Courses Of Stereotactic Radiosurgery Research Articles

RADT-18. DEDICATED 3D-FSE SEQUENCE-BASED RADIOSURGERY REDUCES DISTANT INTRACRANIAL RELAPSE RATES IN A HISTOLOGY-AGNOSTIC PATIENT COHORT

Abstract INTRODUCTION Stereotactic radiosurgery (SRS) is a cornerstone in the treatment of brain metastasis (BM), despite a known risk of distant intracranial failure (DIF). Recent imaging advances, specifically, sensitive 3D-FSE sequences, have started to be incorporated into SRS practice; however, comparisons of outcomes to historical imaging approaches are limited. We evaluated the impact of adding 3D-FSE to MPRAGE in BM detection and prolongation of DIF in a histology-agnostic patient group. METHODS Outcomes of patients treated with SRS for BM between 01/2019-01/2024 were evaluated. MPRAGE sequences were obtained for all; 3D-FSE sequences were implemented in 02/2020. Median times to DIF were estimated using the Kaplan-Meier method. RESULTS 215 patients underwent 332 SRS courses for 1456 BM imaged with MPRAGE and 3D-FSE (primary cohort), compared to the control cohort (92 patients, 135 SRS courses, 462 BM). MPRAGE sequences revealed 1636 lesions in 307 patients (462 in 92 control cohort, 1174 in 215 primary cohort). In the primary cohort, an additional 282 lesions were identified with 3D-FSE (24% increase) by neuroradiologists and multidisciplinary review. There was a statistically significant prolongation in the median time to DIF between the cohorts (11.4 vs. 6.8 months, p=0.029), most pronounced in the 1-4 metastases subgroup (14.7 vs. 8.1 months, p=0.008) and in those with a single BM (36.4 vs. 10.9 months, p=0.001). While patients relapsing on immunotherapy or targeted therapy did not significantly benefit from 3D-FSE (7.2 vs. 5.7 months, p=0.280), those who relapsed on chemotherapy or were off systemic therapy at least four weeks prior to SRS (including synchronous metastases) exhibited a trend towards longer time to DIF with 3D-FSE (14.7 vs. 7.9 months, p=0.057). CONCLUSIONS 3D-FSE added to MPRAGE lengthens time to DIF via improving BM detection, especially for limited BM, and those relapsing on systemic therapy with limited intracranial penetration or no systemic therapy.

Efficacy of 3D-TSE Sequence-based Radiosurgery in Prolonging Time to Distant Intracranial Failure: A Session-wise Analysis in a Histology-Diverse Patient Cohort.

Stereotactic radiosurgery (SRS) for patients with brain metastases (BM) is associated with a risk of distant intracranial failure (DIF). This study evaluates the impact of integrating dedicated 3D-TSE sequences to MPRAGE in BM detection and DIF prolongation in a histology-agnostic patient cohort. The study population included adults treated with SRS from February 2019 to January 2024 who underwent MPRAGE alone or dual-sequence with the addition of 3D-TSE starting from February 2020. Median times to DIF were estimated using the Kaplan-Meier method. The 216 study patients who underwent 332 SRS courses for 1456 BM imaged with MPRAGE and 3D-TSE (primary cohort) were compared to a control cohort (92 patients, 135 SRS courses, 462 BM). In the session-wise analysis, the median time to DIF between the cohorts was significantly prolonged in the primary vs. control cohorts (11.4 vs. 6.8 months, p=0.029), more pronounced in the subgroups with 1-4 metastases (14.7 vs. 8.1 months, p=0.008) and with solitary BM (36.4 vs. 10.9 months, p=0.001). While patients relapsing on immunotherapy or targeted therapy did not significantly benefit from 3D-FSE (7.2 vs. 5.7 months, p=0.280), those who relapsed on chemotherapy or who were off systemic therapy (including synchronous metastases) exhibited a trend towards longer time to DIF with 3D-TSE integration (14.7 vs. 7.9 months, p=0.057). Implementing 3D-TSE sequences into SRS practice increases BM detection across all patients and translates into clinical relevance by prolonging time to DIF, particularly in those with limited intracranial disease and those not receiving CNS-active agents.

Assessing survival in non-small cell lung cancer brain metastases after stereotactic radiosurgery: before and after the start of the targetable mutation era.

Targeted treatment options for non-small cell lung cancer (NSCLC) brain metastases (BMs) may be combined with stereotactic radiosurgery (SRS) to optimize survival. We assessed patient outcomes after SRS for NSCLC BMs, identifying survival trajectories associated with targetable mutations. In this retrospective time-dependent analysis, we analyzed median overall survival of patients who received ≥ 1 SRS courses for BM from NSCLC from 2001 to 2021. We compared survival of patients with and without targetable mutations based on clinical variables and treatment. Among the 213 patients included, 87 (40.8%) had targetable mutations-primarily EGFR (22.5%)-and 126 (59.2%) did not. Patients with targetable mutations were more often female (63.2%, p <.001) and nonsmokers (58.6%, p <.001); had higher initial lung-molGPA (2.0 vs. 1.5, p <.001) and lower cumulative tumor volume (3.7 vs. 10.6 cm3, p <.001); and received more concurrent (55.2% vs. 36.5%, p =.007) and total (median 3 vs. 2, p <.001) systemic therapies. These patients had lower mortality rates (74.7% vs. 91.3%, p <.001) and risk (HR 0.298 [95%CI 0.190-0.469], p <.001) and longer median overall survival (20.2 vs. 7.4 months, p <.001), including survival ≥ 3 years (p =.001). Survival was best predicted by SRS with tumor resection in patients with non-targetable mutations (HR 0.491 [95%CI 0.318-757], p =.001) and by systemic therapy with SRS for those with targetable mutations (HR 0.124 [95%CI 0.013-1.153], p =.067). The presence of targetable mutations enhances survival in patients receiving SRS for NSCLC BM, particularly when used with systemic therapies. Survival for patients without targetable mutations was longest with SRS and surgical resection. These results inform best practices for managing patients with NSCLC BM based on driver mutation status.

