Faculty Bibliography

PURPOSE/OBJECTIVE:Brain metastases (BMs) from male breast cancer (MBC) are exceptionally rare, and the efficacy and safety of stereotactic radiosurgery (SRS) in this population remain poorly characterized. METHODS:We conducted a multicenter retrospective cohort study across 12 institutions. Eligible patients had histologically confirmed MBC with histopathologically or radiologically documented BMs treated with SRS. Lesion-level outcomes were analyzed using generalized estimating equations (GEE) with robust variance estimation. Overall survival (OS) was estimated by the Kaplan-Meier method. Neurological symptom change was assessed with McNemar's exact test, and discriminative ability of dosimetric variables for local failure was evaluated using receiver operating characteristic (ROC) analysis. RESULTS:Nineteen patients harboring 185 SRS-treated lesions were included. Median age at SRS was 59.0 years. The overall crude local control rate was 97.3%. Median OS was 28.0 months. Patients with controlled systemic disease at SRS demonstrated significantly longer median OS than those without (40.0 vs. 22.0 months; p = 0.032). Target volume was the only significant discriminator of local failure on ROC analysis (p < 0.001; optimal threshold 0.98 cc) and independently predicted adverse radiation effects on GEE analysis (p = 0.013). Neurological symptom burden decreased significantly after SRS (63.2% to 26.3%; p = 0.016), and median Karnofsky Performance Status remained stable. CONCLUSION/CONCLUSIONS:SRS achieves high local control with a favorable safety and neurological profile in MBC BMs. Systemic disease control at the time of SRS is the primary determinant of survival, while target volume is the principal dosimetric predictor of both local failure and radiation toxicity. These findings support the application of established SRS practice parameters in this rare population.

INTRODUCTION/BACKGROUND:Patient and arteriovenous malformation (AVM) characteristics that portend success after treatment for low-grade brain AVMs remain unknown. PATIENTS AND METHODS/METHODS:We utilised the MISTA multicentre registry to identify patients with Spetzler-Martin (SM) grade I or II AVMs treated with stand-alone curative-intent intervention (resection, stereotactic radiosurgery [SRS] or endovascular embolisation). Bivariate and multivariable analyses were performed to identify patient and AVM characteristics predictive of complete obliteration or favourable outcome (complete obliteration without new permanent deficit or post-treatment haemorrhage). RESULTS:A total of 522 patients were included (292 microsurgery, 152 SRS, 78 embolisation). Complete obliteration rates differed between microsurgery (95.9%), SRS (75.0%) and embolisation (71.8%) (P < .001); among patients classified as cured, digital subtraction angiography (DSA) confirmed obliteration in 96.1%, 75.9% and 52.4%, respectively. Favourable outcome was achieved in 89.4%, 64.5% and 67.9% (P < .001). In adjusted models for obliteration, elderly age (odds ratio [OR] 0.49, P = .022), larger nidus (OR 0.64, P = .005) and compacted morphology (OR 1.93, P = .019) were independent predictors overall; paediatric age predicted incomplete obliteration after microsurgery (OR 0.05, P = .045), and elderly age (OR 0.19, P = .001) and larger nidus (OR 0.59, P = .015) after SRS. For favourable outcome, SM grade II overall (adjusted OR [aOR] 0.58, P = .031) and elderly age after SRS (aOR 0.31, P = .019) were independent negative predictors. DISCUSSION/CONCLUSIONS:Low-grade AVMs showed high rates of complete obliteration, though DSA-confirmed rates were substantially lower after embolisation, underscoring the importance of angiographic confirmation. CONCLUSION/CONCLUSIONS:The predictors identified in this study may help guide management when 2 or 3 of the primary treatment options carry clinical equipoise.

BACKGROUND AND PURPOSE/OBJECTIVE:Stereotactic radiosurgery (SRS) is an effective management approach for many patients with head and neck paragangliomas (HNPGLs). However, treated paragangliomas may not significantly decrease in volume or subjective enhancement on conventional MRI. We investigated the utility of dynamic contrast-enhanced MRI (DCE-MRI) using golden-angle radial sparse parallel (GRASP) technique to detect vascular changes in HNPGLs after SRS, hypothesizing that controlled paragangliomas would demonstrate evidence of lower permeability post-SRS. MATERIALS AND METHODS/METHODS:We retrospectively analyzed 14 patients with HNPGLs managed with gamma-knife SRS from 2015 to 2024 at our institution who had GRASP DCE-MRI before and after treatment. Tumor enhancement kinetics were quantified using wash-in slope, wash-out slope, peak enhancement, and time to peak, normalized to the superior sagittal sinus. Tumors volumes were calculated from postcontrast images. Pre- and post-SRS parameters were compared using paired statistical tests. RESULTS:Median time between pre- and post-SRS imaging was 26 months. Tumor volume decreased modestly (median change -0.18 mL, p=.001) or remained stable in all but one case. Significant reductions were observed in normalized wash-in slope (p=.01), wash-out slope (p=.01), and peak enhancement (p=.02) following SRS. CONCLUSIONS:GRASP DCE-MRI detected significant changes in enhancement kinetics of HNPGLs following SRS, suggesting that dynamic imaging may serve as a biomarker of treatment response. These findings support the integration of functional imaging alongside conventional MRI sequences in post-treatment assessment of HNPGL.

