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.

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

Metastases to the pineal gland are rare. Surgical excision can be associated with high rates of morbidity. Alternatively, stereotactic radiosurgery (SRS) for brain metastases in the pineal region has not been vigorously studied. We performed a multi-institutional retrospective study for patients treated with SRS for pineal region metastases at treatment centers that comprise the International Radiosurgery Research Foundation (IRRF). Demographics, tumor characteristics, treatment parameters, and clinical outcomes were collected. The primary endpoint was local tumor control (LC). Secondary endpoints included: Overall survival (OS), distant tumor control (DC), and adverse radiation events (AREs). Kaplan-Meier and Cox regression analyses were performed to evaluate time to event endpoints and prognostic factors respectively. Twenty-six patients (16 female, 62

BACKGROUND AND OBJECTIVES: Stereotactic radiosurgery (SRS) for brain arteriovenous malformations (AVMs) can cause radiation-induced changes (RIC), but its interactions with AVM embolization are not well established. The aim of this study was to assess the effect of previous embolization on RIC in SRS-treated AVM patients. METHODS: Data of AVM patients treated with single-session SRS from 1987 to 2018 were retrieved from the International Radiosurgery Research Foundation. Univariable and stepwise backward logistic regression models were used to identify RIC predictors. Patients were stratified into those who received pre-SRS embolization (E + SRS) vs those who did not (SRS-only). Radiologic RIC (rRIC) was the primary end point. Secondary outcomes included symptomatic RIC (sRIC) and permanent symptomatic RIC (pRIC). RESULTS: Among 1187 AVM patients, the mean age was 36.4 years (SD 16.8), with 50.4% female patients. AVMs had a mean untreated AVM volume of 5.2 cm 3 . A total of 130 patients (11%) underwent neoadjuvant embolization (E + SRS). The overall rRIC and sRIC rates were 32.8% and 12.1%, respectively, with time to rRIC and sRIC being significantly longer in the E + SRS vs SRS-only cohorts (103.6 ± 339.4 vs 11.3 ± 12.5 and 60.4 ± 262.9 vs 9.5 ± 9.0 months, respectively). Seizures at presentation and ≥3-cm untreated AVM volume significantly correlated with a higher likelihood of rRIC (adjusted odds ratio [aOR] 2.32 [1.25-4.30] and aOR 2.77 [1.24-6.16], respectively). Age and pre-SRS embolization were associated with a significantly lower risk of rRIC (aOR 0.97 [0.96-0.99] and aOR 0.32 [0.13-0.74], respectively). The E + SRS cohort had significantly reduced odds of rRIC (aOR = 0.37 [0.15-0.89]) and pRIC (aOR = 0.04 [0.00-0.30]) after adjusting for significant covariates. CONCLUSION: Seizures at presentation and larger untreated AVM volume were independently associated with an increased risk of rRIC, whereas older age and pre-SRS embolization were protective. Notably, patients who underwent embolization before SRS had lower odds of rRIC and pRIC, with delayed onset of complications compared with SRS-only.

Background Identifying prognostic factors to improve local tumor control (LTC) after stereotactic radiosurgery (SRS) for brain metastases (BM) is crucial for optimizing patient outcomes. This study synthesizes evidence on the impact of perilesional edema (PLE) on LTC in BM managed with SRS. Methods A systematic search was conducted in PubMed, Scopus, Embase, and Web of Science, to identify relevant studies reporting PLE as a prognostic factor for LTC in BM treated with SRS. Results Nine studies, comprising 829 patients treated for 1742 BM treated with SRS, met the inclusion criteria. For the primary analysis, 8 studies involving 1455 BM were included. A random-effects model demonstrated that higher or present PLE was associated with an increased risk of local failure (hazard ratio [HR] = 1.82; 95% CI, 1.42-2.34; I2 = 13.8%). Subgroup analyses using a fixed-effect model revealed further insights: studies defining PLE using numeric cutoffs showed a higher risk of local failure (HR = 1.71; 95% CI, 1.39-2.10; I² = 0%), whereas studies dichotomizing PLE as present versus absent observed an even greater risk (HR = 2.78; 95% CI, 1.65-4.69; I² = 33.5%). Sensitivity analysis incorporating all 9 studies confirmed a significant association between PLE and local failure but introduced notable heterogeneity (HR = 1.68; 95% CI, 1.17-2.43; I2 = 81.3%). Conclusion Pretreatment PLE in BM is associated with an increased risk of local failure following SRS, with local failure rates more than doubling in lesions exhibiting edema at the time of treatment. Future research should explore the potential of edema-reducing therapies administered at the time of SRS to improve treatment outcomes.