Stereotactic radiosurgery (SRS) for non-small cell lung cancer (NSCLC) in the oncogene-addicted era: A real-world UK tertiary center experience.

e14011 Background: 30-50% of NSCLC patients develop brain metastases (BM). Re-evaluation of the role of SRS is required with evolving understanding of molecular subtypes of NSCLC and increasing intracranial efficacy of systemic agents. Methods: We conducted a retrospective analysis of NSCLC patients receiving SRS at our centre from 05/16-11/23. Primary objective was median overall survival (mOS months). Analysis was performed on Prism 10.1.1. Multivariate analysis was conducted using Cox Proportional Hazards Regression, with age, gender, KPS, BM size, total BM volume and oncogene status as predictor variables. Extraction from medical records was undertaken by authors, with local R&amp;D committee approval. Results: 237 patients were evaluable. 59% (N=139) were oncogene-addicted (oNSCLC) and 41% (N=98) non-oncogene-addicted (non-oNSCLC). Median duration of follow up was 43.3m. m OS was 11.9m overall. For oNSCLC mOS was 13.1m vs 8.8m for non-oNSCLC (HR 1.49, P=0.02). mOS was 20.7m for EGFR sensitizing NSCLC (N=48) vs 10.5m without (HR 1.40 P=0.12). mOS for ALK+ (N=22) was 29.3m vs 11.6m for non-ALK+ (HR 1.90, P=0.05). mOS for KRAS+ (N=32) was 11.6m vs 12.0m without (HR 0.91, P=0.68). Significantly inferior mOS was seen for single (N=186 [78%]) vs multiple (N=51[22%]) SRS courses (8.4m vs 38.8m, [HR 0.34 P=&lt;0.0001]). SRS at diagnosis of BM (N=118) had a mOS of 12.3m vs at nadir (N=9, not reached [HR0.44, P=0.18]), progression on 1st line TKI (N=31, 22.1m [HR 1.1, P=0.79]) and at any other time (N=157, 7.8m [HR 1.33, P=0.11 ]). There was no significant difference in survival for patients diagnosed with brain metastases at the diagnosis of metastatic disease compared to those who developed brain metastases during their disease course (12.3m vs 10.6m [HR 1.18, P=0.33]). Survival of those with 1 site of metastatic disease (18.3m) was numerically improved compared to those with 2 (10.7m, HR 1.26, P=0.25) sites, and statistically significant compared to those with 3 (10.1m, HR 1.69, P&lt;0.02) and ≥4 (4.4m, HR 4.41, P&lt;0.0001) sites. Conclusions: Median OS in oNSCLC was superior to non-oNSCLC, driven by numerically superior survival in EGFR+ and ALK+ cohorts. Significantly improved OS was observed in patients with multiple vs single SRS treatments, however this may be confounded by biases. Patients treated with SRS at nadir had numerically superior OS to those treated at other timepoints, however this must be interpreted with caution due to small sample size. Further prospective research is needed to interrogate these findings and guide local therapies in NSCLC with BM. [Table: see text]

Border Zone Maybe Correlated with Radiation Necrosis After Radiosurgery in Metastatic Brain Tumor

BackgroundRadiation necrosis (RN) after stereotactic radiosurgery (SRS) in brain metastases has been extensively evaluated, and RN is correlated with various risk factors. However, no study comprehensively analyzed the correlation between RN and the border zones of the brain that are vulnerable to ischemia. We hypothesized that patients with tumors in the border zone are at high risk of RN. Hence, the current study aimed to assess the correlation between border zone lesions and RN, with consideration of other predetermined factors. MethodsThis retrospective study included 117 patients with 290 lesions who underwent Gamma Knife® stereotactic radiosurgery (SRS). Radiological and clinical analyses were performed to identify factors possibly correlated with RN. Notably, the lesion location was classified into two groups (border zone and non-border zone) based on the blood supply. ResultsIn total, 22 (18.8%) patients with 22 (7.5%) lesions developed RN. Univariate analysis revealed a significant correlation between RN and external border zone lesions, second course of SRS administered at the same site of the previous SRS, prescribed dose, and tumor volume. Multivariate analysis showed that border zone lesions, second course of SRS at the same site of the previous SRS, and tumor volume were significantly correlated with RN. ConclusionsPatients with tumors in the border zone are at high risk of RN. The potential risks of RN can be attributed hypothetically to hypoperfusion. Hence, the association between RN and border zone lesions seems reasonable.

