reports have posed doubts about the effect of preradiosurgical embolization in brain arteriovenous malformation (AVM) because it makes the planning of stereotactic radiosurgery (SRS) difficult and has the risk of recanalization out of the target. We investigated whether the performance and quality of embolization may influence the success of SRS based on a retrospective case cohort study.

Materials and Methods

Seventy-three patients who underwent embolization followed by SRS between 2003 and 2012 in eight institutes with neurointerventionists were considered. They were divided into the following two groups at 3 years of follow up after the final SRS: “successful occlusion group” (S group), with radiologically complete occlusion of AVM; and “non-successful occlusion group” (N group) with persistent remnant nidus or abnormal vascular networks. Patient background, AVM profile, embolization performance grade and complications were compared in each group. The quality of embolization was evaluated with the new grading system: embolization performance grade (E grade), specializing the achievement of nidus embolization. E grade A was defined as sufficient nidus embolization with more than half of the total number of feeders achieving nidus penetration. E grade B was defined as less than half achievement of nidus embolization, and E grade C was defines as failure to perform nidus embolization.

Results

Forty-three patients were included in the S group, and 29 patients were included in the N group. The size and Spetzler-Martin grade of AVM and the rate of diffuse type was higher in the N group without statistical significance. The embolization performance level according to E grade indicated a significantly higher rate of successful embolization with more than 50% of nidus penetration in the S group (P<0.001). This difference was also confirmed in the subanalysis for limited cases, excluding smaller AVMs with complete occlusion with SRS alone (P=0.001).

Conclusion

The cause of the unsuccessful result of post-embolization SRS might be the large, diffuse angioarchitecture, but proper embolization with a high rate of nidus penetration to avoid recanalization is more important. Effective embolization is essential to contribute to and promote the effect of radiosurgery.