Stereotactic radiosurgery in the treatment of brain metastases: the current evidence

Assessment of scintillation and Cherenkov imaging as beam shape verification method in CyberKnife® radiotherapy

PURPOSE

The goal of this study is to assess the utility of Cherenkov imaging (CI) and scintillation imaging (SI) as high-resolution techniques to measure CyberKnife® beam shape quantitatively at the irradiation surface in quality assurance (QA).

METHODS

The EMCCD camera captured scintillation and Cherenkov photons arising from 6 MV x-ray dose deposition produced by the CyberKnife® VSI System. Two imaging methods were done at source to surface distance of 800 cm with the same field size, ranging from 10 to 60 mm using fixed cones and iris collimators. The output sensitivity and constancy were measured using the SI and CI, and benchmarked against an ionization chamber. Line profiles of each beam measured by optical imaging were compared with film measurement. Position shifts were introduced to test the sensitivity of SI and CI to small beam position deviations. To assess reproducibility, the beam measurements were tested three times on 5 consecutive days.

RESULTS

Both systems exhibited comparable sensitivity to the ionization chamber in response to fluctuations in CyberKnife® output. The beam profiles in SI matched well with the measured film image, with accuracy in the range of ± 0.20 and ± 0.26 mm standard deviation for the circle and iris field, respectively. The corresponding accuracy measured by CI is in the range of ± 0.25 and ± 0.33 mm, respectively. These are all within the tolerance recommended by the guidelines of CyberKnife® QA. The accuracy measured by SI and CI for 1 mm beam position shift within 0.21 and 0.45 mm tolerance, respectively. Repeatability measurements of the beam have shown a standard deviation within 0.94 mm.

CONCLUSIONS

SI and CI techniques are tested to provide a valid way to measure CyberKnife® beam shape in this study. Meanwhile, the systematic comparison of SI and CI also provides evidence for the measurement methods selection appropriately.

Modelling radiobiology

Radiotherapy has played an essential role in cancer treatment for over a century, and remains one of the best-studied methods of cancer treatment. Because of its close links with the physical sciences, it has been the subject of extensive quantitative mathematical modelling, but a complete understanding of the mechanisms of radiotherapy has remained elusive. In part this is because of the complexity and range of scales involved in radiotherapy-from physical radiation interactions occurring over nanometres to evolution of patient responses over months and years. This review presents the current status and ongoing research in modelling radiotherapy responses across these scales, including basic physical mechanisms of DNA damage, the immediate biological responses this triggers, and genetic- and patient-level determinants of response. Finally, some of the major challenges in this field and potential avenues for future improvements are also discussed.

Two-Day Fraction Gamma Knife Radiosurgery for Large Brain Metastasis

OBJECTIVE

We investigated how treating large brain metastasis (LBM) using 2-day fraction Gamma Knife radiosurgery (GKRS) affects tumor control and patient survival. A prescription dose of 10.3 Gy was applied for 2 consecutive days, with a biologically effective dose equivalent to a tumor single-fraction dose of 16.05 Gy and a brain single-fraction dose of 15.12 Gy.

METHODS

Between November 2017 and December 2021, 42 patients (mean age, 68.3 years; range, 50-84 years; male, 29 [69.1%]; female, 13 [30.9%]) with 44 tumors underwent 2-day fraction GKRS to treat large volume brain metastasis. The main cancer types were non-small cell lung cancer (n=16), small cell lung cancer (n=7), colorectal cancer (n=7), breast cancer (n=3), gastric cancer (n=2), and other cancers (n=7). Twenty-one patients (50.0%) had a single LBM, 19 (46.3%) had a single LBM and other metastases, and two had two (4.7%) large brain metastases. At the time of the 2-day fraction GKRS, the tumors had a mean volume of 23.1 mL (range, 12.5-67.4). On each day, radiation was administered at a dose of 10.3 Gy, mainly using a 50% isodose-line.

RESULTS

We obtained clinical and magnetic resonance imaging follow-up data for 34 patients (81%) with 35 tumors, who had undergone 2-day fraction GKRS. These patients did not experience acute or late radiation-induced complications during follow-up. The median and mean progression-free survival (PFS) periods were 188 and 194 days, respectively. The local control rates at 6, 9, and 12 months were 77%, 40%, and 34%, respectively. The prognostic factors related to PFS were prior radiotherapy (p=0.019) and lung cancer origin (p=0.041). Other factors such as tumor volumes, each isodose volumes, and peri-GKRS systemic treatment were not significantly related to PFS. The overall survival period of the 44 patients following repeat stereotactic radiosurgery (SRS) ranged from 15-878 days (median, 263±38 days; mean, 174±43 days) after the 2-day fraction GKRS. Eight patients (18.2%) were still alive.

CONCLUSION

Considering the unsatisfactory tumor control, a higher prescription dose should be needed in this procedure as a salvage management. Moreover, in the treatment for LBM with fractionated SRS, using different isodoses and prescription doses at the treatment planning for LBMs should be important. However, this report might be a basic reference with the same fraction number and prescription dose in the treatment for LBMs with frame-based SRS.

Artificial intelligence-assisted volume isotropic simultaneous interleaved bright- and black-blood examination for brain metastases

PURPOSE

To verify the effectiveness of artificial intelligence-assisted volume isotropic simultaneous interleaved bright-/black-blood examination (AI-VISIBLE) for detecting brain metastases.

METHODS

This retrospective study was approved by our institutional review board and the requirement for written informed consent was waived. Forty patients were included: 20 patients with and without brain metastases each. Seven independent observers (three radiology residents and four neuroradiologists) participated in two reading sessions: in the first, brain metastases were detected using VISIBLE only; in the second, the results of the first session were comprehensively evaluated by adding AI-VISIBLE information. Sensitivity, diagnostic performance, and false positives/case were evaluated. Diagnostic performance was assessed using a figure-of-merit (FOM). Sensitivity and false positives/case were evaluated using McNemar and paired t-tests, respectively.

RESULTS

The McNemar test revealed a significant difference between VISIBLE with/without AI information (P < 0.0001). Significantly higher sensitivity (94.9 ± 1.7% vs. 88.3 ± 5.1%, P = 0.0028) and FOM (0.983 ± 0.009 vs. 0.972 ± 0.013, P = 0.0063) were achieved using VISIBLE with AI information vs. without. No significant difference was observed in false positives/case with and without AI information (0.23 ± 0.19 vs. 0.18 ± 0.15, P = 0.250). AI-assisted results of radiology residents became comparable to results of neuroradiologists (sensitivity, FOM: 85.9 ± 3.4% vs. 90.0 ± 5.9%, 0.969 ± 0.016 vs. 0.974 ± 0.012 without AI information; 94.8 ± 1.3% vs. 95.0 ± 2.1%, 0.977 ± 0.010 vs. 0.988 ± 0.005 with AI information, respectively).

CONCLUSION

AI-VISIBLE improved the sensitivity and performance for diagnosing brain metastases.

Clinical application of a GPU-accelerated monte carlo dose verification for cyberknife M6 with Iris collimator

PURPOSE

To apply an independent GPU-accelerated Monte Carlo (MC) dose verification for CyberKnife M6 with Iris collimator and evaluate the dose calculation accuracy of RayTracing (TPS-RT) algorithm and Monte Carlo (TPS-MC) algorithm in the Precision treatment planning system (TPS).

METHODS

GPU-accelerated MC algorithm (ArcherQA-CK) was integrated into a commercial dose verification system, ArcherQA, to implement the patient-specific quality assurance in the CyberKnife M6 system. 30 clinical cases (10 cases in head, and 10 cases in chest, and 10 cases in abdomen) were collected in this study. For each case, three different dose calculation methods (TPS-MC, TPS-RT and ArcherQA-CK) were implemented based on the same treatment plan and compared with each other. For evaluation, the 3D global gamma analysis and dose parameters of the target volume and organs at risk (OARs) were analyzed comparatively.

RESULTS

For gamma pass rates at the criterion of 2%/2 mm, the results were over 98.0% for TPS-MC vs.TPS-RT, TPS-MC vs. ArcherQA-CK and TPS-RT vs. ArcherQA-CK in head cases, 84.9% for TPS-MC vs.TPS-RT, 98.0% for TPS-MC vs. ArcherQA-CK and 83.3% for TPS-RT vs. ArcherQA-CK in chest cases, 98.2% for TPS-MC vs.TPS-RT, 99.4% for TPS-MC vs. ArcherQA-CK and 94.5% for TPS-RT vs. ArcherQA-CK in abdomen cases. For dose parameters of planning target volume (PTV) in chest cases, the deviations of TPS-RT vs. TPS-MC and ArcherQA-CK vs. TPS-MC had significant difference (P < 0.01), and the deviations of TPS-RT vs. TPS-MC and TPS-RT vs. ArcherQA-CK were similar (P > 0.05). ArcherQA-CK had less calculation time compared with TPS-MC (1.66 min vs. 65.11 min).

CONCLUSIONS

Our proposed MC dose engine (ArcherQA-CK) has a high degree of consistency with the Precision TPS-MC algorithm, which can quickly identify the calculation errors of TPS-RT algorithm for some chest cases. ArcherQA-CK can provide accurate patient-specific quality assurance in clinical practice.

What is the optimal isodose line for stereotactic radiotherapy for single brain metastases using HyperArc?

PURPOSE

The study aimed to investigate the optimal isodose line (IDL) in linear accelerator-based stereotactic radiotherapy for single brain metastasis, using HyperArc. We compared the dosimetric parameters for target and normal brain tissue among six plans with different IDLs.

METHODS

This study included 30 patients with single brain metastasis. We retrospectively generated six plans for each tumor with different IDLs (80%, 70%, 60%, 50%, 40%, and 33%) using HyperArc. All treatment plans were normalized to the prescription dose of 35 Gy in five fractions which was covered by 95% of the planning target volume (PTV), defined by adding a 1.0 mm margin to the gross tumor volume (GTV). The dosimetric parameters were compared among the six plans.

