Epigenetic MLH1 silencing concurs with mismatch repair deficiency in sporadic, naturally occurring colorectal cancer in rhesus macaques.

BACKGROUND: Naturally occurring colorectal cancers (CRC) in rhesus macaques share many features with their human counterparts and are useful models for cancer immunotherapy; but mechanistic data are lacking regarding the comparative molecular pathogenesis of these cancers. METHODS: We conducted state-of-the-art imaging including CT and PET, clinical assessments, and pathological review of 24 rhesus macaques with naturally occurring CRC. Additionally, we molecularly characterized these tumors utilizing immunohistochemistry (IHC), microsatellite instability assays, DNAseq, transcriptomics, and developed a DNA methylation-specific qPCR assay for MLH1, CACNA1G, CDKN2A, CRABP1, and NEUROG1, human markers for CpG island methylator phenotype (CIMP). We furthermore employed Monte-Carlo simulations to in-silico model alterations in DNA topology in transcription-factor binding site-rich promoter regions upon experimentally demonstrated DNA methylation. RESULTS: Similar cancer histology, progression patterns, and co-morbidities could be observed in rhesus as reported for human CRC patients. IHC identified loss of MLH1 and PMS2 in all cases, with functional microsatellite instability. DNA sequencing revealed the close genetic relatedness to human CRCs, including a similar mutational signature, chromosomal instability, and functionally-relevant mutations affecting KRAS (G12D), TP53 (R175H, R273*), APC, AMER1, ALK, and ARID1A. Interestingly, MLH1 mutations were rarely identified on a somatic or germline level. Transcriptomics not only corroborated the similarities of rhesus and human CRCs, but also demonstrated the significant downregulation of MLH1 but not MSH2, MSH6, or PMS2 in rhesus CRCs. Methylation-specific qPCR suggested CIMP-positivity in 9/16 rhesus CRCs, but all 16/16 exhibited significant MLH1 promoter hypermethylation. DNA hypermethylation was modelled to affect DNA topology, particularly propeller twist and roll profiles. Modelling the DNA topology of a transcription factor binding motif (TFAP2A) in the MLH1 promoter that overlapped with a methylation-specific probe, we observed significant differences in DNA topology upon experimentally shown DNA methylation. This suggests a role of transcription factor binding interference in epigenetic silencing of MLH1 in rhesus CRCs. CONCLUSIONS: These data indicate that epigenetic silencing suppresses MLH1 transcription, induces the loss of MLH1 protein, abrogates mismatch repair, and drives genomic instability in naturally occurring CRC in rhesus macaques. We consider this spontaneous, uninduced CRC in immunocompetent, treatment-naïve rhesus macaques to be a uniquely informative model for human CRC.

Brain metastases from renal cell carcinoma: Effects of novel systemic agents on brain metastasis outcomes.

OBJECTIVE: The objective of this study was to examine survival outcomes in 136 patients with renal cell carcinoma with metastases to the brain who were treated with radiation combined with immunotherapy or tyrosine kinase inhibitor compared to those who were treated with radiation therapy alone. METHODS: The Wake Forest Gamma Knife prospective database was searched for all patients with renal cell carcinoma brain metastases. Outcome measurements included overall survival, determined via the Kaplan-Meier Method, and cumulative incidence of local and distant failure, determined using the Fine Gray competing risks analysis with death as a competing risk for the 136 patients included. RESULTS: Overall survival for the entire population at 6 months, 12 months, and 24 months was 67%, 47% and 30%, respectively. For the TKI (non-immunotherapy-treated) population (n = 37), overall survival was 75%, 61%, and 40% at 6 months, 12 months, and 24 months, respectively. For the immunotherapy-treated population (n = 35), overall survival was 85%, 64%, and 50% at 6 months, 12 months, and 24 months, respectively. Overall survival was significantly increased for patients who received radiation with either immunotherapy or TKI (p < 0.0001). CONCLUSION: Prior series of patients with brain metastases of multiple histologies have demonstrated an improvement in the local efficacy of stereotactic radiosurgery when combined with systemic agents. We found that patients treated with targeted agents and patients treated with immunotherapy demonstrated a trend towards improvement over patients treated in the era prior to the advent of either classes of novel therapies.

Total-Body Irradiation Alters White Matter Volume and Microstructural Integrity in Rhesus Macaques.