Determinants of Symptomatic Intracranial Progression After an Initial Stereotactic Radiosurgery Course

Purpose: Clinical and imaging surveillance of patients with brain metastases (BMs) is important after stereotactic radiosurgery (SRS), as many will experience intracranial progression (ITCP) requiring multidisciplinary management. The prognostic significance of neurologic symptoms at the time of ITCP is poorly understood. Materials/MethodsThis was a multi-institutional, retrospective cohort study from 2015-2020, including all patients with BMs completing an initial course of SRS. The primary outcome was overall survival (OS) by presence of neurologic symptoms at ITCP. OS, freedom from ITCP (FF-ITCP), and freedom from symptomatic ITCP (FF-SITCP) were assessed via Kaplan-Meier method. Cox proportional hazard models tested parameters impacting FF-ITCP and FF-SITCP. Results: Among 1383 patients, median age was 63.4 years, 55% were female, and common primaries were non-small cell lung (49%), breast (15%), and melanoma (9%). At a median follow up of 8.72 months, asymptomatic and symptomatic ITCP were observed in 504 (36%) and 194 (14%) patients respectively. The majority of ITCP were distant ITCP (79.5%). OS was worse with SITCP (median 10.2 vs 17.9 months, p<0.001). SITCP was associated with clinical factors including total treatment volume (P = 0.012), melanoma histology (P = 0.001), prior WBRT (P = 0.003), number of brain metastases (P < 0.001), interval of 1-2 years from primary and brain metastasis diagnosis (P = 0.012), controlled extracranial disease (P = 0.042), and receipt of pre-SRS chemotherapy (P = 0.015). Patients who were younger and received post-SRS chemotherapy (P = 0.001), immunotherapy (P < 0.001), and targeted or small-molecule inhibitor therapy (P < 0.026) had better FF-SITCP. Conclusions: In this cohort study of BM patients completing SRS, neurologic symptoms at ITCP is prognostic for OS. This data informs post-SRS surveillance in clinical practice as well as future prospective studies needed in the modern management of BMs.

Incidence and imaging characteristics of difficult to detect retrospectively identified brain metastases in patients receiving repeat courses of stereotactic radiosurgery.

During stereotactic radiosurgery (SRS) planning for brain metastases (BM), brain MRIs are reviewed to select appropriate targets based on radiographic characteristics. Some BM are difficult to detect and/or definitively identify and may go untreated initially, only to become apparent on future imaging. We hypothesized that in patients receiving multiple courses of SRS, reviewing the initial planning MRI would reveal early evidence of lesions that developed into metastases requiring SRS. Patients undergoing two or more courses of SRS to BM within 6months between 2016 and 2018 were included in this single-institution, retrospective study. Brain MRIs from the initial course were reviewed for lesions at the same location as subsequently treated metastases; if present, this lesion was classified as a "retrospectively identified metastasis" or RIM. RIMs were subcategorized as meeting or not meeting diagnostic imaging criteria for BM (+ DC or -DC, respectively). Among 683 patients undergoing 923 SRS courses, 98 patients met inclusion criteria. There were 115 repeat courses of SRS, with 345 treated metastases in the subsequent course, 128 of which were associated with RIMs found in a prior MRI. 58% of RIMs were + DC. 17 (15%) of subsequent courses consisted solely of metastases associated with + DC RIMs. Radiographic evidence of brain metastases requiring future treatment was occasionally present on brain MRIs from prior SRS treatments. Most RIMs were + DC, and some subsequent SRS courses treated only + DC RIMs. These findings suggest enhanced BM detection might enable earlier treatment and reduce the need for additional SRS.

Artificial-intelligence-driven measurements of brain metastases'response to SRS compare favorably with current manual standards of assessment.

Evaluation of treatment response for brain metastases (BMs) following stereotactic radiosurgery (SRS) becomes complex as the number of treated BMs increases. This study uses artificial intelligence (AI) to track BMs after SRS and validates its output compared with manual measurements. Patients with BMs who received at least one course of SRS and followed up with MRI scans were retrospectively identified. A tool for automated detection, segmentation, and tracking of intracranial metastases on longitudinal imaging, MEtastasis Tracking with Repeated Observations (METRO), was applied to the dataset. The longest three-dimensional (3D) diameter identified with METRO was compared with manual measurements of maximum axial BM diameter, and their correlation was analyzed. Change in size of the measured BM identified with METRO after SRS treatment was used to classify BMs as responding, or not responding, to treatment, and its accuracy was determined relative to manual measurements. From 71 patients, 176 BMs were identified and measured with METRO and manual methods. Based on a one-to-one correlation analysis, the correlation coefficient was R2 = 0.76 (P = .0001). Using modified BM response classifications of BM change in size, the longest 3D diameter data identified with METRO had a sensitivity of 0.72 and a specificity of 0.95 in identifying lesions that responded to SRS, when using manual axial diameter measurements as the ground truth. Using AI to automatically measure and track BM volumes following SRS treatment, this study showed a strong correlation between AI-driven measurements and the current clinically used method: manual axial diameter measurements.

Automated Detection, Segmentation, and Tracking of Brain Metastases in Repeated Courses of Stereotactic Radiosurgery Using Integrated Artificial Intelligence.