RESULTS

For GTV > 0.1 cm3, the ratio of brain-GTV volumes receiving 25 Gy to PTV (V25Gy/PTV) was significantly lower at IDL 40%-70% than at IDL 80% and 33% (p < 0.01, retrospectively). For GTV < 0.1 cm3, V25Gy/PTV decreased continuously as IDL decreased. The values of D99% and D80% for GTV increased with decreasing IDL. An IDL of 50% or less was required to achieve D99% of greater than 43 Gy and D80% of greater than 50 Gy. The mean values of D99% and D80% for IDL 50% were 44.3 and 51.9 Gy.

CONCLUSION

The optimal IDL is 40%-50% for GTV > 0.1 cm3. These lower IDLs could increase D99% and D80% of GTV while lowering V25Gy of normal brain tissue, which may help reduce the risk of radiation necrosis and improve local control.

Where Does Auto-Segmentation for Brain Metastases Radiosurgery Stand Today?

Detection and segmentation of brain metastases (BMs) play a pivotal role in diagnosis, treatment planning, and follow-up evaluations for effective BM management. Given the rising prevalence of BM cases and its predominantly multiple onsets, automated segmentation is becoming necessary in stereotactic radiosurgery. It not only alleviates the clinician's manual workload and improves clinical workflow efficiency but also ensures treatment safety, ultimately improving patient care. Recent strides in machine learning, particularly in deep learning (DL), have revolutionized medical image segmentation, achieving state-of-the-art results. This review aims to analyze auto-segmentation strategies, characterize the utilized data, and assess the performance of cutting-edge BM segmentation methodologies. Additionally, we delve into the challenges confronting BM segmentation and share insights gleaned from our algorithmic and clinical implementation experiences.

Reducing false positives in deep learning-based brain metastasis detection by using both gradient-echo and spin-echo contrast-enhanced MRI: validation in a multi-center diagnostic cohort

OBJECTIVES

To develop a deep learning (DL) for detection of brain metastasis (BM) that incorporates both gradient- and turbo spin-echo contrast-enhanced MRI (dual-enhanced DL) and evaluate it in a clinical cohort in comparison with human readers and DL using gradient-echo-based imaging only (GRE DL).

MATERIALS AND METHODS

DL detection was developed using data from 200 patients with BM (training set) and tested in 62 (internal) and 48 (external) consecutive patients who underwent stereotactic radiosurgery and diagnostic dual-enhanced imaging (dual-enhanced DL) and later guide GRE imaging (GRE DL). The detection sensitivity and positive predictive value (PPV) were compared between two DLs. Two neuroradiologists independently analyzed BM and reference standards for BM were separately drawn by another neuroradiologist. The relative differences (RDs) from the reference standard BM numbers were compared between the DLs and neuroradiologists.

RESULTS

Sensitivity was similar between GRE DL (93%, 95% confidence interval [CI]: 90-96%) and dual-enhanced DL (92% [89-94%]). The PPV of the dual-enhanced DL was higher (89% [86-92%], p < .001) than that of GRE DL (76%, [72-80%]). GRE DL significantly overestimated the number of metastases (false positives; RD: 0.05, 95% CI: 0.00-0.58) compared with neuroradiologists (RD: 0.00, 95% CI: - 0.28, 0.15, p < .001), whereas dual-enhanced DL (RD: 0.00, 95% CI: 0.00-0.15) did not show a statistically significant difference from neuroradiologists (RD: 0.00, 95% CI: - 0.20-0.10, p = .913).

CONCLUSION

The dual-enhanced DL showed improved detection of BM and reduced overestimation compared with GRE DL, achieving similar performance to neuroradiologists.

CLINICAL RELEVANCE STATEMENT

The use of deep learning-based brain metastasis detection with turbo spin-echo imaging reduces false positive detections, aiding in the guidance of stereotactic radiosurgery when gradient-echo imaging alone is employed.

KEY POINTS

•Deep learning for brain metastasis detection improved by using both gradient- and turbo spin-echo contrast-enhanced MRI (dual-enhanced deep learning). •Dual-enhanced deep learning increased true positive detections and reduced overestimation. •Dual-enhanced deep learning achieved similar performance to neuroradiologists for brain metastasis counts.

The Role of Stereotactic Radiosurgery in Patients With Brain Metastases From Colorectal Cancers

BACKGROUND AND OBJECTIVES

The role of stereotactic radiosurgery (SRS) in patients with brain metastases (BMs) from colorectal cancers (CRCs) has not been established. The authors present a single-institution experience of patients with CRC who underwent SRS with metastatic brain spread.

METHODS

We retrospectively analyzed 111 patients with metastatic CRC (64 female, 57.7%), with 449 BMs treated with Gamma Knife SRS between 2000 and 2022. The median age during SRS was 63 years (range: 28-86), and the median Karnofsky Performance Scale was 80 (range: 60-100). The primary sites were colon (85 patients, 76.6%) and rectal (26 patients, 23.4%). Three patients underwent hypofractionated SRS (3 sessions) with a median margin dose of 27 Gy (range: 27-30). All other patients underwent single-session SRS with a median margin dose of 18 Gy (range: 13-20).

RESULTS

The median patient survival after SRS was 7 months (range: 1-174). Ninety-eight (88.3%) patients expired at last follow-up and 15 patients (15.3%) died related to progressive intracranial disease. A Karnofsky Performance Scale of <80 at SRS presentation ( P = .02, hazard ratio [HR]: 0.6, 95% CI: 0.4-0.9) and no previous surgical resection ( P < .01, HR: 0.4, 95% CI: 0.3-0.7) were associated with inferior overall survival using multivariate analysis. Seventeen patients (15.3%) had documented local tumor progression after SRS, at a median time of 7 months (range: 3-34) between SRS and progression. Twenty-six patients (23.4%) developed new BMs at a median of 5 months (range: 2-26) between SRS and new tumor detection. Less than three BMs at SRS presentation ( P = .02, HR: 2.6, 95% CI: 1.2-5.6) were associated with better distant tumor control on multivariate analysis. The incidence of adverse radiation effects was 5.4%.

CONCLUSION

SRS effectively controls BMs from CRC with low risk of treatment-related toxicity. During follow-up, the development of additional metastases can be safely treated by repeat SRS.

Evaluating the Efficacy of Perfusion MRI and Conventional MRI in Distinguishing Recurrent Cerebral Metastasis from Brain Radiation Necrosis

Differentiating recurrent cerebral metastasis (CM) from brain radiation necrosis (BRN) is pivotal for guiding appropriate treatment and prognostication. Despite advances in imaging techniques, however, accurately distinguishing these conditions non-invasively is still challenging. This single-center retrospective study reviewed 32 cases (28 patients) with confirmed cerebral metastases who underwent surgical excision of lesions initially diagnosed by MRI and/or MR perfusion scans from 1 January 2015 to 30 September 2020. Diagnostic accuracy was assessed by comparing imaging findings with postoperative histopathology. Conventional MRI accurately identified recurrent CM in 75% of cases. MR perfusion scans showed significantly higher mean maximum relative cerebral blood volume (max. rCBV) in metastasis cases, indicating its potential as a discriminative biomarker. No single imaging modality could definitively distinguish CM from BRN. Survival analysis revealed gender as the only significant factor affecting overall survival, with no significant survival difference observed between patients with CM and BRN after controlling for confounding factors. This study underscores the limitations of both conventional MRI and MR perfusion scans in differentiating recurrent CM from BRN. Histopathological examination remains essential for accurate diagnosis. Further research is needed to improve the reliability of non-invasive imaging and to guide the management of patients with these post-radiation events.

Brain diffusion MRI biomarkers after oncology treatments

In addition to providing a measurement of the tumor's size and dimensions, magnetic resonance imaging (MRI) provides excellent noninvasive radiographic detection of tumor location. The MRI technique is an important modality that has been shown to be useful in the prognosis, diagnosis, treatment planning, and evaluation of response and recurrence in solid cancers. Diffusion-weighted imaging (DWI) is an imaging technique that quantifies water mobility. This imaging approach is good for identifying sub-voxel microstructure of tissues, correlates with tumor cellularity, and has been proven to be valuable in the early assessment of cytotoxic treatment for a variety of malignancies. Diffusion tensor imaging (DTI) is an MRI method that assesses the preferred amount of water transport inside tissues. This enables precise measurements of water diffusion, which changes according to the direction of white matter fibers, their density, and myelination. This measurement corresponds to some related variables: fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), and others. DTI biomarkers can detect subtle changes in white matter microstructure and integrity following radiation therapy (RT) or chemoradiotherapy, which may have implications for cognitive function and quality of life. In our study, these indices were evaluated after brain chemoradiotherapy.

Clinically Driven Alpha/Beta Ratios for Melanoma Brain Metastases and Investigation of Biologically Effective Dose as a Predictor for Local Control After Radiosurgery: A Proof of Concept in a Retrospective Longitudinal Series of 274 Consecutive Lesions

BACKGROUND AND OBJECTIVES

Brain metastases (BM) develop in nearly half of the patients with advanced melanoma. The aim of this retrospective historical cohort study was to analyze radiological response of melanoma BM to single-fraction Gamma Knife radiosurgery (GKRS), in relation to biologically effective dose (BED) for various alpha/beta ratios.

METHODS

Included in the study were 274 lesions. Primary outcome was local control (LC). Mean marginal dose was 21.6 Gy (median 22, range 15-25). Biologically effective dose was calculated for an alpha/beta ratio of 3 (Gy 3 ), 5 (Gy 10 ), 10 (Gy 10 ), and 15 (Gy 15 ).

RESULTS

Receiver operating characteristic value for LC and BED was 85% (most statistically significant odds ratio 1.14 for BED Gy 15 , P = .006), while for LC and physical dose was 79% ( P = .02). When comparing equality of 2 receiver operating characteristic areas, this was statistically significant ( P = .02 and .03). Fractional polynomial regression revealed BED (Gy 10 and Gy 15 ) as statistically significant ( P = .05) with BED of more than 63 Gy 10 or 49 Gy 15 as relevant, also for higher probability of quick decrease in volume first month after GKRS and lower probability of radiation necrosis. Shorter irradiation time was associated with better LC ( P = .001), particularly less than 40 minutes (LC below 90%, P = .05).