PURPOSE: Long-term survivors of brain irradiation can experience irreversible injury and cognitive impairment. T1-weighted and diffusion tensor magnetic resonance imaging (MRI) are used to evaluate brain volume and white matter (WM) microstructure in neurodevelopmental and neurodegenerative conditions. The goal of this study was to evaluate the long-term effects of single-dose total-body irradiation (TBI) or TBI with 5% partial-body sparing on brain volumetrics and WM integrity in macaques. METHODS AND MATERIALS: We used MRI scans from a cohort of male rhesus macaques (age range, 3.6-22.8 years) to compare global and regional brain volumes and WM diffusion in survivors of TBI (T1-weighted, n = 137; diffusion tensor imaging, n = 121; dose range, 3.5-10 Gy) with unirradiated controls (T1-weighted, n = 48; diffusion tensor imaging, n = 38). RESULTS: In all regions of interest, radiation affected age-related changes in fractional anisotropy, which tended to increase across age in both groups but to a lesser extent in the irradiated group (interaction P < .01). Depending on the region of interest, mean diffusivity decreased or remained the same across age in unirradiated animals, whereas it increased or did not change in irradiated animals. The increases in mean diffusivity were driven by changes in radial diffusivity, which followed similar trends across age. Axial diffusivity did not differ by irradiation status. Age-related changes in relative volumes in controls reflected normal trends in humans, with increasing WM and decreasing gray matter until middle age. Cerebrospinal fluid (CSF) volume did not differ across age in controls. WM volume was lower and CSF volume was higher in young irradiated macaques. WM volume was similar between groups, and CSF volume lower in older irradiated macaques. Gray matter volume was unaffected by radiation. CONCLUSIONS: TBI results in delayed WM expansion and long-term disruption of WM integrity. Diffusion changes suggest that myelin injury in WM is a hallmark of late-delayed radiation-induced brain injury.

Assessing cerebrovascular reactivity (CVR) in rhesus macaques (Macaca mulatta) using a hypercapnic challenge and pseudo-continuous arterial spin labeling (pCASL).

Cerebrovascular reactivity (CVR) is a measure of cerebral small vessels' ability to respond to changes in metabolic demand and can be quantified using magnetic resonance imaging (MRI) coupled with a vasoactive stimulus. Reduced CVR occurs with neurodegeneration and is associated with cognitive decline. While commonly measured in humans, few studies have evaluated CVR in animal models. Herein, we describe methods to induce hypercapnia in rhesus macaques (Macaca mulatta) under gas anesthesia to measure cerebral blood flow (CBF) and CVR using pseudo-continuous arterial spin labeling (pCASL). Fifteen (13 M, 2 F) adult rhesus macaques underwent pCASL imaging that included a baseline segment (100% O2) followed by a hypercapnic challenge (isoflurane anesthesia with 5% CO2, 95% O2 mixed gas). Relative hypercapnia was defined as an end-tidal CO2 (ETCO2) ≥5 mmHg above baseline ETCO2. The mean ETCO2 during the baseline segment of the pCASL sequence was 34 mmHg (range: 23-48 mmHg). During this segment, mean whole-brain CBF was 51.48 ml/100g/min (range: 21.47-77.23 ml/100g/min). Significant increases (p<0.0001) in ETCO2 were seen upon inspiration of the mixed gas (5% CO2, 95% O2). The mean increase in ETCO2 was 8.5 mmHg and corresponded with a mean increase in CBF of 37.1% (p<0.0001). The mean CVR measured was 4.3%/mmHg. No anesthetic complications occurred as a result of the CO2 challenge. Our methods were effective at inducing a state of relative hypercapnia that corresponds with a detectable increase in whole brain CBF using pCASL MRI. Using these methods, a CO2 challenge can be performed in conjunction with pCASL imaging to evaluate CBF and CVR in rhesus macaques. The measured CVR in rhesus macaques is comparable to human CVR highlighting the translational utility of rhesus macaques in neuroscience research. These methods present a feasible means to measure CVR in comparative models of neurodegeneration and cerebrovascular dysfunction.

Delayed Imaging Changes 18 Months or Longer After Stereotactic Radiosurgery for Brain Metastases: Necrosis or Progression.