Salvage stereotactic radiosurgery (SRS) for distant brain metastases has been demonstrated as a safe and effective approach for intracranial recurrences after initial SRS. However, accurate tumor detection and segmentation among responding tumors within the irradiated parenchyma can be challenging. The requirement for the registration and reference to the previous course of SRS is very time-consuming and suffers significant inter and intra-reader variability. Artificial intelligence (AI)-assisted system has been proven to improve the accuracy and efficiency in the clinical flow of de-novo SRS. We hypothesize that an integrated AI system can facilitate an automated tumor contouring process for repeated SRS. Three patients who underwent their third course of SRS to brain metastases were selected for the pioneering works. They have had two sessions of SRS with a mean lesion number of 4 and 3.7, respectively. VBrain, an FDA-approved brain tumor management AI platform, was used to co-registered serial MR scans and automatically identify, track, and contour brain metastases for each course of SRS. The AI also indicated new lesions and treated lesions for each course. Three radiation oncologists experienced in brain SRS contoured the gross tumor volumes (GTVs) of the third course of SRS in two reader modes (assisted then unassisted) with a memory washout period of one week between each section. The segmentation ground truth was established through consensus among the three experts. Lesion-wise sensitivity, contouring accuracy, and consuming time were compared between the two contouring modes. In each patient, there were 15, 11, and 9 metastases, with a median diameter of 4.72 (95% CI: 4.05, 6.91) mm. The mean lesion-wise sensitivity was 96.96±2.47% with AI assistance and 76.90 ± 7.10% without assistance. There were two false-positive lesions in the assisted read, resulting in a low average false-positive rate of 0.67 per patient, while no false positive for the unassisted mode. AI assistance improved contouring accuracy. The median Dice similarity coefficient (DSC) was 0.71 (95% CI: 0.55, 0.87) for assisted contouring and 0.65 (95% CI: 0.46, 0.85) for unassisted contouring. We also use average Hausdorff distance (HD) to measure segmentation results. The mean HD was 0.72± 0.13 mm versus 0.73±0.08 mm for the two contouring modes (p = 0.02) Furthermore, the median contouring time per case was significantly shorter with AI assistance than without assistance (20.8 minutes vs. 29.8 minutes; p < 0.001), corresponding to a 43.2% time-saving. Our results suggest that the integration of an AI-based system into repeated brain SRS can significantly improve the accuracy and efficiency of tumor detection and segmentation. This approach has the potential to streamline the treatment planning process for salvage SRS.

Impact of Concurrent Targeted Therapy and Immunotherapy on the Incidence of Radiation Necrosis Following Stereotactic Radiosurgery for Brain Metastases

The management of metastatic disease has evolved with the advent of immunotherapy (IT) and targeted therapies (TT). Yet, there is limited understanding of the toxicity associated with combining these agents with stereotactic radiosurgery (SRS). We retrospectively evaluated the impact of concurrent systemic therapy (ST) on the risk of radiation necrosis (RN) following LINAC-based SRS for brain metastases (BM). A retrospective study was conducted within an integrated health care system from March 2017 to December 2021 of 313 patients who underwent SRS or fractionated SRS in 3 or 5 treatments to a total of 1,644 intact BM. Post-operative cavity SRS and re-irradiated lesions were excluded. RN was diagnosed using perfusion MRI, contrast clearance MRI, or serial standard MRI and graded using CTCAE (v.5). Concurrent ST was defined as administration within 1 month preceding or following SRS. Overall survival (OS) and risk of RN were estimated by the Kaplan-Meier method. Logistics regression analyses were performed to compare risk of RN in patients who received concurrent systemic therapy to those who did not, adjusted for PTV volume and receipt of whole brain radiotherapy (WBRT). Median follow-up was 12.2 months. Median age was 64 years (range: 24-92). Primary sites per patient included lung (48.9%), breast (18.2%), melanoma (11.5%), kidney (6.1%), and other (15.3%). Median total lesions treated was 3 (range: 1-44); 65.9% of patients underwent 1 course of SRS, 23.4% underwent 2 courses, 6.2% underwent 3 courses, 4.5% underwent >4 courses. Seventy-six (24.2%) patients received WBRT. Overall, 70.6% of lesions received concurrent ST including chemotherapy (CT) (32.5%), IT (26.8%), and TT (27.6%); 16.4% received a combination of ST. Median OS was 12.9 months (95% CI: 10.4-15.5). RN was observed in 50 (3.0%) lesions in 42 (13.4%) patients. The 1-year risk of RN was 4.0% per lesion and 15.4% per patient. Symptomatic RN (SRN) was observed in 31 (1.9%) lesions in 24 (7.7%) patients. The 1-year risk of SRN was 2.7% per lesion and 10.1% per patient. When compared to lesions treated without concurrent systemic therapy, there was no increased risk of RN observed in lesions treated with concurrent CT (adjusted OR = 0.86 (95% CI: 0.43-1.73) p = 0.68), concurrent IT (adjusted OR = 0.84 (95% CI: 0.41-1.71) p = 0.84), or concurrent TT (adjusted OR = 0.57 (95% CI: 0.25-1.30) p = 0.18). Treatments of SRN included dexamethasone (96.8%), bevacizumab (22.6%), and laser interstitial thermal therapy (6.5%). Concurrent IT and TT appears well-tolerated in patients who undergo SRS for treatment of BM. No increased risk of RN was observed in lesions treated with concurrent IT or TT compared to lesions treated in the absence of concurrent ST. Further prospective and agent-specific evaluation is necessary to confirm these findings.