CONCLUSION

BED Gy 10 and particularly Gy 15 were more statistically significant than physical dose for LC after GKRS for radioresistant melanoma BM. Irradiation time (per lesion) longer than 40 minutes was predictive for lower rates of LC. Such results need to be validated in larger cohorts.

Bibliometric and visualization analysis of radiation brain injury from 2003 to 2023

Background

Over the past two decades, the field of radiation brain injury has attracted the attention of an increasing number of brain scientists, particularly in the areas of molecular pathology and therapeutic approaches. Characterizing global collaboration networks and mapping development trends over the past 20 years is essential.

Objective

The aim of this paper is to examine significant issues and future directions while shedding light on collaboration and research status in the field of radiation brain injury.

Methods

Bibliometric studies were performed using CiteSpaceR-bibliometrix and VOSviewer software on papers regarding radiation brain injury that were published before November 2023 in the Web of Science Core Collection.

Results

In the final analysis, we found 4,913 records written in 1,219 publications by 21,529 authors from 5,007 institutions in 75 countries. There was a noticeable increase in publications in 2014 and 2021. The majority of records listed were produced by China, the United States, and other high-income countries. The largest nodes in each cluster of the collaboration network were Sun Yat-sen University, University of California-San Francisco, and the University of Toronto. Galldiks N, Barnett GH, Langen KJ and Kim JH are known to be core authors in the field. The top 3 keywords in that time frame are radiation, radiation necrosis, and radiation-therapy.

Conclusions

The objective and thorough bibliometric analysis also identifies current research hotspots and potential future paths, providing a retrospective perspective on RBI and offering useful advice to researchers choosing research topics. Future development directions include the integration of multi-omics methodologies and novel imaging techniques to improve RBI's diagnostic effectiveness and the search for new therapeutic targets.

Impact of Clinical Examination and Gamma Knife Surgery in Stage IV Breast Cancer With Brain Metastasis

Metastatic breast cancer often presents with significant diagnostic and treatment challenges. This case report highlights the crucial role of thorough clinical examination and history-taking in diagnosing and managing a patient with metastatic breast cancer, mainly focusing on the successful integration of Gamma Knife radiosurgery (GKRS). We present a case of a 68-year-old postmenopausal woman with metastatic breast cancer, initially presenting with a primary tumour in the left breast and later developing a solitary brain metastasis (BM) in the left temporal lobe. Following neoadjuvant chemotherapy and left mastectomy, the patient experienced involuntary movements in the right arm, leading to the discovery of the brain lesion. Critical to this diagnosis was a detailed clinical examination emphasising the importance of vigilant monitoring in cancer management. The patient underwent GKRS, offering a focused and less invasive treatment approach with favourable outcomes. This case underscores the value of clinical vigilance in managing complex breast cancer cases. The integration of GKRS as a targeted treatment modality for BM represents a pivotal aspect of modern oncological care, especially for patients with multiple treatment modalities. This report emphasizes the importance of clinical examination in the early detection of complications such as BM in breast cancer patients. Furthermore, it demonstrates the effectiveness of GKRS in managing such metastases, reinforcing its role as a valuable tool in the multidisciplinary treatment approach for advanced breast cancer.

Utility of a prognostic assessment tool to predict survival following surgery for brain metastases

Background

Brain metastases account for more than 50% of all intracranial tumors and are associated with poor outcomes. Treatment decisions in this highly heterogenous cohort remain controversial due to the myriad of treatment options available, and there is no clearly defined standard of care. The prognosis in brain metastasis patients varies widely with tumor type, extracranial disease burden and patient performance status. Decision-making regarding treatment is, therefore, tailored to each patient and their disease.

Methods

This is a retrospective cohort study assessing survival outcomes following surgery for brain metastases over a 50-month period (April 1, 2014-June 30, 2018). We compared predicted survival using the diagnosis-specific Graded Prognostic Assessment (ds-GPA) with actual survival.

Results

A total of 186 patients were included in our cohort. Regression analysis demonstrated no significant correlation between actual and predicted outcome. The most common reason for exclusion was insufficient information being available to the neuro-oncology multidisciplinary team (MDT) meeting to allow GPA calculation.

Conclusions

In this study, we demonstrate that "predicted survival" using the ds-GPA does not correlate with "actual survival" in our operated patient cohort. We also identify a shortcoming in the amount of information available at MDT in order to implement the GPA appropriately. Patient selection for aggressive therapies is crucial, and this study emphasizes the need for treatment decisions to be individualized based on patient and cancer clinical characteristics.

Treating brain metastases in metastatic breast cancer: outcomes after stereotactic radiosurgery examined in a retrospective, single-center cohort analysis

INTRODUCTION

We examined the role of receptor profiles and other prognostic factors in survival outcomes after stereotactic radiosurgery (SRS) for brain metastases in breast cancer patients, to help improve selection of candidates for SRS.

MATERIAL AND METHODS

We included 149 consecutive patients who received SRS between 2012 and 2019 at the University Hospital of Copenhagen, Rigshospitalet, Denmark. Overall survival (OS) following SRS was determined through the Kaplan-Meier method, while CNS progression-free survival (CNS-PFS) was determined through competing risk analysis. Prognostic factors for both OS and CNS-PFS were evaluated through uni- and multivariate Cox regression and Fine-Gray models, respectively. The proportional hazards assumptions were tested through Schoenfeld residuals, and non-proportionality was accounted for by the inclusion of time-dependent variables.

RESULTS

Median OS was 14.8 months for the entire cohort and was as follows for the four receptor profiles: 33.3 months for ER+/HER2+ (ER: estrogen receptor, HER2: human epidermal growth factor receptor 2), 11.0 months for ER+/HER2-, 17.7 months for ER-/HER2+, and 5.3 months for ER-/HER2-. In the multivariate model, the ER-/HER2- receptor profile (hazard ratio (HR): 2.00, 95% confidence interval (CI): 1.09-3.67) and the presence of extracranial visceral metastases (HR: 2.90, 95% CI: 1.53-5.50) were associated with worse OS. The ER+/HER2+ receptor profile (HR: 0.43, 95% CI: 0.19-0.96) and 5+ lines of treatment (HR: 0.40, 95% CI: 0.20-0.82) were both associated with improved OS. For CNS-PFS, 5+ lines of treatment (sub-distributional hazard ratio (SHR): 2.88, 95% CI: 1.06-7.81) was associated with worse CNS-PFS, while extracranial visceral metastases (SHR: 0.54, 95% CI: 0.30-0.97) was associated with reduced risk of CNS progression - which is primarily due to patients with extracranial metastases dying before developing new CNS progression.

CONCLUSION

Extracranial visceral disease and the ER-/HER2- receptor profile were associated with poor survival outcomes following SRS.

Causes of Death in Patients With Brain Metastases

BACKGROUND AND OBJECTIVES

Advances in targeted therapies and wider application of stereotactic radiosurgery (SRS) have redefined outcomes of patients with brain metastases. Under modern treatment paradigms, there remains limited characterization of which aspects of disease drive demise and in what frequencies. This study aims to characterize the primary causes of terminal decline and evaluate differences in underlying intracranial tumor dynamics in patients with metastatic brain cancer. These fundamental details may help guide management, patient counseling, and research priorities.

METHODS

Using NYUMets-Brain-the largest, longitudinal, real-world, open data set of patients with brain metastases-patients treated at New York University Langone Health between 2012 and 2021 with SRS were evaluated. A review of electronic health records allowed for the determination of a primary cause of death in patients who died during the study period. Causes were classified in mutually exclusive, but collectively exhaustive, categories. Multilevel models evaluated for differences in dynamics of intracranial tumors, including changes in volume and number.

RESULTS

Of 439 patients with end-of-life data, 73.1% died secondary to systemic disease, 10.3% died secondary to central nervous system (CNS) disease, and 16.6% died because of other causes. CNS deaths were driven by acute increases in intracranial pressure (11%), development of focal neurological deficits (18%), treatment-resistant seizures (11%), and global decline driven by increased intracranial tumor burden (60%). Rate of influx of new intracranial tumors was almost twice as high in patients who died compared with those who survived ( P < .001), but there was no difference in rates of volume change per intracranial tumor ( P = .95).

CONCLUSION

Most patients with brain metastases die secondary to systemic disease progression. For patients who die because of neurological disease, tumor dynamics and cause of death mechanisms indicate that the primary driver of decline for many may be unchecked systemic disease with unrelenting spread of new tumors to the CNS rather than failure of local growth control.

Plan Assessment Metrics for Dose Painting in Stereotactic Radiosurgery

Purpose

As radiation therapy treatment precision increases with advancements in imaging and radiation delivery, dose painting treatment becomes increasingly feasible, where targets receive a nonuniform radiation dose. The high precision of stereotactic radiosurgery (SRS) makes it a good candidate for dose painting treatments, but no suitable metrics to assess dose painting SRS plans exist. Existing dose painting assessment metrics weigh target overdose and underdose equally but are unsuited for SRS plans, which typically avoid target underdose more. Current SRS metrics also prioritize reducing healthy tissue dose through selectivity and dose fall-off, and these metrics assume single prescriptions. We propose a set of metrics for dose painting SRS that would meet clinical needs and are calculated with nonuniform dose painting prescriptions.

Methods and Materials

Sample dose painting SRS prescriptions are first created from Gamma Knife SRS cases, apparent diffusion coefficient magnetic resonance images, and various image-to-prescription functions. Treatment plans are found through semi-infinite linear programming optimization and using clinically determined isocenters, then assessed with existing and proposed metrics. Modified versions of SRS metrics are proposed, including coverage, selectivity, conformity, efficiency, and gradient indices. Quality factor, a current dose painting metric, is applied both without changes and with modifications. A new metric, integral dose ratio, is proposed as a measure of target overdose.

Results

The merits of existing and modified metrics are demonstrated and discussed. A modified conformity index using mean or minimum prescription dose would be suitable for dose painting SRS with integral or maximum boost methods, respectively. Either modified efficiency index is a suitable replacement for the existing gradient index.

