Gamma Knife Radiosurgery for Third Ventricular Colloid Cysts: A Retrospective Study.

INTRODUCTION: Colloid cysts often occur in the third ventricle, and they are considered benign, slowly growing lesions. They commonly present with symptoms of intracranial hypertension and rarely sudden death due to acute hydrocephalus. The management options include cerebrospinal fluid diversion procedure by shunt, endoscopic or transcranial surgical excision, and stereotactic aspiration. Complications associated with excisional procedures make them undesirable to some patients. Stereotactic radiosurgery has emerged as a noninvasive less risky treatment option. To date, there is no clinical series in the literature reporting on this treatment modality. The aim of the study was to determine the efficacy and safety of gamma knife (GK) radiosurgery in the treatment of third ventricular colloid cysts. METHODS: This is a retrospective study involving 13 patients with third ventricular colloid cysts who underwent GK radiosurgery. GK radiosurgery was used as a primary treatment in all the patients. The median prescription dose was 12 Gy (11-12 Gy). The cyst volumes ranged from 0.2 to 10 cc (median 1.6 cc). RESULTS: The median follow-up was 50 months (18-108 months). Cyst control was achieved in 100% of the patients. Complete or partial response was observed in 12 patients (92%). Eight patients (62%) had hydrocephalus on imaging at the initial diagnosis. Seven of these patients had VP shunt insertion before GK. One patient required shunt insertion after GK. CONCLUSION: GK for third ventricular colloid cysts is a promising treatment, regarding its efficacy and safety, to be added to other treatment options. A longer follow-up is required to confirm long-term control.

Outcome Evaluation of Repeat Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations.

BACKGROUND: Repeat stereotactic radiosurgery (SRS) for persistent cerebral arteriovenous malformation (AVM) has generally favorable patient outcomes. However, reporting studies are limited by small patient numbers and single-institution biases. The purpose of this study was to provide the combined experience of multiple centers, in an effort to fully define the role of repeat SRS for patients with arteriovenous malformation. METHODS: This multicenter, retrospective cohort study included patients treated with repeat, single-fraction SRS between 1987 and 2022. Follow-up began at repeat SRS. The primary outcome was a favorable patient outcome, defined as a composite of nidus obliteration in the absence of hemorrhage or radiation-induced neurological deterioration. Secondary outcomes were obliteration, hemorrhage risk, and symptomatic radiation-induced changes. Competing risk analysis was performed to compute yearly rates and identify predictors for each outcome. RESULTS: The cohort comprised 505 patients (254 [50.3%] males; median [interquartile range] age, 34 [15] years) from 14 centers. The median clinical and magnetic resonance imaging follow-up was 52 (interquartile range, 61) and 47 (interquartile range, 52) months, respectively. At last follow-up, favorable outcome was achieved by 268 (53.1%) patients (5-year probability, 50% [95% CI, 45%-55%]) and obliteration by 300 (59.4%) patients (5-year probability, 56% [95% CI, 51%-61%]). Twenty-eight patients (5.6%) experienced post-SRS hemorrhage with an annual incidence rate of 1.38 per 100 patient-years. Symptomatic radiation-induced changes were evident in 28 (5.6%) patients, with most occurring in the first 3 years. Larger nidus volumes (between 2 and 4 cm3, subdistribution hazard, 0.61 [95% CI, 0.44-0.86]; P=0.005; >4 cm3, subdistribution hazard, 0.47 [95% CI, 0.32-0.7]; P<0.001) and brainstem/basal ganglia involvement (subdistribution hazard, 0.6 [95% CI, 0.45-0.81]; P<0.001) were associated with reduced probability of favorable outcome. CONCLUSIONS: Repeat SRS confers reasonable obliteration rates with a low complication risk. With most complications occurring in the first 3 years, extending the latency period to 5 years generally increases the rate of favorable patient outcomes and reduces the necessity of a third intervention.

Stereotactic radiosurgery for Koos grade IV vestibular schwannoma in patients ≥ 65 years old: a multi-institutional retrospective study.