Intracranial Control with Combined Dual Immune-Checkpoint Blockade and SRS for Melanoma and NSCLC Brain Metastases

It is unknown whether the use of dual immune-checkpoint inhibition (D-ICI) combined with stereotactic radiosurgery (SRS) affects local control of brain metastases (BMs). We sought to characterize the efficacy of SRS and D-ICI in patients with BMs in a large, single-institution cohort. Patients with melanoma and non-small cell lung cancer (NSCLC) BMs treated with SRS from January 1, 2016 to August 1, 2022 were evaluated. Patients were stratified by treatment with D-ICI versus single ICI (S-ICI). Concurrent ICI was defined as ICI given within four weeks of SRS. Local recurrence (LR), intracranial progression (IP), and overall survival (OS) were estimated using competing risk and Kaplan-Meier analyses. IP included both local and distant intracranial recurrence. One thousand seven hundred four SRS-treated BMs from 288 patients met inclusion criteria. 55% of patients were symptomatic from their BMs at presentation. Median age, KPS, number of lesions, and SRS courses were 64 (Q1Q3:56-70.5), 90 (80-90), 2 (1-4), and 1 (1-2), respectively. One hundred twenty-eight (44%) melanoma and 160 (56%) NSCLC patients were included. 82 (28.5%), 129 (44.8%), and 77 (26.7%) patients were treated with D-ICI, S-ICI, or SRS alone. Median SRS dose, fractions, and PTV were 20 (Q1Q3:20-25), 1 (1-5), and 0.3cc3 (0.1-1.2). The median follow-up was 14.3 months. One hundred twenty-seven (7.45%) BMs recurred post-SRS and the median time to LR was 4.8 months (Q1Q3:3.0-9.2). On competing risk analysis, LR was significantly reduced with D-ICI (HR: 0.452, p = 0.0024), but not with S-ICI (HR: 0.693, p = 0.0596) compared to SRS alone. The 1-year LR was 3.77% (95% CI = 2.19-6.00), 6.8% (5.19-8.70), and 8.96% (6.48-11.93) with D-ICI, S-ICI, and SRS alone. The median time to IP was 4.1 months (Q1Q3 = 2.9-9.5). On competing risk analysis, IP was significantly reduced with D-ICI (HR = 0.638, p = 0.031), but not with S-ICI (HR = 0.756, p = 0.106) compared to SRS alone. 1-year IP was 40.05% (95% CI = 29.14-50.70), 51.86% (42.78-60.19), and 58.49% (46.30-68.84) with D-ICI, S-ICI, and SRS alone. Concurrent delivery of D-ICI and SRS significantly reduced IP (HR = 0.463, p = 0.0071), whereas other combinations of timing and ICI did not reach significance. Median OS was 11.9 months after SRS. On Kaplan Meier analysis, OS was significantly improved with D-ICI (HR = 0.616, 95% CI = 0.412-0.923, p = 0.019), but not with S-ICI (HR = 0.877, 95% CI = 0.633-1.217, p = 0.433) compared to SRS alone. Hospitalizations (p = 0.021) and immune-related adverse events (irAEs) (p<0.001) were increased with D-ICI. Any grade radiation necrosis (RN) was also increased with D-ICI (p = 0.013), but neurologic adverse events were comparable across cohorts (p = 0.572). D-ICI combined with SRS was associated with improved local control, intracranial control, and overall survival compared to SRS alone, whereas S-ICI was not associated with an improvement in these outcomes. However, D-ICI was also associated with increased risks of irAEs and RN.

CLRM-01 DETERMINANTS OF SYMPTOMATIC INTRACRANIAL PROGRESSION FOLLOWING AN INITIAL STEREOTACTIC RADIOSURGERY COURSE

Abstract To determine the prognostic significance of neurologic symptoms at progression for patients with brain metastases (BM) undergoing stereotactic radiosurgery (SRS), all patients completing an initial course of SRS between 1/2015 and 12/2020 were identified across two institutions. Intracranial progression (ICP) was recorded, with symptomatic ICP (SICP) defined as new/worsening neurologic symptoms without another etiology. Overall survival (OS), freedom from ICP (FFICP), and freedom from symptomatic ICP (FFSICP) were assessed via Kaplan-Meier method. For FFSICP, patients were censored at time of death or asymptomatic ICP. Logistic regression models tested parameter association to neurologic symptoms. Cox proportional hazard models tested parameters impacting FFICP and FFSICP. Among 1383 patients, median age was 63.4 years, 54.8% were female, and 45.6% had KPS ≥90. Common primary sites were non-small cell lung (48.7%), breast (14.7%), and melanoma (8.5%). 46.9% had oligometastatic disease (≤5 foci), and 53.4% had &amp;gt;1 BM. 26.1% patients had prior surgical resection, and 10.3% had WBRT. With a median follow up of 8.7 months, 504 (36%) and 194 (14%) experienced asymptomatic and symptomatic ICP respectively. OS was worse for patients experiencing SICP (median 10.2 vs 17.9 months, p&amp;lt;0.001). Among patients with ICP, SICP was associated with total treated tumor volume (per-ml, OR 1.01, 95% CI 1.00-1.02), while those with more recent MRI imaging and post-SRS systemic therapy was associated with asymptomatic ICP. Patients who received post-SRS chemotherapy (HR 0.64, 95% CI 0.45-0.90), immunotherapy (HR 0.49, 95% CI 0.34-0.71), or targeted therapy (HR 0.49, 95% CI 0.33-0.73) had better FFSCIP. Worse FFSCIP was associated with melanoma (HR 2.56, 95% CI 1.49-4.38), and greater than 2 BMs (HR 2.24, 95% CI 1.56-3.22). SICP is prognostic for OS, and is associated with melanoma, no systemic therapy post-SRS, and greater number of BMs. These data further support the use of SICP as a meaningful clinical endpoint.

