BACKGROUND AND OBJECTIVES:Stereotactic radiosurgery (SRS) has been increasingly employed in the multimodal management of primary central nervous system lymphoma. Here, we evaluate the outcomes of SRS for the treatment of primary central nervous system lymphoma through a multicenter, international cohort study. METHODS:A multicenter, retrospective cohort study was conducted through the International Radiosurgery Research Foundation. Subgroups were defined according to treatment setting: up-front (primary treatment), boost (SRS after consolidative chemotherapy with or without whole-brain radiotherapy), and relapsed/refractory (recurrent/progressive disease after first-line therapy). The primary end point was local tumor control. Time-to-event analysis was conducted using the Kaplan-Meier method. Variables associated with local control were assessed using the Cox proportional hazard modeling. RESULTS:Fifty-four patients with 127 tumor sites were included in this analysis. Actuarial 12-month local and distant control rates for the entire cohort were 75.7% and 63.7%, respectively, with a median overall survival (OS) of 18 months (range: 1-176). Actuarial 12-month local control rates were significantly different at 95.6%, 78.3%, and 42.1% (P < .0001) for the up-front, relapsed/refractory groups, and boost cohorts, respectively. OS across all cohorts were similar with 12-month OS rates of 55.2%, 51.3%, and 53.5% for the up-front, relapsed/refractory, and boost cohorts, respectively. Rates of radiation necrosis were 18.5%, 20.8%, 15.4%, and 11.8% for the entire cohort, relapsed/refractory, boost, and up-front cohorts, respectively. Diminished OS was significantly associated with treatment volumes >27 cm3 (hazard ratio: 2.5, P = .04). CONCLUSION:SRS shows promising local tumor control rates for up-front and relapsed cohorts. Despite this, distant tumor progression limits total tumor control and may adversely affect OS.

Introduction Hemangioblastomas (HGB) are the most common primary intra-axial tumors in the posterior fossa in adults, with an overall occurrence of 7-10%. They occur sporadically or as part of von Hippel-Lindau (VHL) disease. The role of stereotactic radiosurgery (SRS) as a minimally invasive treatment in larger HGB (>2cc) has not been thoroughly investigated. Methods This multi-center study retrospectively analyzed data from 91 patients with large HGB (>2cc) treated between 1993 and 2023. Patients were stratified into VHL-associated and sporadic groups, with assessments including radiosurgical parameters, tumor response, overall survival (OS), and progression-free survival (PFS). Results Patients with VHL-associated HGB were younger at diagnosis (median: 33 years vs. 52 years, p < 0.001) and presented more frequently with multiple tumors (68.8% vs. 23.2%, p < 0.001). Cerebellar lesions were the most common location (70%), followed by brainstem lesions (21%). The median target tumor volume was smaller in VHL cases (3.49 cc vs. 6.5 cc, p = 0.038). Tumor control was achieved in 70% of cases across groups, with no significant differences in outcomes between VHL and sporadic cases. OS (170 months for VHL and 199 months for sporadic cases) and PFS (108 months for both groups) were comparable. Radiation necrosis was observed in 8.8% of patients. Conclusions SRS may provide favorable tumor control with low morbidity in both VHL-associated and sporadic cases of larger HGB (>2 cc).Future studies should compare SRS with resection for larger HGB and explore molecular predictors of favorable response to SRS.

