BACKGROUND:The conventional method of assessing radiotherapy outcome in brain metastases (BM) is based on monitoring tumor size alterations on serial magnetic resonance imaging (MRI). To accurately determine changes in tumor dimensions, targets require delineations on several volumetric images acquired before treatment and at multiple follow-up scans after radiotherapy. However, manual tumor delineation on serial MRI is labor-intensive, imposes a significant burden on the clinical workflow, and is prone to variability especially for smaller lesions. PURPOSE:This study proposes a novel multi-step transformer-based automated framework with a 3D neighborhood attention mechanism, specifically designed to enhance the segmentation precision for BM of various sizes on standard longitudinal MRI. This framework leverages the hierarchical encoding capabilities of transformer architecture to capture intricate tumor characteristics, with a particular focus on improving the delineation of small metastases (<1 cm), which are often overlooked by existing models. METHODS:The proposed framework was trained on the BraTS and BraTS-METS datasets and evaluated on independent external data acquired from 212 patients (508 BM lesions) treated with stereotactic radiosurgery. The framework's performance was evaluated in segmenting tumors across various size categories, monitoring post-treatment changes in tumor size on serial MRI, and automatically detecting local control/failure (LC/LF) and adverse radiation effect (ARE) following radiosurgery. RESULTS:The framework achieved a dice score of 89.8 ± 3.4%, 92.0 ± 3.0%, and 93.1 ± 2.3% for tumors with a size of less than 1 cm, between 1 and 2 cm, and larger than 2 cm, respectively. It also demonstrated high performance in longitudinal monitoring of tumor size changes and in detecting LC/LF and ARE, achieving accuracies greater than 96% across different tumor size categories compared to the clinical outcome assessment. The results exhibited a substantial improvement over state-of-the-art segmentation models, particularly for smaller lesions. CONCLUSIONS:This study represents a step forward toward deploying AI-driven decision support tools to the neuro-oncology workflow, reducing the assessment burden on oncologists, and improving consistency in routine radiotherapy outcome assessments.

PURPOSE:Inclusion of the peritumoral FLAIR-hyperintense-region (FHR) within the clinical target volume (CTV) for glioblastoma (GBM) varies across guidelines. Using data from a prospective phase 2 trial employing small-margin MR-guided adaptive radiotherapy (RT), we evaluated whether inclusion of FHR influences the pattern-of-failure (POF) and clinical outcomes. METHODS:Patients with newly diagnosed GBM underwent chemoRT with weekly online-adaptive planning on an MR-Linac (NCT04726397). The gross tumor volume (GTV) included the resection cavity and residual enhancing tumor. The CTV was defined as GTV + 5 mm, with inclusion of FHR beyond 5 mm at the clinician's discretion. For this post hoc analysis, three contour categories were identified: no FHR beyond 5 mm (NF), FHR present but not included (FNI), and FHR included (FI). At radiographic progression, the recurrent GTV (rGTV) was delineated on co-registered MRIs to quantify overlap with the CTV and summed RT dose. rGTV coverage, dose/volume histogram metrics, progression-free survival (PFS), and overall survival (OS) were compared among groups. RESULTS:Among 98 patients, 24 were NF, 27 FNI, and 47 FI. Recurrences (n = 69) were predominantly central (65-72%) with no difference between groups (p = 0.717). Median rGTV coverage within the CTV was 97.9% and was comparable across strategies (p = 0.105), as was estimated rGTV dose. Median PFS and OS for the NF, FNI, and FI cohorts were 10.5, 8.0, and 8.6 months (p = 0.279) and 16.9, 15.8, and 13.4 months (p = 0.389), respectively. Multivariable analysis revealed no significant differences between contouring strategies on outcomes. CONCLUSION:Within a small-margin MR-guided adaptive RT paradigm, omission of FHR did not negatively influence the POF or survival outcomes.

Optimal management of patients with brain metastases relies on both accurate detection on initial imaging and accurate differentiation between treatment-related effects from progression on follow-up imaging. Contrast-enhanced MRI remains the standard technique for initial and follow-up imaging, though advanced MRI techniques, such as perfusion MRI, diffusion-weighted MRI, MR spectroscopy, and chemical exchange saturation transfer (CEST), have also emerged as complementary examinations, particularly in distinguishing TRE from true progression. Molecular imaging with PET, especially using amino acid tracers, also demonstrates high diagnostic accuracy in discriminating between treatment-related effects and tumour progression. Artificial intelligence models, including those using radiomics and deep learning approaches, have been developed to enhance diagnostic performance and to streamline workflow. However, their clinical utility is limited by significant inter-study heterogeneity, lack of standardization, and lack of large-scale external validation. This review summarizes the current literature on advanced imaging techniques in BM diagnosis and response assessment.