OBJECTIVE: Imaging changes after stereotactic radiosurgery (SRS) can occur for years after treatment, although the available data on the incidence of tumor progression and adverse radiation effects (ARE) are generally limited to the first 2 years after treatment. METHODS: A single-institution retrospective review was conducted of patients who had >18 months of imaging follow-up available. Patients who had ≥1 metastatic brain lesions treated with Gamma Knife SRS were assessed for the time to radiographic progression. Those with progression ≥18 months after the initial treatment were included in the present study. The lesions that progressed were characterized as either ARE or tumor progression based on the tissue diagnosis or imaging characteristics over time. RESULTS: The cumulative incidence of delayed imaging radiographic progression was 35% at 5 years after the initial SRS. The cumulative incidence curves of the time to radiographic progression for lesions determined to be ARE and lesions determined to be tumor progression were not significantly different statistically. The cumulative incidence of delayed ARE and delayed tumor progression was 17% and 16% at 5 years, respectively. Multivariate analysis indicated that the number of metastatic brain lesions present at the initial SRS was the only factor associated with late radiographic progression. CONCLUSIONS: The timing of late radiographic progression does not differ between ARE and tumor progression. The number of metastatic brain lesions at the initial SRS is a risk factor for late radiographic progression.

Use of comprehensive genomic profiling for biomarker discovery for the management of non-small cell lung cancer brain metastases.

Background: Clinical biomarkers for brain metastases remain elusive. Increased availability of genomic profiling has brought discovery of these biomarkers to the forefront of research interests. Method: In this single institution retrospective series, 130 patients presenting with brain metastasis secondary to Non-Small Cell Lung Cancer (NSCLC) underwent comprehensive genomic profiling conducted using next generation circulating tumor deoxyribonucleic acid (DNA) (Guardant Health, Redwood City, CA). A total of 77 genetic mutation identified and correlated with nine clinical outcomes using appropriate statistical tests (general linear models, Mantel-Haenzel Chi Square test, and Cox proportional hazard regression models). For each outcome, a genetic signature composite score was created by summing the total genes wherein genes predictive of a clinically unfavorable outcome assigned a positive score, and genes with favorable clinical outcome assigned negative score. Results: Seventy-two genes appeared in at least one gene signature including: 14 genes had only unfavorable associations, 36 genes had only favorable associations, and 22 genes had mixed effects. Statistically significant associated signatures were found for the clinical endpoints of brain metastasis velocity, time to distant brain failure, lowest radiosurgery dose, extent of extracranial metastatic disease, concurrent diagnosis of brain metastasis and NSCLC, number of brain metastases at diagnosis as well as distant brain failure. Some genes were solely associated with multiple favorable or unfavorable outcomes. Conclusion: Genetic signatures were derived that showed strong associations with different clinical outcomes in NSCLC brain metastases patients. While these data remain to be validated, they may have prognostic and/or therapeutic impact in the future. Statement of translation relevance: Using Liquid biopsy in NSCLC brain metastases patients, the genetic signatures identified in this series are associated with multiple clinical outcomes particularly these ones that lead to early or more numerous metastases. These findings can be reverse-translated in laboratory studies to determine if they are part of the genetic pathway leading to brain metastasis formation.

Translating radiology reports into plain language using ChatGPT and GPT-4 with prompt learning: results, limitations, and potential.

The large language model called ChatGPT has drawn extensively attention because of its human-like expression and reasoning abilities. In this study, we investigate the feasibility of using ChatGPT in experiments on translating radiology reports into plain language for patients and healthcare providers so that they are educated for improved healthcare. Radiology reports from 62 low-dose chest computed tomography lung cancer screening scans and 76 brain magnetic resonance imaging metastases screening scans were collected in the first half of February for this study. According to the evaluation by radiologists, ChatGPT can successfully translate radiology reports into plain language with an average score of 4.27 in the five-point system with 0.08 places of information missing and 0.07 places of misinformation. In terms of the suggestions provided by ChatGPT, they are generally relevant such as keeping following-up with doctors and closely monitoring any symptoms, and for about 37% of 138 cases in total ChatGPT offers specific suggestions based on findings in the report. ChatGPT also presents some randomness in its responses with occasionally over-simplified or neglected information, which can be mitigated using a more detailed prompt. Furthermore, ChatGPT results are compared with a newly released large model GPT-4, showing that GPT-4 can significantly improve the quality of translated reports. Our results show that it is feasible to utilize large language models in clinical education, and further efforts are needed to address limitations and maximize their potential.

Five-year survivors from brain metastases treated with stereotactic radiosurgery: Biology, improving treatments, or just plain luck?