BACKGROUND AND OBJECTIVES:Even with multimodal therapy, glioblastoma invariably recurs. Reirradiation with stereotactic radiosurgery (SRS) and reoperation are frequent salvage treatment options for recurrent glioblastoma (rGBM) isocitrate dehydrogenase-wildtype. No study has compared the safety and efficacy of these treatments in a homogeneous rGBM population. In this study, we evaluate gamma knife (GK)-SRS vs reoperation in rGBM. METHODS:This retrospective study evaluated surgically accessible rGBM between 2005 and 2022. All patients received adjuvant radiotherapy and were evaluated for GK-SRS or reoperation on recurrence. Cox multivariable analysis and propensity-score matching were performed to address confounders in outcomes. Post-recurrence survival (PRS) was the primary endpoint. RESULTS:We identified 119 patients. Among these, 38 underwent GK-SRS and 81 underwent reoperation. Although patients undergoing GK-SRS had improved PRS and overall survival compared with reoperation, they had significant differences in baseline characteristics, particularly in tumor volume (reoperation group: 8.7 cm3 [IQR = 3.4-17.8 cm3] vs GK-SRS 1.7 cm3 [IQR = 0.2-6 cm3], P < .001). Given these significant differences, a propensity-score matching accounting for tumor volume and Karnofsky performance status was performed, comparing patients in which equipoise between GK-SRS and resection existed (GK-SRS 2.5 cm3 vs reoperation 2.6 cm3 and Karnofsky performance status 80 for both). Among these patients (23 in each group), PRS (19.2 months vs 15.1 months, P = .617) and overall survival (31.9 months vs 25.5 months, P = .176) were similar. Nevertheless, complications remained higher in the reoperation group (26.1% vs 4.3%, P = .040). CONCLUSION:In patients with small, surgically accessible first recurrent glioblastoma, GK-SRS achieved survival outcomes comparable to reoperation after matching for key baseline differences, while demonstrating a lower complication rate. These findings support GK-SRS as a reasonable local salvage option in carefully selected low-volume recurrences.

Re-irradiation with stereotactic radiosurgery (SRS) is an increasingly used treatment for recurrent high-grade glioma (HGG). We analyzed the patterns of failure after salvage SRS to better identify which patients would most benefit. We reviewed all patients who received SRS for recurrent HGG over 12 years at our institution. Pattern of failure was defined by the distance of recurrence from the SRS isodose line. Overall-survival (OS), progression-free survival (PFS), and local-failure-free survival (LFS) were estimated using Kaplan-Meier methods, and regression model analysis was performed to analyze clinical predictors of failure. 146 patients with HGG underwent SRS treatment to 410 target lesions. The median target volume was 3.3 cm3 and median total dose was 18 Gy. Sixty-one (41.8

OBJECTIVE:Ruptured, large pediatric arteriovenous malformations (AVMs) pose a significant management challenge due to high rerupture risk and the morbidity of conventional treatments. Volume-staged stereotactic radiosurgery (VS-SRS) has emerged as an alternative; however, evidence for its use in this specific population is limited. This study aimed to evaluate the long-term efficacy and safety of VS-SRS for ruptured, large AVMs in a dedicated pediatric cohort. METHODS:This international, multicenter, retrospective cohort study from 21 centers analyzed outcomes for 42 pediatric patients (age < 18 years) with previously ruptured, large AVMs treated with VS-SRS. The primary outcome was complete AVM obliteration, and secondary outcomes included post-SRS hemorrhage, radiation-induced changes (RICs), and favorable outcome. Favorable outcome in this study was defined as obliteration without post-SRS hemorrhage or permanent RIC. RESULTS:At the initial SRS, the median patient age was 14.5 years, and the median AVM volume was 15.0 cm3; most AVMs were high grade (Spetzler-Martin grades IV and V). With a median follow-up of 41.5 months, complete AVM obliteration was achieved in 21 patients (50.0%). The cumulative obliteration rate was 37% at 5 years and 56% at 10 years. Patients with a nidus volume of ≤ 10 cm3 had significantly higher cumulative obliteration rates than those with a nidus volume > 10 cm3 (log-rank test, p = 0.021). Similarly, patients treated with a prescription dose > 17 Gy showed significantly higher cumulative obliteration rates compared to those treated with a dose ≤ 17 Gy (log-rank test, p = 0.012). The cumulative 5-year incidences of hemorrhage and RICs following VS-SRS were 19% and 7%, respectively. In multivariable analysis, only larger total AVM volume was an independent predictor of a lower likelihood of favorable outcome (hazard ratio 0.89, 95% CI 0.80-0.99; p = 0.036). CONCLUSIONS:In this multicenter pediatric cohort, VS-SRS for ruptured, large AVMs provides a reasonable chance of long-term obliteration, but generally acceptable risks of post-SRS hemorrhage and RICs exist. VS-SRS should be considered as an option for pediatric patients with large, ruptured AVMs.