Purpose The Spinal Instability in Neoplasia Score (SINS) is the gold standard to determine if the metastatically involved spine is stable, potentially unstable, or frankly unstable. In potentially unstable spines, clarity is needed about the risk of post-stereotactic body radiation therapy (SBRT) vertebral compression fracture (VCF) and which patients may benefit from early stabilization. We aimed to identify predictors of VCF following spine SBRT in patients with potentially unstable SINS spinal metastases.. Methods and Materials A retrospective review of a prospectively maintained database of patients treated with SBRT for spinal metastases from January 2008 to December 2022 was performed. This analysis included only spine segments categorized as potentially unstable (SINS 7-12). The primary outcome was the rate of VCF. The cumulative incidence of VCF and the impact of covariates were estimated. Results Five hundred twenty-four patients with 976 treated spinal segments were SINS potentially unstable. Out of 976, 168 patients (17.2%) experienced a VCF after SBRT. Out of 168, 107 patients (63.7%) were iatrogenic and 61 (36.3%) concurrent with tumor progression. The 12-month incidence of iatrogenic VCF was 9.3% (95% CI, 7.4%-11.5%) as opposed to 23.4% (95% CI, 17.4%-29.9%) when concurrent with tumor progression (P < .0001). Multivariable analysis confirmed iatrogenic VCF associated with pre-existing VCF (hazard ratios [HR] = 1.83; 95% CI, 1.235-2.714; P = .003), no previous spine surgery (HR = 1.67; 95% CI, 1.024-2.710; P = .040), SINS total ≥10 (HR = 1.68; 95% CI, 1.122-2.512; P = . 012), and an increasing D90 clinical target volume in equivalent dose in 2 Gy (HR = 1.03; 95% CI, 1.010-1.055; P = .004). In the setting of concurrent tumor progression, only an increasing D90 to the clinical target volume in equivalent dose in 2 Gy fractions (HR = 1.04; 95% CI, 1.013-1.076; P = .005) predicted for VCF. Conclusions Tumor control outweighs the risk of VCF associated with spine SBRT in potentially unstable metastases. Prophylactic stabilization could be considered in segments with a total SINS ranging from 10 to 12, a pre-existing VCF, and when treating with high doses.

PURPOSE:We previously demonstrated that adherence to sacral stereotactic body radiation therapy (SBRT) clinical target volume (CTV) contouring guidelines is independently associated with reduced risk of local failure (LF). We hypothesized that this benefit results from coverage of involved and adjacent boney sectors at risk of subclinical disease and performed a pattern-of-failure analysis to evaluate the impact of including or excluding these guideline-recommended sectors in the CTV. METHODS AND MATERIALS:Of 209 sacral segments treated with SBRT between 2010 and 2021, 48 developed magnetic resonance imaging-based LF and were analyzed. Failures were mapped by boney sectors and classified as contoured per guidelines (adherent) or recommended but not included in the treated CTV (nonadherent). Dose-volume histogram metrics in nonadherent sectors with subsequent LF were compared with the treated CTV for that segment. RESULTS:Most metastases developing LF involved S1 (42%, 20/48) and S2 (31%, 15/48), were radioresistant (54%, 26/48), and had baseline extraosseous extension (71%, 34/48). Sixty-nine percent (33/48) of segments with LF were adherent, whereas 31% (15/48) were nonadherent. Among all 209 segments, those treated with a nonadherent CTV had higher rates of failure in the involved (37.1% vs 17.8%; P = .021) and guideline-recommended adjacent sectors (22.9% vs 2.3%; P < .001) than adherent CTV segments. Among adherent segments, most failures occurred exclusively within boney sectors included in the CTV (91%, 30/33). In contrast, 73% (11/15) of failures among nonadherent segments occurred in boney sectors that were recommended but incompletely contoured or omitted from the CTV. The mean equivalent dose in 2-Gy fractions (α/β = 10) was significantly lower at 38.7 Gy (IQR, 30.6-42.2) within those nonadherent sectors with tumor progression as compared with the dose in the corresponding treated CTV at 48.2 Gy (IQR, 46.6-49.4; P < .001). CONCLUSIONS:Anatomic and dosimetric sector-based pattern-of-failure analyses specific to sacral SBRT support CTV practice guidelines.