Conclusions

The proposed modified SRS metrics are appropriate measures of plan quality for dose painting SRS plans and have the advantage of giving equal values as the original SRS metrics when applied to single-prescription plans.

Proton craniospinal irradiation with bevacizumab and pembrolizumab for leptomeningeal disease: a case report

Leptomeningeal disease (LMD) remains a challenging condition with a dismal prognosis. In this case study, we report partial response of LMD in a patient with metastatic large cell neuroendocrine carcinoma following treatment with proton craniospinal irradiation (CSI), bevacizumab, and pembrolizumab. Two years after the initial diagnosis, he presented with LMD. He underwent proton CSI with bevacizumab followed by combination therapy with pembrolizumab and bevacizumab. He had a partial disease response with progression-free survival after LMD diagnosis of 4.6 months. He unfortunately developed pembrolizumab induced hypophysitis, after which he experienced rapid neurologic clinical progression. Overall, this novel combination led to a durable partial response which warrants prospective evaluation.

Cost-effectiveness analysis of 3 radiation treatment strategies for patients with multiple brain metastases

Background

Patients diagnosed with multiple brain metastases often survive for less than 2 years, and clinicians must carefully evaluate the impact of interventions on quality of life. Three types of radiation treatment are widely accepted for patients with multiple brain metastases: Whole brain radiation therapy (WBRT), hippocampal avoidance whole-brain radiation therapy (HA-WBRT), and stereotactic radiosurgery (SRS). WBRT, the standard option, is less costly than its newer alternatives but causes more severe adverse effects such as memory loss. To determine whether the cost-effectiveness ratio of HA-WBRT and SRS are superior to WBRT, we used published data to simulate cases of multiple brain metastases.

Methods

We designed a Markov model using data from previously published studies to simulate the disease course of patients with 5 to 15 brain metastases and determine the cost-effectiveness of HA-WBRT and SRS relative to WBRT. Incremental cost-effectiveness ratios (ICERs) were calculated and compared against a willingness-to-pay threshold of $100 000 per quality-adjusted life year.

Results

SRS met the threshold for cost-effectiveness, with ICERs ranging $41 198-$54 852 for patients with 5 to 15 brain metastases; however, HA-WBRT was not cost-effective, with an ICER of $163 915 for all simulated patients. Model results were robust to sensitivity analyses.

Conclusions

We propose that SRS, but not HA-WBRT, should be offered to patients with multiple brain metastases as a treatment alternative to standard WBRT. Incorporating these findings into clinical practice will help promote patient-centered care and decrease national healthcare expenditures, thereby addressing issues around health equity and access to care.

Tyrosine kinase inhibitors in HER2-positive breast cancer brain metastases: A systematic review and meta-analysis

BACKGROUND

Small tyrosine kinase inhibitors (TKIs) show activity against breast cancer brain metastases (BCBM) of the human epidermal growth factor receptor 2 (HER2)-positive subtype. This meta-analysis aimed to objectively explore the efficacy and safety of TKIs.

METHODS

Electronic databases were searched for relevant clinical trials. We conducted a pairwise meta-analysis, pooled analysis, and estimated summary survival curves to compare survival outcomes following TKIs therapy for BCBM patients using Stata version 16.0 or R x64 4.0.5.

RESULTS

Thirteen clinical trials involving 987 HER2-positive BCBM patients were analyzed. A trend of longer progression-free survival (PFS) was observed in the TKI-containing arm compared to the non-TKI-containing arm (hazard ratio = 0.64, 95% confidence interval [CI]: 0.35-1.15, p = 0.132), although the difference is not statistically significant. Summary survival curves reported the summary median PFS and overall survival were 7.9 months and 12.3 months. Subgroup analysis revealed that TKIs combined with capecitabine (TKI + Cap) regimens resulted in improved survival outcomes. Tucatinib may be more effective in BCBM patients. The main grade 3-5 adverse events (AEs) were diarrhea (22%, 95% CI: 14%-32%), neutropenia (11%, 95% CI: 5%-18%), hepatic toxicity (7%, 95% CI: 1%-16%), and sensory neuropathy (6%, 95% CI: 2%-12%).

CONCLUSION

TKIs therapy improved the survival outcomes of HER2-positive BCBM patients, especially when combined with capecitabine and tolerable AEs. We also identified the clinical value of tucatinib, which appears to be the most favorable TKI drug for BCBM patients.

Incidence and clinical profile of brain metastasis treated with whole brain radiotherapy in a tertiary hospital in eastern India: A retrospective audit

Introduction

Management of brain metastases (BM) is witnessing marked advancement worldwide and modern technologies with better outcomes are gradually being adopted in developing countries. However, data regarding current practice in this field is lacking from the Indian subcontinent prompting us to plan the current study.

Materials and Methods

A retrospective, single institutional audit was performed on 112 patients with solid tumors metastasizing to the brain treated over the last 4 years at a tertiary care center in eastern India, of which 79 were ultimately evaluable. Demography, patterns of incidence, and overall survival (OS) were determined.

Results

The prevalence of BM was 5.65% among all patients with solid tumors. The median age was 55 years with a slight male preponderance. Lung followed by breast were the most common primary subsites. Multiple BM (54%), left-sided (61%), and frontal lobe lesions (54%) were the more common. Metachronous BM was found in 76% of patients. All patients received whole brain radiation therapy (WBRT). The median OS for the entire cohort was 7 months (95% confidence interval [CI]: 4 - 19 months). The median OS for lung and breast primaries were 6.5 and 8 months and for recursive partitioning analysis (RPA) classes I, II, and III the OS were 11.5, 7, and 3 months, respectively. Median OS did not differ by number of or other sites of metastases.

Conclusions

The outcomes from our series about BM from solid tumors in patients from eastern Indian are in congruence to those available in the literature. Patients with BM are still largely treated with WBRT in resource-limited settings.

Extended Survival in Patients With Non-Small-Cell Lung Cancer-Associated Brain Metastases in the Modern Era

BACKGROUND

Brain metastases (BM) have long been considered a terminal diagnosis with management mainly aimed at palliation and little hope for extended survival. Use of brain stereotactic radiosurgery (SRS) and/or resection, in addition to novel systemic therapies, has enabled improvements in overall and progression-free (PFS) survival.

OBJECTIVE

To explore the possibility of extended survival in patients with non-small-cell lung cancer (NSCLC) BM in the current era.

METHODS

During the years 2008 to 2020, 606 patients with NSCLC underwent their first Gamma Knife SRS for BM at our institution with point-of-care data collection. We reviewed clinical, molecular, imaging, and treatment parameters to explore the relationship of such factors with survival.

RESULTS

The median overall survival was 17 months (95% CI, 13-40). Predictors of increased survival in a multivariable analysis included age <65 years ( P < .001), KPS ≥80 ( P < .001), absence of extracranial metastases ( P < .001), fewer BM at first SRS (≤3, P = .003), and targeted therapy ( P = .005), whereas chemotherapy alone was associated with shorter survival ( P = .04). In a subgroup of patients managed before 2016 (n = 264), 38 (14%) were long-term survivors (≥5 years), of which 16% required no active cancer treatment (systemic or brain) for ≥3 years by the end of their follow-up.

CONCLUSION

Long-term survival in patients with brain metastases from NSCLC is feasible in the current era of SRS when combined with the use of effective targeted therapeutics. Of those living ≥5 years, the chance for living with stable disease without the need for active treatment for ≥3 years was 16%.

Time interval from diagnosis to treatment of brain metastases with stereotactic radiosurgery is not associated with radionecrosis or local failure

Introduction

Brain metastases are the most common intracranial tumor diagnosed in adults. In patients treated with stereotactic radiosurgery, the incidence of post-treatment radionecrosis appears to be rising, which has been attributed to improved patient survival as well as novel systemic treatments. The impacts of concomitant immunotherapy and the interval between diagnosis and treatment on patient outcomes are unclear.

Methods

This single institution, retrospective study consisted of patients who received single or multi-fraction stereotactic radiosurgery for intact brain metastases. Exclusion criteria included neurosurgical resection prior to treatment and treatment of non-malignant histologies or primary central nervous system malignancies. A univariate screen was implemented to determine which factors were associated with radionecrosis. The chi-square test or Fisher’s exact test was used to compare the two groups for categorical variables, and the two-sample t-test or Mann-Whitney test was used for continuous data. Those factors that appeared to be associated with radionecrosis on univariate analyses were included in a multivariable model. Univariable and multivariable Cox proportional hazards models were used to assess potential predictors of time to local failure and time to regional failure.

Results

A total of 107 evaluable patients with a total of 256 individual brain metastases were identified. The majority of metastases were non-small cell lung cancer (58.98%), followed by breast cancer (16.02%). Multivariable analyses demonstrated increased risk of radionecrosis with increasing MRI maximum axial dimension (OR 1.10, p=0.0123) and a history of previous whole brain radiation therapy (OR 3.48, p=0.0243). Receipt of stereotactic radiosurgery with concurrent immunotherapy was associated with a decreased risk of local failure (HR 0.31, p=0.0159). Time interval between diagnostic MRI and first treatment, time interval between CT simulation and first treatment, and concurrent immunotherapy had no impact on incidence of radionecrosis or regional failure.

Discussion

An optimal time interval between diagnosis and treatment for intact brain metastases that minimizes radionecrosis and maximizes local and regional control could not be identified. Concurrent immunotherapy does not appear to increase the risk of radionecrosis and may improve local control. These data further support the safety and synergistic efficacy of stereotactic radiosurgery with concurrent immunotherapy.

Screening and treatment of brain metastasis from papillary thyroid carcinoma: a case series

BACKGROUND

The brain metastasis from differentiated thyroid carcinoma (DTC) is a rare condition and its prognosis is poor. The standard protocol for screening and treatment of patients with brain metastases from papillary thyroid cancer (PTC) remains controversial. This report aims to share the experience of a single center in the management of brain metastases from DTC.

MATERIAL AND METHODS

Five patients with brain metastases were identified from 5000 patients with DTC attending the department of nuclear medicine, Hospital 108 between 2016 to 2022. The statistical software Statistical Package for Social Sciences (SPSS) 20.0 (SPSS Inc., Chicago, IL, USA) was used to analyze the data.

