Faculty Bibliography

BACKGROUND AND OBJECTIVES/OBJECTIVE:Dose selection for brain metastases stereotactic radiosurgery (SRS) classically has been based on tumor diameter with a reduction of dose in the settings of prior brain irradiation, larger tumor volumes, and critical brain location. However, retrospective series have shown local control rates to be suboptimal with reduced doses. We hypothesized that lower doses could be effective for specific tumor biologies with concomitant systemic therapies. This study aims to report the local control (LC) and toxicity when using low-dose SRS in the era of modern systemic therapy. METHODS:We reviewed 102 patients with 688 tumors managed between 2014 and 2021 who had low-margin dose radiosurgery, defined as ≤14 Gy. Tumor control was correlated with demographic, clinical, and dosimetric data. RESULTS:The main primary cancer types were lung in 48 (47.1%), breast in 31 (30.4%), melanoma in 8 (7.8%), and others in 15 patients (11.7%). The median tumor volume was 0.037cc (0.002-26.31 cm3), and the median margin dose was 14 Gy (range 10-14). The local failure (LF) cumulative incidence at 1 and 2 years was 6% and 12%, respectively. On competing risk regression analysis, larger volume, melanoma histology, and margin dose were predictors of LF. The 1-year and 2-year cumulative incidence of adverse radiation effects (ARE: an adverse imaging-defined response includes increased enhancement and peritumoral edema) was 0.8% and 2%. CONCLUSION/CONCLUSIONS:It is feasible to achieve acceptable LC in BMs with low-dose SRS. Volume, melanoma histology, and margin dose seem to be predictors for LF. The value of a low-dose approach may be in the management of patients with higher numbers of small or adjacent tumors with a history of whole brain radio therapy or multiple SRS sessions and in tumors in critical locations with the aim of LC and preservation of neurological function.

PURPOSE/OBJECTIVE:Patients with EGFR-mutated NSCLC represent a unique subset of lung cancer patients with distinct clinical and molecular characteristics. Previous studies have shown a higher incidence of brain metastases (BM) in this subgroup of patients, and neurologic death has been reported to be as high as 40% and correlates with leptomeningeal disease (LMD). METHODS:Between 2012 and 2021, a retrospective review of our prospective registry identified 606 patients with BM from NSCLC, with 170 patients having an EGFR mutation. Demographic, clinical, radiographic, and treatment characteristics were correlated to the incidence of LMD and survival. RESULTS:LMD was identified in 22.3% of patients (n = 38) at a median follow-up of 19 (2-98) months from initial SRS. Multivariate regression analysis showed targeted therapy and a cumulative number of metastases as significant predictors of LMD (p = 0.034, HR = 0.44), (p = .04, HR = 1.02). The median survival time after SRS of the 170 patients was 24 months (CI 95% 19.1-28.1). In a multivariate Cox regression analysis, RPA, exon 19 deletion, and osimertinib treatment were significant predictors of overall survival. The cumulative incidence of neurological death at 2 and 4 years post initial stereotactic radiosurgery (SRS) was 8% and 11%, respectively, and correlated with LMD. CONCLUSION/CONCLUSIONS:The study shows that current-generation targeted therapy for EGFR-mutated NSCLC patients may prevent the development and progression of LMD, leading to improved survival outcomes. Nevertheless, LMD is associated with poor outcomes and neurologic death, making innovative strategies to treat LMD essential.

BACKGROUND:Brain metastases (BM) have long been considered a terminal diagnosis with management mainly aimed at palliation and little hope for extended survival. Use of brain stereotactic radiosurgery (SRS) and/or resection, in addition to novel systemic therapies, has enabled improvements in overall and progression-free (PFS) survival. OBJECTIVE:To explore the possibility of extended survival in patients with non-small-cell lung cancer (NSCLC) BM in the current era. METHODS:During the years 2008 to 2020, 606 patients with NSCLC underwent their first Gamma Knife SRS for BM at our institution with point-of-care data collection. We reviewed clinical, molecular, imaging, and treatment parameters to explore the relationship of such factors with survival. RESULTS:The median overall survival was 17 months (95% CI, 13-40). Predictors of increased survival in a multivariable analysis included age <65 years (P < .001), KPS ≥80 (P < .001), absence of extracranial metastases (P < .001), fewer BM at first SRS (≤3, P = .003), and targeted therapy (P = .005), whereas chemotherapy alone was associated with shorter survival (P = .04). In a subgroup of patients managed before 2016 (n = 264), 38 (14%) were long-term survivors (≥5 years), of which 16% required no active cancer treatment (systemic or brain) for ≥3 years by the end of their follow-up. CONCLUSION/CONCLUSIONS:Long-term survival in patients with brain metastases from NSCLC is feasible in the current era of SRS when combined with the use of effective targeted therapeutics. Of those living ≥5 years, the chance for living with stable disease without the need for active treatment for ≥3 years was 16%.