Purpose To assess the dosimetric impact on organs-at-risk (OARs) and target coverage of a small-margin weekly adaptive treatment for glioblastoma delivered on an MR-Linac. Methods and Materials The UNIty-Based MR-Linac Guided AdapTive Radiation thErapy for High GraDe Glioma (UNITED) phase 2 prospective trial used a 5 mm clinical target volume (CTV) margin compared to conventional 1.5 to 3 cm CTV margins. Margin reduction was supported by weekly administration of gadolinium contrast and adaptation to gross tumor volume changes using onboard MR imaging. In the present study, dosimetric data from 29 patients with UNITED plans (PUNITED) treated with 60 Gy in 30 fractions were retrospectively replanned with conventional margins (PConv) and compared. For each patient, 6 weekly adapted and 1 conventional margin nonadapted plan were included in the analysis. Relevant OAR dose metrics were compared using Friedman tests followed by Nemenyi post hoc analysis (α = 0.005, corrected for multiple comparisons). Results A substantial and statistically significant reduction in irradiated normal brain volume was achieved with the median V60Gy lowered from 146.3-157.3 cm3 (range of median weekly values) with PConvto 84.2-93.4 cm3 for PUNITED (P < .0001). The median max dose to the brainstem and optic chiasm was reduced from 56.1 Gy to 49.0 Gy (P = .0001) and from 41.5 Gy to 38.4 Gy (P < .0001), respectively. In addition to OAR sparing, 10 of 29 patients experienced suboptimal target coverage when conventional margin dose distributions were applied to weekly adapted contours, with 5 patients showing consistent underdosing and CTV D98% below 50 Gy, highlighting the importance of adaptation for maintaining target coverage. Conclusions The UNITED small-margin weekly adaptive treatment protocol for glioblastoma improves OAR sparing and reduces the irradiated normal brain volume while maintaining consistent target coverage.

Spinal metastases can cause disabling pain and neurological deterioration and have historically been treated with palliative intent and conventional external beam radiotherapy (cEBRT). A fundamental shift away from the short-term palliative goals associated with cEBRT has taken place over the past two decades following the availability of stereotactic body radiotherapy (SBRT). This technique has enabled durable pain relief and local control owing to the ability to precisely deliver high radiation doses across typically up to five fractions, with level 1 evidence supporting superior complete pain response rates and local tumour control compared with cEBRT. The development of spinal SBRT has also resulted in greater multidisciplinary collaboration, with neuroradiologists, spinal surgeons, interventional radiologists, biomechanical engineers, medical physicists, medical oncologists and radiation oncologists working together with the common goal of improving our understanding of the pathophysiology and treatment of spinal metastases. As a result, substantial gains have been realized in refining patient selection and treatment sequencing, and particularly the development of less-invasive surgical procedures. In this Review, we summarize the development and role of SBRT in the management of spinal metastases.

Abstract Gliomas are among the most common primary CNS tumors in adolescents and young adults (AYAs; ages 15–39 years), and several subtypes are associated with prolonged survival. As a result, fertility preservation and pregnancy management have become increasingly important components of survivorship care; however, current evidence remains scarce. Despite family planning needs, many patients receive limited counselling, and both referral to and access to reproductive specialists remains inconsistent. Glioma‑directed therapies may impair fertility through gonadotoxic chemotherapy, hypothalamic–pituitary dysfunction, or prolonged exposure to targeted agents with poorly defined reproductive effects. Pregnancy after glioma diagnosis introduces additional complexities, including concerns regarding tumor progression, optimal timing of conception, antiseizure medication selection, and obstetric and neonatal risks. Evidence describing the interaction between pregnancy and glioma biology is limited to small retrospective series with heterogeneous imaging practices and minimal molecular characterization. Available data suggest that tumor behavior during pregnancy largely reflects underlying histology, grade, and prior treatment, with progression more frequently reported in higher‑grade disease and transient increases in growth kinetics described in some IDH‑mutant diffuse gliomas. Overall survival does not appear adversely affected by pregnancy. This review synthesizes current guidelines and evidence across fertility preservation, preconception planning, and cancer management during pregnancy, emphasizing multidisciplinary care and highlighting key evidence gaps—particularly regarding targeted therapies, optimal surveillance, and molecularly informed risk stratification—to guide future research and clinical practice.

