Diagnosis and Management of Radiation Necrosis in Patients With Brain Metastases

Differentiating radiation necrosis from tumor recurrence: a systematic review and diagnostic meta-analysis comparing imaging modalities

PURPSOSE

Cerebral radiation necrosis (RN) is often a delayed phenomenon occurring several months to years after the completion of radiation treatment. Differentiating RN from tumor recurrence presents a diagnostic challenge on standard MRI. To date, no evidence-based guidelines exist regarding imaging modalities best suited for this purpose. We aim to review the current literature and perform a diagnostic meta-analysis comparing various imaging modalities that have been studied to differentiate tumor recurrence and RN.

METHODS

A systematic search adherent to PRISMA guidelines was performed using Scopus, PubMed/MEDLINE, and Embase. Pooled sensitivities and specificities were determined using a random-effects or fixed-effects proportional meta-analysis based on heterogeneity. Using diagnostic odds ratios, a diagnostic frequentist random-effects network meta-analysis was performed, and studies were ranked using P-score hierarchical ranking.

RESULTS

The analysis included 127 studies with a total of 220 imaging datasets, including the following imaging modalities: MRI (n = 10), MR Spectroscopy (MRS) (n = 28), dynamic contrast-enhanced MRI (n = 7), dynamic susceptibility contrast MRI (n = 36), MR arterial spin labeling (n = 5), diffusion-weighted imaging (n = 13), diffusion tensor imaging (DTI) (n = 2), PET (n = 89), and single photon emission computed tomography (SPECT) (n = 30). MRS had the highest pooled sensitivity (90.7%). DTI had the highest pooled specificity (90.5%). Our hierarchical ranking ranked SPECT and MRS as most preferable, and MRI was ranked as least preferable.

CONCLUSION

These findings suggest SPECT and MRS carry greater utility than standard MRI in distinguishing RN from tumor recurrence.

Dosimetric and clinical analysis of pseudo-progression versus recurrence after hypo-fractionated radiotherapy for brain metastases

BACKGROUND

The main challenge in follow-up duration of patients with brain metastases after stereotactic radiotherapy is to distinguish between pseudo-progression and tumor recurrence. The objective of this study is to retrospectively analyze the predictive factors.

METHODS

The study included 123 patients with enlarged brain metastases after hypo-fractionated radiotherapy in our center from March 2009 to October 2019, and the baseline clinical features, radiotherapy planning parameters, and enhanced magnetic resonance imaging before and after radiation therapy were analyzed. Logistic regression was performed to compare the differences between groups. Independent risk factors with P < 0.05 and associated with recurrence were used to establish a nomogram prediction model and validated by Bootstrap repeated sampling, which was validated in an internal cohort (n = 23) from October 2019 to December 2021.

RESULTS

The median follow-up time was 68.4 months (range, 8.9-146.2 months). A total of 76 (61.8%) patients were evaluated as pseudo-progression, 47 patients (38.2%) were evaluated as tumor recurrence. The median time to pseudo-progression and tumor recurrence were 18.3 months (quartile range, 9.4-27.8 months) and 12.9 months (quartile range, 8.7-19.6 months) respectively. Variables associated with tumor recurrence included: gross tumor volume ≥ 6 cc, biological effective dose < 60 Gy, target coverage < 96% and no targeted therapy. The area under curve values were 0.730 and 0.967 in the training and validation cohorts, respectively. Thirty-one patients received salvage therapy in the tumor recurrence group. The survival time in pseudo-progression and tumor recurrence groups were 66.3 months (95% CI 56.8-75.9 months) and 39.6 months (95% CI 29.2-50.0 months, respectively; P = 0.001).

CONCLUSIONS

Clinical and dosimetry features of hypo-fractionated radiation therapy based on enhanced brain magnetic resonance can help distinguish pseudo-progression from tumor recurrence after hypo-fractionated radiotherapy for brain metastases. Gross tumor volume, biological effective dose, target coverage, and having received targeted therapy or not were factors associated with the occurrence of tumor recurrence, and the individual risk could be estimated by the nomogram effectively.

Neurocognitive and radiological changes after cranial radiation therapy in humans and rodents: a systematic review

BACKGROUND

Radiation-induced brain injury is a common long-term side effect for brain cancer survivors, leading to a reduced quality of life. Although there is growing research pertaining to this topic, the relationship between cognitive and radiologically detected lesions of radiation-induced brain injury in humans remains unclear. Furthermore, clinically translatable similarities between rodent models and human findings are also undefined. The objective of this review is to then identify the current evidence of radiation-induced brain injury in humans and to compare these findings to current rodent models of radiation-induced brain injury.

METHODS

This review includes an examination of the current literature on cognitive and radiological characteristics of radiation-induced brain injury in humans and rodents. A thorough search was conducted on PubMed, Web of Science, and Scopus to identify studies that performed cognitive assessments and magnetic resonance imaging techniques on either humans or rodents after cranial radiation therapy. A qualitative synthesis of the data is herein reported.

RESULTS

A total of 153 studies pertaining to cognitively or radiologically detected radiation injury of the brain are included in this systematic review; 106 studies provided data on humans while 47 studies provided data on rodents. Cognitive deficits in humans manifest across multiple domains after brain irradiation. Radiological evidence in humans highlight various neuroimaging-detectable changes post-irradiation. It is unclear, however, whether these findings reflect ground truth or research interests. Additionally, rodent models do not comprehensively reproduce characteristics of cognitive and radiological injury currently identified in humans.

CONCLUSION

This systematic review demonstrates that associations between and within cognitive and radiological radiation-induced brain injuries often rely on the type of assessment. Well-designed studies that evaluate the spectrum of potential injury are required for a precise understanding of not only the clinical significance of radiation-induced brain injury in humans, but also how to replicate injury development in pre-clinical models.

Local thermal ablative therapies for extracranial oligometastatic disease of non-small-cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Clinically, 40-50% of patients with NSCLC are found to have systemic metastasis at the initial diagnosis. Meanwhile, 30-75% of patients with lung cancer who have undergone radical surgical resection have local recurrence and distant metastases. However, not all distant metastases are multiple, and some are potentially curable. In this study, among the patients with NSCLC having distant organ metastasis, approximately 7% showed extrapulmonary solitary metastasis and remained in this relatively stable state for a long time. This form of metastasis is known as NSCLC oligometastases. This review describes the concept and classification of oligometastases, as well as the local treatment and prognosis of extracranial oligometastases.

Concurrent Administration of Immune Checkpoint Inhibitors and Single Fraction Stereotactic Radiosurgery in Patients With Non-Small Cell Lung Cancer, Melanoma, and Renal Cell Carcinoma Brain Metastases is Not Associated With an Increased Risk of Radiation Necrosis Over Nonconcurrent Treatment: An International Multicenter Study of 657 Patients

PURPOSE

Stereotactic radiosurgery (SRS) and immune checkpoint inhibitors (ICI) are highly effective treatments for brain metastases, particularly when these therapies are administered concurrently. However, there are limited data reporting the risk of radiation necrosis (RN) in this setting.

METHODS AND MATERIALS

Patients with brain metastases from primary non-small cell lung cancer, renal cell carcinoma, or melanoma treated with SRS and ICI were considered. Time-to-event analyses were conducted for any grade RN and symptomatic RN (SRN) with death incorporated as a competing risk. As a secondary analysis, recursive partitioning analysis (RPA) was used for model development, and a loop of potential models was analyzed, with the highest-fidelity model selected. Brain V12 Gy thresholds identified on RPA were then incorporated into the competing risks analysis. Concurrent SRS and ICI administration.

RESULTS

Six hundred fifty-seven patients with 4182 brain metastases across 11 international institutions were analyzed. The median follow-up for all patients was 13.4 months. The median follow-up was 12.8 months and 14.1 months for the concurrent and nonconcurrent groups, respectively (P = .03). The median patient age was 66 years, and the median Karnofsky Performance Status was 90. In patients with any grade RN, 1- and 2-year rates were 6.4% and 9.9%, respectively. In patients with SRN, 1- and 2-year rates were 4.8% and 7.2%, respectively. On RPA, the highest-fidelity models consistently identified V12 Gy as the dominant variable predictive of RN. Three risk groups were identified by V12 Gy: (1) < 12 cm³; (2) 20 cm³ ≥ V12 Gy ≥ 12 cm³; (3) V12 Gy > 20 cm³. In patients with any grade RN, 1-year rates were 3.7% (V12 Gy < 12 cm³), 10.3% (20 cm³ ≥ V12 Gy ≥ 12 cm³), and 12.6% (V12 Gy > 20 cm³); the 2-year rates were 7.5% (V12 Gy < 12 cm³), 13.8% (20 cm³ ≥ V12 Gy ≥ 12 cm³), and 15.4% (V12 Gy > 20 cm³) (P < 0.001). In patients with any SRN, 1-year rates were 2.4% (V12 Gy < 12 cm³), 8.9% (20 cm³ ≥ V12 Gy ≥ 12 cm³), and 10.3% (V12 Gy > 20 cm³); the 2-year rates were 4.4% (V12 Gy < 12 cm³), 12.4% (20 cm³ ≥ V12 Gy ≥ 12 cm³), and 13.1% (V12 Gy > 20 cm³; P < 0.001). There were no statistically significant differences in rates of any grade RN or SRN when accounting for therapy timing for all patients and by V12 risk group identified on RPA.