BACKGROUND: Surgery is the preferred treatment for large vestibular schwannomas (VS). Good tumor control and cranial nerve outcomes were described in selected Koos IV VS after single-session stereotactic radiosurgery (SRS), but outcomes in elderly patients have never been specifically studied. The aim of this study is to report clinical and radiological outcomes after single-session SRS for Koos IV VS in patients ≥ 65 years old. METHOD: This multicenter, retrospective study included patients ≥ 65 years old, treated with primary, single-session SRS for a Koos IV VS, and at least 12 months of follow-up. Patients with life-threatening or incapacitating symptoms were excluded. Tumor control rate, hearing, trigeminal, and facial nerve function were studied at last follow-up. RESULTS: One-hundred and fifty patients (median age of 71.0 (IQR 9.0) years old with a median tumor volume of 8.3 cc (IQR 4.4)) were included. The median prescription dose was 12.0 Gy (IQR 1.4). The local tumor control rate was 96.0% and 86.2% at 5 and 10 years, respectively. Early tumor expansion occurred in 6.7% and was symptomatic in 40% of cases. A serviceable hearing was present in 16.1% prior to SRS and in 7.4% at a last follow-up of 46.5 months (IQR 55.8). The actuarial serviceable hearing preservation rate was 69.3% and 50.9% at 5 and 10 years, respectively. Facial nerve function preservation or improvement rates at 5 and 10 years were 98.7% and 91.0%, respectively. At last follow-up, the trigeminal nerve function was improved in 14.0%, stable in 80.7%, and worsened in 5.3% of the patients. ARE were noted in 12.7%. New hydrocephalus was seen in 8.0% of patients. CONCLUSION: SRS can be a safe alternative to surgery for selected Koos IV VS in patients ≥ 65 years old. Further follow-up is warranted.

Stereotactic radiosurgery versus active surveillance for incidental, convexity meningiomas: a matched cohort analysis from the IMPASSE study.

BACKGROUND: The optimal treatment strategy of asymptomatic, convexity meningiomas, remains unclear. OBJECTIVE: The purpose of this study was to define the safety and efficacy of stereotactic radiosurgery (SRS) in the management of patients with asymptomatic convexity meningiomas. METHODS: Data of SRS-treated patients from 14 participating centers and patients managed conservatively for an asymptomatic, convexity-located meningioma were compared. Local tumor control rate and development of new neurologic deficits were evaluated in the active surveillance and in the SRS-treated cohorts. RESULTS: In the unmatched cohorts, there were 99 SRS-treated patients and 140 patients managed conservatively for an asymptomatic, convexity meningioma. Following propensity score matching for age, there were 98 patients in each cohort. In the matched cohorts, tumor control was achieved in 99% of SRS-treated, and in 69.4% of conservatively managed patients (p < 0.001). New neurological deficits occurred in 2.0% of patients in each of the matched cohorts (p = 1.00). Increasing age was predictive of tumor growth [(OR 1.1; 95% CI (1.04 - 1.2), (p < 0.001)]. CONCLUSION: This is one of the first reports to suggest that SRS is a low risk and effective treatment strategy for asymptomatic incidentally discovered convexity meningiomas. In this study, tumor control was achieved in significantly more patients after radiosurgery compared to those managed with active surveillance. SRS may be offered at diagnosis of an asymptomatic convexity meningioma and should be recommended when meningioma growth is noted on follow-up.

Stereotactic radiosurgery versus active surveillance for asymptomatic, skull-based meningiomas: an international, multicenter matched cohort study.

OBJECTIVE: The optimal management of asymptomatic, skull-based meningiomas is not well defined. The aim of this study is to compare the imaging and clinical outcomes of patients with asymptomatic, skull-based meningiomas managed either with upfront stereotactic radiosurgery (SRS) or active surveillance. METHODS: This retrospective, multicenter study involved patients with asymptomatic, skull-based meningiomas. The study end-points included local tumor control and the development of new neurological deficits attributable to the tumor. Factors associated with tumor progression and neurological morbidity were also analyzed. RESULTS: The combined unmatched cohort included 417 patients. Following propensity score matching for age, tumor volume, and follow-up 110 patients remained in each cohort. Tumor control was achieved in 98.2% and 61.8% of the SRS and active surveillance cohorts, respectively. SRS was associated with superior local tumor control (p < 0.001, HR = 0.01, 95% CI = 0.002-0.13) compared to active surveillance. Three patients (2.7%) in the SRS cohort and six (5.5%) in the active surveillance cohort exhibited neurological deterioration. One (0.9%) patient in the SRS-treated and 11 (10%) patients in the active surveillance cohort required surgical management of their meningioma during follow-up. CONCLUSIONS: SRS is associated with superior local control of asymptomatic, skull-based meningiomas as compared to active surveillance and does so with low morbidity rates. SRS should be offered as an alternative to active surveillance as the initial management of asymptomatic skull base meningiomas. Active surveillance policies do not currently specify the optimal time to intervention when meningioma growth is noted. Our results indicate that if active surveillance is the initial management of choice, SRS should be recommended when radiologic tumor progression is noted and prior to clinical progression.