BACKGROUND:Contrast-enhanced 3D T1-weighted MRI is the imaging reference for detection and follow-up of brain metastases. Volumetric GRE-based sequences, such as MPRAGE, are widely used but remain prone to susceptibility and lower lesion conspicuity. 3D black-blood TSE-based sequences, such as Sampling Perfection with Application-Optimized Contrasts by using different flip angle Evolutions (SPACE), have been increasingly embedded into routine workflow and are thought to improve lesion detection in part through vessel signal suppression. PURPOSE:We aimed to investigate the comparative diagnostic performance of 3D T1 TSE versus GRE sequences for the detection of brain metastases. DATA SOURCES:Studies comparing the diagnostic performance of postcontrast 3D T1 SE and GRE sequences in adults with brain metastases were searched on MEDLINE, EMBASE, Cochrane Central, Google Scholar, and PROSPERO, from inception through April 2025. STUDY SELECTION:Fifteen studies encompassing 544 patients with 4338 metastases were included. DATA ANALYSIS:Data on diagnostic accuracy parameters, image quality, and inter-rater agreement were extracted. Random-effects models were applied to compute pooled sensitivity and comparative OR for lesion detection. Risk of bias was assessed using QUADAS-2 and QUADAS-C tools. DATA SYNTHESIS:Pooled sensitivities for detection of brain metastases were 97.4% (95%CI, 93.2%-99.0%) for TSE and 76.1% (95%CI, 69.3-81.9) for GRE-based sequences, with a comparative OR of 12.0 (95%CI, 5.45-26.6, P <.0001). Detectability of small lesions (<5 mm) was significantly better on TSE (96.1%; 95%CI, 87.7-98.8) than GRE (58.4%; 95%CI, 47.9-68.2), while both techniques performed comparably for larger (≥5 mm) lesions (98.2% for TSE, 94.4% for GRE). OR estimates were 17.2 (95%CI, 4.50-66.1) for small and 2.81 (95%CI, 0.92-8.56) for large lesions. Contrast-to-noise-ratio and inter-rater agreements were slightly higher on TSE than GRE. False positives were more common with TSE, mostly related to incomplete vessel suppression (49 FP counts in TSE, 35 in GRE). LIMITATIONS:Our meta-analysis is limited by high heterogeneity, case-only studies, possible small-study effects, and high risk of bias for the reference standard domain. CONCLUSIONS:Postcontrast 3D T1 TSE sequences provide higher sensitivity and improved lesion conspicuity compared with GRE sequence, particularly for small metastases, though at the cost of slightly higher false positives.

Importance:Stereotactic body radiotherapy (SBRT) and high-dose-rate brachytherapy monotherapy (HDR-BT) are options for intermediate-risk prostate cancer. However, no prospective evidence is available to compare these modalities. Objective:To compare the biochemical failure (BCF), late patient-reported quality of life (PR-QoL), and acute and late adverse events (AEs) associated with SBRT and HDR-BT using prospective data. Data Sources:This was an individual patient data post hoc pooled analysis of 5 prospective trials with recruitment from 2010 to 2018. Statistical analyses were performed in September 2024. Study Selection:This was a post hoc analysis of these 5 sprospective trials. Eligibility criteria comprised men with intermediate-risk prostate cancer undergoing 5- or 2-fraction SBRT or 2-fraction HDR-BT. No androgen deprivation therapy was permitted. Data Extraction and Synthesis:Baseline patient and clinicopathological characteristics were requested. Main Outcomes and Measures:BCF, a minimal clinically important change on the PR-QoL, and clinician-reported AEs were the main outcomes. Results:After a median (IQR) follow-up of 9.5 (5.5-10.6) years, 247 men met the eligibility criteria, including 180 men undergoing SBRT (72.8%; mean [SD] age, 69.5 [6.7] years) and 67 men undergoing HDR-BT (27.1%; mean [SD] age, 66.0 [6.5] years). HDR-BT was associated with increased BCF. At 5 years, BCF was 7.8% (95% CI, 1.0%-14.6%) for HDR compared with 3.0% (95% CI, 0.4%-5.6%) for SBRT. At 10 years, BCF was 38.0% (95% CI, 19.8%-56.1%) for HDR compared with 10.4% (95% CI, 4.3%-16.6%) for SBRT (P < .001). The HDR-BT cohort had a significantly higher incidence of acute grade 2 or greater genitourinary AEs compared with SBRT (50 men [74.6%] vs 31 men [51.7%]; P = .007). There were no significant differences in any other acute or late AEs or late PR-QoL. Conclusions and Relevance:This post hoc pooled analysis reports a long-term comparison of SBRT and HDR-BT using prospective data. SBRT had significantly lower BCF and acute genitourinary AEs, and there was no significant difference in late PR-QoL.