BACKGROUND AND OBJECTIVES/OBJECTIVE:Multiple-choice questions are the primary assessment format for neurosurgical board certification. Creating high-quality examination questions requires significant expert time and resources. The goal of this study was to develop an automated system to generate board-style neurosurgical multiple-choice questions using state-of-the-art vision-language models and compare their quality with authentic self-assessment questions. METHODS:articles. We generated 89 587 synthetic questions: 45 689 with GPT-4o and 43 898 with Claude. Each question was associated with a single image extracted from the articles' figures. We evaluated the quality of synthetic questions through 5 surveys comparing 20 synthetic questions (10 from each model) with 10 authentic questions from the Self-Assessment for Neurological Surgeons (SANS) question bank. Each survey was completed by a neurosurgery resident and an attending who guessed the source [human vs artificial intelligence (AI)-generated] and rated suitability for board examination use. We also evaluated the question-answering performance of the generalist GPT-4o and the specialized CNS-Obsidian. RESULTS:). CONCLUSION/CONCLUSIONS:Although quality gaps exist between AI-generated and human-created neurosurgical board examination questions, our approach demonstrates the potential of vision-language models to augment assessment development in specialized medical fields, reducing the burden on examination boards and credentialing organizations.

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.

INTRODUCTION/BACKGROUND:Craniopharyngioma is histologically benign yet locally aggressive, with frequent recurrence. Long-term multicenter outcomes after stereotactic radiosurgery (SRS) remain incompletely defined. METHODS: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. RESULTS:Actuarial 1-, 5-, and 10-year LC was 93.5%, 76.2%, and 70.1%. Actuarial 1-, 5-, and 10-year OS was 98.2%, 93.6%, and 85.2%, and PFS was 92.4%, 73.6%, and 64.8%. Mixed solid-cystic phenotype had worse LC than non-mixed tumors (log-rank p = 0.025); non-mixed phenotype remained independently associated with improved LC (HR 0.53, p = 0.026). Visual fields improved in 10%, were unchanged in 86%, and deteriorated in 4%; visual acuity improved in 6%, was unchanged in 91%, and worsened in 3%. Ten-year freedom from endocrine deterioration was 96.7%. Diabetes insipidus improved in 6.3%, worsened in 0.5% and other pituitary dysfunction was noted in 2.6%, CONCLUSION: In this international multi-institutional experience, SRS achieved durable long-term control with favorable survival and low incidence of visual and endocrinologic dysfunction. Mixed phenotype was an important determinant of LC. CLINICAL TRIAL NUMBER/BACKGROUND:Not applicable.

BACKGROUND: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. OBJECTIVE:To develop and internally validate a multicenter survival model to predict imaging-defined time to progression after SRS for craniopharyngioma. METHODS: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% confidence intervals, integrated Brier score (IBS) over 0-60 months, and risk-stratified calibration. Benchmarks included a penalized Cox model and a Kaplan-Meier baseline. RESULTS:Among 277 patients (event rate 13.0%; median imaging follow-up 57.0 months by reverse Kaplan-Meier), RSF achieved an out-of-fold C-index of 0.905. Time-dependent AUC was 0.895 (95% CI 0.828-0.959) at 12 months, 0.897 (95% CI 0.833-0.952) at 24 months, and 0.934 (95% CI 0.889-0.969) at 60 months. IBS (0-60 months) was 0.050 with favorable calibration. CONCLUSIONS:A multicenter machine learning survival model can provide individualized, well-calibrated estimates of local control over time after SRS for craniopharyngioma to support non-prescriptive decision support. CLINICAL TRIAL NUMBER/BACKGROUND:Not applicable.

INTRODUCTION/BACKGROUND:Essential tremor is a common movement disorder that can cause substantial functional disability when symptoms become medically refractory. Stereotactic radiosurgery (SRS) is a minimal access treatment strategy for tremor control, but multicenter outcome data remain limited. METHODS:We performed a retrospective multi-institutional cohort study of 232 stereotactic radiosurgical thalamotomy procedures for medically refractory essential tremor. The median age at treatment was 76.0 years, median tremor duration was 17.0 years, median margin dose was 70.0 Gy, and median maximum dose was 140.0 Gy. The primary endpoint was clinically meaningful tremor improvement. Secondary endpoints included tremor arrest, recurrence, adverse radiation effects (AREs), and change in Fahn-Tolosa-Marín (FTM) scores. Logistic regression was used to evaluate outcome predictors. RESULTS:Significant tremor improvement was observed in 92.1% of patients, with a median time to improvement of 4.0 months. Complete tremor relief occurred in 26.1%. Symptomatic AREs occurred in 4.3%. Tremor recurrence was noted in 12.4% at median follow-up of 2 years. Among procedures, mean unilateral hand FTM score improved from 12.53 to 5.07, corresponding to a mean improvement of 7.46 points (p < 0.001). Significant improvement was also observed across tremor, writing, drawing, and drinking sub scores (all p < 0.001). On multivariable analysis, a maximum lesion dose ≥ 140 Gy was independently associated with greater odds of clinical benefit (OR 3.44, p = 0.019). CONCLUSION/CONCLUSIONS:In this multi-institutional cohort, SRS was associated with high rates of clinically meaningful tremor improvement, significant functional improvement, and durable tremor control in medically refractory essential tremor.

BACKGROUND AND OBJECTIVES/OBJECTIVE: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/CONCLUSIONS: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.

Stereotactic radiosurgery evolved from the desire to achieve highly precise and accurate target ablation using radiation energy. Over the past 3 decades, the range of indications for stereotactic radiosurgery has expanded significantly, making it a valuable treatment option-and often a first-line approach-for various intracranial conditions, including benign and malignant brain tumors, vascular malformations, and functional disorders. This narrative review offers a comprehensive, yet not exhaustive, overview of the current evidence, technical considerations, and areas of nuance and controversy regarding these indications and dose selection. It serves as a quick reference guide for neurosurgeons and radiation oncologists working in this field. In addition, tables are included that detail the indications, expected results, dose prescriptions, and anticipated outcomes, assisting clinicians in both clinical settings and procedural planning.