LMAP-08 MULTI-INSTITUTIONAL CLINICAL OUTCOMES FOLLOWING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES FROM GYNECOLOGIC MALIGNANCIES

Abstract Brain metastases (BM) are rare in patients with gynecologic (GYN) malignancies. We identified and analyzed all patients who completed a course of stereotactic radiosurgery (SRS) between 1/2015 and 12/2020 across two institutions. Demographic and clinical parameters were collected. Intracranial progression (ICP) was defined as any concern on post-SRS imaging for recurrence determined by multidisciplinary consensus. Clinical parameter distributions were compared across GYN and non-GYN patients utilizing chi-squared tests and t-tests. Overall survival (OS) and freedom from intracranial progression (FFICP) were estimated via the Kaplan Meier method. From a cohort of 1383 patients who completed SRS for BMs, 2.4% (n=33) had a BM from a GYN malignancy. Subsites included endometrial (n=19), ovarian (n=11), vulvar (n=2), cervical (n=1). There was no difference in age between GYN and non-GYN patients (mean 67.1 years vs. 63.0 years, p=0.06). GYN patients with BMs compared to non-GYN patients were more likely to have resection of BMs (48.5% vs. 25.6%, p=0.003), larger planned target volumes of all BMs (mean 23.6cc vs mean 15.2cc, p=0.02), and pre-SRS chemotherapy (72.7% vs. 49.6%, p=0.009). GYN patients were less likely to have whole brain radiation therapy prior to SRS (0 vs. 10.5%, p=0.049). GYN patients had worse OS compared to non-GYN patients (median 6.6 months (95% CI 3.3-12.4) vs. 10.0 months (95% CI 9.1-11.2), (HR 1.62 (95% CI 1.11-2.36), p=0.011)). Median FFICP for GYN patients was 9.5 months (95% CI 4.0-not reached) and for non-GYN patients was 8.7 months (95% CI 7.7-9.5). There was no difference in FFICP for GYN patients compared to non-GYN patients (HR 0.84 (95% CI 0.5-1.5), p=0.55). When comparing patients with BMs from endometrial cancer versus ovarian cancer, there was no difference in OS (p=0.13) or FFICP (p=0.58). These data may help guide treatment decisions and post-therapy surveillance in patients with BMs of GYN origin.

Effects of Ataxia-Telangiectasia Mutated Variants on Radionecrosis and Local Control After Stereotactic Radiation Surgery for Non-Small Cell Lung Cancer Brain Metastases

Genetic variants affecting the radiation response protein ataxia-telangiectasia mutated (ATM) have been associated with increased adverse effects of radiation but also with improved local control after conventional radiation therapy. However, it is unknown whether ATM variants affect rates of radionecrosis (RN) and local intracranial progression (LIP) after stereotactic radiosurgery (SRS) for brain metastases. Patients undergoing an initial course of SRS for non-small cell lung cancer (NSCLC) brain metastases at a single institution were retrospectively identified. Kaplan-Meier estimates were calculated and Cox proportional hazards testing was performed based on ATM variant status. A total of 541 patients completed SRS for brain metastasis secondary to NSCLC, of whom 260 completed molecular profiling. Variants of ATM were identified in 36 cases (13.8%). Among patients who completed molecular profiling, RN incidence was 4.9% (95% CI, 1.6%-8.2%) at 6 months and 9.9% (95% CI, 4.8%-15.0%) at 12 months. Incidence of RN was not significantly increased among patients with ATM variants, with an RN incidence of 5.3% (95% CI, 0.0%-15.3%) at both 6 and 12 months (P=.46). For all patients who completed genomic profiling, LIP was 5.4% (95% CI, 2.4%-8.4%) at 6 months and 9.8% (5.5%-14.1%) at 12 months. A significant improvement in LIP was not detected among patients with ATM variants, with an LIP incidence of 3.1% (0.0%-9.1%) at both 6 and 12 months (P=.26). Although differences according to ATM variant type (pathologic variant or variant of unknown significance) did not reach significance, no patients with ATM pathologic variants experienced LIP. We did not detect significant associations between ATM variant status and RN or LIP after SRS for NSCLC brain metastases. The current data set allows estimation of patient cohort sizes needed to power future investigations to identify genetic variants that associate with significant differences in outcomes after SRS.

Automatically tracking brain metastases after stereotactic radiosurgery.

Patients with brain metastases (BMs) are surviving longer and returning for multiple courses of stereotactic radiosurgery. BMs are monitored after radiation with follow-up magnetic resonance (MR) imaging every 2-3months. This study investigated whether it is possible to automatically track BMs on longitudinal imaging and quantify the tumor response after radiotherapy. The METRO process (MEtastasis Tracking with Repeated Observations was developed to automatically process patient data and track BMs. A longitudinal intrapatient registration method for T1 MR post-Gd was conceived and validated on 20 patients. Detections and volumetric measurements of BMs were obtained from a deep learning model. BM tracking was validated on 32 separate patients by comparing results with manual measurements of BM response and radiologists' assessments of new BMs. Linear regression and residual analysis were used to assess accuracy in determining tumor response and size change. A total of 123 irradiated BMs and 38 new BMs were successfully tracked. 66 irradiated BMs were visible on follow-up imaging 3-9months after radiotherapy. Comparing their longest diameter changes measured manually vs. METRO, the Pearson correlation coefficient was 0.88 (p<0.001); the mean residual error was -8±17%. The mean registration error was 1.5±0.2mm. Automatic, longitudinal tracking of BMs using deep learning methods is feasible. In particular, the software system METRO fulfills a need to automatically track and quantify volumetric changes of BMs prior to, and in response to, radiation therapy.