RESULTS

Five patients with brain metastases from DTC were revealed by MRI, ¹⁸F-FDG PET/CT with contrast enhancement, and ¹³¹I-SPECT/CT. The median time of overall survival (OS) was 15 months, ranging from 10 to 65 months. Two out of the five patients underwent surgery, and futher 2 patients were treated with stereotactic surgery (SRS). All patients are still alive.

CONCLUSIONS

Brain metastases from DTC are rare. MRI is the preferred imaging mobility to screen brain lesions in DTC. The primary treatment modalities are surgery and SRS.

Concurrent Administration of Immune Checkpoint Inhibitors and Stereotactic Radiosurgery Is Well-Tolerated in Patients With Melanoma Brain Metastases: An International Multicenter Study of 203 Patients

BACKGROUND

Melanoma brain metastases are commonly treated with stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICIs). However, the toxicity of these 2 treatments is largely unknown when administered concurrently.

OBJECTIVE

To evaluate the risk of radiation necrosis (RN) with concurrent and nonconcurrent SRS and ICIs.

METHODS

The guidelines from the Strengthening the Reporting of Observational Studies in Epidemiology checklist were used. Inverse probability of treatment weighting, univariable and multivariable logistic regression, and the Kaplan-Meier method was utilized.

RESULTS

There were 203 patients with 1388 brain metastases across 11 international institutions in 4 countries with a median follow-up of 15.6 months. The rates of symptomatic RN were 9.4% and 8.2% in the concurrent and nonconcurrent groups, respectively ( P =.766). On multivariable logistic regression, V12 ≥ 10 cm 3 (odds ratio [OR]: 2.76; P =.006) and presence of BRAF mutation (OR: 2.20; P =.040) were associated with an increased risk of developing symptomatic RN; the use of concurrent over nonconcurrent therapy was not associated with an increased risk (OR: 1.06; P =.877). There were 20 grade 3 toxic events reported, and no grade 4 events reported. One patient experienced a grade 5 intracranial hemorrhage. The median overall survival was 36.1 and 19.8 months for the concurrent and nonconcurrent groups (log-rank P =.051), respectively.

CONCLUSION

Concurrent administration of ICIs and SRS are not associated with an increased risk of RN. Tumors harboring BRAF mutation, or perhaps prior exposure to targeted agents, may increase this risk. Radiosurgical optimization to maintain V12 < 10 cm 3 is a potential strategy to reduce the risk of RN.

ISRS Technical Guidelines for Stereotactic Radiosurgery: Treatment of Small Brain Metastases (≤1 cm in Diameter)

PURPOSE

The objective of this literature review was to develop International Stereotactic Radiosurgery Society (ISRS) consensus technical guidelines for the treatment of small, ≤1 cm in maximal diameter, intracranial metastases with stereotactic radiosurgery. Although different stereotactic radiosurgery technologies are available, most of them have similar treatment workflows and common technical challenges that are described.

METHODS AND MATERIALS

A systematic review of the literature published between 2009 and 2020 was performed in Pubmed using the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) methodology. The search terms were limited to those related to radiosurgery of brain metastases and to publications in the English language.

RESULTS

From 484 collected abstract 37 articles were included into the detailed review and bibliographic analysis. An additional 44 papers were identified as relevant from a search of the references. The 81 papers, including additional 7 international guidelines, were deemed relevant to at least one of five areas that were considered paramount for this report. These areas of technical focus have been employed to structure these guidelines: imaging specifications, target volume delineation and localization practices, use of margins, treatment planning techniques, and patient positioning.

CONCLUSION

This systematic review has demonstrated that Stereotactic Radiosurgery (SRS) for small (1 cm) brain metastases can be safely performed on both Gamma Knife (GK) and CyberKnife (CK) as well as on modern LINACs, specifically tailored for radiosurgical procedures, However, considerable expertise and resources are required for a program based on the latest evidence for best practice.

WDR5 is a prognostic biomarker of brain metastasis from non-small cell lung cancer

Background

Lung cancer (LC) is the most frequent caner type and causes the most cancer-related death. Brain metastases (BM) are the deadliest complications of lung cancer, and the prognostic biomarkers of BM are urgently needed.

Materials and methods

In our study, we established an inception cohort including 122 patients with asynchronous BM from NSCLC, and further selected 70 patients who received surgical resection, which compromised the validation cohort. With immunohistochemistry, we investigated the expression of WDR5 in the cohort. By chi-square method, the correlations between WDR5 and clinicopathological factors were analyzed. The prognostic indicators were analyzed with the univariate analysis, and independent prognostic factors were identified by multivariate analysis with Cox-regression model.

Results

WDR5 is frequently expressed in the cytoplasm of BM from NSCLC. Patients with low or high expression of WDR5 account for 60% and 40% respectively. High expression of WDR5 indicates poor prognosis of BM from NSCLC (P=0.001). In addition to WDR5, KPS is also a prognostic factor of BM, and high KPS predicts favorable prognosis (P=0.006). WDR5 is an independent prognostic biomarker for poor prognosis of BM from NSCLC, with the cancer-related odds as 2.48.

Conclusions

High expression of WDR5 can predict the poor prognosis of BM, and WDR5 is an independent prognostic biomarker of BM from NSCLC. Patients with WDR5 overexpression are more high-risk to suffer BM-related death and should receive more intense post-operational supervision.

Characterizing metastatic uveal melanoma patients who develop symptomatic brain metastases

Metastatic uveal melanoma (mUM) is an advanced ocular malignancy characterized by a hepatotropic pattern of spread. As the incidence of brain metastases (BM) in mUM patients has been thought to be low, routine CNS surveillance has not been recommended. Notably, no formal assessment of BM incidence in mUM has to date been published to support this clinical practice. We aimed to determine the true rate of BM in mUM and to clarify the clinical and genomic risk factors associated with BM patients through a collaborative multicenter, retrospective research effort. Data collected from 1,845 mUM patients in databases across four NCI-designated comprehensive cancer centers from 2006-2021 were retrospectively analyzed to identify patients with BM. Brain imaging in most cases were performed due to onset of neurological symptoms and not for routine surveillance. An analysis of demographics, therapies, gene expression profile, tumor next generation sequencing (NGS) data, time to metastasis (brain or other), and survival in the BM cohort was completed. 116/1,845 (6.3%) mUM patients were identified with BM. The median age at time of UM diagnosis was 54 years old (range: 18-77). The median time to any metastasis was 4.2 years (range: 0-30.8). The most common initial metastatic site was the liver (75.9%). 15/116 (12.9%) BM patients presented with BM at the time of initial metastatic diagnosis. Median survival after a diagnosis of BM was 7.6 months (range: 0.4-73.9). The median number of organs involved at time of BM diagnosis was 3 (range: 1-9). DecisionDX-UM profiling was completed on 13 patients: 10-Class 2, 2-Class 1B, and 1-Class 1A. NGS and cytogenetic data were available for 34 and 21 patients, respectively. BM was identified in 6.3% of mUM cases and was associated with high disease burden and a median survival of under 8 months once diagnosed. Since most patients in this cohort were symptomatic, the incidence of asymptomatic BM remains unknown. These data suggest the use of routine brain imaging in all mUM patients at risk for developing BM for early detection.

Flattening filter free Stereotactic radiosurgery for brain metastases using dynamic conformal arcs: 6 MV or 10 MV?

Introduction:

Stereotactic radiosurgery (SRS) has proven itself as an effective tool in the treatment of intracranial lesions. Image-guided high dose single fraction treatments have the potential to deliver ablative doses to tumours; however, treatment times can be long. Flattening filter free (FFF) beams are available on most modern linacs and offer a higher dose rate compared to conventional flattened beams which should reduce treatment times. This study aimed to compare 6 MV FFF and 10 MV FFF to a 6 MV flattened beam for single fraction dynamic conformal arc SRS for a Varian Truebeam linac.

Materials and methods:

In total, 21 individual clinical treatment plans for 21 brain metastases treated with 6 MV were retrospectively replanned using both 6 MV FFF and 10 MV FFF. Plan quality and efficiency metrics were evaluated by analysing dose coverage, dose conformity, dose gradients, dose to normal brain, beam-on-time (BOT), treatment time and monitor units.

Results:

FFF resulted in a significant reduction in median BOT for both 6 MV FFF (57·9%; p < 0·001) and 10 MV FFF (76·3%; p < 0·001) which led to reductions in treatment times of 16·8 and 21·5% respectively. However, 6 MV FFF showed superior normal brain dose sparing (p < 0·001) and dose gradient (p < 0·001) compared to 10 MV FFF. No differences were observed for conformity.

Conclusion:

6 MV FFF offers a significant reduction in average treatment time compared to 6 MV (3·7 minutes; p = 0·002) while maintaining plan quality.

Design Principles of Hybrid Nanomaterials for Radiotherapy Enhanced by Photodynamic Therapy

Radiation (RT) remains the most frequently used treatment against cancer. The main limitation of RT is its lack of specificity for cancer tissues and the limited maximum radiation dose that can be safely delivered without damaging the surrounding healthy tissues. A step forward in the development of better RT is achieved by coupling it with other treatments, such as photodynamic therapy (PDT). PDT is an anti-cancer therapy that relies on the light activation of non-toxic molecules-called photosensitizers-to generate ROS such as singlet oxygen. By conjugating photosensitizers to dense nanoscintillators in hybrid architectures, the PDT could be activated during RT, leading to cell death through an additional pathway with respect to the one activated by RT alone. Therefore, combining RT and PDT can lead to a synergistic enhancement of the overall efficacy of RT. However, the involvement of hybrids in combination with ionizing radiation is not trivial: the comprehension of the relationship among RT, scintillation emission of the nanoscintillator, and therapeutic effects of the locally excited photosensitizers is desirable to optimize the design of the hybrid nanoparticles for improved effects in radio-oncology. Here, we discuss the working principles of the PDT-activated RT methods, pointing out the guidelines for the development of effective coadjutants to be tested in clinics.