Background: Improvements in therapies have led to an increasing number of long-term survivors of brain metastases. The present series compares a population of 5-year survivors of brain metastases to a generalized brain metastases population to assess for factors attributable to long-term survival. Methods: A single institution retrospective review was performed to identify 5-year survivors of brain metastases who received stereotactic radiosurgery (SRS). A historical control population of 737 patients with brain metastases was used to assess similarities and differences between the long-term survivor population and the general population treated with SRS. Results: A total of 98 patients with brain metastases were found to have survived over 60 months. No differences between long-term survivors and controls were identified with regards to the age at first SRS (P = .19), primary cancer distribution (P = .80), and the number of metastases at first SRS (P = .90). Cumulative incidence of neurologic death at 6, 8 and 10 years for the long-term survivor cohort was 4.8%, 16%, and 16% respectively. In the historical controls, cumulative incidence of neurologic death reached a plateau at 40% after 4.9 years. A significant difference in the distribution of burden of disease at the time of the first SRS was found between the 5-year survivors and the control (P = .0049). 58% of 5-year survivors showed no evidence of clinical disease at the last follow-up. Conclusion: Five-year survivors of brain metastases represent a diverse histologic population, suggesting a small population of oligometastatic and indolent cancers exist for each cancer type.

Long term survivors of stereotactic radiosurgery for brain metastases: do distant brain failures reach a plateau and what factors are associated with a brain metastasis velocity of zero?

PURPOSE: Life expectancy continues to increase for patients with brain metastases treated with stereotactic radiosurgery (SRS). The present study sought to retrospectively analyze brain metastasis patients who have survived 2 years or more, and assess for what factors may predict for a final brain metastasis velocity (BMV) of zero. METHODS: This was a single-institution retrospective study of 300 patients treated with SRS from 2001 to 2019 for brain metastases who survived greater than 2 years after first SRS. Final BMV is calculated by summing all metastases through the observed time divided by the total time in years. A BMV of zero is defined as at least 2 years of imaging follow-up without distant brain failure (DBF). RESULTS: Median age at first SRS is 61 (IQR: 53, 70). Kaplan-Meier estimated median overall survival is 4.9 years and time to DBF is 1.5 years (95% CI 1.2, 2.0). Twenty-eight (9.3%) patients underwent subsequent WBRT. One hundred and one (33.7%) patients never had any further brain metastases (BMV = 0) at a median follow-up time of 3.3 years. Median BMV is 0.4 (IQR: 0, 1.4). Distant brain failures reach a plateau at 4 years where the cumulative incidence of DBF is 82%. 70% of first time DBFs have occurred by 2 years. Factors significantly associated with a BMV of zero include fewer brain metastases at first SRS (HR 1.1; p = 0.0004) and Caucasian race (HR 1.5; p = 0.03). CONCLUSION: Approximately one third of brain metastasis patients who live beyond 2 years after initial SRS have a BMV of zero. DBFs appear to reach a plateau at 4 years. Factors significantly associated with a BMV of zero include Caucasian race and having had a single brain metastasis at first SRS.

A transformer-based deep-learning approach for classifying brain metastases into primary organ sites using clinical whole-brain MRI images.

Treatment decisions for brain metastatic disease rely on knowledge of the primary organ site and are currently made with biopsy and histology. Here, we develop a deep-learning approach for accurate non-invasive digital histology with whole-brain magnetic resonance imaging (MRI) data. Contrast-enhanced T1-weighted and fast spoiled gradient echo brain MRI exams (n = 1,582) were preprocessed and input to the proposed deep-learning workflow for tumor segmentation, modality transfer, and primary site classification into one of five classes. Tenfold cross-validation generated an overall area under the receiver operating characteristic curve (AUC) of 0.878 (95% confidence interval [CI]: 0.873,0.883). These data establish that whole-brain imaging features are discriminative enough to allow accurate diagnosis of the primary organ site of malignancy. Our end-to-end deep radiomic approach has great potential for classifying metastatic tumor types from whole-brain MRI images. Further refinement may offer an invaluable clinical tool to expedite primary cancer site identification for precision treatment and improved outcomes.

Upfront immunotherapy leads to lower brain metastasis velocity in patients undergoing stereotactic radiosurgery for brain metastases.