Stereotactic radiosurgery for Koos grade IV vestibular schwannoma in young patients: a multi-institutional study.

PURPOSE: Surgery is the treatment of choice for large vestibular schwannomas (VS). Stereotactic radiosurgery (SRS) has been suggested as an alternative to resection in selected patients. However, the safety and efficacy of SRS in Koos grade IV patients ≤ 45 years old has not been evaluated. The aim of this study is to describe the clinical and radiological outcomes of Koos grade IV in young patient managed with a single-session SRS. METHODS: This retrospective, multicenter analysis included SRS-treated patients, ≤ 45 years old presenting with non-life threatening or incapacitating symptoms due to a Koos Grade IV VS and with follow-up ≥ 12 months. Tumor control and neurological outcomes were evaluated. RESULTS: 176 patients [median age of 36.0 (IQR 9) and median tumor volume of 9.3 cm3 (IQR 4.7)] were included. The median prescription dose was 12 Gy (IQR 0.5). Median follow-up period was 37.5 (IQR 53.5) months. The 5- and 10-year progression-free survival was 90.9% and 86.7%. Early tumor enlargement occurred in 10.9% of cases and was associated with tumor progression at the last follow-up. The probability of serviceable hearing preservation at 5- and 10-years was 56.8% and 45.2%, respectively. The probability of improvement or preservation of facial nerve function was 95.7% at 5 and 10-years. Adverse radiation effects were noted in 19.9%. New-onset hydrocephalus occurred in 4.0%. CONCLUSION: Single-session SRS is a safe and effective alternative to surgical resection in selected patients ≤ 45 years old particularly those with medical co-morbidities and those who decline resection. Longer term follow up is warranted.

Stereotactic radiosurgery for asymptomatic petroclival region meningiomas: a focused analysis from the IMPASSE study.

BACKGROUND: The optimal management of asymptomatic, petroclival meningiomas remains incompletely defined. The purpose of this study was to evaluate the safety and efficacy of upfront stereotactic radiosurgery (SRS) for patients with asymptomatic, petroclival region meningiomas. METHODS: This retrospective, international, multicenter study involved patients treated with SRS for an asymptomatic, petroclival region meningioma. Study endpoints included local tumor control rate, procedural complications, and the emergence of new neurological deficits. RESULTS: There were 72 patients (22 males, mean age 59.53 years (SD ± 11.9)) with an asymptomatic meningioma located in the petroclival region who were treated with upfront SRS. Mean margin dose and maximum dose were 13.26 (SD ± 2.72) Gy and 26.14 (SD ± 6.75) Gy respectively. Median radiological and clinical follow-up periods post-SRS were 52.5 (IQR 61.75) and 47.5 months (IQR 69.75) respectively. At last follow-up, tumor control was achieved in all patients. SRS-related complications occurred in 6 (8.33%) patients, with 3 of them (4.17%) exhibiting new neurological deficits. CONCLUSIONS: Upfront SRS for asymptomatic, petroclival region meningiomas affords excellent local tumor control and does so with a relatively low risk of SRS-related complications. SRS can be considered at diagnosis of an asymptomatic petroclival region meningioma. If active surveillance is initially chosen, SRS should be recommended when growth is noted during radiological follow-up.

Stereotactic radiosurgery for clinoid meningiomas: a multi-institutional study.

PURPOSE: Resection of clinoid meningiomas can be associated with significant morbidity. Experience with stereotactic radiosurgery (SRS) for clinoid meningiomas remains limited. We studied the safety and effectiveness of SRS for clinoid meningiomas. METHODS: From twelve institutions participating in the International Radiosurgery Research Foundation, we pooled patients treated with SRS for radiologically suspected or histologically confirmed WHO grade I clinoid meningiomas. RESULTS: Two hundred seven patients (median age: 56 years) underwent SRS for clinoid meningiomas. Median treatment volume was 8.02 cm3, and 87% of tumors were immediately adjacent to the optic apparatus. The median tumor prescription dose was 12 Gy, and the median maximal dose to the anterior optic apparatus was 8.5 Gy. During a median post-SRS imaging follow-up of 51.1 months, 7% of patients experienced tumor progression. Greater margin SRS dose (HR = 0.700, p = 0.007) and pre-SRS radiotherapy (HR = 0.004, p < 0.001) were independent predictors of better tumor control. During median visual follow-up of 48 months, visual function declined in 8% of patients. Pre-SRS visual deficit (HR = 2.938, p = 0.048) and maximal radiation dose to the optic apparatus of ≥ 10 Gy (HR = 11.297, p = 0.02) independently predicted greater risk of post-SRS visual decline. Four patients experienced new post-SRS cranial nerve V neuropathy. CONCLUSIONS: SRS allows durable control of clinoid meningiomas and visual preservation in the majority of patients. Greater radiosurgical prescription dose is associated with better tumor control. Radiation dose to the optic apparatus of ≥ 10 Gy and visual impairment before the SRS increase risk of visual deterioration.