BACKGROUND:Transvenous embolization (TVE) is a new treatment of brain arteriovenous malformations (AVMs). The safety and efficacy of TVE have not been compared with transarterial embolization (TAE). The primary hypothesis of this trial was that TVE would increase the proportion of AVM occlusion from 40% to 80%. METHODS:The TATAM (Transvenous Approach for the Treatment of Cerebral AVMs) was an investigator-initiated, multicenter, prospective, phase 2, open-label, controlled randomized trial comparing TVE versus TAE alone (1:1). Patients with symptomatic or asymptomatic AVMs considered curable with 2 endovascular sessions were reviewed by a case selection committee. Participating centers were experienced (>20 cases) or proctored by experts. The primary outcome was complete occlusion of the AVM, confirmed by catheter angiography at 3 to 6 months. There was no blinding. Primary analyses were intent-to-treat. RESULTS:From May 2019 to April 2023, 77 patients were recruited in 7 French and 2 Canadian centers. After exclusions, results from 69 patients were analyzed; 35 were allocated TVE and 34 TAE. The mean age of participants was 43.3 years; 29 of 69 (42%) were female. There were 2 crossovers. The primary outcome was reached in 29 of 35 patients with TVE (83% [95% CI, 67%-92%]) compared with 20 of 34 patients allocated TAE (59% [95% CI, 42%-74%]; P=0.036). Poor outcomes (modified Rankin Scale score >2 at 3-6 months) occurred in 7 of 35 patients with TVE (20% [95% CI, 10%-36%]) and 9 of 34 patients with TAE (27% [95% CI, 15%-43%]; P=0.578) and related serious adverse events in 12 of 35 patients with TVE (34% [95% CI, 21%-51%]) and 14 of 34 patients with TAE (41% [95% CI, 26%-58%]; P=0.624). CONCLUSIONS:TVE was more effective than TAE in terms of angiographic results at 3 to 6 months. Morbidity was similar but high for both groups. More studies are needed to determine the role of curative embolization in managing patients with brain AVM. REGISTRATION:URL: https://www.clinicaltrials.gov; Unique identifier: NCT03691870.

Management for elderly patients (> 65yo) with incidental meningiomas remains unclear. This study aims to characterize the functional and tumor outcomes of expectant and stereotactic radiosurgery (SRS) management of asymptomatic meningioma elderly patients. Using retrospectively collected data from 14 centers, SRS outcomes were compared to radiographic and clinical observation of asymptomatic meningiomas in elderly patients following propensity score matching. Following propensity score matching, 114 patients were in each cohort. Tumor control was achieved at 97.37