Fractionated Gamma Knife radiosurgery after cyst aspiration for large cystic brain metastases: case series and literature review

Tumor cyst aspiration followed by Gamma Knife radiosurgery (GKRS) for large cystic brain metastases is a reasonable and effective management strategy. However, even with aspiration, the target lesion tends to exceed the dimensions of an ideal target for stereotactic radiosurgery. In this case, the local tumor control rate and the risk of complication might be a critical challenge. This study is aimed to investigate whether fractionated GKRS (f-GKRS) could solve these problems. Between May 2018 and April 2021, eight consecutive patients with nine lesions were treated with f-GKRS in five or ten sessions after cyst aspiration. The aspiration was repeated as needed throughout the treatment course to maintain the cyst size and shape. The patient characteristics, radiologic tumor response, and clinical course were reviewed using medical records. The mean follow-up duration was 10.2 (2-28) months. The mean pre-GKRS volume and maximum diameter were 16.7 (5-55.8) mL and 39.0 (31-79) mm, respectively. The mean tumor volume reduction achieved by aspiration was 55.4%. The tumor volume decreased for all lesions, and symptoms were alleviated in all patients. The median overall survival was 10.0 months, and the estimated 1-year survival rate was 41.7% (95% CI: 10.9-70.8%). The local tumor control rate was 100%. No irradiation-related adverse events were observed. f-GKRS for aspirated cystic brain metastasis is a safe, effective, and less invasive management option for large cystic brain metastases.

Aggressive Stereotactic Radiosurgery Coupled With Immune and Targeted Therapy for Recurrent Melanoma Brain Metastases: A Case Report and Literature Review

Melanoma is a complex disease with a high propensity for brain metastatic spread. Stereotactic radiosurgery (SRS) is a minimally invasive procedure to treat intracranial metastasis with a high rate of local tumor control. In this report, we describe the ongoing management of a patient with interval development of both new and recurrent brain metastases that required seven SRS procedures for a total of 48 brain metastases during a two-year interval while receiving concurrent immunotherapy with ipilimumab and nivolumab. The most recent imaging of the patient showed three brain areas of likely tumor progression despite maintenance nivolumab, and the treatment was recently changed to encorafenib and binimetinib. Combined management with immunotherapy, initial craniotomy, and repeated SRS for new brain metastases resulted in extended survival while preserving neurological function and reducing adverse treatment effects in a patient with advanced metastatic brain melanoma.

Impact of socio-economic factors on radiation treatment after resection of metastatic brain tumors: trends from a private insurance database

BACKGROUND

Stereotactic radiosurgery (SRS) to the surgical bed of resected brain metastases is now considered the standard of care due to its advantages over whole brain radiation therapy (WBRT). Despite the upward trend in SRS adoption since the 2000s, disparities have been reported suggesting that socio-economic factors can influence SRS utilization.

OBJECTIVE

To analyze recent trends in SRS use and identify factors that influence treatment.

METHODS

We conducted a retrospective cohort study with the Optum Commercial Claims and Encounters Database and included all patients from 2004 to 2021 who received SRS or WBRT within 60 days after resection of tumors metastatic to the brain.

RESULTS

A total of 3495 patients met the inclusion and exclusion criteria. There were 1998 patients in the SRS group and 1497 patients in the WBRT group. SRS use now supersedes WBRT by a wide margin. Lung, breast and colon were the most common sites of primary tumor. Although we found no significant differences based on race among the treatment groups, patients with annual household income greater than $75,000 and those with some college or higher education are significantly more likely to receive SRS (OR 1.44 and 1.30; 95% CI 1.18-1.76 and 1.08-1.56; P = 0.001 and 0.005, respective). Patients with Elixhauser Comorbidity Index of three or more were significantly more likely to receive SRS treatment.

CONCLUSION

The use of post-surgical SRS for brain metastasis has increased significantly over time, however education and income were associated with differential SRS utilization.

A deep convolutional neural network-based automatic detection of brain metastases with and without blood vessel suppression

OBJECTIVES

To develop an automated model to detect brain metastases using a convolutional neural network (CNN) and volume isotropic simultaneous interleaved bright-blood and black-blood examination (VISIBLE) and to compare its diagnostic performance with the observer test.

METHODS

This retrospective study included patients with clinical suspicion of brain metastases imaged with VISIBLE from March 2016 to July 2019 to create a model. Images with and without blood vessel suppression were used for training an existing CNN (DeepMedic). Diagnostic performance was evaluated using sensitivity and false-positive results per case (FPs/case). We compared the diagnostic performance of the CNN model with that of the twelve radiologists.

RESULTS

Fifty patients (30 males and 20 females; age range 29-86 years; mean 63.3 ± 12.8 years; a total of 165 metastases) who were clinically diagnosed with brain metastasis on follow-up were used for the training. The sensitivity of our model was 91.7%, which was higher than that of the observer test (mean ± standard deviation; 88.7 ± 3.7%). The number of FPs/case in our model was 1.5, which was greater than that by the observer test (0.17 ± 0.09).

CONCLUSIONS

Compared to radiologists, our model created by VISIBLE and CNN to diagnose brain metastases showed higher sensitivity. The number of FPs/case by our model was greater than that by the observer test of radiologists; however, it was less than that in most of the previous studies with deep learning.

KEY POINTS

• Our convolutional neural network based on bright-blood and black-blood examination to diagnose brain metastases showed a higher sensitivity than that by the observer test. • The number of false-positives/case by our model was greater than that by the previous observer test; however, it was less than those from most previous studies. • In our model, false-positives were found in the vessels, choroid plexus, and image noise or unknown causes.

How to dose-stage large or high-risk brain metastases: an alternative two-fraction radiosurgical treatment approach

OBJECTIVE

The authors sought to evaluate clinical outcome in patients with large, high-risk brain metastases (BMs) treated with different dose strategies by use of two-fraction dose-staged Gamma Knife radiosurgery (GKRS).

METHODS

A retrospective analysis was performed with data from 142 patients from two centers who had been treated with two-fraction dose-staged GKRS between June 2015 and January 2020. Depending on the changes in marginal dose between the first (GKRS1) and second (GKRS2) GKRS treatments, the study population was divided into three treatment groups: dose escalation, dose maintenance, and dose de-escalation.

RESULTS

The 142 study patients underwent two-fraction dose-staged GKRS treatments for 166 large, high-risk BMs. The median tumor volume of 7.4 cm3 decreased significantly from GKRS1 to GKRS2 (4.4 cm3; p < 0.001), and to the last follow-up (1.8 cm3; p < 0.001). These significant differences in BM volume reduction were achieved in all three treatment groups. However, differences according to the primary tumor histology were apparent: while dose maintenance seemed to be the most effective treatment strategy for BMs from lung cancer or melanoma, dose escalation was the most beneficial treatment option for BMs from breast, gastrointestinal, or genitourinary cancer. Of note, the vast majority of patients who underwent dose-staged BM treatment did not show any significant postradiosurgical complications.

CONCLUSIONS

In patients with large, high-risk BMs, dose-staged GKRS treatment represents an effective local treatment method with acceptable complication risks. Different dose-strategy options are available that may be chosen according to the primary tumor histology and treatment volume but may also be tailored to the findings at GKRS2.

Histopathology and surgical outcome of symptomatic treatment-related changes after gamma knife radiosurgery in patients with brain metastases

A late-onset treatment-related changes (TRCs), which represent radiographic radiation necrosis (RN), frequently occur after stereotactic radiosurgery (SRS) for brain metastases and often need surgical treatment. This study aimed to validate the true pathology and investigate clinical implication of surgically resected TRCs on advanced magnetic resonance imaging (MRI). Retrospective analyses of 86 patients who underwent surgical resection after radiosurgery of brain metastases were performed. Fifty-four patients displayed TRCs on preoperative MRI, comprising pure RN in 19 patients (TRC-RN group) and mixed viable tumor cells in 35 patients (TRC-PD group). Thirty-two patients revealed the consistent diagnosis of progressive disease in both MRI and histopathology (PD-PD group). The TRC-PD group showed larger prescription isodose volume (9.4 cm3) than the TRC-RN (4.06 cm3, p = 0.014) group and a shorter time interval from SRS to preoperative MRI diagnosis (median 4.07 months) than the PD-PD group (median 8.77 months, p = 0.004). Progression-free survival was significantly different among the three groups (p < 0.001), but not between TRC-RN and TRC-PD (post hoc test, p = 1.00), while no difference was observed in overall survival (p = 0.067). Brain metastases featured as TRCs after SRS frequently contained viable tumor cells. However, this histologic heterogeneity had a minor impact on benign local prognosis of TRCs after surgical resection.

A Century of Fractionated Radiotherapy: How Mathematical Oncology Can Break the Rules

Radiotherapy is involved in 50% of all cancer treatments and 40% of cancer cures. Most of these treatments are delivered in fractions of equal doses of radiation (Fractional Equivalent Dosing (FED)) in days to weeks. This treatment paradigm has remained unchanged in the past century and does not account for the development of radioresistance during treatment. Even if under-optimized, deviating from a century of successful therapy delivered in FED can be difficult. One way of exploring the infinite space of fraction size and scheduling to identify optimal fractionation schedules is through mathematical oncology simulations that allow for in silico evaluation. This review article explores the evidence that current fractionation promotes the development of radioresistance, summarizes mathematical solutions to account for radioresistance, both in the curative and non-curative setting, and reviews current clinical data investigating non-FED fractionated radiotherapy.

Analysis of prognostic factors in patients with brain metastases affecting survival

INTRODUCTION

Brain metastases (BM) are associated with dismal prognosis as they cause significant morbidity and affect the quality of life of patients. Management of BM depends on the following factors: age, patient performance, size and the number of lesions, location of the tumor, comorbidities, primary tumor type, and extracranial disease burden. In the present study, the pattern of occurrence, clinical characteristics, treatment outcome of brain metastases, and factors, tumor characteristics, and treatment that may impact BM patients' overall survival were analyzed.

METHODS

Retrospective analysis of medical records of 116 patients with histologically proven primary site solid tumors with brain metastases was done in the present study. Clinicoradiological and pathological parameters were documented. The relationship between variables and outcome was assessed by univariate analysis using the Cox proportional regression model to reach a significance of p < 0.05, to determine independent predictors of overall survival.