OBJECTIVE:The incidence of vestibular schwannoma (VS) diagnosis among octogenarians has increased due to longer life expectancy and greater MRI accessibility and utilization. Stereotactic radiosurgery (SRS) offers a safe management strategy for these patients. METHODS:The authors retrospectively analyzed the data of octogenarians with VS managed with SRS across 27 institutions, assessing clinical and audiological outcomes, including survival rates, tumor control responses, complications, and posttreatment functional outcomes. RESULTS:Among 309 octogenarians with VS managed with single-fraction SRS, overall survival was 97.8% at 1 year, 88.5% at 3 years, and 78.1% at 5 years; the corresponding progression-free survival rates were 95.8%, 81.1%, and 71.1%, respectively. In competing risk analysis, tumor progression occurred in 5.2% of patients by 5 years, whereas death without progression reached 19.8%. Tumor control was achieved in 94.8% at 3 and 5 years. At last imaging follow-up (median 33.5 months, IQR 14-60 months), 29.1% showed volume regression. Communicating hydrocephalus developed in 4.2% and was successfully managed with CSF diversion. Age, sex, tumor volume, Koos grade, and margin dose were not significant predictors of patient survival or tumor progression. CONCLUSIONS:Single-fraction SRS is a safe and effective management modality for octogenarians with VS, providing durable tumor control with minimal morbidity.

BACKGROUND AND OBJECTIVES:Glioblastoma (GBM) isocitrate dehydrogenase-wildtype remains a devastating brain tumor with a poor prognosis despite optimal treatment. Even after supramaximal or complete contrast-enhancing (CE) resection, patient outcomes vary significantly, with some experiencing short-term survival (STS) and others long-term survival (LTS). This study aims to identify clinical and molecular markers predicting the survival of patients with GBM in these high-resection categories. METHODS:We retrospectively analyzed patients with newly diagnosed GBM who underwent supramaximal or complete CE resection, followed by next-generation sequencing at our institution (2009-2025). Patients were categorized as STS (survival ≤12 months), non-STS (survival >12 months), or LTS (survival ≥36 months). We compared clinical, radiological, and molecular features between these groups to identify potential prognostic markers. RESULTS:Among 85 patients who met the inclusion criteria, 24 (28%) were STSs and 61 were non-STS (from which 16 [18.8%] were LTSs), with no significant molecular differences observed between these groups. On comparing STS and LTS patients, CDKN2A/B loss (83.3% vs 43.8%, P = .01) and EGFR amplification (58.3% vs 25%, P = .05) were more frequent in STS patients vs LTS. Tumor location varied, with STS patients having more frontal lobe tumors (45.8%) and LTS patients having more temporal lobe tumors (62.5%). A trend, although not statistically significant, toward increased nonlocal recurrence rates was observed in STS patients (27.2%). CONCLUSION:Despite aggressive extent of resection in GBM, the prevalence of STS patients remains notable at ∼28% and survival beyond 3 years remains limited at ∼18.8%. CDKN2A/B loss and EGFR amplification might correlate with shortened survival after supramaximal or complete CE resection. The impact of nonlocal recurrence remains uncertain among STSs. These findings highlight the need for collaborative studies to advance understanding of the biology of GBM as their behavior differs despite aggressive surgical and medical therapies.

Craniopharyngioma is histologically benign yet locally aggressive, with frequent recurrence. Long-term multicenter outcomes after stereotactic radiosurgery (SRS) remain incompletely defined. We performed a retrospective multi-institutional cohort study through the International Radiosurgery Research Foundation including 296 patients from 13 centers. Median age at first SRS was 33.6 years. Median tumor volume was 1.32 cm³ and median margin dose was 12.0 Gy. The primary endpoint was local control (LC); secondary endpoints were progression-free survival (PFS) and overall survival (OS). Kaplan–Meier methods estimated outcomes, and Cox proportional hazards models evaluated predictors of LC. Actuarial 1-, 5-, and 10-year LC was 93.5

Stereotactic radiosurgery (SRS) is used in selected patients with craniopharyngioma, yet counseling and follow-up planning often rely on population-level local control rates rather than individualized expectations over time. To develop and internally validate a multicenter survival model to predict imaging-defined time to progression after SRS for craniopharyngioma. We analyzed a multicenter IRRF registry of SRS-treated craniopharyngioma patients. Imaging progression was defined by the overall last imaging response (PD vs. non-PD), with censoring at last imaging follow-up when progression was not observed. A Random Survival Forest (RSF) model was evaluated using 5-fold out-of-fold cross-validation. Performance was assessed using the concordance index, time-dependent AUC at 12, 24, and 60 months with bootstrap 95