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: Stereotactic radiosurgery (SRS) represents an effective treatment for nonfunctioning pituitary adenomas (NFPAs). However, no data have yet been published regarding results of SRS on NFPAs after multiple previous resections. METHODS: Retrospective multicentric data of patients diagnosed with NFPA and who underwent multiple resections (>= 2) before SRS were reviewed and analyzed. The treatment interval spanned the period of 1992 to 2022. Cox regression and Kaplan-Meier curves were used to assess predictive factors and the probability of tumor control and hypopituitarism. RESULTS: Among the 311 patients (median age: 50.2 [IQR: 18.0] years), 226 (72.7%) had undergone >= 2 previous resections. The median margin dose was 14 Gy (IQR: 4.0 Gy), and the median tumor volume 3.6 cm3 (IQR: 4.8). Overall, the probability of tumor control after SRS was 93.3% (CI 95%: 89.9-96.9) and 86.7% (CI 95%: 81.1-92.6) at 5 and 10 years, respectively. A margin dose >14 Gy was associated with a decreased risk of tumor progression (hazard ratio = 0.33, CI 95% = 0.15-0.75, P = .008). At a last clinical follow-up of 4.1 (IQR 6.1) years, 10.1% (30/296) developed at least 1 new hormone deficiency after SRS. The cumulative probability of new hormone deficiency was 6.1% (95% CI: 3.0-9.1), 10.3% (95% CI: 5.8-14.6), and 18.9% (95% CI: 11.5-25.8) at 3, 5, and 10 years after SRS, respectively. The average latency between SRS and development of new hormone deficiencies was 3.3 years (IQR 4.1). A maximum point dose to the pituitary stalk >10 Gy was associated with a new deficiency (hazard ratio = 4.06, CI 95% = 1.57-10.5, P-value = .004). CONCLUSION: For patients with NFPA with multiple previous resections, SRS offers effective local tumor control and a low risk of delayed hypopituitarism for managing these challenging adenomas. SRS should be strongly considered in patients with NFPA with 2 previous resections compared with considering a third resection.

Whether the number or cumulative volume of brain metastases affects survival in patients with metastatic non-small cell lung cancer (NSCLC) remains controversial. We conducted a volume matched multi-center study to determine whether patients with a single metastasis had better outcomes than patients with > 20 brain metastases. Between 2014 and 2022, 317 NSCLC patients (21.14

INTRODUCTION: The appropriate management of Koos grade I vestibular schwannomas (VS) remains controversial. METHODS: In a multicenter study, this report gathered and analyzed data retrospectively on Koos grade I VS patients who underwent SRS (SRS group) or were observed (observation group). Propensity score matching was utilized to equilibrate demographics, tumor size, and audiometric data across groups. The outcome analyzed included tumor control, preservation of serviceable hearing (SHP), and neurological function. RESULTS: The study matched 142 patients, providing a median follow-up period of 36 months. SRS significantly enhanced tumor control compared to observation, with a 100% control rate at both 5- and 8-year marks in the SRS group versus 49.7% and 33% in the observation group at the same time intervals, respectively (P<0.001). SHP outcomes between groups showed no significant difference at 5 and 8 years, ensuring a comparable quality of auditory function (SRS 70.1% vs. observation 53.4% at 5 years; P=0.33). Furthermore, SRS was associated with a reduced likelihood of tinnitus (OR=0.46, P=0.04), vestibular dysfunction (OR=0.17, P=0.002), and overall cranial nerve dysfunction (OR=0.49, P=0.03) at last follow up. CONCLUSIONS: SRS management of Koos grade I VS patients was associated with superior tumor control and reduced odds for dysfunction of various cranial nerves, while not compromising hearing preservation compared to observation. These findings support the safety and efficacy of SRS as a potential management modality for this patient population.

BACKGROUND AND OBJECTIVES:The therapeutic approach for small- and medium-sized vestibular schwannoma (VS) with normal hearing function remains controversial, with limited comparative data regarding hearing outcomes after stereotactic radiosurgery (SRS) or observation (OBS). We evaluated the serviceable hearing preservation, loss of American Academy of Otolaryngology-Head and Neck Surgery class A hearing, and tumor control (TC) across individuals with Koos grade I and II VSs and normal hearing at presentation who underwent SRS or OBS. METHODS:In this multicenter international study, we retrospectively analyzed the hearing, radiological, and neurological outcomes of patients who underwent SRS (SRS group) or OBS (OBS group). The cohorts were matched using propensity scores based on age, sex, tumor volume, pure-tone average, and speech discrimination score at a 1:1 ratio without replacement. RESULTS:After matching, each group comprised 57 patients. The median follow-up was 49 and 37 months for the SRS and the OBS groups, respectively ( P = .3). The 5- and 9-year serviceable hearing preservation rates in the SRS group were 76.2% and 42.4% vs 56.1% and 16.8% in the OBS group ( P = .17). Class A preservation occurred in 57.9% (33/57) of the SRS and 52.6% (30/57) of the OBS cohorts ( P = .70). Regarding the TC rates, SRS was associated with significantly higher TC rates ( P < .0001). CONCLUSION:We found that SRS is significantly superior regarding TC and provided noninferior hearing outcomes compared with OBS in VS patients with American Academy of Otolaryngology-Head and Neck Surgery class A hearing at presentation. Therefore, we suggest performing SRS in individuals with VS and normal hearing function.