Intracranial and Extracranial Progression and Their Correlation With Overall Survival After Stereotactic Radiosurgery in a Multi-institutional Cohort With Brain Metastases

Clinical trials for metastatic malignant neoplasms are increasingly being extended to patients with brain metastases. Despite the preeminence of progression-free survival (PFS) as a primary oncologic end point, the correlation of intracranial progression (ICP) and extracranial progression (ECP) events with overall survival (OS) is poorly understood for patients with brain metastases following stereotactic radiosurgery (SRS). To determine the correlation of ICP and ECP with OS among patients with brain metastases completing an initial SRS course. This multi-institutional retrospective cohort study was conducted from January 1, 2015, to December 31, 2020. We included patients who completed an initial course of SRS for brain metastases during the study period, including receipt of single and/or multifraction SRS, prior whole-brain radiotherapy, and brain metastasis resection. Data analysis was performed on November 15, 2022. Non-OS end points included intracranial PFS, extracranial PFS, PFS, time to ICP, time to ECP, and any time to progression. Progression events were radiologically defined, incorporating multidisciplinary clinical consensus. The primary outcome was correlation of surrogate end points to OS. Clinical end points were estimated from time of SRS completion via the Kaplan-Meier method, while end-point correlation to OS was measured using normal scores rank correlation with the iterative multiple imputation approach. This study included 1383 patients, with a mean age of 63.1 years (range, 20.9-92.8 years) and a median follow-up of 8.72 months (IQR, 3.25-19.68 months). The majority of participants were White (1032 [75%]), and more than half (758 [55%]) were women. Common primary tumor sites included the lung (757 [55%]), breast (203 [15%]), and skin (melanoma; 100 [7%]). Intracranial progression was observed in 698 patients (50%), preceding 492 of 1000 observed deaths (49%). Extracranial progression was observed in 800 patients (58%), preceding 627 of 1000 observed deaths (63%). Irrespective of deaths, 482 patients (35%) experienced both ICP and ECP, 534 (39%) experienced ICP (216 [16%]) or ECP (318 [23%]), and 367 (27%) experienced neither. The median OS was 9.93 months (95% CI, 9.08-11.05 months). Intracranial PFS had the highest correlation with OS (ρ = 0.84 [95% CI, 0.82-0.85]; median, 4.39 months [95% CI, 4.02-4.92 months]). Time to ICP had the lowest correlation with OS (ρ = 0.42 [95% CI, 0.34-0.50]) and the longest median time to event (median, 8.76 months [95% CI, 7.70-9.48 months]). Across specific primary tumor types, correlations of intracranial PFS and extracranial PFS with OS were consistently high despite corresponding differences in median outcome durations. The results of this cohort study of patients with brain metastases completing SRS suggest that intracranial PFS, extracranial PFS, and PFS had the highest correlations with OS and time to ICP had the lowest correlation with OS. These data may inform future patient inclusion and end-point selection for clinical trials.

Hypofractionated stereotactic radiosurgery (HSRS) as a salvage treatment for brain metastases failing prior stereotactic radiosurgery (SRS)

Various treatment options exist to salvage stereotactic radiosurgery (SRS) failures for brain metastases, including repeat SRS and hypofractionated SRS (HSRS). Our objective was to report outcomes specific to salvage HSRS for brain metastases that failed prior HSRS/SRS. Patients treated with HSRS to salvage local failures (LF) following initial HSRS/SRS, between July 2010 and April 2020, were retrospectively reviewed. The primary outcomes were the rates of LF, radiation necrosis (RN), and symptomatic radiation necrosis (SRN). Univariable (UVA) and multivariable (MVA) analyses using competing risk regression were performed to identify predictive factors for each endpoint. 120 Metastases in 91 patients were identified. The median clinical follow up was 13.4 months (range 1.1-111.1), and the median interval between SRS courses was 13.1 months (range 3.0-56.5). 115 metastases were salvaged with 20-35Gy in 5 fractions and the remaining five with a total dose ranging from 20 to 24Gy in 3-fractions. 67 targets (56%) were postoperative cavities. The median re-treatment target volume and biological effective dose (BED10) was 9.5cc and 37.5Gy, respectively. The 6- and 12- month LF rates were 18.9% and 27.7%, for RN 13% and 15.6%, and for SRN were 6.1% and 7.0%, respectively. MVA identified larger re-irradiation volume (hazard ratio [HR] 1.02, p = 0.04) and shorter interval between radiosurgery courses (HR 0.93, p < 0.001) as predictors of LF. Treatment of an intact target was associated with a higher risk of RN (HR 2.29, p = 0.04). Salvage HSRS results in high local control rates and toxicity rates that compare favorably to thosesingle fraction SRS re-irradiationexperiences reported in the literature.