Glioblastoma isocitrate dehydrogenase (IDH)-wildtype (GBM) has been reclassified based on molecular and phenotypic features. Intratumoral hemorrhage is a phenotypic subtype with poorly understood molecular and clinical characteristics. We aimed to characterize the molecular profile and outcomes of hemorrhagic glioblastoma (hGBM) compared with non-hGBM. A retrospective analysis of GBMs with pre-operative and post-operative MRI and comprehensive next-generation sequencing of 205 genes was performed. Patients were classified as hGBM or non-hGBM using the Visually Accessible Rembrandt Images criteria. Univariable and multivariable survival analyses were performed. Genes were compared using the Fisher-exact test and corrected for multiple comparisons with the Benjamini-Hochberg method. 176 patients were included, of whom 105 had hGBM. Compared to non-hGBMs, hGBMs were more likely Hispanic (20.0

BACKGROUND AND OBJECTIVES:Pediatric large-volume brain arteriovenous malformations (AVMs) carry a substantial lifelong hemorrhage risk, neurological symptoms, and treatment morbidity. Single-session stereotactic radiosurgery (SRS) is often unsuitable due to constraints on dose-volume toxicity. Volume-staged SRS (VS-SRS) enables sequential dosing of large nidus volumes, potentially enhancing safety while maintaining efficacy. Evidence in children remains limited. We aimed to evaluate outcomes of VS-SRS for large AVMs in pediatric patients. METHODS:A multicenter retrospective cohort was assembled from 21 centers, including patients aged younger than 21 years treated with VS-SRS for AVMs >10 cm3. Clinical and radiological end points included obliteration, hemorrhage, and permanent symptomatic radiation-induced changes (RIC). RESULTS:A total of 103 patients were included (median age 14 years; IQR, 12-17). The median nidus volume at first stage was 18.2 cm3 (IQR, 12.3-25.6). Median prescription dose per stage was 17 Gy (IQR, 16-18). The median clinical follow-up from the first stage was 57.5 months (IQR, 25-138). Obliteration occurred in 42 of 103 patients (40.8%), with actuarial rates of 6.9% (95% CI: 2.8-14) at 3 years and 29% (95% CI: 20-39) at 5 years. Hemorrhage occurred in 17 of 103 patients (16.5%) during follow-up, and permanent RIC was observed in 9 of 103 patients (8.7%). CONCLUSION:VS-SRS is a reasonably safe, selected option for pediatric large-volume AVMs when microsurgical or endovascular cure is not feasible or prudent. Delivering ≥17 Gy per stage while limiting each treatment volume to <15 cm3 supports durable nidus control with acceptable toxicity. VS-SRS represents a key modality in multidisciplinary management of this historically difficult-to-treat population.

BACKGROUND AND OBJECTIVES:The American Society for Radiation Oncology guidelines for stereotactic radiosurgery dose suggestions for brain metastases provide excellent local control but at the expense of higher adverse radiation effects (ARE). This study provides evidence that lower single-fraction prescription doses for patients with melanoma metastases who are concurrently receiving immunotherapy or targeted therapy are equally effective and safe. METHODS:This retrospective, multicenter study included 335 patients with melanoma brain metastases who underwent stereotactic radiosurgery between 2009 and 2024. After covariate balancing, 137 patients with 590 metastases were included in the high dose (HD) group and 59 patients with 590 metastases in the reduced dose (RD) group. The RD limits were set at <20 Gy for <2 cm lesions and <18 Gy for ≥2 to <3 cm lesions. RESULTS:After matching, the median diameter (6 vs 5.8 mm, P = .5) and imaging follow-up (6 vs 6 months, P = .13) were comparable. Cumulative incidence of progressing metastases was significantly higher in the HD group compared with the RD group (P < .001) overall, but lower prescription doses resulted in higher progression rates for metastases >2 cm (P = .023). Higher prescription volumes and HD-group prescription doses were linked with local progression in multivariable analysis. Radiographic AREs were significantly more common in the HD group compared with the RD group overall (P < .001) but similar for metastases >2 cm (P = .7). Higher prescription volumes, HD-group prescription doses, and concurrent BRAF or other tyrosine kinase inhibitors were linked with an increased risk of radiographic ARE, whereas concurrent immunotherapy was associated with lower rates of radiographic ARE. CONCLUSION:This study provides evidence that treatment with prescription doses under the currently the American Society for Radiation Oncology-suggested doses for brain melanoma metastases <2 cm is safe, having at least equal local control rate and lower radiographic AREs. Reducing prescription dose for lesions between 2 and 3 cm does not seem to convey reduced ARE rates and could potentially increase local failure.