Glioblastoma is the most common and aggressive malignant brain tumor in adults, with an increasing incidence and a poor prognosis. Current challenges in glioblastoma management include rapid tumor growth, limited treatment effectiveness, high recurrence rates, and a significant impact on patients’ quality of life. Given the complexity of glioblastoma care and recent advancements in diagnostic and treatment modalities, updated guidelines are needed in Canada. This Delphi study aimed to develop Canadian consensus recommendations for the diagnosis, classification, and management of newly diagnosed and recurrent glioblastoma. A multidisciplinary panel of 14 Canadian experts in glioblastoma care was convened, and a comprehensive literature review was conducted to synthesize evidence and formulate initial recommendations. Consensus was achieved through three Delphi rounds, in which panelists rated their agreement with recommendation statements on a five-point Likert scale. Statements with ≥75% agreement were accepted, and others were revised for re-voting. Final recommendations were formulated based on the consensus level, strength of evidence, clinical expertise, and consideration of the Canadian healthcare context. These recommendations aim to standardize glioblastoma diagnosis and classification across Canada, provide evidence-based guidance for optimal treatment selection, integrate novel therapies, and enhance the overall quality of care for glioblastoma patients.

BACKGROUND AND OBJECTIVES:Oligodendrogliomas are primary brain tumors classified as isocitrate deshydrogenase-mutant and 1p19q codeleted in the 2021 World Health Organization Classification of central nervous system tumors. Surgical resection, radiotherapy, and chemotherapy are well-established management options for these tumors. Few studies have evaluated the efficacy of stereotactic radiosurgery (SRS) for oligodendroglioma. As these tumors are less infiltrative than astrocytomas and typically recur locally, focal therapy such as SRS is an appealing option. METHODS:This study was performed through the International Radiosurgery Research Foundation. The objective was to collect retrospective multicenter data on tumor control, clinical response, and morbidity after SRS for oligodendroglioma. Inclusion criteria were age of 18 years or more, single-fraction SRS, and histological confirmation of grade 2 or 3 oligodendroglioma. The primary end points were progression-free survival (PFS) and overall survival from SRS. Secondary end points included clinical evolution and occurrence of adverse radiation events or other complications. Descriptive statistics, Kaplan-Meier analyses, and univariate and multivariate analyses were performed. RESULTS:Eight institutions submitted data for a total of 55 patients. The median follow-up time was 24 months. The median age at SRS was 46 years, and the median Karnofsky Performance Status was 90%. The median marginal dose used was 15 Gy. The median PFS was 17 months, with actuarial rates of 60% at 1 year, 31% at 2 years, and 24% at 5 years after SRS. Factors significantly associated with worsened PFS were World Health Organization grade 3, previous radiotherapy and chemotherapy, and higher marginal dose. The median overall survival post-SRS was 58 months, with actuarial rates of 92% at 1 year, 83% at 2 years, and 49% at 5 years. Karnofsky Performance Status remained stable post-SRS in 51% and worsened in 47% of patients, most often because of tumor progression (73%). Radiation-induced changes occurred in 30% of patients, of which only 4 were symptomatic. CONCLUSION:SRS is a reasonable management option for patients with oligodendroglioma.