RESULTS

One hundred sixteen patients of BM from various solid malignancies were included. Age ranged from 18 to 81 years (median 53.5). One hundred four patients received WBRT with a dose range of 8-40Gy/1-15fr, 7 received SRS with a dose of 18-24Gy depending on the size of the metastatic lesion, and 2 received SRT 27-33Gy/3fr. At the time of final analysis, 47 patients with BM had expired, 60 were lost to follow-up, and 9 were alive. Median survival was 8.25 (0.5-32.5 months) months. Female gender (χ² = 8.423; p = 0.015), RPA I (χ² = 9.353; p = 0.05), and metachronous BM (χ² = 3.793; p = 0.03) were associated with better survival. Patients with age 41-50 years, adenocarcinoma lung histology, and supratentorial location survived more than 2 years but did not show any statistical significance.

CONCLUSION

Brain metastases portend a very dismal prognosis. Certain clinicoradiological and pathologic factors have been identified to affect survival. More prospective multicentric trials, with a larger sample size, need to be conducted to assess the benefit of radiation in patients with limited life expectancy and identify prognostic and predictive factors for survival.

Anti-PD1 Therapy Plus Whole-Brain Radiation Therapy May Prolong PFS in Selected Non-Small Cell Lung Cancer Patients with Brain Metastases: A Retrospective Study

Background

Whole-brain radiotherapy (WBRT) remains an essential modality of treatment for brain metastases (BMs) derived from non-small cell lung cancer (NSCLC) patients and anti-PD-1 therapy has demonstrated intracranial responses in these patients. We aimed to evaluate if the combination of the two treatments could yield additive efficacy.

Methods

A retrospective review of our institution’s database was carried out to identify NSCLC patients with BMs who had been treated with anti-PD1 therapy and/or WBRT between 2015 and 2020. Patient characteristics, main outcomes, including progression-free survival (PFS) and overall survival (OS), and factors affecting these outcomes were analyzed. SPSS 24 was used for statistical analysis. Appropriate statistical tests were employed according to the type of data.

Results

Overall, 21 NSCLC BM patients were identified that had received WBRT. Of these, ten had been additionally treated with anti-PD1 therapy within 30 days of WBRT initiation. Median PFS was 3 (95% CI 0.8–5.1) months with WBRT alone versus 11 (95% CI 6.3–15.6) months with combined treatment. Risk of disease progression was 71% lower with the combined approach (HR 0.29, 95% CI 0.11–0.80; p=0.016). A trend toward improved OS was also observed with the combined approach (HR 0.33, 95% CI 0.08–1.12; p=0.107). Concurrent treatment (p=0.028) and male sex (p=0.052) were associated with improved PFS, while OS was associated only with age (p=0.02).

Conclusion

Concurrent WBRT and anti-PD1 therapy may delay progression and improve survival in BM patients with confirmed EGFR- and ALK-negative NSCLC histology. Prospective studies are warranted to validate and elucidate on the additive effect of the two modalities.

Radiation Plus Anti-PD-1 Therapy for NSCLC Brain Metastases: A Retrospective Study

BACKGROUND

Radiation therapy (RT) is the mainstay of brain metastases (BMs), and anti-PD-1 blockade has led to intracranial responses in non-small cell lung carcinoma (NSCLC) patients with BMs.

OBJECTIVE

This study aimed to evaluate the efficacy and safety of adding anti-PD-1 blockade to RT in the management of NSCLC patients with BM in terms of survival outcome.

MATERIALS AND METHODS

We retrospectively reviewed 70 NSCLC patients with BMs who were treated with whole brain radiation therapy (WBRT) between January 2016 and January 2021. Of the 70 patients, 29 additionally received anti-PD-1 therapy within 30 days of WBRT initiation. Baseline characteristics of the patients and efficacy outcomes such as progression-free survival (PFS) and overall survival (OS) were statistically compared using SPSS v26. Results were obtained using the Chi-square test/Fisher exact test, t-test, Kaplan-Meier, and Cox regression survival analyses.

RESULTS

The median survival for the entire cohort was 24 months (95% CI, 19.5-28.5). The median survival times for WBRT alone and WBRT plus anti-PD-1 therapy cohorts were 20 months (95% CI, 11.6-28.3) and 27 months (95% CI, 19.5-28.5), respectively (p=0.035). There was no statistical difference in PFS for the treatment cohorts (median PFS for WBRT alone: 7 months vs. 12 months for WBRT plus anti-PD-1, p=0.247). In EGFR wild-type subgroup (n=31), both PFS (p=0.037) and OS (p=0.012) were significantly improved. Only the treatment group (WBRT plus anti-PD-1) was a significant predictor of OS on univariate and multivariate analyses (p=0.040). There were no significant differences in adverse events among the treatment groups.

CONCLUSIONS

NSCLC patients with BM receiving additional anti-PD-1 therapy may derive better OS than WBRT alone without any increase in adverse events. Prospective well-designed studies are warranted to validate and elucidate the additive effects of the two modalities in this group of patients.

Gamma Knife Radiosurgery-Based Combination Treatment Strategies Improve Survival in Patients With Central Nervous System Metastases From Epithelial Ovarian Cancer: A Retrospective Analysis of Two Academic Institutions in Korea and Taiwan

Central nervous system (CNS) metastases from epithelial ovarian cancer (EOC) are rare. We investigated the clinico-pathological prognostic factors of patients with CNS metastases from EOC and compared the outcomes of various treatment modalities. We retrospectively reviewed the records of patients with CNS metastases from EOC between 2000 and 2020. Information on the clinical and pathological characteristics, treatment, and outcomes of these patients was retrieved from Samsung Medical Center and National Taiwan University Hospital. A total of 94 patients with CNS metastases were identified among 6,300 cases of EOC, resulting in an incidence of 1.49%. Serous histological type [hazard ratio (HR): 0.49 (95% confidence interval [CI] 0.25-0.95), p=0.03], progressive disease [HR: 2.29 (95% CI 1.16-4.54), p=0.01], CNS involvement in first disease relapse [HR: 0.36 (95% CI 0.18-0.70), p=0.002], and gamma knife radiosurgery (GKS)-based combination treatment for EOC patients with CNS lesions [HR: 0.59 (95% CI 0.44-0.79), p<0.001] significantly impacted survival after diagnosis of CNS metastases. In a subgroup analysis, superior survival was observed in patients with CNS involvement not in first tumor recurrence who underwent GKS-based combination therapeutic regimens. The survival benefit of GKS-based treatment was not significant in patients with CNS involvement in first disease relapse, but a trend for longer survival was still observed. In conclusion, GKS-based combination treatment can be considered for the treatment of EOC patients with CNS metastases. The patients with CNS involvement not in first disease relapse could significantly benefit from GKS-based combination strategies.

Stereotactic Radiosurgery (SRS) experience on brain metastases: A 3-year retrospective study at King Abdulaziz University Hospital

Objectives

Stereotactic radiosurgery (SRS), a non-invasive surgical procedure had been utilized for treatment of patients with brain metastases. This study aims to determine the survival, local control of brain metastases and treatment outcome to SRS-treated patients based on radiological imaging.

Methods

The MRI scans of SRS-treated patients with brain metastases (n = 24) from the Radiology Department of King Abdulaziz University from January 2016 to September 2019 were examined. The data was analyzed using descriptive statistics and Chi-square test.

Results

Out of 24 patients, most had brain metastases (95.8%, n = 23) with mean interval development (after primary site) of 21.88 ± 25.2 months. Radiological imaging revealed tumor characteristics of smallest (n = 11) and biggest lesions (n = 24) of patients to be 0.98 ± 0.7 and 2.23 ± 0.9, respectively and number of lesion to be 4-5 lesions (n = 3), 3 lesions (n = 6), 2 lesions (n = 4) and 1 lesion (n = 11). After SRS treatment, findings showed 17.6% (n = 3) no recurrence among the patients. Those with recurrences have decrease in lesion enhancement (11.8%, n = 2), decrease in size (29.4%, n = 5) and decrease in both enhancement and size (29.4%). Overall survival obtained was 16.7% (n = 2) at 313.83 ± 376.0 days (n = 23) survival period. Chi-square test showed that radiological findings were significantly associated with tumor recurrence (p = 0.010), having SRS-treated patients with recurrences (n = 12) to experience significant decrease (p = 0.010) in tumor enhancement, size, and both enhancement and size.

Conclusion

A significant decrease in tumor size and enhancement was observed in SRS-treated patients, suggesting SRS treatment to have associated benefit with prolonged survival duration.

Trends in physician reimbursements and procedural volumes for radiosurgery versus open surgery in brain tumor care: an analysis of Medicare data from 2009 to 2018

OBJECTIVE

Given its minimally invasive nature and effectiveness, stereotactic radiosurgery (SRS) has become a mainstay for the multimodal treatment of intracranial neoplasm. However, no studies have evaluated recent trends in the use of SRS versus those of open resection for the management of brain tumor or trends in the involvement of neurosurgeons in SRS (which is primarily delivered by radiation oncologists). Here, the authors used publicly available Medicare data from 2009 to 2018 to elucidate trends in the treatment of intracranial neoplasm and to compare reimbursements between these approaches.

METHODS

By using CPT Professional 2019, the authors identified 10 open resection and 9 SRS codes (4 for neurosurgery and 5 for radiation oncology) for the treatment of intracranial neoplasm. Medicare payments (inflation adjusted) and allowed services (number of reimbursed procedures) for each code were abstracted from the Centers for Medicare and Medicaid Services Part B National Summary Data File (2009-2018). Payments per procedure and procedures per 100,000 Medicare enrollees were analyzed with linear regression and compared with tests for equality of slopes (α = 0.05). The average payment per procedure over the study period was compared by using the 2-tailed Welsh unequal variances t-test, and more granular comparisons were conducted by using ANOVA with post hoc Tukey honestly significant difference (HSD) tests.