Pediatric cerebral cavernous malformations and stereotactic radiosurgery: an analysis of 50 cases from a multicentric study.

OBJECTIVE: Cerebral cavernous malformations (CCMs) are the second most common vascular anomaly affecting the CNS in children. Although stereotactic radiosurgery (SRS) has been proposed as an alternative to microsurgery in the management of selected cases in adults, there is a paucity of studies focusing on pediatric patients. The aim of this study was to present the outcomes and associated risks of SRS in this subgroup of patients. METHODS: This retrospective multicenter study included pediatric patients treated with single-session SRS for CCMs. The annual hemorrhage rate (AHR) was calculated before and after SRS in hemorrhagic lesions. The Engel classification was used to describe post-SRS epileptic control. Adverse radiation effects (AREs) and the occurrence of new neurological deficits were recorded. RESULTS: The study included 50 patients (median age 15.1 [IQR 5.6] years) harboring 62 CCMs. Forty-two (84%) and 22 (44%) patients had a history of hemorrhage or epilepsy prior to SRS, respectively. The AHR from diagnosis to SRS excluding the first hemorrhage was 7.19 per 100 CCM-years, dropping to 3.15 per 100 CCM-years after treatment. The cumulative risk of first hemorrhage after SRS was 7.4% (95% CI 0%-14.3%) at 5 years and 23.6% (95% CI 0%-42.2%) at 10 years. Eight hemorrhagic events involving 6 CCMs in 6 patients were recorded in the post-SRS follow-up period; 4 patients presented with transient symptoms and 4 with permanent symptoms. Of the 22 patients with pre-SRS seizures, 11 were seizure free at the last follow-up (Engel class I), 6 experienced improvement (Engel class II or III), 5 had no improvement (Engel class IVA or IVB), and 1 experienced worsening (Engel class IVC). Radiographic AREs were documented in 14.5% (9/62) of CCMs, with 4 being symptomatic. CONCLUSIONS: Single-session SRS reduces the CCM hemorrhage rate in the pediatric population and provides adequate seizure control.

Intratumoral Hemorrhage in Vestibular Schwannomas After Stereotactic Radiosurgery: Multi-Institutional Study.

BACKGROUND AND OBJECTIVES: Intratumoral hemorrhage (ITH) in vestibular schwannoma (VS) after stereotactic radiosurgery (SRS) is exceedingly rare. The aim of this study was to define its incidence and describe its management and outcomes in this subset of patients. METHODS: A retrospective multi-institutional study was conducted, screening 9565 patients with VS managed with SRS at 10 centers affiliated with the International Radiosurgery Research Foundation. RESULTS: A total of 25 patients developed ITH (cumulative incidence of 0.26%) after SRS management, with a median ITH size of 1.2 cm 3 . Most of the patients had Koos grade II-IV VS, and the median age was 62 years. After ITH development, 21 patients were observed, 2 had urgent surgical intervention, and 2 were initially observed and had late resection because of delayed hemorrhagic expansion and/or clinical deterioration. The histopathology of the resected tumors showed typical, benign VS histology without sclerosis, along with chronic inflammatory cells and multiple fragments of hemorrhage. At the last follow-up, 17 patients improved and 8 remained clinically stable. CONCLUSION: ITH after SRS for VS is extremely rare but has various clinical manifestations and severity. The management paradigm should be individualized based on patient-specific factors, rapidity of clinical and/or radiographic progression, ITH expansion, and overall patient condition.

Stereotactic radiosurgery for nonfunctioning pituitary tumor: A multicenter study of new pituitary hormone deficiency.