Background: While immunotherapy has been shown to improve survival and decrease neurologic death in patients with brain metastases, it remains unclear whether this improvement is due to prevention of new metastasis to the brain. Method: We performed a retrospective review of patients presenting with brain metastases simultaneously with the first diagnosis of metastatic disease and were treated with upfront immunotherapy as part of their treatment regimen and stereotactic radiosurgery (SRS) to the brain metastases. We compared this cohort with a historical control population (prior to the immunotherapy era) who were treated with pre-immunotherapy standard of care systemic therapy and with SRS to the brain metastases. Results: Median overall survival time was improved in the patients receiving upfront immunotherapy compared to the historical cohort (48 months vs 8.4 months, p=0.001). Median time to distant brain failure was statistically equivalent (p=0.3) between the upfront immunotherapy cohort and historical control cohort (10.3 vs 12.6 months). Brain metastasis velocity was lower in the upfront immunotherapy cohort (median 3.72 metastases per year) than in the historical controls (median 9.48 metastases per year, p=0.001). Cumulative incidence of neurologic death at one year was 12% in the upfront immunotherapy cohort and 28% in the historical control cohort (p=0.1). Conclusions: Upfront immunotherapy appears to improve overall survival and decrease BMV compared to historical controls. While these data remain to be validated, they suggest that brain metastasis patients may benefit from concurrent immunotherapy with SRS.

Clinical outcomes of dose-escalated re-irradiation in patients with recurrent high-grade glioma.

Background: Re-irradiation for recurrent gliomas is a controversial treatment option with no clear standard dose or concurrent systemic therapy. Methods: This series represents a single-institution retrospective review of patients treated with re-irradiation for recurrent high-grade glioma. After 2012, patients were commonly offered concurrent bevacizumab as a cytoprotective agent against radiation necrosis. Kaplan-Meier method was used to estimate overall survival and progression-free survival. Cox proportional hazards regression was used to identify factors associated with overall survival and progression-free survival. Results: Between 2001 and 2021, 52 patients underwent re-irradiation for a diagnosis of recurrent high-grade glioma. 36 patients (69.2%) had a histologic diagnosis of glioblastoma at the time of re-irradiation. The median BED10 (biological equivalent dose 10 Gy) of re-irradiation was 53.1 Gy. Twenty-one patients (40.4%) received concurrent bevacizumab with re-irradiation. Median survival for the entire cohort and for glioblastoma at the time of recurrence patients was 6.7 months and 6.0 months, respectively. For patients with glioblastoma at the time of recurrence, completing re-irradiation (HR 0.03, P < .001), use of concurrent bevacizumab (HR 0.3, P = .009), and the BED10 (HR 0.9, P = .005) were predictive of overall survival. Nine patients developed grade 3-5 toxicity; of these, 2 received concurrent bevacizumab and 7 did not (P = .15). Conclusion: High dose re-irradiation with concurrent bevacizumab is feasible in patients with recurrent gliomas. Concurrent bevacizumab and increasing radiation dose may improve survival in patients with recurrent glioblastoma.

Comparison of linear and volumetric criteria for the determination of therapeutic response in dogs with intracranial gliomas.

BACKGROUND: Brain tumor therapeutic responses can be quantified from magnetic resonance images (MRI) using 1- (1D) and 2-dimensional (2D) linear and volumetric methods, but few studies in dogs compare these techniques. HYPOTHESES: Linear methods will be obtained faster, but have less agreement than volumetric measurements. Therapeutic response agreement will be highest with the total T2W tumor volumetric (TTV) method. Therapeutic response at 6-weeks will correlate with overall survival (OS). ANIMALS: Forty-six dogs with intracranial gliomas. METHODS: Prospective study. Three raters measured tumors using 1D and 2D linear, TTV, and contrast-enhancing volumetric (CEV) techniques on 143 brain MRI to determine agreement between methods, define therapeutic responses, and assess relations with OS. RESULTS: Raters performed 1D the fastest (2.9 ± 0.57 minutes) and CEV slowest (17.8 ± 6.2 minutes). Inter- and intraobserver agreements were excellent (intraclass correlations ≥.91) across methods. Correlations between linear (1D vs 2D; ρ > .91) and volumetric (TTV vs CEV; ρ > .73) methods were stronger than linear to volumetric comparisons (ρ range, .26-.59). Incorporating clinical and imaging data resulted in fewer discordant therapeutic responses across methods. Dogs having partial tumor responses at 6 weeks had a lower death hazard than dogs with stable or progressive disease when assessed using 2D, CEV, and TTV (hazard ration 2.1; 95% confidence interval, 1.22-3.63; P = .008). CONCLUSIONS AND CLINICAL IMPORTANCE: One-dimensional, 2D, CEV, and TTV are comparable for determining therapeutic response. Given the simplicity, universal applicability, and superior performance of the TTV, we recommend its use to standardize glioma therapeutic response criteria.

Initial Evaluations of the Microtubule-Based PET Radiotracer, [11C]MPC-6827 in a Rodent Model of Cocaine Abuse.