BACKGROUND:Patients presenting with large brain metastases (LBM) pose a management challenge to the multidisciplinary neuro-oncologic team. Treatment options include surgery, whole-brain or large-field radiation therapy (WBRT), stereotactic radiosurgery (SRS), or a combination of these. OBJECTIVE:To determine if corticosteroid therapy followed by SRS allows for efficient minimally invasive care in patients with LBMs not compromised by mass effect. METHODS:We analyzed the change in tumor volume to determine the efficacy of single-session SRS in the treatment of LBM in comparison to other treatment modalities. Twenty-nine patients with systemic cancer and brain metastasis (≥ 2.7 cm in greatest diameter) who underwent single-session SRS were included. RESULTS:(range 1.56-25.31). The median margin dose was 16 Gy (range 12-18). The average percent decrease in tumor volume compared to pre-SRS volume was 55% on imaging at 1-2 months, 58% at 3-5 months, 64% at 6-8 months, and 57% at > 8 months. There were no adverse events immediately following SRS. Median corticosteroid use after SRS was 21 days. Median survival after radiosurgery was 15 months. CONCLUSION/CONCLUSIONS:Initial high-dose corticosteroid therapy followed by prompt single-stage SRS is a safe and efficacious method to manage patients with LBMs (defined as ≥ 2.7 cm).

INTRODUCTION/BACKGROUND:Clinical trial data comparing outcomes after administration of stereotactic radiosurgery (SRS) or whole-brain radiotherapy (WBRT) to patients with brain metastases (BM) suggest that SRS better preserves cognitive function and quality of life without negatively impacting overall survival. Here, we estimate the maximum number of BM that can be treated using single and multi-session SRS while limiting the dose of radiation delivered to normal brain tissue to that associated with WBRT. METHODS:Multiple-tumor SRS was simulated using a Monte Carlo - type approach and a pre-calculated dose kernel method. Tumors with diameters ≤36 mm were randomly placed throughout the contoured brain parenchyma until the brain mean dose reached 3 Gy, equivalent to the radiation dose delivered during a single fraction of a standard course of WBRT (a total dose of 30 Gy in 10 daily fractions of 3 Gy). Distribution of tumor sizes, dose coverage, selectivity, normalization, and maximum dose data used in the simulations were based on institutional clinical metastases data. RESULTS:The mean number of tumors treated, mean volume of healthy brain tissue receiving > 12 Gy (V12) per tumor, and total tumor volume treated using mixed tumor size distributions were 12.7 ± 4.2, 2.2 cc, and 12.9 cc, respectively. Thus, we estimate that treating 12-13 tumors per day over 10 days would deliver the dose of radiation to healthy brain tissue typically associated with a standard course of WBRT. CONCLUSION/CONCLUSIONS:Although in clinical practice, treatment with SRS is often limited to patients with ≤15 BM, our findings suggest that many more lesions could be targeted while still minimizing the negative impacts on quality of life and neurocognition often associated with WBRT. Results from this in silico analysis require clinical validation.