BACKGROUND: Stereotactic radiosurgery (SRS) is used to treat recurrent or residual nonfunctioning pituitary neuroendocrine tumors (NFPA). The objective of the study was to assess imaging and development of new pituitary hormone deficiency. METHODS: Patients treated with single-session SRS for a NFPA were included in this retrospective, multicenter study. Tumor control and new pituitary dysfunction were evaluated using Cox analysis and Kaplan-Meier curves. RESULTS: A total of 869 patients (male 476 [54.8%], median age at SRS 52.5 years [Interquartile range (IQR): 18.9]) were treated using a median margin dose of 14Gy (IQR: 4) for a median tumor volume of 3.4 cc (IQR: 4.3). With a median radiological follow-up of 3.7 years (IQR: 4.8), volumetric tumor reduction occurred in 451 patients (51.9%), stability in 364 (41.9%) and 54 patients (6.2%) showed tumor progression.The probability of tumor control was 95.5% (95% Confidence Interval [CI]: 93.8-97.3) and 88.8% (95%CI: 85.2-92.5) at 5 and 10 years, respectively. A margin dose >14 Gy was associated with tumor control (Hazard Ratio [HR]:0.33, 95% CI: 0.18-0.60, P < 0.001). The probability of new hypopituitarism was 9.9% (95% CI: 7.3-12.5) and 15.3% (95% CI: 11-19.4) at 5 and 10 years, respectively. A maximum point dose >10 Gy in the pituitary stalk was associated with new pituitary hormone deficiency (HR: 3.47, 95% CI: 1.95-6.19). The cumulative probability of new cortisol, thyroid, gonadotroph, and growth hormone deficiency was 8% (95% CI: 3.9-11.9), 8.3% (95% CI: 3.9-12.5), 3.5% (95% CI: 1.7-5.2), and 4.7% (95% CI: 1.9-7.4), respectively at 10 years. CONCLUSIONS: SRS provides long-term tumor control with a 15.3% risk of hypopituitarism at 10 years.

Long-term radiographic and endocrinological outcomes of stereotactic radiosurgery for recurrent or residual nonfunctioning pituitary adenomas.

OBJECTIVE: Stereotactic radiosurgery (SRS) is used for the treatment of residual/recurrent nonfunctional pituitary adenoma (NFPA). The aim of this study was to evaluate the factors related to long-term tumor control and delayed endocrinopathies following SRS. METHODS: This retrospective, multicenter study included patients with recurrent/residual NFPA treated with single-fraction SRS; they were then divided into two arms. The first arm included patients with at least 5 years of radiographic follow-up and all patients with local tumor progression. The second arm included patients with at least 5 years of endocrinological follow-up and all patients who developed endocrinopathy. Study endpoints were tumor control and new or worsening hypopituitarism after SRS and were analyzed using Cox regression and Kaplan-Meier methodology. RESULTS: There were 360 patients in the tumor control arm (median age 52.7 [IQR 42.9-61] years, 193 [53.6%] males) and 351 patients in the hypopituitarism arm (median age 52.5 [IQR 43-61] years, 186 [53.0%] males). The median follow-up in the tumor control evaluation group was 7.95 (IQR 5.7-10.5) years. Tumor control rates at 5, 8, 10, and 15 years were 93% (95% CI 90%-95%), 87% (95% CI 83%-91%), 86% (95% CI 82%-90%), and 69% (95% CI 59%-81%), respectively. The median follow-up in the endocrinopathy evaluation group was 8 (IQR 5.9-10.7) years. Pituitary function preservation rates at 5, 8, 10, and 15 years were 83% (95% CI 80%-87%), 81% (95% CI 77%-85%), 78% (95% CI 74%-83%), and 71% (95% CI 63%-79%), respectively. A margin dose > 15 Gy (HR 0.8, 95% CI 0.7-0.9; p < 0.001) and a delay from last resection to SRS > 1 year (HR 0.9, 95% CI 0.7-0.9; p = 0.04) were significant factors related to tumor control in multivariable analysis. A maximum dose to the pituitary stalk ≤ 10 Gy (HR 1.1, 95% CI 1.09-1.2; p < 0.001) was associated with pituitary function preservation. New visual deficits after SRS occurred in 7 (1.94%) patients in the tumor control group and 8 (2.3%) patients in the endocrinopathy group. Other new cranial nerve deficits post-SRS occurred in 4 of 160 patients with data in the tumor control group and 3 of 140 patients with data in the endocrinopathy group. CONCLUSIONS: SRS affords favorable and durable tumor control for the vast majority of NFPAs. Post-SRS hypopituitarism occurs in a minority of patients, but this risk increases with time and warrants long-term follow-up.

Stereotactic radiosurgery (SRS) for patients with brainstem cerebral cavernous malformations (CCMs): an international, multicentric study.