Despite advances in metastatic breast cancer (MBC) management, leptomeningeal disease (LMD) prognosis remains poor. This study evaluates clinicopathological and treatment factors influencing outcomes of MBC patients with LMD treated with radiotherapy (RT). We conducted a retrospective analysis of patients with MBC treated with RT for brain metastases (BrM) between 2005 and 2019. LMD diagnosis was made via magnetic resonance imaging (MRI). Multivariable analysis (MVA) identified variables associated with brain-specific progression-free survival (bsPFS) and overall survival (OS). Among 691 MBC patients treated with RT for BrM, 161 (23%) had LMD, either at initial presentation (50/161) or after BrM treatment. Patients with LMD were younger, more likely to have ER + disease, more likely to have undergone surgery for BrM, and less likely to have received prior whole-brain RT. HER2+ LMD was associated with longer bsPFS (HR 0.47, 95% CI: 0.25-0.86, p = 0.01) and OS (HR 0.38, 95% CI: 0.2-0.75, p = 0.002). Median OS for triple-negative breast cancer was 3.7 months, 5.1 months for HR+/HER2 - and 15.4 months for HER2 + MBC. HER2-targeted therapy, either at or after LMD diagnosis, improved long-term survival (> 2 years) (Fisher's test, p < 0.05). Low Karnofsky Performance Status (KPS < 60) was linked to shorter bsPFS (HR 2.91, 95% CI: 1.49-5.69, p < 0.01) and OS (HR 3.37, 95% CI: 1.78-6.41, p < 0.001). These findings highlight the need for effective CNS-penetrating systemic therapies for HER2-negative breast cancer.

Purpose Apparent diffusion coefficient (ADC) from diffusion-weighted imaging has been shown to detect early treatment response in glioblastoma. This prospective observational serial imaging study aimed to compare ADC changes in gross tumor volume (GTV) regions that developed recurrence versus those that remained recurrence-free. Methods and Materials Patients with glioblastoma underwent diffusion-weighted imaging at radiation planning (baseline, fraction 0), fraction 10, fraction 20, and 1 month after completing a 6-week course of chemoradiation. Recurrence was contoured at the earliest magnetic resonance imaging showing progression. The intersection of the GTV and recurrence was labeled resistant-GTV, whereas nonintersecting GTV was labeled sensitive-GTV. ADC values and percentage changes from fraction 0 were compared between these regions. Results Eighty patients were analyzed. Median absolute ADC values for resistant (0.94 μm2/ms; IQR, 0.84-1.08) and sensitive-GTV (0.93 μm2/ms; IQR, 0.87-1.13) were similar at baseline (P = .193), but statistically significant differences were observed from the start of radiation therapy. Median ADC changes from baseline for resistant- and sensitive-GTV were +2.5% versus +15.1% at fraction 10 (P < .001), +8.1% versus +23.1% at fraction 20 (P < .001), and +21.2% versus +36.4% at 1 month after completing a 6-week course of chemoradiation (P <.001), respectively. Smaller ADC changes at fraction 10 (odds ratio, 0.95; P = .005) and fraction 20 (odds ratio, 0.95; P = .010) were independent predictors of increased risk of GTV failure, adjusting for O6-methylguanine DNA methyltransferase promoter methylation and extent of surgical resection. Conclusions Temporal ADC changes are promising imaging biomarkers for treatment response and spatial recurrence prediction and may provide a target for magnetic resonance imaging-guided biologically adapted radiation clinical trials.