BACKGROUND:Intracranial solitary fibrous tumors (SFTs) are rare, aggressive neoplasms with high local recurrence. This study evaluates the efficacy and prognostic factors of single-fraction stereotactic radiosurgery (SRS). METHODS:This multicenter retrospective study included 107 patients (253 SFTs) treated with single-fraction SRS at 18 centers (1989-2024). We analyzed local control (LC), intracranial tumor control (ITC), overall tumor control (OTC), progression-free survival (PFS), disease-specific survival (DSS), and overall survival (OS). Cox regression identified prognostic factors. RESULTS:Median follow-up was 33 months. LC was 68.4% (5-year: 56.8% and 10-year: 38.8%). ITC 54.2% (5-year: 48.5%) and OTC 50.5% (5-year: 44.0%). PFS was 56.3% and 30.2% at 5 and 10 years, respectively. DSS remained high at 89.7% (5-year) and 79.7% (10-year), while OS was 79.3% (5-year) and 55.2% (10-year). Independent predictors of LC included recurrent versus metastatic SFTs (HR: 1.96, P = 0.028), margin dose ≤16 Gy (HR: 2.35, P = 0.006), larger tumor volume (HR: 1.05, P < 0.001), and longer diagnosis-to-SRS duration (HR: 1.02, P < 0.001). Older age (HR: 1.03, P = 0.014) and longer resection-to-SRS duration (HR: 1.02, P = 0.018) predicted worse ITC. Age significantly affected OS (HR: 1.06, P < 0.001) and PFS (HR: 1.03, P = 0.037). Longer diagnosis-to-SRS (HR: 1.03, P = 0.002) and resection-to-SRS durations (HR: 1.02, P = 0.030) predicted worse PFS. KPS score >70 predicted better outcomes across ITC, OTC, DSS, and OS. Radiation-related adverse effects occurred in 2.8%. CONCLUSION:Single-fraction stereotactic radiosurgery offers reasonable tumor control and favorable long-term survival in the adjuvant and salvage setting for patients with residual, recurrent, or metastatic intracranial SFTs. Key prognostic factors included tumor volume, recurrence status, and timing of SRS.

In the past decade, studies have reclassified infiltrating glioblastomas (GBM) IDH-wildtype utilizing molecular and phenotypic features. Cystic GBMs are one such phenotypic subtype whose genetic and clinical characteristics remain incompletely understood. The goal of this study was to genetically characterize cystic GBMs and examine patient outcomes as compared to non-cystic GBMs. Retrospective analysis of GBM IDH-wildtype with pre-operative and post-operative MRI and comprehensive next-generation sequencing were performed with evaluation of 205 genes. Tumors were evaluated by their cystic characteristics. Benjamini-Hochberg’s false discovery rate (BH-FDR) was performed for multiple comparison adjustments. Univariable and multivariable analysis for survival was performed. 176 GBM IDH-WT patients met the inclusion criteria. Of these, 17 patients were identified as having a cystic component. Compared to non-cystic GBMs, cystic GBMs had a higher incidence of mutation in PDGFRA (41.2