Purpose: Microtubules (MTs) are structural units made of α and ß tubulin subunits in the cytoskeleton responsible for axonal transport, information processing, and signaling mechanisms-critical for healthy brain function. Chronic cocaine exposure affects the function, organization, and stability of MTs in the brain, thereby impairing overall neurochemical and cognitive processes. At present, we have no reliable, non-invasive methods to image MTs for cocaine use disorder (CUD). Recently we reported the effect of cocaine in patient-derived neuroblastoma SH-SY5Y cells. Here we report preliminary results of a potential imaging biomarker of CUD using the brain penetrant MT-based radiotracer, [11C]MPC-6827, in an established rodent model of cocaine self-administration (SA). Methods: Cell uptake studies were performed with [11C]MPC-6827 in SH-SY5Y cells, treated with or without cocaine (n = 6/group) at 30 and 60 min incubations. MicroPET/CT brain scans were performed in rats at baseline and 35 days after cocaine self-administration and compared with saline-treated rats as controls (n = 4/sex). Whole-body post-PET biodistribution, plasma metabolite assay, and brain autoradiography were performed in the same rats from imaging. Results: Cocaine-treated SH-SY5Y cells demonstrated a ∼26(±4)% decrease in radioactive uptake compared to non-treated controls. Both microPET/CT imaging and biodistribution results showed lower (∼35 ± 3%) [11C]MPC-6827 brain uptake in rats that had a history of cocaine self-administration compared to the saline-treated controls. Plasma metabolite assays demonstrate the stability (≥95%) of the radiotracer in both groups. In vitro autoradiography also demonstrated lower radioactive uptake in cocaine rats compared to the control rats. [11C]MPC-6827's in vitro SH-SY5Y neuronal cell uptake, in vivo positron emission tomography (PET) imaging, ex vivo biodistribution, and in vitro autoradiography results corroborated well with each other, demonstrating decreased radioactive brain uptake in cocaine self-administered rats versus controls. There were no significant differences either in cocaine intake or in [11C]MPC-6827 uptake between the male and female rats. Conclusions: This project is the first to validate in vivo imaging of the MT-associations with CUD in a rodent model. Our initial observations suggest that [11C]MPC-6827 uptake decreases in cocaine self-administered rats and that it may selectively bind to destabilized tubulin units in the brain. Further longitudinal studies correlating cocaine intake with [11C]MPC-6827 PET brain measures could potentially establish the MT scaffold as an imaging biomarker for CUD, providing researchers and clinicians with a sensitive tool to better understand the biological underpinnings of CUD and tailor new treatments.

Local control outcomes for combination of stereotactic radiosurgery and immunotherapy for non-small cell lung cancer brain metastases.

BACKGROUND: Previous series have demonstrated CNS activity for immune checkpoint inhibitors, yet no prior data exists regarding whether this activity can improve outcomes of stereotactic radiosurgery. METHODS: In this single institution retrospective series, the clinical outcomes of 80 consecutive lung cancer patients treated with concurrent immune checkpoint inhibitors and stereotactic radiosurgery were compared to 235 in the historical control cohort in which patients were treated prior to immune checkpoint inhibition being standard upfront therapy. Overall survival was estimated using the Kaplan Meier method. Cumulative incidence of local progression was estimated using a competing risk model. RESULTS: Median overall survival time was improved in patients receiving upfront immunotherapy compared to the historical control group (40 months vs 8 months, p < 0.001). Factors affected overall survival include concurrent immunotherapy (HR 0.23, p < 0.0001) and KPS (HR 0.97, p = 0.0001). Cumulative incidence of local failure in the historical control group was 10% at 1 year, compared to 1.1% at 1 year in the concurrent immunotherapy group (p = 0.025). Factors affected local control included use of concurrent immunotherapy (HR 0.09, p = 0.012), and lowest margin dose delivered to a metastasis (HR 0.8, p = 0.0018). CONCLUSION: Local control and overall survival were both improved in patients receiving concurrent immune checkpoint inhibitors with radiosurgery compared to historical controls. While these data remain to be validated, they suggest that brain metastasis patients may benefit from concurrent use of immunotherapy with SRS.

Cumulative strain-based metrics for predicting subconcussive head impact exposure-related imaging changes in a cohort of American youth football players.