Brainstem cerebral cavernous malformations (CCM) are clinically more aggressive compared to superficial CCMs. Due to their location, resection can be challenging, making stereotactic radiosurgery (SRS) an attractive alternative for symptomatic patient. Brainstem CCM patients (n = 170) were treated with Gamma Knife SRS at 11 radiosurgical centers. Hemorrhagic risk reduction, risk factors of post-SRS hemorrhage, and clinical outcomes were retrospectively analyzed. Most patients had a single (165/170 patients) brainstem CCMs treated; the majority of CCMs (165/181) presented with bleeding. Single-session SRS decreased the risk of repeat hemorrhage in patients with hemorrhagic brainstem CCM (HR: 0.17, p < 0.001) using recurrent multivariate analysis. The annual hemorrhage rate decreased from 14.8 per 100 CCM-years before SRS to 2.3 after treatment. Using univariate Cox-analysis, the probability of a new hemorrhages after SRS was reduced for patient older than 35 years (HR = 0.21, p = 0.002) and increased with a margin dose > 13 Gy (HR = 2.57, p = 0.044). Adverse radiation effect (ARE) occurred in 9 patients (5.3%) and was symptomatic in four (2.4%). At a median follow-up of 3.4 years (Inter-quartile range: 5.4), 13 patients (8.0%) had a worsened clinical status, with the treated CCM being the cause in 5.6% (10) of the patients. Single-session SRS decreased the risk of repeat hemorrhage in patients with hemorrhagic brainstem CCM and conveyed this benefit with a low risk of advrse radiation effects (ARE) and worsening clinical status.

Pleomorphic Xanthoastrocytoma: Multi-Institutional Evaluation of Stereotactic Radiosurgery.

BACKGROUND AND OBJECTIVES: Pleomorphic xanthoastrocytoma (PXA) is a rare low-grade glial tumor primarily affecting young individuals. Surgery is the primary treatment option; however, managing residual/recurrent tumors remains uncertain. This international multi-institutional study retrospectively assessed the use of stereotactic radiosurgery (SRS) for PXA. METHODS: A total of 36 PXA patients (53 tumors) treated at 11 institutions between 1996 and 2023 were analyzed. Data included demographics, clinical variables, SRS parameters, tumor control, and clinical outcomes. Kaplan-Meier estimates summarized the local control (LC), progression-free survival, and overall survival (OS). Secondary end points addressed adverse radiation effects and the risk of malignant transformation. Cox regression analysis was used. RESULTS: A total of 38 tumors were grade 2, and 15 tumors were grade 3. Nine patients underwent initial gross total resection, and 10 received adjuvant therapy. The main reason for SRS was residual tumors (41.5%). The median follow-up was 34 months (range, 2-324 months). LC was achieved in 77.4% of tumors, with 6-month, 1-year, and 2-year LC estimates at 86.7%, 82.3%, and 77.8%, respectively. Younger age at SRS (hazard ratios [HR] 3.164), absence of peritumoral edema (HR 4.685), and higher marginal dose (HR 6.190) were significantly associated with better LC. OS estimates at 1, 2, and 5 years were 86%, 74%, and 49.3%, respectively, with a median OS of 44 months. Four patients died due to disease progression. Radiological adverse radiation effects included edema (n = 8) and hemorrhagic change (n = 1). One grade 3 PXA transformed into glioblastoma 13 months after SRS. CONCLUSION: SRS offers promising outcomes for PXA management, providing effective LC, reasonable progression-free survival, and minimal adverse events.

Repeat stereotactic radiosurgery for persistent cerebral arteriovenous malformations in pediatric patients.

OBJECTIVE: The purpose of this study was to describe the long-term outcomes and associated risks related to repeat stereotactic radiosurgery (SRS) for persistent arteriovenous malformations (AVMs) in pediatric patients. METHODS: Under the auspices of the International Radiosurgery Research Foundation, this retrospective multicenter study analyzed pediatric patients who underwent repeat, single-session SRS between 1987 and 2022. The primary outcome variable was a favorable outcome, defined as nidus obliteration without hemorrhage or neurological deterioration. Secondary outcomes included rates and probabilities of hemorrhage, radiation-induced changes (RICs), and cyst or tumor formation. RESULTS: The cohort included 83 pediatric patients. The median patient age was 11 years at initial SRS and 15 years at repeat SRS. Fifty-seven children (68.7%) were managed exclusively using SRS, and 42 (50.6%) experienced hemorrhage prior to SRS. Median AVM diameter and volume were substantially different between the first (25 mm and 4.5 cm3, respectively) and second (16.5 mm and 1.6 cm3, respectively) SRS, while prescription dose and isodose line remained similar. At the 5-year follow-up evaluation from the second SRS, nidus obliteration was achieved in 42 patients (50.6%), with favorable outcome in 37 (44.6%). The median time to nidus obliteration and hemorrhage was 35.5 and 38.5 months, respectively. The yearly cumulative probability of favorable outcome increased from 2.5% (95% CI 0.5%-7.8%) at 1 year to 44% (95% CI 32%-55%) at 5 years. The probability of achieving obliteration followed a similar pattern and reached 51% (95% CI 38%-62%) at 5 years. The 5-year risk of hemorrhage during the latency period after the second SRS reached 8% (95% CI 3.2%-16%). Radiographically, 25 children (30.1%) had RICs, but only 5 (6%) were symptomatic. Delayed cyst formation occurred in 7.2% of patients, with a median onset of 47 months. No radiation-induced neoplasia was observed. CONCLUSIONS: The study results showed nidus obliteration in most pediatric patients who underwent repeat SRS for persistent AVMs. The risks of symptomatic RICs and latency period hemorrhage were quite low. These findings suggest that repeat radiosurgery should be considered when treating pediatric patients with residual AVM after prior SRS. Further study is needed to define the role of repeat SRS more fully in this population.