Upfront and Repeated Stereotactic Radiosurgery in Patients With Brain Metastases From NSCLC

IntroductionApproximately 40% of non-small-cell lung cancer (NSCLC) patients develop brain metastases (BM). Stereotactic radiosurgery (SRS) instead of whole-brain radiotherapy (WBRT) is increasingly administered as an upfront treatment to patients with a limited number of BM. We present outcomes and validation of prognostic scores for these patients treated with upfront SRS. MethodsWe retrospectively analyzed 199 patients with a total of 268 SRS courses for 539 brain metastases. Median patient age was 63 years. For larger BM, dose reduction to 18 Gy or hypofractionated SRS in 6 fractions was applied. We analyzed the BMV-, the RPA-, the GPA- and the lung-mol GPA score. Cox proportional hazards models with univariate and multivariate analyses were fitted for overall survival (OS) and intracranial progression-free survival (icPFS). ResultsSixty-four patients died, 7 of them of neurological causes. Thirty eight patients (19,3%) required a salvage WBRT. Median OS was 38, 8 months (IQR: 6-NA). In univariate analysis as well as multivariate analysis, the Karnofsky performance scale index (KPI) ≥90% (P = 0, 012 and P = 0, 041) remained as independent prognostic factor for longer OS. All 4 prognostic scoring indices could be validated for OS assessment (BMV P = 0, 007; RPA P = 0, 026; GPA P = 0, 003; lung-mol GPA P = 0, 05). ConclusionIn this large cohort of NSCLC patients with BM treated with upfront and repeated SRS, OS was markedly favourable, in comparison to literature. Upfront SRS is an effective treatment approach in those patients and can decidedly reduce the impact of BM on overall prognosis. Furthermore, the analysed scores are useful prognostic tools for OS prediction.

A Deep Learning-Based Computer Aided Detection (CAD) System for Difficult-to-Detect Brain Metastases

We sought to develop a computer-aided detection (CAD) system that optimally augments human performance, excelling especially at identifying small inconspicuous brain metastases (BMs), by training a convolutional neural network on a unique magnetic resonance imaging (MRI) data set containing subtle BMs that were not detected prospectively during routine clinical care. Patients receiving stereotactic radiosurgery (SRS) for BMs at our institution from 2016 to 2018 without prior brain-directed therapy or small cell histology were eligible. For patients who underwent 2 consecutive courses of SRS, treatment planning MRIs from their initial course were reviewed for radiographic evidence of an emerging metastasis at the same location as metastases treated in their second SRS course. If present, these previously unidentified lesions were contoured and categorized as retrospectively identified metastases (RIMs). RIMs were further subcategorized according to whether they did (+DC) or did not (-DC) meet diagnostic imaging-based criteria to definitively classify them as metastases based upon their appearance in the initial MRI alone. Prospectively identified metastases (PIMs) from these patients, and from patients who only underwent a single course of SRS, were also included. An open-source convolutional neural network architecture was adapted and trained to detect both RIMs and PIMs on thin-slice, contrast-enhanced, spoiled gradient echo MRIs. Patients were randomized into 5 groups: 4 for training/cross-validation and 1 for testing. One hundred thirty-five patients with 563 metastases, including 72 RIMS, met criteria. For the test group, CAD sensitivity was 94% for PIMs, 80% for +DC RIMs, and 79% for PIMs and +DC RIMs with diameter <3 mm, with a median of 2 false positives per patient and a Dice coefficient of 0.79. Our CAD model, trained on a novel data set and using a single common MR sequence, demonstrated high sensitivity and specificity overall, outperforming published CAD results for small metastases and RIMs - the lesion types most in need of human performance augmentation.

Early Imaging Characteristics Associated with Development of Future Brain Metastases in Patients Undergoing Stereotactic Radiosurgery

<h3>Purpose/Objective(s)</h3> Brain MRIs are carefully reviewed during the process of stereotactic radiosurgery (SRS) planning to select targets with radiographic characteristics typical of brain metastases (BM). Some BMs, especially ones that are small, dural-based, appear similar to blood vessels or resemble microinfarcts, are difficult to definitively identify and may go untreated initially, only to become apparent on future imaging. We hypothesized that in patients receiving multiple courses of SRS, retrospective review of the initial planning MRI would reveal early evidence of lesions that would subsequently develop into metastases requiring SRS. <h3>Materials/Methods</h3> Patients undergoing two or more courses of SRS to BMs within a 6-month interval between 2016 and 2018 were included in this single-institution, retrospective study. Exclusion criteria included small cell histology or previous whole-brain radiation therapy. Brain MRIs from the initial treatment course were reviewed for the presence of a contrast enhancing lesion at the same location as a lesion treated in a subsequent course of SRS, which was classified as a "retrospectively identified metastasis" or RIM. <h3>Results</h3> Of the 683 patients who underwent 923 courses of SRS within the study period, 98 patients met inclusion criteria. There were 120 repeat courses of SRS, with 345 treated metastases in the subsequent course, 128 of which were RIMs. 48% were within 5mm of the dura: 12% were abutting blood vessels: 8% became symptomatic. 23% of subsequent courses consisted of metastases that were all identified as RIMs. <h3>Conclusion</h3> Radiographic evidence of lesions requiring future treatment was occasionally present on brain MRIs from prior SRS treatments. RIMs are typically small, often abut blood vessels and/or the dura, and rarely become symptomatic. In some patients undergoing SRS, RIMs alone were treated, suggesting that enhanced detection of RIMs could reduce the need for additional courses of SRS.