INTRODUCTION:Hemangioblastomas are rare benign CNS tumors, occurring sporadically or with von Hippel-Lindau disease. While surgical resection is the primary treatment, GKRS serves as an adjuvant or salvage option when resection is not feasible. This study evaluates long-term outcomes of GKRS in patients with sporadic hemangioblastomas. METHODS:We retrospectively analyzed 82 patients with sporadic hemangioblastomas treated with GKRS across 17 International Radiosurgery Research Foundation centers (1993-2022). Univariate and multivariate analysis was conducted to identify variables influencing local control and tumor regression. RESULTS:Among 82 patients (52.4 % male, median age 51.5 years [IQR: 40.3-63.0]), most tumors were cerebellar (70.7 %), solid (63.4 %), with a median volume of 1.8 cc [IQR: 0.8-6.1]. The median margin dose was 16.0 Gy [IQR: 14.0-18.0]. With a median follow-up of 51.5 months [IQR: 21.0-92.0], local control was achieved in 69.5 % of cases (40.2 % regression, 29.3 % stability). Local control rates were 95 % (90 %, 100 %) at 6 months but declined to 75 % (65 %, 87 %) at 60 months. Radiation necrosis occurred in 6.1 % of patients (5/82), and no tumor-related deaths were reported among the 11.1 % overall mortality. Brainstem location was significantly linked to lower odds of tumor regression in the multivariate analysis (OR: 0.29, 95 % CI: 0.09-0.98, p = 0.045). CONCLUSION:GKRS demonstrated efficacy and safety in treating sporadic hemangioblastomas, achieving reasonable long-term local control rates with minimal complications. Our findings support its role as a viable treatment option, particularly for surgically challenging cases.

BACKGROUND AND OBJECTIVES:Hemangioblastomas (HGBs) are rare, benign, World Health Organization grade 1 vascular tumors, which are most commonly located in the cerebellum, and may occur sporadically or in association with von Hippel-Lindau (VHL) disease, a hereditary VHL-mutated tumor syndrome. Limited data are available regarding factors affecting outcomes after stereotactic radiosurgery (SRS). We aim to provide a contemporary evaluation of SRS for HGBs through an international, multicenter study. In this study, we assess local tumor control and SRS-related complications in patients with intracranial HGBs. METHODS:A retrospective analysis from 17 centers was performed. Data on patient characteristics, SRS parameters, and outcomes were collected. The study included 104 patients with VHL and 89 sporadic cases, with 433 and 137 tumors, respectively. The median follow-up after the initial SRS was 52 months for patients with VHL and 44 months for sporadic cases. RESULTS:At the last follow-up, tumor control was achieved in 85% of VHL tumors and 76% of sporadic tumors. Radiation-induced changes were identified in 13 (3.5%) VHL cases and 5 (3.8%) sporadic cases. The overall 3-year and 5-year cumulative incidences of tumor progression were 13% and 22% for all tumors, 14% and 25% for VHL, and 13% and 17% for sporadic cases. Tumor progression was more common in cystic than in solid tumors in the sporadic group. Overall survival probability and progression-free survival were better in VHL cases compared with the sporadic group. Older age at SRS, male sex, and multiple tumors were associated with reduced local tumor control in all tumors and in the VHL group, whereas a margin dose >15 Gy was associated with improved local tumor control in both groups. CONCLUSION:SRS offers an effective treatment of intracranial HGBs, whether VHL-associated or sporadic, with a favorable risk profile. HGBs without a cystic component were more likely to be controlled after SRS in the sporadic group.

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.

BACKGROUND AND OBJECTIVES:Single-session stereotactic radiosurgery (SRS) has limited role for large arteriovenous malformations (AVM). Volume-staged SRS (VS-SRS) is used to optimize outcomes, but studies reporting results are limited. METHODS:This multicenter retrospective cohort of 378 patients from 21 centers reports results of VS-SRS for the entire AVM nidus. We report favorable outcome, obliteration, hemorrhage, and permanent symptomatic adverse radiation effect rates. RESULTS:The median age was 31 years (IQR: 19-44) at the first volume stage, with patients treated in 2-4 stages. The median total nidus volume was 21 cm 3 (IQR: 13.9-30.1 cm 3 ), and a median prescription dose of 17 Gy (IQR: 16-18 Gy) was used. The median radiographic and clinical follow-up were 48 and 55 months, respectively. Seventy-seven patients (20.4%) had a favorable outcome, with the 3-year and 5-year rates being 3.9% and 18%, respectively. 127 patients (33.6%) achieved obliteration, with the 3-year and 5-year rates being 6.8% and 26%, respectively. Obliteration rates of AVMs <15 cm 3 were 81% and 31%, respectively. The latency period hemorrhage incidence rate was 3.02 cases per 100 patient-years; 52 patients (13.8%) had a bleed. Seventy-two patients (19%) had symptomatic adverse radiation effect; in 38 patients (10.1%), these were permanent. Total nidus volume, prescription dose at first stage, diffuse nidus, and prior hemorrhage were all independent affecting outcome rates. CONCLUSION:VS-SRS can be used to treat large AVMs as a standalone treatment. Obliteration rates and favorable outcomes are lower than that with smaller AVMs, and repeat treatment is often required. Optimizing treatment plans, by increasing prescription doses, reducing treatment volume at each stage, and increasing the number of stages, may lead to better outcomes.