OBJECTIVE: Youth football athletes are exposed to repetitive subconcussive head impacts during normal participation in the sport, and there is increasing concern about the long-term effects of these impacts. The objective of the current study was to determine if strain-based cumulative exposure measures are superior to kinematic-based exposure measures for predicting imaging changes in the brain. METHODS: This prospective, longitudinal cohort study was conducted from 2012 to 2017 and assessed youth, male football athletes. Kinematic data were collected at all practices and games from enrolled athletes participating in local youth football organizations in Winston-Salem, North Carolina, and were used to calculate multiple risk-weighted cumulative exposure (RWE) kinematic metrics and 36 strain-based exposure metrics. Pre- and postseason imaging was performed at Wake Forest School of Medicine, and diffusion tensor imaging (DTI) measures, including fractional anisotropy (FA), and its components (CL, CP, and CS), and mean diffusivity (MD), were investigated. Included participants were youth football players ranging in age from 9 to 13 years. Exclusion criteria included any history of previous neurological illness, psychiatric illness, brain tumor, concussion within the past 6 months, and/or contraindication to MRI. RESULTS: A total of 95 male athletes (mean age 11.9 years [SD 1.0 years]) participated between 2012 and 2017, with some participating for multiple seasons, resulting in 116 unique athlete-seasons. Regression analysis revealed statistically significant linear relationships between the FA, linear coefficient (CL), and spherical coefficient (CS) and all strain exposure measures, and well as the planar coefficient (CP) and 8 strain measures. For the kinematic exposure measures, there were statistically significant relationships between FA and RWE linear (RWEL) and RWE combined probability (RWECP) as well as CS and RWEL. According to area under the receiver operating characteristic (ROC) curve (AUC) analysis, the best-performing metrics were all strain measures, and included metrics based on tensile, compressive, and shear strain. CONCLUSIONS: Using ROC curves and AUC analysis, all exposure metrics were ranked in order of performance, and the results demonstrated that all the strain-based metrics performed better than any of the kinematic metrics, indicating that strain-based metrics are better discriminators of imaging changes than kinematic-based measures. Studies relating the biomechanics of head impacts with brain imaging and cognitive function may allow equipment designers, care providers, and organizations to prevent, identify, and treat injuries in order to make football a safer activity.

Apolipoprotein E levels in the amygdala and prefrontal cortex predict relative regional brain volumes in irradiated Rhesus macaques.

In the brain, apolipoprotein E (apoE) plays an important role in lipid transport and response to environmental and age-related challenges, including neuronal repair following injury. While much has been learned from radiation studies in rodents, a gap in our knowledge is how radiation might affect the brain in primates. This is important for assessing risk to the brain following radiotherapy as part of cancer treatment or environmental radiation exposure as part of a nuclear accident, bioterrorism, or a nuclear attack. In this study, we investigated the effects of ionizing radiation on brain volumes and apoE levels in the prefrontal cortex, amygdala, and hippocampus of Rhesus macaques that were part of the Nonhuman Primate Radiation Survivor Cohort at the Wake Forest University. This unique cohort is composed of Rhesus macaques that had previously received single total body doses of 6.5-8.05 Gy of ionizing radiation. Regional apoE levels predicted regional volume in the amygdala and the prefrontal cortex. In addition, apoE levels in the amygdala, but not the hippocampus, strongly predicted relative hippocampal volume. Finally, radiation dose negatively affected relative hippocampal volume when apoE levels in the amygdala were controlled for, suggesting a protective compensatory role of regional apoE levels following radiation exposure. In a supplementary analysis, there also was a robust positive relationship between the neuroprotective protein α-klotho and apoE levels in the amygdala, further supporting the potentially protective role of apoE. Increased understanding of the effects of IR in the primate brain and the role of apoE in the irradiated brain could inform future therapies to mitigate the adverse effects of IR on the CNS.

Feasibility and Biological Activity of a Ketogenic/Intermittent-Fasting Diet in Patients With Glioma.