Spine stereotactic body radiation therapy (SBRT) is increasingly utilized for oligometastatic and symptomatic breast cancer spinal metastases (BCSM), yet primary site-specific outcomes remain lacking. This study evaluates outcomes of SBRT for BCSM, focusing on predictors of local failure (LF), vertebral compression fraction (VCF) and overall survival (OS). We retrospectively analyzed 409 BCSM in 168 patients treated with SBRT between 2008 and 2022. Receptor status was grouped based on ER+/Her2-, HER2+, and ER-/HER2-. Follow-up included full-spine magnetic resonance imaging (MRI) and clinical assessment every 3–6 months post-SBRT. The primary endpoint was radiological LF, and secondary endpoints were OS and VCF. Median follow-up was 33 months (range, 3.3–123 months), most were ECOG 0–1 (95

To assess the safety of weekly on-line MR-Linac (MRL) adaptive RT with concurrent temozolomide (chemoRT), with a reduced 5 mm clinical target volume (CTV) margin, for patients with GBM. Methods: Patients with newly diagnosed GBM planned for chemoRT with either 60 Gy/30 # (long course) or 40 Gy/15 # (short course) were eligible. A reduced 5 mm CTV was applied to the gross tumor/surgical cavity. All patients were treated using a 1.5T integrated MRL with contrast-enhanced imaging every 5th fraction and daily plan adaptation. The primary endpoint was the risk of a marginal failure (MF) at the time of recurrence powered for non-inferiority compared historical rates of MF of 11%. Secondary endpoints included progression-free survival (PFS) and overall survival (OS) according to treatment schedule (long versus short course). Results: Adaptive RT was delivered to 98 patients (59 long course and 39 short course). All tumors were IDH-wt and 53% were MGMT methylated. MF events were observed in 4/98 (4%) patients, establishing non-inferiority (p<0.001); the most common pattern of failure was central (52%). Median PFS / OS was 11.6 / 18.5 mo (long course), and 6.8 / 10.6 mo (short course). Conclusion: This is the first trial evaluating on-line MRL adaptive chemoRT for GBM with a limited CTV. Safety and feasibility was demonstrated with a low risk of MF (4%) without compromising PFS or OS. Further trials are required to test whether the reduction in radiated normal brain tissue using this approach results in neurocognitive and quality of life benefits.

Background/Objectives: Radiotherapy for tumors of the central nervous system (CNS) could be improved by incorporating advanced imaging techniques into treatment planning and response assessment. The objective of this narrative review is to highlight the recent developments in magnetic resonance imaging (MRI) and positron emission tomography (PET) for applications in CNS radiotherapy. Methods: Recent articles were selected for discussion, covering the following topics: advanced imaging on MRI-linear accelerators for early response assessment in glioma; PET for guiding treatment planning and response assessment in glioma; and contrast-enhanced imaging and metabolic imaging for differentiating tumor progression and radiation necrosis for brain metastasis treatment. Where necessary, searches of scholarly databases (e.g., Google Scholar, PubMed) were used to find papers for each topic. The topics were chosen based on the perception of promise in advancing specific applications of CNS radiotherapy and not covered in detail elsewhere. This review is not intended to be comprehensive. Results: Advanced MRI sequences and PET could have a substantial impact on CNS radiotherapy. For gliomas, the tumor response to therapy could be assessed much earlier than using the conventional technique of measuring changes in tumor size. Using advanced imaging on combined imaging/therapy devices like MR-Linacs would enable response monitoring throughout radiotherapy. For brain metastases, radiation necrosis and tumor progression might be reliably differentiated with imaging techniques sensitive to perfusion or metabolism. However, the lack of level 1 evidence supporting specific uses for each imaging technique is an impediment to widespread use. Conclusions: Advanced MRI and PET have great promise to change the standard of care for CNS radiotherapy, but clinical trials validating specific applications are needed.

The relationship between spine SBRT outcomes and the extent of epidural cauda equina compression (ECEC) by malignant epidural disease has yet to be reported. Our objective was to determine clinical, anatomic and dosimetric factors that predict for local failure (LF) and overall survival (OS) specific to ECEC. Consecutive patients with ECEC treated with spine SBRT were retrospectively reviewed. ECEC parameters including anatomic measurements, lumbar stenosis grading, anatomic disease position and various dosimetric factors, were analyzed for their prognostic utility. Covariates with a p-value ≤ 0.20 on univariate analysis were selected for multivariable analysis (MVA), and those statistically significant (p < 0.05) were included in the final model. Ninety-four spinal segments (79 patients) with ECEC were identified, 69 (73