Clinical and Imaging Outcomes After Trigeminal Schwannoma Radiosurgery: Results From a Multicenter, International Cohort Study.

BACKGROUND AND OBJECTIVES: An international, multicenter, retrospective study was conducted to evaluate the long-term clinical outcomes and tumor control rates after stereotactic radiosurgery (SRS) for trigeminal schwannoma. METHODS: Patient data (N = 309) were collected from 14 international radiosurgery centers. The median patient age was 50 years (range 11-87 years). Sixty patients (19%) had prior resections. Abnormal facial sensation was the commonest complaint (49%). The anatomic locations were root (N = 40), ganglion (N = 141), or dumbbell type (N = 128). The median tumor volume was 4 cc (range, 0.2-30.1 cc), and median margin dose was 13 Gy (range, 10-20 Gy). Factors associated with tumor control, symptom improvement, and adverse radiation events were assessed. RESULTS: The median and mean time to last follow-up was 49 and 65 months (range 6-242 months). Greater than 5-year follow-up was available for 139 patients (45%), and 50 patients (16%) had longer than 10-year follow-up. The overall tumor control rate was 94.5%. Tumors regressed in 146 patients (47.2%), remained unchanged in 128 patients (41.4%), and stabilized after initial expansion in 20 patients (6.5%). Progression-free survival rates at 3 years, 5 years, and 10 years were 91%, 86%, and 80 %. Smaller tumor volume (less than 8 cc) was associated with significantly better progression-free survival ( P = .02). Seventeen patients with sustained growth underwent further intervention at a median of 27 months (3-144 months). Symptom improvement was noted in 140 patients (45%) at a median of 7 months. In multivariate analysis primary, SRS ( P = .003) and smaller tumor volume ( P = .01) were associated with better symptom improvement. Adverse radiation events were documented in 29 patients (9%). CONCLUSION: SRS was associated with long-term freedom (10 year) from additional management in 80% of patients. SRS proved to be a valuable salvage option after resection. When used as a primary management for smaller volume tumors, both clinical improvement and prevention of new deficits were optimized.

Effect of cerebral arteriovenous malformation location on outcomes of repeat, single-fraction stereotactic radiosurgery: a matched-cohort analysis.

OBJECTIVE: Patients with deep-seated arteriovenous malformations (AVMs) have a higher rate of unfavorable outcome and lower rate of nidus obliteration after primary stereotactic radiosurgery (SRS). The aim of this study was to evaluate and quantify the effect of AVM location on repeat SRS outcomes. METHODS: This retrospective, multicenter study involved 505 AVM patients managed with repeat, single-session SRS. The endpoints were nidus obliteration, hemorrhage in the latency period, radiation-induced changes (RICs), and favorable outcome. Patients were split on the basis of AVM location into the deep (brainstem, basal ganglia, thalamus, deep cerebellum, and corpus callosum) and superficial cohorts. The cohorts were matched 1:1 on the basis of the covariate balancing score for volume, eloquence of location, and prescription dose. RESULTS: After matching, 149 patients remained in each cohort. The 5-year cumulative probability rates for favorable outcome (probability difference -18%, 95% CI -30.9 to -5.8%, p = 0.004) and AVM obliteration (probability difference -18%, 95% CI -30.1% to -6.4%, p = 0.007) were significantly lower in the deep AVM cohort. No significant differences were observed in the 5-year cumulative probability rates for hemorrhage (probability difference 3%, 95% CI -2.4% to 8.5%, p = 0.28) or RICs (probability difference 1%, 95% CI -10.6% to 11.7%, p = 0.92). The median time to delayed cyst formation was longer with deep-seated AVMs (deep 62 months vs superficial 12 months, p = 0.047). CONCLUSIONS: AVMs located in deep regions had significantly lower favorable outcomes and obliteration rates compared with superficial lesions after repeat SRS. Although the rates of hemorrhage in the latency period and RICs in the two cohorts were comparable, delayed cyst formation occurred later in patients with deep-seated AVMs.