CONCLUSIONS

The use of SRS and ICI results in a low risk of any grade RN and SRN. This risk is not increased with concurrent administration. Therefore, ICI can safely be administered within 4-weeks of SRS. Three risk groups based on V12 Gy were identified, which clinicians may consider to further reduce rates of RN.

Investigating the role of delayed contrast magnetic resonance imaging (MRI) to differentiate radiation necrosis from tumour recurrence in brain metastases after stereotactic radiosurgery

INTRODUCTION

The incidence of radionecrosis (RN) after stereotactic radiosurgery (SRS) to brain metastases is increasing. An overlap in the conventional MRI appearances of RN and tumour recurrence (TR) is diagnostically challenging. Delayed contrast MRI compares contrast enhancement over two time periods to create treatment response assessment maps (TRAMs). We aim to assess the utility of TRAMs in brain metastases patients.

METHODS

Delayed contrast MRI scans were performed on ten brain metastases patients, previously treated with SRS, who developed equivocal lesion(s) on routine MRI follow-up. T1-weighted images were obtained five minutes and 60-75 min after contrast injection, followed by Brain Lab software analysis to create TRAMs. TRAMs patterns were then compared with the patient's clinical status, subsequent imaging, and histology results.

RESULTS

We identified three regions on TRAMs: central, peripheral, and surrounding. Each region could be described either as contrast accumulation (red colour and representing non-tumour tissue) or contrast clearance (blue colour and representing tumour tissue). Our analysis demonstrated similarities in the TRAMs pattern between TR and RN, though to varying degrees.

CONCLUSION

In conclusion, the TRAMs appearances of RN and TR overlap. Our findings suggest that the previously-described correlation between contrast clearance and TR is at least partially attributable to more solid initial enhancement, rather than convincingly a difference in the underlying tissue properties, and the additional diagnostic value of TRAMs may be limited. Thus, further research on TRAMs is necessary prior to incorporating it into routine clinical management after SRS for brain metastases.

Recurrent Brain Metastasis Versus Radiation-Induced Necrosis: A Case Report and Literature Review

Radiotherapy is the cornerstone of brain metastasis management. With the advancement of therapies, patients are living longer, exposing them to the long-term effects of radiotherapy. Using concurrent or sequential chemotherapy, targeted agents, and immune checkpoint inhibitors may increase the incidence and severity of radiation-induced toxicity. Recurrent metastasis and radiation necrosis (RN) appear indistinguishable on neuroimaging, making it a diagnostic dilemma for clinicians. Here, we present a case of RN in a 65-year-old male patient who previously had brain metastasis (BM) from primary lung cancer, misdiagnosed initially as recurrent BM.

Towards differentiation of brain tumor from radiation necrosis using multi-parametric MRI: Preliminary results at 4.7 T using rodent models

BACKGROUND

It remains a clinical challenge to differentiate brain tumors from radiation-induced necrosis in the brain. Despite significant improvements, no single MRI method has been validated adequately in the clinical setting.

METHODS

Multi-parametric MRI (mpMRI) was performed to differentiate 9L gliosarcoma from radiation necrosis in animal models. Five types of MRI methods probed complementary information on different scales i.e., T2 (relaxation), CEST based APT (probing mobile proteins/peptides) and rNOE (mobile macromolecules), qMT (macromolecules), diffusion based ADC (cell density) and SSIFT iAUC (cell size), and perfusion based DSC (blood volume and flow).

RESULTS

For single MRI parameters, iAUC and ADC provide the best discrimination of radiation necrosis and brain tumor. For mpMRI, a combination of iAUC, ADC, and APT shows the best classification performance based on a two-step analysis with the Lasso and Ridge regressions.

CONCLUSION

A general mpMRI approach is introduced to choosing candidate multiple MRI methods, identifying the most effective parameters from all the mpMRI parameters, and finding the appropriate combination of chosen parameters to maximize the classification performance to differentiate tumors from radiation necrosis.

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.

Deep Learning-Based Automatic Detection of Brain Metastases in Heterogenous Multi-Institutional Magnetic Resonance Imaging Sets: An Exploratory Analysis of NRG-CC001

PURPOSE

Deep learning-based algorithms have been shown to be able to automatically detect and segment brain metastases (BMs) in magnetic resonance imaging, mostly based on single-institutional data sets. This work aimed to investigate the use of deep convolutional neural networks (DCNN) for BM detection and segmentation on a highly heterogeneous multi-institutional data set.

METHODS AND MATERIALS

A total of 407 patients from 98 institutions were randomly split into 326 patients from 78 institutions for training/validation and 81 patients from 20 institutions for unbiased testing. The data set contained T1-weighted gadolinium and T2-weighted fluid-attenuated inversion recovery magnetic resonance imaging acquired on diverse scanners using different pulse sequences and various acquisition parameters. Several variants of 3-dimensional U-Net based DCNN models were trained and tuned using 5-fold cross validation on the training set. Performances of different models were compared based on Dice similarity coefficient for segmentation and sensitivity and false positive rate (FPR) for detection. The best performing model was evaluated on the test set.

RESULTS

A DCNN with an input size of 64 × 64 × 64 and an equal number of 128 kernels for all convolutional layers using instance normalization was identified as the best performing model (Dice similarity coefficient 0.73, sensitivity 0.86, and FPR 1.9) in the 5-fold cross validation experiments. The best performing model demonstrated consistent behavior on the test set (Dice similarity coefficient 0.73, sensitivity 0.91, and FPR 1.7) and successfully detected 7 BMs (out of 327) that were missed during manual delineation. For large BMs with diameters greater than 12 mm, the sensitivity and FPR improved to 0.98 and 0.3, respectively.

CONCLUSIONS

The DCNN model developed can automatically detect and segment brain metastases with reasonable accuracy, high sensitivity, and low FPR on a multi-institutional data set with nonprespecified and highly variable magnetic resonance imaging sequences. For large BMs, the model achieved clinically relevant results. The model is robust and may be potentially used in real-world situations.

Risk Factors of Second Local Recurrence in Surgically Treated Recurrent Brain Metastases: An Exploratory Analysis

BACKGROUND

A first local recurrence is common after resection or radiotherapy for brain metastasis (BM). However, patients with BMs can develop multiple local recurrences over time. Published data on second local recurrences are scarce. This study aimed to report predictors associated with a second local recurrence in patients with BMs who underwent a craniotomy for a first locally recurrent BM.

METHODS

Patients were identified from a database at Brigham and Women's Hospital in Boston. Hazard ratios and 95% confidence intervals for predictors of a second local recurrence were computed using a Cox proportional hazards model.

RESULTS

Of 170 identified surgically treated first locally recurrent lesions, 74 (43.5%) progressed to second locally recurrent lesions at a median of 7 months after craniotomy. Subtotal resection of the first local BM recurrence was significantly associated with shorter time to second local recurrence (hazard ratio = 2.09; 95% confidence interval, 1.27-3.45). Infratentorial location was associated with a worse second local recurrence prognosis (hazard ratio = 2.22; 95% confidence interval, 1.24-3.96).

CONCLUSIONS

A second local recurrence occurred after 43.5% of craniotomies for first recurrent lesions. Subtotal resection and infratentorial location were the strongest risk factors for worse second local recurrence prognosis following resection of first recurrent BM.

Management of Brain Metastases from Human Epidermal Growth Factor Receptor 2 Positive (HER2+) Breast Cancer

Simple Summary

Treatment options for patients with Human Epidermal growth factor Receptor 2 positive (HER2+) metastatic breast cancer are rapidly changing, especially for patients with brain metastasis. Historically, treatment options for brain metastasis were focused on local therapies, radiation and surgery. There are now multiple targeted therapies that are able to treat brain metastasis and prolong the lives of patients with HER2+ breast cancer. With the growing number of treatment options, making medical decisions for patients and clinicians is more complicated. This paper reviews the treatment options for patients with HER2+ breast cancer brain metastasis and provides a simplified algorithm for when to consider delaying local treatments.

Abstract

In the past 5 years, the treatment options available to patients with HER2+ breast cancer brain metastasis (BCBM) have expanded. The longer survival of patients with HER2+ BCBM renders understanding the toxicities of local therapies even more important to consider. After reviewing the available literature for HER2 targeted systemic therapies as well as local therapies, we present a simplified algorithm for when to prioritize systemic therapies over local therapies in patients with HER2+ BCBM.