OBJECTIVE:Paraspinal involvement has been consistently reported as a negative predictor of local control following stereotactic body radiation therapy (SBRT) for spinal metastases. The aim of this study was to investigate the characteristics of paraspinal disease and determine the impact on outcomes. METHODS:Patients who underwent SBRT for spinal metastases with paraspinal involvement, identified from a single-institutional prospective database, were retrospectively reviewed. Those with prior radiation therapy/surgery were excluded. The treated clinical target volume (CTV) was segmented into paraspinal (CTV_PS), neuroforaminal (CTV_NF), epidural (CTV_EP), and osseous bone (CTV_bone) components. The extent of extraosseous disease was classified according to the involvement of rib, neuroforamina, and muscle. Volume and dosimetric parameters were collected and dichotomized using recursive binary partitioning. The outcomes of interest were the cumulative incidence of local failure (LF), overall survival (OS), and reirradiation rates. RESULTS:One hundred fourteen patients with 125 treated spinal sites were identified. There were 38% (47/125), 66% (82/125), and 19% (24/125) treated spinal sites with involvement of rib, neuroforamina, and muscle, respectively. The median follow-up duration of the cohort was 17.34 months (IQR 7.79-40.11 months). The 12-month and 24-month cumulative incidence rates of LF were 19.5% (95% CI 12.6%-27.4%) and 29.8% (95% CI 21.4%-38.7%), respectively. The 12-month cumulative incidence rates of LF were 12.0% (95% CI 5.9%-20.5%) and 36.3% (95% CI 20.2%-52.6%) for patients with CTV_PS < 42.9 mL and those with ≥ 42.9 mL (p < 0.001), respectively, and 55.6% (95% CI 28.7%-75.8%) and 12.2% (95% CI 6.5%-19.9%) for patients with and without muscle invasion (p = 0.001), respectively. In the multivariable analysis, only CTV_PS remained statistically associated with LF. CTV_PS ≥ 42.9 mL was associated with 2.3 times (95% CI 1.13-4.83, p = 0.02) increased risk of LF compared with CTV_PS < 42.9 mL. The 12-month and 24-month OS rates were 56% (95% CI 47%-65%) and 41% (95% CI 32%-50%), respectively. Patients with an Eastern Cooperative Oncology Group performance status score < 1 and oligometastatic disease (≤ 5 metastases) were associated with better OS in the multivariable analysis. The 12-month and 24-month reirradiation rates were 7.3% (95% CI 3.4%-13.3%) and 16.5% (95% CI 10.2%-24.1%), respectively. CONCLUSIONS:Spinal metastases with high-volume paraspinal involvement were associated with increased risk of LF following SBRT, and strategies to optimize local control are required.

Background and Purpose:Targeting tumour vasculature during radiotherapy is a direction of current investigation for radiotherapy strategies in glioblastoma. Arterial spin labelling (ASL), a perfusion imaging technique that uses arterial water as an endogenous tracer, on magnetic resonance imaging (MRI)-guided linear accelerators (MRI-linacs) could guide adaptation to changes in perfusion. However, since ASL is unavailable as a stock sequence on MRI-linac systems, our objective was to implement the first MRI-linac ASL sequence, characterize its performance, and measure tumour perfusion dynamics. Materials and Methods:Forty-seven glioblastoma patients were imaged using 3D pseudo-continuous ASL on a 1.5 T MRI-linac during treatment. ASL labeling efficiency was measured in two healthy volunteers and three patients on the MRI-linac and a 1.5 T MR-simulation scanner. ASL cerebral blood flow (CBF) values and repeatability were characterized. Regions of high tumour CBF were evaluated for overlap with the gross tumour volume (GTV) and temporal dynamics. Results:The labelling efficiency was lower for the MRI-linac compared to the MR-sim and literature consensus values (0.59 vs. 0.88 vs. 0.85). Corrected grey matter CBF was comparable between the MRI-linac and literature (38 ± 13 ml/100 g/min vs. 36.5 ± 8.2 ml/100 g/min, p = 0.41). The within-subject coefficient of variation was similar to literature values (16 % vs. 11 ± 5 %). Across patients, approximately half of the high-CBF region did not overlap the GTV (median 47 %). The high-CBF region tended to decrease in volume during radiotherapy, from - 24 % at week 3 (p = 0.016) to - 45 % (p = 0.044) by week 5 relative to week 1. Conclusion:MRI-linac ASL could allow targeting and adaptation for highly perfused tumour in future trials for glioblastoma.