BACKGROUND:There are limited data on dosimetric predictors of radiation-induced changes (RICs) for brainstem metastases or arteriovenous malformations (AVMs) following single-fraction stereotactic radiosurgery (SRS). METHODS:We examined a multi-institutional cohort of patients with brainstem metastases or AVMs treated with SRS. We evaluated predictors of RICs graded per CTCAE(Common Terminology Criteria for Adverse Events), including D5%, D95%, D0.03 cc, and D0.5 cc (brainstem minus lesion). Univariate logistic regressions were initially performed with independent variables trending towards significance included on multivariate logistic regression. RESULTS:A total of 124 brainstem lesions treated with SRS were analyzed (21 AVMs and 103 metastases). The median prescription dose was 16 Gy(range: 13-23 Gy), and the median treatment volume was 0.48 cc(range: 0.002-11.19 cc). The incidence of RICs was 9.7 % (with 3/12 being Grade 3-4 and no Grade 5). All cases occurred in brainstem metastases, with no cases among those of the midbrain-pons transition. Treatment volumes ≥ 1cc were correlated with a higher symptomatic RIC incidence(6/57 vs. 6/65; p = 0.04). Notably, all RIC cases had a D0.5 cc ≥ 15 Gy(12/87 vs. 0/32). Both D5%≥6 Gy(9/55 vs. 3/69; p = 0.04) and D95%≥1 Gy(7/31 vs. 5/93; p = 0.01) were significantly correlated with higher incidence of RICs and D0.03 cc ≥ 22 Gy was correlated with a lower risk(2/61 vs. 9/63; p = 0.03). On MVA, D0.03 cc ≥ 22 Gy remained a significant predictor of a lower incidence of RICs(odds ratio = -1.72 (95 % CI: -3.32 to -0.12; p = 0.04). CONCLUSIONS:Incidence of RICs was low following SRS for brainstem metastases and AVMs. We recommend optimizing radiosurgical plans for D0.5 cc < 15 Gy with consideration of D5% and D95%, with less emphasis on D0.03 cc to allow to meet the former metrics as feasible.

BACKGROUND:There is a paucity of data on treatment outcomes following stereotactic radiosurgery (SRS) for brain metastases from sarcoma primaries. METHODS:The International Radiosurgery Research Foundation member-sites were queried for patients with brain metastases from sarcoma primaries treated with SRS. Overall survival (OS) and local control (LC) were calculated via Kaplan-Meier analysis. Univariate analyses examined prognostic factors associated with LC and OS via log-rank t-tests and multivariate analyses (MVA) via Cox proportional hazards model. RESULTS:A total of 146 patients with 309 brain metastases were identified. Two-hundred and thirty lesions were treated with single-fraction SRS with a median dose of 20 Gy (15-24 Gy). Ninety-five patients had extracranial metastases, including 75 oligometastatic patients. One- and 2-year OS and LC rates were 47.7% and 37.3%, and 78.3% and 62.2%, respectively. On univariate analyses, superior 1-year OS was noted among leiomyosarcomas (69.7% vs. 42.6%; p = .02) with poorer outcomes among pleomorphic histologies (10.5% vs. 50.7%; p = .002). Pleomorphic histologies were associated with poorer OS on MVA (hazard ratio [HR], 3.13; p = .006). On MVA, LC was inferior among patients of age ≥45 years (HR, 3.78; p < .001) and superior among leiomyosarcomas (HR, 0.31; p = .03). OS was prognosticated based on adverse factors (ie, nonleiomyosarcoma histology and progressive extracranial metastases). Two-year OS for patients with and without adverse features were 78.6% and 31.5%, respectively. CONCLUSIONS:LC outcomes were driven by histology and age with superior LC among leiomyosarcomas and patients of age <45 years. OS was driven by nonleiomyosarcoma histology and the presence of progressive extracranial disease.