Selective Cell Size MRI Differentiates Brain Tumors from Radiation Necrosis

Brain metastasis is a common characteristic of late-stage lung cancers. High doses of targeted radiotherapy can control tumor growth in the brain but can also result in radiotherapy-induced necrosis. Current methods are limited for distinguishing whether new parenchymal lesions following radiotherapy are recurrent tumors or radiotherapy-induced necrosis, but the clinical management of these two classes of lesions differs significantly. Here, we developed, validated, and evaluated a new MRI technique termed selective size imaging using filters via diffusion times (SSIFT) to differentiate brain tumors from radiotherapy necrosis in the brain. This approach generates a signal filter that leverages diffusion time dependence to establish a cell size-weighted map. Computer simulations in silico, cultured cancer cells in vitro, and animals with brain tumors in vivo were used to comprehensively validate the specificity of SSIFT for detecting typical large cancer cells and the ability to differentiate brain tumors from radiotherapy necrosis. SSIFT was also implemented in patients with metastatic brain cancer and radiotherapy necrosis. SSIFT showed high correlation with mean cell sizes in the relevant range of less than 20 μm. The specificity of SSIFT for brain tumors and reduced contrast in other brain etiologies allowed SSIFT to differentiate brain tumors from peritumoral edema and radiotherapy necrosis. In conclusion, this new, cell size-based MRI method provides a unique contrast to differentiate brain tumors from other pathologies in the brain.

SIGNIFICANCE

This work introduces and provides preclinical validation of a new diffusion MRI method that exploits intrinsic differences in cell sizes to distinguish brain tumors and radiotherapy necrosis.

Brain metastases: A Society for Neuro-Oncology (SNO) consensus review on current management and future directions

Brain metastases occur commonly in patients with advanced solid malignancies. Yet, less is known about brain metastases than cancer-related entities of similar incidence. Advances in oncologic care have heightened the importance of intracranial management. Here, in this consensus review supported by the Society for Neuro-Oncology (SNO), we review the landscape of brain metastases with particular attention to management approaches and ongoing efforts with potential to shape future paradigms of care. Each coauthor carried an area of expertise within the field of brain metastases and initially composed, edited, or reviewed their specific subsection of interest. After each subsection was accordingly written, multiple drafts of the manuscript were circulated to the entire list of authors for group discussion and feedback. The hope is that the these consensus guidelines will accelerate progress in the understanding and management of patients with brain metastases, and highlight key areas in need of further exploration that will lead to dedicated trials and other research investigations designed to advance the field.

Outcomes and Principles of Patient Selection for Laser Interstitial Thermal Therapy for Metastatic Brain Tumor Management: A Multisite Institutional Case Series

BACKGROUND

Laser interstitial thermal therapy (LITT) is an emerging treatment modality for both primary brain tumors and metastases. We report initial outcomes after LITT for metastatic brain tumors across 3 sites at our institution and discuss potential strategies for optimal patient selection and outcomes.

METHODS

International Classification of Diseases, Ninth Revision and Tenth Revision codes were used to identify patients with malignant brain tumors treated via LITT across all 3 Mayo Clinic sites with at least 6 months follow-up. Local control was based on radiologic and clinical evidence. Overall survival was measured from time of receiving LITT until death or end of the study period.

RESULTS

Twenty-three patients were treated for progression of a single (n = 21) or multiple (n = 2) previously radiated metastatic lesions and/or radiation necrosis. Median age was 56 years (interquartile range, 47-66.5 years). LITT achieved local control of the lesion in most patients with metastatic tumors or radiation necrosis (n = 18; 81.8%) for the duration of follow-up. One patient did not have local control data available. Thirteen (56.5%) patients remained alive at the end of the study period. No other patients died of their treated disease during the study period; 5 of 10 deaths were attributable to central nervous system progression outside the treated lesion. Although median survival for this cohort has not yet been reached, the current median survival is 16 months (interquartile range, 12-48.5 months) after LITT for metastatic/radiation necrosis lesions.

CONCLUSIONS

LITT was associated with sustained local control in 81.8% of patients treated for radiographic progression of metastatic central nervous system disease.

Iatrogenic Influence on Prognosis of Radiation-Induced Contrast Enhancements in Patients with Glioma WHO 1-3 following Photon and Proton Radiotherapy

BACKGROUND AND PURPOSE

Radiation-induced contrast enhancement (RICE) is a common side effect following radiotherapy for glioma, but both diagnosis and handling are challenging. Due to the potential risks associated with RICE and its challenges in differentiating RICE from tumor progression, it is critical to better understand how RICE prognosis depends on iatrogenic influence.

MATERIALS AND METHODS

We identified 99 patients diagnosed with RICE who were previously treated with either photon or proton therapy for World Health Organization (WHO) grade 1-3 primary gliomas. Post-treatment brain MRI-based volumetric analysis and clinical data collection was performed at multiple time points.

RESULTS

The most common histologic subtypes were astrocytoma (50%) and oligodendroglioma (46%). In 67%, it was graded WHO grade 2 and in 86% an IDH mutation was present. RICE first occurred after 16 months (range: 1 - 160) in median. At initial RICE occurrence, 39% were misinterpreted as tumor progression. A tumor-specific therapy including chemotherapy or re-irradiation led to a RICE size progression in 86% and 92% of cases, respectively and RICE symptom progression in 57% and 65% of cases, respectively. A RICE-specific therapy such as corticosteroids or Bevacizumab for larger or symptomatic RICE led to a RICE size regression in 81% of cases with symptom stability or regression in 62% of cases.

CONCLUSIONS

While with chemotherapy and re-irradiation a RICE progression was frequently observed, anti-edematous or anti-VEGF treatment frequently went along with a RICE regression. For RICE, correct diagnosis and treatment decisions are challenging and critical and should be made interdisciplinarily.

Predicting Adverse Radiation Effects in Brain Tumors After Stereotactic Radiotherapy With Deep Learning and Handcrafted Radiomics

Introduction

There is a cumulative risk of 20–40% of developing brain metastases (BM) in solid cancers. Stereotactic radiotherapy (SRT) enables the application of high focal doses of radiation to a volume and is often used for BM treatment. However, SRT can cause adverse radiation effects (ARE), such as radiation necrosis, which sometimes cause irreversible damage to the brain. It is therefore of clinical interest to identify patients at a high risk of developing ARE. We hypothesized that models trained with radiomics features, deep learning (DL) features, and patient characteristics or their combination can predict ARE risk in patients with BM before SRT.

Methods

Gadolinium-enhanced T1-weighted MRIs and characteristics from patients treated with SRT for BM were collected for a training and testing cohort (N = 1,404) and a validation cohort (N = 237) from a separate institute. From each lesion in the training set, radiomics features were extracted and used to train an extreme gradient boosting (XGBoost) model. A DL model was trained on the same cohort to make a separate prediction and to extract the last layer of features. Different models using XGBoost were built using only radiomics features, DL features, and patient characteristics or a combination of them. Evaluation was performed using the area under the curve (AUC) of the receiver operating characteristic curve on the external dataset. Predictions for individual lesions and per patient developing ARE were investigated.

Results

The best-performing XGBoost model on a lesion level was trained on a combination of radiomics features and DL features (AUC of 0.71 and recall of 0.80). On a patient level, a combination of radiomics features, DL features, and patient characteristics obtained the best performance (AUC of 0.72 and recall of 0.84). The DL model achieved an AUC of 0.64 and recall of 0.85 per lesion and an AUC of 0.70 and recall of 0.60 per patient.

Conclusion

Machine learning models built on radiomics features and DL features extracted from BM combined with patient characteristics show potential to predict ARE at the patient and lesion levels. These models could be used in clinical decision making, informing patients on their risk of ARE and allowing physicians to opt for different therapies.

The Value of FET PET/CT in Recurrent Glioma with a Different IDH Mutation Status: The Relationship between Imaging and Molecular Biomarkers

The evaluation of treatment response remains a challenge in glioma cases because the neuro oncological therapy can lead to the development of treatment-related changes (TRC) that mimic true progression (TP). Positron emission tomography (PET) using O-(2-[¹⁸F] fluoroethyl-)-L-tyrosine (¹⁸F-FET) has been shown to be a useful tool for detecting TRC and TP. We assessed the diagnostic performance of different ¹⁸F-FET PET segmentation approaches and different imaging biomarkers for differentiation between late TRC and TP in glioma patients. Isocitrate dehydrogenase (IDH) status was evaluated as a predictor of disease outcome. In our study, the proportion of TRC in IDH wild type (IDHwt) and IDH mutant (IDHm) subgroups was without significant difference. We found that the diagnostic value of static and dynamic biomarkers of ¹⁸F-FET PET for discrimination between TRC and TP depends on the IDH mutation status of the tumor. Dynamic ¹⁸F-FET PET acquisition proved helpful in the IDH wild type (IDHwt) subgroup, as opposed to the IDH mutant (IDHm) subgroup, providing an early indication to discontinue dynamic imaging in the IDHm subgroup.