OBJECTIVE: To examine the feasibility, safety, systemic biological activity, and cerebral activity of a ketogenic dietary intervention in patients with glioma. METHODS: Twenty-five patients with biopsy-confirmed World Health Organization grade 2 to 4 astrocytoma with stable disease after adjuvant chemotherapy were enrolled in an 8-week Glioma Atkins-Based Diet (GLAD). GLAD consisted of 2 fasting days (calories <20% calculated estimated needs) interleaved between 5 modified Atkins diet days (net carbohydrates ≤20 g/d) each week. The primary outcome was dietary adherence by food records. Markers of systemic and cerebral activity included weekly urine ketones, serum insulin, glucose, hemoglobin A1c, insulin-like growth factor-1, and magnetic resonance spectroscopy at baseline and week 8. RESULTS: Twenty-one patients (84%) completed the study. Eighty percent of patients reached ≥40 mg/dL urine acetoacetate during the study. Forty-eight percent of patients were adherent by food record. The diet was well tolerated, with two grade 3 adverse events (neutropenia, seizure). Measures of systemic activity, including hemoglobin A1c, insulin, and fat body mass, decreased significantly, while lean body mass increased. Magnetic resonance spectroscopy demonstrated increased ketone concentrations (ß-hydroxybutyrate [bHB] and acetone) in both lesional and contralateral brain compared to baseline. Average ketonuria correlated with cerebral ketones in lesional (tumor) and contralateral brain (bHB R s = 0.52, p = 0.05). Subgroup analysis of isocitrate dehydrogenase-mutant glioma showed no differences in cerebral metabolites after controlling for ketonuria. CONCLUSION: The GLAD dietary intervention, while demanding, produced meaningful ketonuria and significant systemic and cerebral metabolic changes in participants. Ketonuria in participants correlated with cerebral ketone concentration and appears to be a better indicator of systemic activity than patient-reported food records. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov Identifier: NCT02286167.

Convection-Enhanced Arborizing Catheter System Improves Local/Regional Delivery of Infusates Versus a Single-Port Catheter in Ex Vivo Porcine Brain Tissue.

Standard treatment for glioblastoma is noncurative and only partially effective. Convection-enhanced delivery (CED) was developed as an alternative approach for effective loco-regional delivery of drugs via a small catheter inserted into the diseased brain. However, previous CED clinical trials revealed the need for improved catheters for controlled and satisfactory distribution of therapeutics. In this study, the arborizing catheter, consisting of six infusion ports, was compared to a reflux-preventing single-port catheter. Infusions of iohexol at a flow rate of 1 µL/min/microneedle were performed, using the arborizing catheter on one hemisphere and a single-port catheter on the contralateral hemisphere of excised pig brains. The volume dispersed (Vd) of the contrast agent was quantified for each catheter. Vd for the arborizing catheter was significantly higher than for the single-port catheter, 2235.8 ± 569.7 mm3 and 382.2 ± 243.0 mm3, respectively (n = 7). Minimal reflux was observed; however, high Vd values were achieved with the arborizing catheter. With simultaneous infusion using multiple ports of the arborizing catheter, high Vd was achieved at a low infusion rate. Thus, the arborizing catheter promises a highly desirable large volume of distribution of drugs delivered to the brain for the purpose of treating brain tumors.

Predictors of Adverse Radiation Effect in Brain Metastasis Patients Treated With Stereotactic Radiosurgery and Immune Checkpoint Inhibitor Therapy.

PURPOSE: Immune checkpoint inhibitor (ICI) therapy has recently been found to improve survival in patients with a number of cancers, including those with metastatic disease. There is an association of adverse radiation effect (ARE) in patients with brain metastases who have been treated with stereotactic radiosurgery (SRS) and ICIs. METHODS AND MATERIALS: Single-institution retrospective review identified 1118 brain metastases treated with SRS between 2013 and 2018 that had received ICI therapy and 886 metastases that did not receive ICI. Toxicity grading was done via the Common Terminology Criteria for Adverse Events v4.0 grading criteria. Cumulative incidence of ARE was estimated using competing risks methodology; univariate and multivariable regression models were generated to estimate the subdistribution hazard (sHR) of ARE. RESULTS: Two-year cumulative incidence of ARE was 4.5% and 2.1% in patients treated with and without ICI, respectively (Gray's P = .004). Of the 52 metastases exhibiting ARE during the follow-up period, ARE severity by Common Terminology Criteria for Adverse Events v4 was grade 1 in 14 patients, grade 2 in 15, grade 3 in 9, and grade 4 in 14. There were no grade 5 events. Factors associated with an increased sHR of ARE on univariate analysis included ICI, metastasis volume, SRS dose, prescription isodose line, cavity-directed SRS, and V12. Multivariable analysis revealed prescription isodose line (sHR 0.95, P < .01) and ICI (sHR 2.58, P < .01) as significant predictors of ARE. Increasing V12 was associated with a rapidly increasing risk of adverse radiation effect in patients who received ICI. CONCLUSIONS: Our findings suggest that patients receiving ICI have an increased risk of ARE after radiosurgery for brain metastases, with large metastases being at particularly high risk.