BACKGROUND/UNASSIGNED:Laser interstitial thermal therapy (LITT) in the setting of post-SRS radiation necrosis (RN) for patients with brain metastases has growing evidence for efficacy. However, questions remain regarding hospitalization, local control, symptom control, and concurrent use of therapies. METHODS/UNASSIGNED:Demographics, intraprocedural data, safety, Karnofsky performance status (KPS), and survival data were prospectively collected and then analyzed on patients who consented between 2016-2020 and who were undergoing LITT for biopsy-proven RN at one of 14 US centers. Data were monitored for accuracy. Statistical analysis included individual variable summaries, multivariable Fine and Gray analysis, and Kaplan-Meier estimated survival. RESULTS/UNASSIGNED:Ninety patients met the inclusion criteria. Four patients underwent 2 ablations on the same day. Median hospitalization time was 32.5 hours. The median time to corticosteroid cessation after LITT was 13.0 days (0.0, 1229.0) and cumulative incidence of lesional progression was 19% at 1 year. Median post-procedure overall survival was 2.55 years [1.66, infinity] and 77.1% at one year as estimated by KaplanMeier. Median KPS remained at 80 through 2-year follow-up. Seizure prevalence was 12% within 1-month post-LITT and 7.9% at 3 months; down from 34.4% within 60-day prior to procedure. CONCLUSIONS/UNASSIGNED:LITT for RN was not only again found to be safe with low patient morbidity but was also a highly effective treatment for RN for both local control and symptom management (including seizures). In addition to averting expected neurological death, LITT facilitates ongoing systemic therapy (in particular immunotherapy) by enabling the rapid cessation of steroids, thereby facilitating maximal possible survival for these patients.

Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) is increasingly utilized in the treatment of spine metastasis. Preliminary data suggest that higher doses may improve local control, but may also increase risk of toxicity including vertebral compression fracture (VCF). Our single institution study recently found that a minimum dose of at least 21 Gy to 80% of planning target volume (PTV D80%) in 2 fractions was associated with higher risk of VCF. The purpose of this study is to assess this variable's relationship with local failure (LF) and VCF in an international, multi-institutional cohort. Materials/Methods: Patients with radiation naive solid tumor spine metastases treated with SBRT at 5 international institutions from 2010 - 2020 were included. Patients with surgical stabilization were excluded. LF was defined per spine response assessment in neuro-oncology criteria. Variables examined included spinal instability neoplastic score (SINS) factors and dosimetric/volumetric characteristics of radiation planning. All fractionation scheme doses were converted to 2-fraction equivalent doses (2fxED) using the linear quadratic model with an alpha/beta of 3 and used in analyses of PTV D80%. Univariate and multivariate Cox proportional hazard models for LF and VCF were constructed using the Fine and Gray competing risk method.
Result(s): 357 vertebral segments from 234 patients were treated with SBRT. Common primary tumor types were prostate (n = 50, 22%), non-small cell lung cancer (n = 42, 18%), breast (n = 35, 15%), and kidney (n = 25, 11%). Most (n = 199 pts, 242 segments) were treated with 2 or 3 fractions with a median prescription dose of 24 Gy or 27 Gy, respectively (range: 14-45 Gy in 1-5 fractions). Median follow was 21.1 months (0.6-88.4 mo). LF was 12.6% and 18.1% at 1- and 2-years, respectively. Variables associated with increased LF on univariate analysis were lower PTV D80% at 2fxED <=21 Gy (HR 0.36, 95% CI 0.20-0.65, p = 0.001) and lower prescription dose BED3 (HR 0.98 as continuous variable, CI 0.97-0.99, p = 0.03). On multivariate analysis, only PTV D80% at 2fxED <=21 Gy remained associated with increased risk of LF (HR 0.46, CI 0.24-0.85, p = 0.01). VCF incidence was low, at 4.2% and 6.7% at 1- and 2-years, respectively. Higher SINS was predictive of VCF (HR 1.22, CI 1.1-1.36, p <0.001). Patients with higher PTVD80% at 2fxED>21 Gy had a higher, albeit non-significant, risk of VCF (HR 3.30, CI 0.80-13.6, p = 0.10), consistent with our previous single institution study.
Conclusion(s): This multi-institutional, international study suggests that a PTV D80% at 2fxED <=21 Gy may increase the risk of LF, while >21 Gy may increase the likelihood of VCF. Prospective studies are needed to further explore this complex relationship and identify the dose/fractionation schedule that best balances local control with normal tissue toxicity including VCF.
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BACKGROUND:For patients with vestibular schwannoma (VS), stereotactic radiosurgery (SRS) has proven effective in controlling tumor growth while hearing preservation remains a key goal. OBJECTIVE:To evaluate hearing outcomes in the modern era of cochlear dose restriction. METHODS:During the years 2013 to 2018, 353 patients underwent Gamma knife surgery for VS at our institution. We followed 175 patients with pre-SRS serviceable hearing (Gardner-Robertson Score, GR 1 and 2). Volumetric and dosimetry data were collected, including biological effective dose, integral doses of total and intracanalicular tumor components, and hearing outcomes. RESULTS:The mean age was 56 years, 74 patients (42%) had a baseline GR of 2, and the mean cochlear dose was 3.5 Gy. The time to serviceable hearing loss (GR 3-4) was 38 months (95% CI 26-46), with 77% and 62% hearing preservation in the first and second years, respectively. Patients optimal for best hearing outcomes were younger than 58 years with a baseline GR of 1, free canal space ≥0.041 cc (diameter of 4.5 mm), and mean cochlear dose <3.1 Gy. For such patients, hearing preservation rates were 92% by 12 months and 81% by 2 years, staying stable for >5 years post-SRS, significantly higher than the rest of the population. CONCLUSION/CONCLUSIONS:Hearing preservation after SRS for patients with VS with serviceable hearing is correlated to the specific baseline GR score (1 or 2), age, cochlear dose, and biological effective dose. Increased tumor-free canal space correlates with better outcomes. The most durable hearing preservation correlates with factors commonly associated with smaller tumors away from the cochlea.