Dynamic 18F-FET PET/CT to differentiate recurrent primary brain tumor and brain metastases from radiation necrosis after single-session robotic radiosurgery

OBJECTIVE

Cyberknife robotic radiosurgery (RRS) provides single-session high-dose radiotherapy of brain tumors with a steep dose gradient and precise real-time image-guided motion correction. Although RRS appears to cause more radiation necrosis (RN), the radiometabolic changes after RRS have not been fully clarified. ¹⁸F-FET-PET/CT is used to differentiate recurrent tumor (RT) from RN after radiosurgery when MRI findings are indecisive. We explored the usefulness of dynamic parameters derived from ¹⁸F-FET PET in differentiating RT from RN after Cyberknife treatment in a single-center study population.

METHODS

We retrospectively identified brain tumor patients with static and dynamic ¹⁸F-FET-PET/CT for suspected RN after Cyberknife. Static (tumor-to-background ratio) and dynamic PET parameters (time-activity curve, time-to-peak) were quantified. Analyses were performed for all lesions taken together (TOTAL) and for brain metastases only (METS). Diagnostic accuracy of PET parameters (using mean tumor-to-background ratio >1.95 and time-to-peak of 20 min for RT as cut-offs) and their respective improvement of diagnostic probability were analyzed.

RESULTS

Fourteen patients with 28 brain tumors were included in quantitative analysis. Time-activity curves alone provided the highest sensitivities (TOTAL: 95%, METS: 100%) at the cost of specificity (TOTAL: 50%, METS: 57%). Combined mean tumor-to-background ratio and time-activity curve had the highest specificities (TOTAL: 63%, METS: 71%) and led to the highest increase in diagnosis probability of up to 16% p. - versus 5% p. when only static parameters were used.

CONCLUSIONS

This preliminary study shows that combined dynamic and static ¹⁸F-FET PET/CT parameters can be used in differentiating RT from RN after RRS.

Systemic Therapy Type and Timing Effects on Radiation Necrosis Risk in HER2+ Breast Cancer Brain Metastases Patients Treated With Stereotactic Radiosurgery

Background

There is a concern that HER2-directed systemic therapies, when administered concurrently with stereotactic radiosurgery (SRS), may increase the risk of radiation necrosis (RN). This study explores the impact of timing and type of systemic therapies on the development of RN in patients treated with SRS for HER2+ breast cancer brain metastasis (BCBrM).

Methods

This was a single-institution, retrospective study including patients >18 years of age with HER2+ BCBrM who received SRS between 2013 and 2018 and with at least 12-month post-SRS follow-up. Presence of RN was determined via imaging at one-year post-SRS, with confirmation by biopsy in some patients. Demographics, radiotherapy parameters, and timing (“during” defined as four weeks pre- to four weeks post-SRS) and type of systemic therapy (e.g., chemotherapy, HER2-directed) were evaluated.

Results

Among 46 patients with HER2+ BCBrM who received SRS, 28 (60.9%) developed RN and 18 (39.1%) did not based on imaging criteria. Of the 11 patients who underwent biopsy, 10/10 (100%) who were diagnosed with RN on imaging were confirmed to be RN positive on biopsy and 1/1 (100%) who was not diagnosed with RN was confirmed to be RN negative on biopsy. Age (mean 53.3 vs 50.4 years, respectively), radiotherapy parameters (including total dose, fractionation, CTV and size target volume, all p>0.05), and receipt of any type of systemic therapy during SRS (60.7% vs 55.6%, p=0.97) did not differ between patients who did or did not develop RN. However, there was a trend for patients who developed RN to have received more than one agent of HER2-directed therapy independent of SRS timing compared to those who did not develop RN (75.0% vs 44.4%, p=0.08). Moreover, a significantly higher proportion of those who developed RN received more than one agent of HER2-directed therapy during SRS treatment compared to those who did not develop RN (35.7% vs 5.6%, p=0.047).

Conclusions

Patients with HER2 BCBrM who receive multiple HER2-directed therapies during SRS for BCBrM may be at higher risk of RN. Collectively, these data suggest that, in the eight-week window around SRS administration, if HER2-directed therapy is medically necessary, it is preferable that patients receive a single agent.

Novel Imaging Biomarkers to Assess Oncologic Treatment-Related Changes

Cancer therapeutics cause various treatment-related changes that may impact patient follow-up and disease monitoring. Although atypical responses such as pseudoprogression may be misinterpreted as treatment nonresponse, other changes, such as hyperprogressive disease seen with immunotherapy, must be recognized early for timely management. Radiation necrosis in the brain is a known response to radiotherapy and must be distinguished from local tumor recurrence. Radiotherapy can also cause adverse effects such as pneumonitis and local tissue toxicity. Systemic therapies, like chemotherapy and targeted therapies, are known to cause long-term cardiovascular effects. Thus, there is a need for robust biomarkers to identify, distinguish, and predict cancer treatment-related changes. Radiomics, which refers to the high-throughput extraction of subvisual features from radiologic images, has been widely explored for disease classification, risk stratification, and treatment-response prediction. Lately, there has been much interest in investigating the role of radiomics to assess oncologic treatment-related changes. We review the utility and various applications of radiomics in identifying and distinguishing atypical responses to treatments, as well as in predicting adverse effects. Although artificial intelligence tools show promise, several challenges-including multi-institutional clinical validation, deployment in health care settings, and artificial-intelligence bias-must be addressed for seamless clinical translation of these tools.

What Does PET Imaging Bring to Neuro-Oncology in 2022? A Review

Simple Summary

Positron emission tomography (PET) imaging is increasingly used to supplement MRI in the management of patient with brain tumors. In this article, we provide a review of the current place and perspectives of PET imaging for the diagnosis and follow-up of from primary brain tumors such as gliomas, meningiomas and central nervous system lymphomas, as well as brain metastases. Different PET radiotracers targeting different biological processes are used to accurately depict these brain tumors and provide unique metabolic and biologic information. Radiolabeled amino acids such as [¹⁸F]FDOPA or [¹⁸F]FET are used for imaging of gliomas while both [¹⁸F]FDG and amino acids can be used for brain metastases. Meningiomas can be seen with a high contrast using radiolabeled ligands of somatostatin receptors, which they usually carry. Unconventional tracers that allow the study of other biological processes such as cell proliferation, hypoxia, or neo-angiogenesis are currently being studied for brain tumors imaging.

Abstract

PET imaging is being increasingly used to supplement MRI in the clinical management of brain tumors. The main radiotracers implemented in clinical practice include [¹⁸F]FDG, radiolabeled amino acids ([¹¹C]MET, [¹⁸F]FDOPA, [¹⁸F]FET) and [⁶⁸Ga]Ga-DOTA-SSTR, targeting glucose metabolism, L-amino-acid transport and somatostatin receptors expression, respectively. This review aims at addressing the current place and perspectives of brain PET imaging for patients who suffer from primary or secondary brain tumors, at diagnosis and during follow-up. A special focus is given to the following: radiolabeled amino acids PET imaging for tumor characterization and follow-up in gliomas; the role of amino acid PET and [¹⁸F]FDG PET for detecting brain metastases recurrence; [⁶⁸Ga]Ga-DOTA-SSTR PET for guiding treatment in meningioma and particularly before targeted radiotherapy.

Successful treatment of quadriparesis from radiation myelopathy with bevacizumab in a patient with metastatic breast cancer

Radiation myelopathy (RM) is rare condition defined as injury to the spinal cord by ionising radiation. Due to improved survival in patients with advanced malignancies, there is a renewed interest in recognition and treatment of RM. There are very few reports on treatment of RM. A 64-year-old woman with metastatic oestrogen receptor, progesterone receptor weakly positive and human epidermal growth factor 2 negative breast, stereotactic radiosurgeries to brain metastases and a history of reradiation to the cervical spinal cord presented with neck pain, arm weakness, hyperreflexia and gait ataxia. RM was suspected and the patient was started on high dose corticosteroid therapy. However, the patient's condition deteriorated and she developed quadriparesis. A timely treatment with an antivascular endothelial growth factor antibody, bevacizumab reversed her neurological deficits and preserved her walking ability. Our case illustrates a prompt diagnosis and successful treatment of RM with bevacizumab.

Treatment of Radiation-Induced Brain Necrosis

Radiation-induced brain necrosis (RBN) is a serious complication of intracranial as well as skull base tumors after radiotherapy. In the past, due to the lack of effective treatment, radiation brain necrosis was considered to be progressive and irreversible. With better understanding in histopathology and neuroimaging, the occurrence and development of RBN have been gradually clarified, and new treatment methods are constantly emerging. In recent years, some scholars have tried to treat RBN with bevacizumab, nerve growth factor, and gangliosides and have achieved similar results. Some cases of brain necrosis can be repairable and reversible. We aimed to summarize the incidence, pathogenesis, and treatment of RBN.