RESULTS

From 2009 to 2018, the number of SRS treatments per 100,000 Medicare enrollees for intracranial neoplasm increased by 3.97 cases/year (R2 = 0.99, p < 0.001), while comparable open resections decreased by 0.34 cases/year (R2 = 0.85, p < 0.001) (t16 = 7.5, p < 0.001). By 2018, 2.6 times more SRS treatments were performed per 100,000 enrollees than open resections (74.9 vs 28.7 procedures). However, neurosurgeon involvement in SRS treatment declined over the study period, from 23.4% to 11.5% of SRS treatments; simultaneously, the number of lesions treated per session increased from 1.46 to 1.84 (R2 = 0.98, p < 0.001). Overall, physician payments from 2013 to 2018 averaged $1816.08 (95% CI $1788.71-$1843.44) per SRS treatment and $1565.59 (95% CI $1535.83-$1595.34) per open resection (t10 = 15.9, p < 0.001). For neurosurgeons specifically, reimbursements averaged $1566 per open resection, but this decreased to $1031-$1198 per SRS session; comparatively, radiation oncologists were reimbursed even less (average $359-$898) per SRS session (p < 0.05 according to the Tukey HSD test for all comparisons).

CONCLUSIONS

Over a decade, the number of open resections for intracranial neoplasm in Medicare enrollees declined slightly, while the number of SRS procedures increased greatly. This latter expansion is largely attributable to radiation oncologists; meanwhile, neurosurgeons have shifted their involvement in SRS toward sessions for the management of multiple lesions.

Quality of Automated Stereotactic Radiosurgery Plans in Patients with 4 to 10 Brain Metastases

Simple Summary

Stereotactic radiosurgery (SRS) and hypofractionated stereotactic radiotherapy (SRT) are promising treatment options for patients with multiple brain metastases in the current era of personalized medicine. Recent international guidelines propose SRS also in patients with more than three brain metastases with low-volume disease. Optimal treatment quality with sparing of healthy brain tissue is essential to avoid SRS/SRT complications such as brain necrosis. The aim of this study was to compare linac (linear accelerator)-based SRS/SRT plan quality of automated planning, intensity modulated radiotherapy (IMRT), volumetric modulated arc radiotherapy (VMAT) and manually planned dynamic conformal arc (DCA) plans as well as single- and multiple-isocenter techniques. We found that automated planning with DCA or IMRT can make linac-based SRS/SRT plan quality with single isocenter comparable with a manually planned DCA plan with a separate isocenter for each metastasis.

Abstract

The purpose was to compare linac-based stereotactic radiosurgery and hypofractionated radiotherapy plan quality of automated planning, intensity modulated radiotherapy (IMRT) and manual dynamic conformal arc (DCA) plans as well as single- and multiple-isocenter techniques for multiple brain metastases (BM). For twelve patients with four to ten BM, seven non-coplanar linac-based plans were created: a manually planned DCA plan with a separate isocenter for each metastasis, a single-isocenter dynamic IMRT plan, an automatically generated single-isocenter volumetric modulated arc radiotherapy (VMAT) plan, four automatically generated single-isocenter DCA plans with three or five couch angles, with high or low sparing of normal tissue. Paddick conformity index, gradient index (GI), mean dose, total V_12Gy and V_5Gy of uninvolved brain, number of monitor units (MUs), irradiation time and pass rate were compared. The GI was significantly higher for VMAT than for separate-isocenter, IMRT, and all automatically generated plans. The number of MUs was lowest for VMAT, followed by automatically generated DCA and IMRT plans and highest for manual DCA plans. Irradiation time was the shortest for automatically planned DCA plans. Automatically generated linac-based single-isocenter plans for multiple BM reduce the number of MUs and irradiation time with at least comparable GI and V_5Gy relative to the reference separate-isocenter DCA plans.

A Systems Approach to Brain Tumor Treatment

Brain tumors are among the most lethal tumors. Glioblastoma, the most frequent primary brain tumor in adults, has a median survival time of approximately 15 months after diagnosis or a five-year survival rate of 10%; the recurrence rate is nearly 90%. Unfortunately, this prognosis has not improved for several decades. The lack of progress in the treatment of brain tumors has been attributed to their high rate of primary therapy resistance. Challenges such as pronounced inter-patient variability, intratumoral heterogeneity, and drug delivery across the blood-brain barrier hinder progress. A comprehensive, multiscale understanding of the disease, from the molecular to the whole tumor level, is needed to address the intratumor heterogeneity resulting from the coexistence of a diversity of neoplastic and non-neoplastic cell types in the tumor tissue. By contrast, inter-patient variability must be addressed by subtyping brain tumors to stratify patients and identify the best-matched drug(s) and therapies for a particular patient or cohort of patients. Accomplishing these diverse tasks will require a new framework, one involving a systems perspective in assessing the immense complexity of brain tumors. This would in turn entail a shift in how clinical medicine interfaces with the rapidly advancing high-throughput (HTP) technologies that have enabled the omics-scale profiling of molecular features of brain tumors from the single-cell to the tissue level. However, several gaps must be closed before such a framework can fulfill the promise of precision and personalized medicine for brain tumors. Ultimately, the goal is to integrate seamlessly multiscale systems analyses of patient tumors and clinical medicine. Accomplishing this goal would facilitate the rational design of therapeutic strategies matched to the characteristics of patients and their tumors. Here, we discuss some of the technologies, methodologies, and computational tools that will facilitate the realization of this vision to practice.

Implantable NMR Microcoils in Rats: A New Tool for Exploring Tumor Metabolism at Sub-Microliter Scale?

The aim of this study was to evaluate the potential of a miniaturized implantable nuclear magnetic resonance (NMR) coil to acquire in vivo proton NMR spectra in sub-microliter regions of interest and to obtain metabolic information using magnetic resonance spectroscopy (MRS) in these small volumes. For this purpose, the NMR microcoils were implanted in the right cortex of healthy rats and in C6 glioma-bearing rats. The dimensions of the microcoil were 450 micrometers wide and 3 mm long. The MRS acquisitions were performed at 7 Tesla using volume coil for RF excitation and microcoil for signal reception. The detection volume of the microcoil was measured equal to 450 nL. A gain in sensitivity equal to 76 was found in favor of implanted microcoil as compared to external surface coil. Nine resonances from metabolites were assigned in the spectra acquired in healthy rats (n = 5) and in glioma-bearing rat (n = 1). The differences in relative amplitude of choline, lactate and creatine resonances observed in glioma-bearing animal were in agreement with published findings on this tumor model. In conclusion, the designed implantable microcoil is suitable for in vivo MRS and can be used for probing the metabolism in localized and very small regions of interest in a tumor.

A focused very high energy electron beam for fractionated stereotactic radiotherapy

An electron beam of very high energy (50-250 MeV) can potentially produce a more favourable radiotherapy dose distribution compared to a state-of-the-art photon based radiotherapy technique. To produce an electron beam of sufficiently high energy to allow for a long penetration depth (several cm), very large accelerating structures are needed when using conventional radio-frequency technology, which may not be possible due to economical or spatial constraints. In this paper, we show transport and focusing of laser wakefield accelerated electron beams with a maximum energy of 160 MeV using electromagnetic quadrupole magnets in a point-to-point imaging configuration, yielding a spatial uncertainty of less than 0.1 mm, a total charge variation below [Formula: see text] and a focal spot of [Formula: see text]. The electron beam was focused to control the depth dose distribution and to improve the dose conformality inside a phantom of cast acrylic slabs and radiochromic film. The phantom was irradiated from 36 different angles to obtain a dose distribution mimicking a stereotactic radiotherapy treatment, with a peak fractional dose of 2.72 Gy and a total maximum dose of 65 Gy. This was achieved with realistic constraints, including 23 cm of propagation through air before any dose deposition in the phantom.

Bevacizumab for radiation necrosis following radiotherapy of brain metastatic disease: a systematic review & meta-analysis

Background

Radiotherapy is the mainstay of brain metastasis (BM) management. Radiation necrosis (RN) is a serious complication of radiotherapy. Bevacizumab (BV), an anti-vascular endothelial growth factor monoclonal antibody, has been increasingly used for RN treatment. We systematically reviewed the medical literature for studies reporting the efficacy and safety of bevacizumab for treatment of RN in BM patients.

Materials and methods

PubMed, Medline, EMBASE, and Cochrane library were searched with various search keywords such as “bevacizumab” OR “anti-VEGF monoclonal antibody” AND “radiation necrosis” OR “radiation-induced brain necrosis” OR “RN” OR “RBN” AND “Brain metastases” OR “BM” until 1st Aug 2020. Studies reporting the efficacy and safety of BV treatment for BM patients with RN were retrieved. Study selection and data extraction were carried out by independent investigators. Open Meta Analyst software was used as a random effects model for meta-analysis to obtain mean reduction rates.

Results

Two prospective, seven retrospective, and three case report studies involving 89 patients with RN treated with BV were included in this systematic review and meta-analysis. In total, 83 (93%) patients had a recorded radiographic response to BV therapy, and six (6.7%) had experienced progressive disease. Seven studies (n = 73) reported mean volume reductions on gadolinium-enhanced T1 (mean: 47.03%, +/− 24.4) and T2-weighted fluid-attenuated inversion recovery (FLAIR) MRI images (mean: 61.9%, +/− 23.3). Pooling together the T1 and T2 MRI reduction rates by random effects model revealed a mean of 48.58 (95% CI: 38.32–58.85) for T1 reduction rate and 62.017 (95% CI: 52.235–71.799) for T2W imaging studies. Eighty-five patients presented with neurological symptoms. After BV treatment, nine (10%) had stable symptoms, 39 (48%) had improved, and 34 (40%) patients had complete resolution of their symptoms. Individual patient data was available for 54 patients. Dexamethasone discontinuation or reduction in dosage was observed in 30 (97%) of 31 patients who had recorded dosage before and after BV treatment. Side effects were mild.

Conclusions

Bevacizumab presents a promising treatment strategy for patients with RN and brain metastatic disease. Radiographic response and clinical improvement was observed without any serious adverse events. Further class I evidence would be required to establish a bevacizumab recommendation in this group of patients.