OBJECTIVE:Morphological and angioarchitectural features of cerebral arteriovenous malformations (AVMs) have been widely described and associated with outcomes; however, few studies have conducted a quantitative analysis of AVM flow. The authors examined brain AVM flow and transit time on angiograms using direct visual analysis and a computer-based method and correlated these factors with the obliteration response after Gamma Knife radiosurgery. METHODS:A retrospective analysis was conducted at a single institution using a prospective registry of patients managed from January 2013 to December 2019: 71 patients were analyzed using a visual method of flow determination and 38 were analyzed using a computer-based method. After comparison and validation of the two methods, obliteration response was correlated to flow analysis, demographic, angioarchitectural, and dosimetric data. RESULTS:The mean AVM volume was 3.84 cm3 (range 0.64-19.8 cm3), 32 AVMs (45%) were in critical functional locations, and the mean margin radiosurgical dose was 18.8 Gy (range 16-22 Gy). Twenty-seven AVMs (38%) were classified as high flow, 37 (52%) as moderate flow, and 7 (10%) as low flow. Complete obliteration was achieved in 44 patients (62%) at the time of the study; the mean time to obliteration was 28 months for low-flow, 34 months for moderate-flow, and 47 months for high-flow AVMs. Univariate and multivariate analyses of factors predicting obliteration included AVM nidus volume, age, and flow. Adverse radiation effects were identified in 5 patients (7%), and 67 patients (94%) remained free of any functional deterioration during follow-up. CONCLUSIONS:AVM flow analysis and categorization in terms of transit time are useful predictors of the probability of and the time to obliteration. The authors believe that a more quantitative understanding of flow can help to guide stereotactic radiosurgery treatment and set accurate outcome expectations.

PURPOSE/OBJECTIVE:New therapies for melanoma have been associated with increasing survival expectations, as opposed to the dismal outcomes of only a decade ago. Using a prospective registry, we aimed to define current survival goals for melanoma patients with brain metastases (BM), based on state-of-the-art multimodality care. METHODS:We reviewed 171 melanoma patients with BM receiving stereotactic radiosurgery (SRS) who were followed with point-of-care data collection between 2012 and 2020. Clinical, molecular and imaging data were collected, including systemic treatment and radiosurgical parameters. RESULTS:SRS were predictors of long-term survival ([Formula: see text] 5 years) from initial SRS (p = 0.023 and p = 0.018, respectively). Five patients (16%) of the long-term survivors required no active treatment for [Formula: see text] 5 years. CONCLUSION/CONCLUSIONS:Long-term survival in patients with melanoma BM is achievable in the current era of SRS combined with immunotherapies. For those alive [Formula: see text] 5 years after first SRS, 16% had been also off systemic or local brain therapy for over 5 years. Given late recurrences of melanoma, caution is warranted, however prolonged survival off active treatment in a subset of our patients raises the potential for cure.