Radiation induced tissue necrosis mimicking orbital apex syndrome

We are reporting a unique case with findings resembling orbital apex syndrome due to radiation-induced ischemic tissue necrosis following the treatment of meningiomatosis. In our patient, radiation injury caused multiple neuropathies including: 2nd, 3rd, 4th, 5th, and 6th neuropathies with oculosympathetic pathway involvement. To our knowledge, our patient has some unique features of complications related to radiation necrosis. Describing this case will help clinicians to have a better understanding of the extent of ocular manifestations secondary to radiation necrosis.

Radiomics as an emerging tool in the management of brain metastases

Brain metastases (BM) are associated with significant morbidity and mortality in patients with advanced cancer. Despite significant advances in surgical, radiation, and systemic therapy in recent years, the median overall survival of patients with BM is less than 1 year. The acquisition of medical images, such as computed tomography (CT) and magnetic resonance imaging (MRI), is critical for the diagnosis and stratification of patients to appropriate treatments. Radiomic analyses have the potential to improve the standard of care for patients with BM by applying artificial intelligence (AI) with already acquired medical images to predict clinical outcomes and direct the personalized care of BM patients. Herein, we outline the existing literature applying radiomics for the clinical management of BM. This includes predicting patient response to radiotherapy and identifying radiation necrosis, performing virtual biopsies to predict tumor mutation status, and determining the cancer of origin in brain tumors identified via imaging. With further development, radiomics has the potential to aid in BM patient stratification while circumventing the need for invasive tissue sampling, particularly for patients not eligible for surgical resection.

Pyrotinib treatment enhances the radiosensitivity in HER2-positive brain metastatic breast cancer patients

Brain metastasis is a common cause of death in HER2-positive breast cancer patients. Currently, it is mainly treated by whole-brain radiotherapy. Pyrotinib is an irreversible pan-ErbB inhibitor, which has demonstrated promising tumor-suppressing activity and acceptable tolerance in previous phase trials. In the present study, we evaluated the efficacy of pyrotinib on HER2-positive brain metastatic breast cancer patients treated with whole-brain radiotherapy. A total of 20 such patients were separated into pyrotinib plus capecitabine and capecitabine-only groups in a 1:1 ratio. All patients met either the primary or secondary endpoints. Oral admission of pyrotinib together with radiotherapy can significantly increase the overall response rate, progression-free survival, time to progression and duration of response of HER2+ brain metastatic breast cancer patients, without causing extra adverse events. In addition, pyrotinib can enhance the radiosensitivity of in-vitro cultured HER2+ breast cancer cell lines. The outcome of our study suggests that pyrotinib might be an effective medication to enhance the tumor radiosensitivity of HER2-positive brain metastatic breast cancer patients.

Radiation induced contrast enhancement after proton beam therapy in patients with low grade glioma - How safe are protons?

PURPOSE

The optimal treatment strategy for low-grade glioma (LGG) is still a matter of controversy. Considering that the prognosis is typically favorable, the prevention of late sequelae is of particular importance. Proton beam therapy (PRT) has the potential to further reduce the burden of treatment related side effects. We set out to evaluate the clinical outcome of proton irradiation with a particular focus on morphologic features on magnetic resonance imaging (MRI).

METHODS

We assessed prospectively 110 patients who received radiotherapy with protons for histologically proven LGG. Clinical and radiological information were analyzed resulting in more than 1200 available MRI examinations with a median follow-up of 39 months. Newly diagnosed contrast-enhancing lesions on MRI were delineated and correlated with parameters of the corresponding treatment plan. A voxel-based dose-matched paired analysis of the linear energy transfer (LET) inside vs outside lesions was performed.

RESULTS

Proton beam irradiation of patients with low-grade glioma results in overall survival (OS) of 90% after seven years. Median progression free survival had not yet been reached with surviving fraction of 54% after seven years. The incidence of temporary or clinically silent radiation induced contrast enhancement was significantly higher than previously assumed, however, symptomatic radiation necrosis was only detected in one patient. These radiation-induced contrast-enhancing lesions were almost exclusively seen at the distal beam end of the proton beam. In 22 out of 23 patients, the average LET of voxels inside contrast-enhancing lesions was significantly increased, compared to dose-matched voxels outside the lesions.

CONCLUSION

Symptomatic radiation necrosis following PRT was as rare as conventional photon-based treatment series suggest. However, the increased incidence of asymptomatic radiation-induced brain injuries with an increased average LET observed in this cohort provides strong clinical evidence to support the hypothesis that the relative biological effectiveness of protons is variable and different to the fixed factor of 1.1 currently used worldwide.

Multiparametric radiomic tissue signature and machine learning for distinguishing radiation necrosis from tumor progression after stereotactic radiosurgery

Background

Stereotactic radiosurgery (SRS) may cause radiation necrosis (RN) that is difficult to distinguish from tumor progression (TP) by conventional MRI. We hypothesize that MRI-based multiparametric radiomics (mpRad) and machine learning (ML) can differentiate TP from RN in a multi-institutional cohort.

Methods

Patients with growing brain metastases after SRS at 2 institutions underwent surgery, and RN or TP were confirmed by histopathology. A radiomic tissue signature (RTS) was selected from mpRad, as well as single T₁ post-contrast (T₁c) and T₂ fluid-attenuated inversion recovery (T₂-FLAIR) radiomic features. Feature selection and supervised ML were performed in a randomly selected training cohort (N = 95) and validated in the remaining cases (N = 40) using surgical pathology as the gold standard.

Results

One hundred and thirty-five discrete lesions (37 RN, 98 TP) from 109 patients were included. Radiographic diagnoses by an experienced neuroradiologist were concordant with histopathology in 67% of cases (sensitivity 69%, specificity 59% for TP). Radiomic analysis indicated institutional origin as a significant confounding factor for diagnosis. A random forest model incorporating 1 mpRad, 4 T₁c, and 4 T₂-FLAIR features had an AUC of 0.77 (95% confidence interval [CI]: 0.66–0.88), sensitivity of 67% and specificity of 86% in the training cohort, and AUC of 0.71 (95% CI: 0.51–0.91), sensitivity of 52% and specificity of 90% in the validation cohort.

Conclusions

MRI-based mpRad and ML can distinguish TP from RN with high specificity, which may facilitate the triage of patients with growing brain metastases after SRS for repeat radiation versus surgical intervention.

Salvage Surgical Resection after Linac-Based Stereotactic Radiosurgery for Newly Diagnosed Brain Metastasis

Background: This study aimed to assess the clinical outcomes of salvage surgical resection (SSR) after stereotactic radiosurgery and fractionated stereotactic radiotherapy (SRS/fSRT) for newly diagnosed brain metastasis. Methods: Between November 2009 and May 2020, 318 consecutive patients with 1114 brain metastases were treated with SRS/fSRT for newly diagnosed brain metastasis at our hospital. During this study period, 21 of 318 patients (6.6%) and 21 of 1114 brain metastases (1.9%) went on to receive SSR after SRS/fSRT. Three patients underwent multiple surgical resections. Twenty-one consecutive patients underwent twenty-four SSRs. Results: The median time from initial SRS/fSRT to SSR was 14 months (range: 2–96 months). The median follow-up after SSR was 17 months (range: 2–78 months). The range of tumor volume at initial SRS/fSRT was 0.12–21.46 cm³ (median: 1.02 cm³). Histopathological diagnosis after SSR was recurrence in 15 cases, and radiation necrosis (RN) or cyst formation in 6 cases. The time from SRS/fSRT to SSR was shorter in the recurrence than in the RNs and cyst formation, but these differences did not reach statistical significance (p = 0.067). The median survival time from SSR and from initial SRS/fSRT was 17 and 74 months, respectively. The cases with recurrence had a shorter survival time from initial SRS/fSRT than those without recurrence (p = 0.061). Conclusions: The patients treated with SRS/fSRT for brain metastasis need long-term follow-up. SSR is a safe and effective treatment for the recurrence, RN, and cyst formation after SRS/fSRT for brain metastasis.

The role of feature-based radiomics for predicting response and radiation injury after stereotactic radiation therapy for brain metastases: A critical review by the Young Group of the Italian Association of Radiotherapy and Clinical Oncology (yAIRO)

Introduction

differential diagnosis of tumor recurrence and radiation injury after stereotactic radiotherapy (SRT) is challenging. The advances in imaging techniques and feature-based radiomics could aid to discriminate radionecrosis from progression.

Methods

we performed a systematic review of current literature, key references were obtained from a PubMed query. Data extraction was performed by 3 researchers and disagreements were resolved with a discussion among the authors.