Single-session stereotactic radiosurgery for large perioptic meningiomas.

OBJECTIVE: Meningiomas close to the optic pathway are commonly candidates for microsurgical decompression, more so if they are large perioptic meningiomas. However, microsurgery itself imposes risk to vision, and the larger the tumor, the more the risk and the lower the possibility of postoperative visual recovery. Fractionated stereotactic radiotherapy is usually reserved for such cases. The purpose of this study was to assess the long-term efficacy and safety of single-session stereotactic radiosurgery (SRS) for large (≥ 10 cm3) perioptic intracranial benign meningiomas. METHODS: This retrospective study included 175 patients with large perioptic benign meningiomas (≥ 10 cm3) who were treated by single-session SRS. Perioptic meningiomas were defined as meningiomas touching, compressing, or within 3 mm of the optic pathway. The median tumor volume was 15 cm3 (range 10-57.3 cm3, IQR 8.4 cm3). The median prescription dose was 12 Gy (range 9-14 Gy, IQR 1 Gy). RESULTS: The median follow-up period was 72 months (range 13-217 months, IQR 65 months). The tumor control rate was 92%. The progression-free survival rates at 5 and 10 years were 97% and 80%, respectively. Favorable (better/stable) visual outcome was reported in 169 patients (97%) and unfavorable (worse) outcome in 6 patients (3%). Temporary adverse radiation effects were observed in 21 patients (12%), but only 7 patients (4%) were symptomatic. Sixty-three patients had a blind/nonuseful eye according to the pretreatment visual field examination. Visual improvement was observed in the blind/nonuseful eye in 17 patients (27%), while vision remained unchanged in 46 patients (73%). Ocular nerve palsy improved in 36 patients (61%). Tumor shrinkage was not a prerequisite for cranial nerve improvement. CONCLUSIONS: SRS provides an effective and safe treatment option for large perioptic meningiomas.

Stereotactic radiosurgery for haemorrhagic cerebral cavernous malformation: a multi-institutional, retrospective study.

BACKGROUND: Cerebral cavernous malformations (CCMs) frequently manifest with haemorrhages. Stereotactic radiosurgery (SRS) has been employed for CCM not suitable for resection. Its effect on reducing haemorrhage risk is still controversial. The aim of this study was to expand on the safety and efficacy of SRS for haemorrhagic CCM. METHODS: This retrospective multicentric study included CCM with at least one haemorrhage treated with single-session SRS. The annual haemorrhagic rate (AHR) was calculated before and after SRS. Recurrent event analysis and Cox regression were used to evaluate factors associated with haemorrhage. Adverse radiation effects (AREs) and occurrence of new neurological deficits were recorded. RESULTS: The study included 381 patients (median age: 37.5 years (Q1-Q3: 25.8-51.9) with 414 CCMs. The AHR from diagnosis to SRS excluding the first haemorrhage was 11.08 per 100 CCM-years and was reduced to 2.7 per 100 CCM-years after treatment. In recurrent event analysis, SRS, HR 0.27 (95% CI 0.17 to 0.44), p<0.0001 was associated with a decreased risk of haemorrhage, and the presence of developmental venous anomaly (DVA) with an increased risk, HR 1.60 (95% CI 1.07 to 2.40), p=0.022. The cumulative risk of first haemorrhage after SRS was 9.4% (95% CI 6% to 12.6%) at 5 years and 15.6% (95% CI% 9 to 21.8%) at 10 years. Margin doses> 13 Gy, HR 2.27 (95% CI 1.20 to 4.32), p=0.012 and the presence of DVA, HR 2.08 (95% CI 1.00 to 4.31), p=0.049 were factors associated with higher probability of post-SRS haemorrhage. Post-SRS haemorrhage was symptomatic in 22 out of 381 (5.8%) patients, presenting with transient (15/381) or permanent (7/381) neurological deficit. ARE occurred in 11.1% (46/414) CCM and was responsible for transient neurological deficit in 3.9% (15/381) of the patients and permanent deficit in 1.1% (4/381) of the patients. Margin doses >13 Gy and CCM volume >0.7 cc were associated with increased risk of ARE. CONCLUSION: Single-session SRS for haemorrhagic CCM is associated with a decrease in haemorrhage rate. Margin doses ≤13 Gy seem advisable.