Affecting 2.93 per 100,000 in the U.S., vestibular schwannomas (VS) are benign tumors of the eighth nerve. The management includes observation, operative resection, and stereotactic radiosurgery (SRS). A retrospective, multicentric analysis was conducted, focusing on patients with Koos grade II VS who either received SRS (SRS group) or were observed (observation group). To ensure comparability between groups, propensity score matching was employed, including factors such as demographic characteristics, tumor dimensions, and hearing assessments. The primary endpoints examined were tumor control, maintenance of serviceable hearing, and neurological outcomes. A total of 92 patients were equally matched across both cohorts, with a median follow-up of 37 months for the SRS group and 27.5 months for those observed. The SRS cohort exhibited superior tumor control over observation across 3, 5, and 8 years, achieving a 100% control rate versus 47.9%, 40.1%, and 34.3% for the observation group at these time intervals, respectively (P<0.001). Hearing preservation rates were comparable between the two groups throughout 3, 5, and 7 years (72.9% for SRS vs. 65.4% for observation at 3 years; P=0.86). Moreover, SRS management correlated with a lower incidence of vestibular dysfunction (OR=0.11, P=0.002), with no significant disparity in the deterioration of cranial nerve (CN) V or CN VII functions. Notably, the likelihood of experiencing any CN impairment was significantly diminished in the SRS cohort (OR=0.47, P=0.04). For patients with Koos grade II VS, SRS offers superior tumor control rate and a lower risk of cranial nerve dysfunction without sacrificing hearing preservation.

BACKGROUND AND OBJECTIVES:Repeat stereotactic radiosurgery (SRS) is a noninvasive option for recurrent vestibular schwannoma (VS). This study evaluates outcomes in patients with long-term follow-up. METHODS:This retrospective multicenter study analyzed 81 patients with recurrent unilateral sporadic VS after initial SRS, with ≥12 months of follow-up. Outcomes included tumor control, hearing preservation, cranial nerve function, and adverse radiation effects (ARE). Kaplan-Meier and Cox regression identified factors affecting outcomes. RESULTS:The median age at the second SRS was 60 years, with a median interval of 58 months between procedures. The median margin doses were 12.0 Gy (single-fraction), 17.25 Gy (3-fraction), and 25 Gy (5-fraction). Tumor control was achieved in 69 patients (85.2%), with 5- and 10-year local control rates of 82% and 76.5%, respectively. Significant predictors of local failure included tumor volume >2.2 cm 3 (area under the curve = 0.757, P = .018), prescription biological effective dose (BED) ≤70.3 Gy (hazard ratio [HR]: 0.89, P = .003), and interval between treatments >27.5 months (HR: 1.02, P = .015). In single-fraction SRS, higher prescription dose reduced failure risk (HR: 0.31, P = .002) with a margin dose ≥12 Gy being critical for improved tumor control ( P < .001). Serviceable hearing was retained in 12 of 18 cases (66.7%), and facial nerve function was preserved in 72 of 80 cases (90%). ARE occurred in 11 patients (13.6%), most commonly perilesional edema (63.7%). ARE correlated with higher brainstem maximum BED in the entire cohort (HR: 1.02, P = .016) and in single-fraction SRS (HR: 1.02, P = .006). Pseudoprogression (9.8%) was linked to younger age (HR: 0.88, P = .023) and shorter time between SRS (HR: 0.87, P = .012). CONCLUSION:Repeat SRS is an effective option for recurrent sporadic VS, offering high tumor control and functional preservation. Outcomes depend on age, interval between treatments, tumor volume, and BED. With careful planning, adverse effects are rare and typically transient.

Stereotactic radiosurgery (SRS) is used to treat residual and recurrent nonfunctioning pituitary adenomas (NFPA). Hypopituitarism is the most common complication with increasing rates over time. We present the largest multicentric cohort evaluating outcomes after radiosurgery for NFPA. Twelve centers contributed retrospective data on 869 patients treated with SRS between 1992 and 2022. Tumor progression was defined as a volumetric increase of =20% from baseline. New-onset hypopituitarism was defined as dysfunction of at least 1 pituitary axis. Kaplan–Meier curves were plotted for the probability of tumor control and new onset hypopituitarism. Cox regression was used to assess predictive factors for tumor control and new pituitary hormone deficiency. A total of 869 patients (median age 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 3.4cc (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. 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. 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 10-year cumulative probability of new cortisol, thyroid, gonadotroph, and growth hormone deficiency was 8%, 8.3%, 3.5%, and 4.7%, respectively. SRS for NFPA affords long-term tumor control (10 year:>88%) and low rates of pituitary dysfunction (10-year:15.3%).

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.