Results

we identified 15 retrospective series, one prospective trial, one critical review and one editorial paper. Radiomics involves a wide range of imaging features referred to necrotic regions, rate of contrast-enhancing area or the measure of edema surrounding the metastases. Features were mainly defined through a multistep extraction/reduction/selection process and a final validation and comparison.

Conclusions

feature-based radiomics has an optimal potential to accurately predict response and radionecrosis after SRT of BM and facilitate differential diagnosis. Further validation studies are eagerly awaited to confirm radiomics reliability.

Oligoprogression in Non-Small Cell Lung Cancer

Simple Summary

Several retrospective studies present evidence of oligoprogressive disease (OPD) in patients with non-small cell lung cancer (NSCLC) with driver mutations such as EGFR. The strategy of local ablative therapy (LAT) with radiotherapy, followed by the continuation of the same anticancer drug therapy beyond progression disease, is recommended in the current NCCN guideline. Although evidence of the use of this strategy in the treatment of the driver mutation-negative NSCLC is missing, LAT with radiotherapy for OPD after combination therapy of immune checkpoint inhibitor with cytotoxic chemotherapy is expected. Tumors outside of the radiation field may further respond to the immune checkpoint inhibitors due to an abscopal effect. In the future, to achieve long-term survival in advanced NSCLC, it will be important to validate this treatment strategy via prospective comparative studies and to actively implement it in clinical practice.

Abstract

We reviewed the literature on oligoprogressive disease (OPD) and local ablative therapy (LAT) in patients with advanced non-small cell lung cancer (NSCLC). The frequency of OPD varies depending on its definition and is estimated to be between 15–47%. The implications of the strategy of continuing the same anticancer agents beyond progressive disease after LAT with radiation therapy for OPD are based on the concept of progression in which only a small number of lesions, not more than about four, proliferate after chemotherapy. In the case of OPD harboring driver mutations such as EGFR, prospective studies are underway. However, evidence from retrospective studies support this strategy, which is currently recommended in some guidelines. The prognosis in OPD cases during the administration of an immune checkpoint inhibitor (ICI) is relatively promising. Additionally, LAT with radiation for OPD after the first-line treatment of ICI with cytotoxic chemotherapy may overcome the resistance to the combination drug therapy due to an abscopal effect. To achieve long-term survival in advanced-stage NSCLC, it is important to verify the optimal method and timing of the therapy through prospective comparative studies as well as patient selection based on patient characteristics and biomarker levels.

Modern Radiation Therapy for the Management of Brain Metastases From Non-Small Cell Lung Cancer: Current Approaches and Future Directions

Brain metastases (BMs) represent the most frequent event during the course of Non-Small Cell Lung Cancer (NSCLC) disease. Recent advancements in the diagnostic and therapeutic procedures result in increased incidence and earlier diagnosis of BMs, with an emerging need to optimize the prognosis of these patients through the adoption of tailored treatment solutions. Nowadays a personalized and multidisciplinary approach should rely on several clinical and molecular factors like patient’s performance status, extent and location of brain involvement, extracranial disease control and the presence of any “druggable” molecular target. Radiation therapy (RT), in all its focal (radiosurgery and fractionated stereotactic radiotherapy) or extended (whole brain radiotherapy) declinations, is a cornerstone of BMs management, either alone or combined with surgery and systemic therapies. Our review aims to provide an overview of the many modern RT solutions available for the treatment of BMs from NSCLC in the different clinical scenarios (single lesion, oligo and poly-metastasis, leptomeningeal carcinomatosis). This includes a detailed review of the current standard of care in each setting, with a presentation of the literature data and of the possible technical solutions to offer a “state-of-art” treatment to these patients. In addition to the validated treatment options, we will also discuss the future perspectives on emerging RT technical strategies (e.g., hippocampal avoidance whole brain RT, simultaneous integrated boost, radiosurgery for multiple lesions), and present the innovative and promising findings regarding the combination of novel targeted agents such as tyrosine kinase inhibitors and immune checkpoint inhibitors with brain irradiation.

Risk of symptomatic radiation necrosis in patients treated with stereotactic radiosurgery for brain metastases

INTRODUCTIO

Stereotactic radiosurgery (SRS) is a treatment option in the initial management of patients with brain metastases. While its efficacy has been demonstrated in several prior studies, treatment-related complications, particularly symptomatic radiation necrosis (RN), remains as an obstacle for wider implementation of this treatment modality. We thus examined risk factors associated with the development of symptomatic RN in patients treated with SRS for brain metastases.

PATIENTS AND METHODS

We performed a retrospective review of our institutional database to identify patients with brain metastases treated with SRS. Diagnosis of symptomatic RN was determined by appearance on serial MRIs, MR spectroscopy, requirement of therapy, and the development of new neurological complaints without evidence of disease progression.

RESULTS

We identified 323 brain metastases treated with SRS in 170 patients from 2009 to 2018. Thirteen patients (4%) experienced symptomatic RN after treatment of 23 (7%) lesions. After SRS, the median time to symptomatic RN was 8.3 months. Patients with symptomatic RN had a larger mean target volume (p<0.0001), and thus larger V100% (p<0.0001), V50% (p<0.0001), V12Gy (p<0.0001), and V10Gy (p=0.0002), compared to the rest of the cohort. Single-fraction treatment (p=0.0025) and diabetes (p=0.019) were also significantly associated with symptomatic RN.

CONCLUSION

SRS is an effective treatment option for patients with brain metastases; however, a subset of patients may develop symptomatic RN. We found that patients with larger tumor size, larger plan V100%, V50%, V12Gy, or V10Gy, who received single-fraction SRS, or who had diabetes were all at higher risk of symptomatic RN.

A Single-Institution Retrospective Study of Patients Treated With Laser-Interstitial Thermal Therapy for Radiation Necrosis of the Brain

Object Laser-interstitial thermal therapy (LITT) has been proposed as an alternative treatment to surgery for radiation necrosis (RN) in patients treated with stereotactic radiosurgery (SRS) for brain metastases. The present study sought to retrospectively analyze LITT outcomes in patients with RN from SRS. Methods This was a single-institution retrospective study of 30 patients treated from 2011-2018 with pathologically-proven RN after SRS for brain metastases (n=28) or proximally treated extracranial lesions treated with external beam radiotherapy (n=2). Same-day biopsy was performed in all cases. Patients were prospectively followed with Functional Assessment of Cancer Therapy - Brain (FACT-Br), EuroQol-5 Dimension (EQ-5D), Hopkins Verbal Learning Test (HVLT) and clinical history and examination. Adjusted means, standard errors and tests comparing visits to pre-LITT were generated. Kaplan-Meier method was used to estimate time overall survival. Competing risk analysis was used to estimate cumulative incidence of LITT failure. Results In our patient population, median time from radiotherapy to LITT was 13.1 months. Median SRS dose and median LITT treatment target volume were 20 Gy (IQR 18-22) and 3.5 cc (IQR 2.2-4.6), respectively. Seventy-seven percent of our patients tapered off steroids within one month. There were only two instances of RN recurrence after LITT, with recurrence defined as recurrence of symptoms after initial improvement. These recurrences occurred at 1.9 and 3.4 months. The three-, six- and nine-month freedom from recurrence rates were 95.7%, 90.9%, and 90.9%. Median survival in our patient population with pathologically confirmed RN treated with LITT was 2.1 years. Regarding the quality of life questionnaires with which some patients were followed as part of different prospective studies, completion rates were 22/30 for FACT-Br, 16/30 for the EQ-5D and 8/30 for HVLT. Quality of life questionnaire results were overall stable from baseline. Mean FACT-Br scores were stable from baseline (17.9, 16.6, 21.4 and 22.8) to three months (18.8, 15.4, 18.4 and 23.4) (p=0.38, 0.53, 0.09 and 0.59). The mean EQ-5D Aggregate score was stable from baseline (7.1) to one month (7.6) (p=0.25). Mean HVLT-R Total Recall was stable from baseline (20.6) to three months (18.4) (p=0.09). There was a statistically significant decrease in mean Karnofsky Performance Scale (KPS) score from baseline (84) to three-month follow-up (75) (p=0.03). Conclusions LITT represents a safe and durably effective treatment option for RN in the brain. Results demonstrate a median survival of 2.1 years from LITT with only two recurrences, both within four months of treatment and salvageable. Patient-reported outcomes showed no severe declines after LITT. Quality of life questionnaires demonstrated stable well-being and functionality from baseline. LITT should be considered for definitive treatment of RN, especially in cases where patients have significant side effects from standards medical therapies such as steroids or if steroids are minimally effective.

Central Nervous System Metastases

The proportion of patients developing central nervous system (CNS) metastasis is increasing. Most are identified once symptomatic. Surgical resection is indicated for solitary or symptomatic brain metastases, separation surgery for compressive radioresistant spinal metastases, and instrumentation for unstable spinal lesions. Surgical biopsies are performed when histological diagnoses are required. Stereotactic radiosurgery is an option for limited small brain metastases and radioresistant spinal metastases. Whole-brain radiotherapy is reserved for extensive brain metastases and leptomeningeal disease with approaches to reduce cognitive side effects. Radiosensitive and inoperable spinal metastases typically receive external beam radiotherapy. Systemic therapy is increasingly being utilized for CNS metastases.

The centrally restricted diffusion sign on MRI for assessment of radiation necrosis in metastases treated with stereotactic radiosurgery

Purpose

Differentiation of radiation necrosis from tumor progression in brain metastases treated with stereotactic radiosurgery (SRS) is challenging. For this, we assessed the performance of the centrally restricted diffusion sign.

Methods

Patients with brain metastases treated with SRS who underwent a subsequent intervention (biopsy/resection) for a ring-enhancing lesion on preoperative MRI between 2000 and 2020 were included. Excluded were lesions containing increased susceptibility limiting assessment of DWI. Two neuroradiologists classified the location of the diffusion restriction with respect to the post-contrast T1 images as centrally within the ring-enhancement (the centrally restricted diffusion sign), peripherally correlating to the rim of contrast enhancement, both locations, or none. Measures of diagnostic accuracy and 95% CI were calculated for the centrally restricted diffusion sign. Cohen's kappa was calculated to identify the interobserver agreement.

Results

Fifty-nine patients (36 female; mean age 59, range 40 to 80) were included, 36 with tumor progression and 23 with radiation necrosis based on histopathology. Primary tumors included 34 lung, 12 breast, 5 melanoma, 3 colorectal, 2 esophagus, 1 head and neck, 1 endometrium, and 1 thyroid. The centrally restricted diffusion sign was seen in 19/23 radiation necrosis cases (sensitivity 83% (95% CI 63 to 93%), specificity 64% (95% CI 48 to 78%), PPV 59% (95% CI 42 to 74%), NPV 85% (95% CI 68 to 94%)) and 13/36 tumor progression cases (difference p < 0.001). Interobserver agreement was substantial, at 0.61 (95% CI 0.45 to 70.8).

Conclusion

We found a low probability of radiation necrosis in the absence of the centrally restricted diffusion sign.

Reirradiation With Stereotactic Radiosurgery After Local or Marginal Recurrence of Brain Metastases From Previous Radiosurgery

PURPOSE

Brain metastases represent a major indication for stereotactic radiosurgery (SRS), but further study is needed regarding repeat SRS (SRS2) after local or marginal recurrence after prior SRS (SRS1). We report local tumor control (LC) after SRS2 and identify predictors of radiation necrosis (RN) and symptomatic RN (SRN).

METHODS AND MATERIALS

Patients had biopsy-proven non-small cell lung cancer and at least 1 brain metastasis previously treated with SRS. SRS2 was performed from 2015 to 2020 and required overlap of the prescription isodose lines with those from SRS1. Patients treated with preoperative SRS were excluded. Primary endpoints were LC by Response Assessment in Neuro-oncology criteria, RN, and SRN.

RESULTS

From 8 institutions, 102 patients with 123 treated lesions were included. SRS2 was performed at a median 12 months after SRS1. SRS2 delivered a median 18 Gy (interquartile range [IQR], 16-18) margin dose to the 50% (IQR, 50%-70%) isodose line, maximum dose of 30.5 Gy (IQR, 25.0-36.0), and V12Gy of 3.38 cm³ (IQR, 0.83-7.64). One-year and 2-year LC were 79% and 72%, respectively. Local tumor control was improved with tumor volume ≤1 cm³ (P < .005). There were 25 (20%) cases of RN and 9 (7%) cases of SRN. For SRS1 and SRS2, SRN rates were higher with maximum doses ≥40 Gy or SRS2 V12Gy >9 cm³ (P < .025 for each). SRS1 and SRS2 maximum dose ≥40 Gy was also predictive of increased RN (P < .05 for each). Prior immunotherapy was not predictive of RN or SRN.

CONCLUSIONS

Repeat SRS afforded a high rate of local tumor control and a low rate of SRN. At SRS2, V12Gy ≤9 cm³ and maximum dose <40 Gy may reduce the risks of RN and SRN. These results are most applicable to lesions with approximately 1 cm³ volume and 1-year interval between SRS courses.

Potential role of functional imaging in predicting outcome for patients treated with carbon ion therapy: a review

OBJECTIVE

Carbon ion radiation therapy (CIRT) is an emerging radiation technique with advantageous physical and radiobiologic properties compared to conventional radiotherapy (RT) providing better response in case of radioresistant and hypoxic tumors. Our aim is to critically review if functional imaging techniques could play a role in predicting outcome of CIRT-treated tumors, as already proven for conventional RT.

METHODS

14 studies, concerning Magnetic resonance imaging (MRI) and Positron Emission Tomography (PET), were selected after a comprehensive search on multiple electronic databases from January 2000 to March 2020.

RESULTS

MRI studies (n = 5) focused on diffusion-weighted MRI and, even though quantitative parameters were the same in all studies (apparent diffusion coefficient, ADC), results were not univocal, probably due to different imaging acquisition protocols and tumoral histology. For PET studies (n = 9), different tracers were used such as [¹⁸F]FDG and other uncommon tracers ([¹¹C]MET, [¹⁸F]FLT), with a relevant heterogeneity regarding parameters used for outcome assessment.

CONCLUSION

No conclusion can be drawn on the predictive value of functional imaging in CIRT-treated tumors. A standardization of image acquisition, multi-institutional large trials and external validations are needed in order to establish the prognostic value of functional imaging in CIRT and to guide clinical practice.

ADVANCES IN KNOWLEDGE

Emerging studies focused on functional imaging's role in predicting CIRT outcome. Due to the heterogeneity of images acquisition and studies, results are conflicting and prospective large studies with imaging standardized protocol are needed.

Study of relationship between dose, LET and the risk of brain necrosis after proton therapy for skull base tumors

PURPOSE

We investigated the relationship between RBE-weighted dose (DRBE) calculated with constant (cRBE) and variable RBE (vRBE), dose-averaged linear energy transfer (LETd) and the risk of radiographic changes in skull base patients treated with protons.

METHODS

Clinical treatment plans of 45 patients were recalculated with Monte Carlo tool FRED. Radiographic changes (i.e. edema and/or necrosis) were identified by MRI. Dosimetric parameters for cRBE and vRBE were computed. Biological margin extension and voxel-based analysis were employed looking for association of DRBE(vRBE) and LETd with brain edema and/or necrosis.

RESULTS

When using vRBE, Dmax in the brain was above the highest dose limits for 38% of patients, while such limit was never exceeded assuming cRBE. Similar values of Dmax were observed in necrotic regions, brain and temporal lobes. Most of the brain necrosis was in proximity to the PTV. The voxel-based analysis did not show evidence of an association with high LETd values.

CONCLUSIONS

When looking at standard dosimetric parameters, the higher dose associated with vRBE seems to be responsible for an enhanced risk of radiographic changes. However, as revealed by a voxel-based analysis, the large inter-patient variability hinders the identification of a clear effect for high LETd.

Integration of Systemic Therapy and Stereotactic Radiosurgery for Brain Metastases

Simple Summary

In the multi-modal treatment of brain metastasis (BM), the role of systemic therapy has undergone a recent revolution. Due to the development of multiple agents with modest central nervous system penetration of the blood-brain barrier, targeted therapies and immune checkpoint inhibitors are increasingly being utilized alone or in combination with radiation therapy. However, the adoption of sequential or concurrent strategies varies considerably, and treatment strategies employed in clinical practice have rapidly outpaced evidence development. Therefore, this review critically analyzes the data regarding combinatorial approaches for a variety of systemic therapeutics with stereotactic radiosurgery and provides an overview of ongoing clinical trials.

Abstract

Brain metastasis (BM) represents a common complication of cancer, and in the modern era requires multi-modal management approaches and multi-disciplinary care. Traditionally, due to the limited efficacy of cytotoxic chemotherapy, treatment strategies are focused on local treatments alone, such as whole-brain radiotherapy (WBRT), stereotactic radiosurgery (SRS), and resection. However, the increased availability of molecular-based therapies with central nervous system (CNS) penetration now permits the individualized selection of tailored systemic therapies to be used alongside local treatments. Moreover, the introduction of immune checkpoint inhibitors (ICIs), with demonstrated CNS activity has further revolutionized the management of BM patients. The rapid introduction of these cancer therapeutics into clinical practice, however, has led to a significant dearth in the published literature about the optimal timing, sequencing, and combination of these systemic therapies along with SRS. This manuscript reviews the impact of tumor biology and molecular profiles on the management paradigm for BM patients and critically analyzes the current landscape of SRS, with a specific focus on integration with systemic therapy. We also discuss emerging treatment strategies combining SRS and ICIs, the impact of timing and the sequencing of these therapies around SRS, the effect of corticosteroids, and review post-treatment imaging findings, including pseudo-progression and radiation necrosis.

The effect of surgery on radiation necrosis in irradiated brain metastases: extent of resection and long-term clinical and radiographic outcomes

OBJECTIVE

Radiation therapy is a cornerstone of brain metastasis (BrM) management but carries the risk of radiation necrosis (RN), which can require resection for palliation or diagnosis. We sought to determine the relationship between extent of resection (EOR) of pathologically-confirmed RN and postoperative radiographic and symptomatic outcomes.

METHODS

A single-center retrospective review was performed at an NCI-designated Comprehensive Cancer Center to identify all surgically-resected, previously-irradiated necrotic BrM without admixed recurrent malignancy from 2003 to 2018. Clinical, pathologic and radiographic parameters were collected. Volumetric analysis determined EOR and longitudinally evaluated perilesional T2-FLAIR signal preoperatively, postoperatively, and at 3-, 6-, 12-, and 24-months postoperatively when available. Rates of time to 50% T2-FLAIR reduction was calculated using cumulative incidence in the competing risks setting with last follow-up and death as competing events. The Spearman method was used to calculate correlation coefficients, and continuous variables for T2-FLAIR signal change, including EOR, were compared across groups.

RESULTS

Forty-six patients were included. Most underwent prior stereotactic radiosurgery with or without whole-brain irradiation (N = 42, 91%). Twenty-seven operations resulted in gross-total resection (59%; GTR). For the full cohort, T2-FLAIR edema decreased by a mean of 78% by 6 months postoperatively that was durable to last follow-up (p < 0.05). EOR correlated with edema reduction at last follow-up, with significantly greater T2-FLAIR reduction with GTR versus subtotal resection (p < 0.05). Among surviving patients, a significant proportion were able to decrease their steroid use: steroid-dependency decreased from 54% preoperatively to 15% at 12 months postoperatively (p = 0.001).

CONCLUSIONS

RN resection conferred both durable T2-FLAIR reduction, which correlated with EOR; and reduced steroid dependency.

Reliability of Magnetic Resonance Spectroscopy and Positron Emission Tomography Computed Tomography in Differentiating Metastatic Brain Tumor Recurrence from Radiation Necrosis

BACKGROUND

Clinical and/or neuroimaging changes after whole-brain radiation therapy (WBRT) or stereotactic radiosurgery (SRS) for metastatic brain tumor(s) present the clinical dilemma of differentiating tumor recurrence from radiation necrosis. Several imaging modalities attempt to answer this clinical question, including magnetic resonance spectroscopy (MRS) and positron emission tomography (PET) computed tomography (CT). We evaluated our experience regarding the ability of MRS and PET CT to differentiate tumor recurrence from radiation necrosis in patients who have received WBRT or SRS.

METHODS

We retrospectively reviewed records of 242 patients with previous WBRT or SRS to identify those who had MRS and/or PET CT to differentiate tumor recurrence from radiation necrosis. Patients were sorted into true-positive, false-positive, false-negative, and true-negative groups on the basis of imaging interpretation and clinical course combined with surgical pathology results or reaction to nonsurgical treatments including SRS, dexamethasone, or observation. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were then calculated.

RESULTS

Of 25 patients presenting such diagnostic questions, 19 were evaluated with MRS and 13 with PET CT. MRS sensitivity was 100%, specificity was 50%, and accuracy was 81.8%, whereas PET CT sensitivity was 36.4%, specificity was 66.7%, and accuracy was 42.9%.

CONCLUSIONS

MRS has better accuracy than PET CT and a high negative predictive value, therefore making it more useful in distinguishing recurrent tumor from radiation necrosis. We encourage correlation with symptoms at imaging to aid in clinical decision making.

Laser interstitial thermal therapy for treatment of cerebral radiation necrosis

Radiation necrosis is a well described complication after radiosurgical treatment of intracranial pathologies - best recognized after the treatment of patients with arteriovenous malformations and brain metastases but possibly also affecting patients treated with radiosurgery for meningioma. The pathophysiology of radiation necrosis is still not well understood but is most likely a secondary local tissue inflammatory response to brain tissue injured by radiation. Radiation necrosis in brain metastases patients may present radiographically and behave clinically like recurrent tumor. Differentiation between radiation necrosis and recurrent tumor has been difficult based on radiographic changes alone. Biopsy or craniotomy therefore remains the gold standard method of diagnosis. For symptomatic patients, corticosteroids are first-line therapy, but patients may fail medical management due to intolerance of chronic steroids or persistence of symptoms. In these cases, open surgical resection has been shown to be successful in management of surgically amenable lesions but may be suboptimal in patients with deep-seated lesions or extensive prior cranial surgical history, both carrying high risk for peri-operative morbidity. Laser interstitial thermal therapy has emerged as a viable, alternative surgical option. In addition to allowing access to tissue for diagnosis, thermal treatment of the lesion can also be delivered precisely and accurately under real-time imaging guidance. This review highlights the pertinent studies that have shaped the impetus for use of laser interstitial thermal therapy in the treatment of radiation necrosis, reviewing indications, outcomes, and nuances toward successful application of this technology in patients with suspected radiation necrosis.

Local Ablative Therapies for Oligometastatic and Oligoprogressive Non-Small Cell Lung Cancer

More than half of all patients with non-small cell lung cancer (NSCLC) have metastatic disease at the time of diagnosis. A subset of these patients has oligometastatic disease, which exists in an intermediary state between locoregional and disseminated metastatic disease. In addition, some metastatic patients on systemic therapy may have limited disease progression, or oligoprogression. Historically, treatment of metastatic NSCLC was palliative in nature, with little expectation of long-term survival. However, an accumulation of evidence over the past 3 decades now demonstrates that local ablative therapy to sites of limited metastases or progression can improve patient outcomes for this complex disease. This review examines the evidence behind local ablative therapy in oligometastatic and oligoprogressive NSCLC, with a focus on surgery, stereotactic radiotherapy, and radiofrequency ablation.

Increased Radiosurgery Toxicity Associated With Treatment of Vestibular Schwannoma in Multiple Sclerosis

OBJECTIVE

Explore the risk of radiation-induced neurotoxicity in patients with multiple sclerosis (MS) treated with stereotactic radiosurgery (SRS) and better understand the pathophysiology of radiation-induced injury in the central nervous system (CNS).

PATIENTS/INTERVENTION

We present the clinical course and magnetic resonance imaging (MRI) findings of a 52-year-old woman with a history of relapsing remitting MS, who developed radiation-induced neurotoxicity following CyberKnife SRS (25 Gy in five fractions) for a left-sided vestibular schwannoma (VS).

MAIN OUTCOME MEASURE

Risk of radiation-induced damage following SRS to the CNS, including radiation type and dose, toxicity, and time to symptom onset, in patients with MS.

RESULTS

Our patient developed increased imbalance (grade 2 toxicity) 3 months following CyberKnife SRS. Brain MRI showed new fluid-attenuated inversion recovery (FLAIR) hyperintensity in the pons and cerebellum. Neurotoxicity from SRS is rare. However, our literature review showed that 19 patients with MS who underwent intracranial radiation therapy sustained radiation-induced toxicity. The potential mechanisms for increased toxicity in MS could be due to a combination of demyelination, inflammatory, and/or vascular changes. Efficacy of treatments including steroids, bevacizumab, and hyperbaric oxygen therapy is currently unknown.

CONCLUSION

Treatment options of SRS and surgery for VS should be carefully considered as patients with known MS may be at increased risk for radiation-induced damage following SRS to the CNS. Thoughtful radiosurgical planning and dosing accounting for this inherent risk is essential for managing patients with MS and VS.

Early-onset symptomatic radiation necrosis after stereotactic radiosurgery in the setting of COVID-19 infection

In this brief report, we describe the case of a previously healthy 51-year gentleman who was treated with stereotactic radiosurgery to a dose of 12 Gy to a small right-sided vestibular schwannoma. MRI of the brain performed after treatment revealed stable treated disease but subsequently, the patient developed symptomatic COVID-19 based on PCR along with multiple cranial neurologic deficits, including right facial paralysis, hemifacial anesthesia, and anesthesia of the ipsilateral hard palate and tongue. MRI of the brain was repeated and demonstrated radiation necrosis in the adjacent brainstem for which he was treated with Pentoxifylline and Vitamin E, dexamethasone, and Bevacizumab with only partial improvement. The dose-volume metrics of the brainstem from his radiotherapy plan as well as the trajectory of his imaging findings do not match this clinical picture from radiotherapy alone. We review the basic pathogenesis of the inflammatory response to infection from the SARS-CoV-2 virus as well as the pathogenesis of radiation necrosis. Heightened awareness about potential risks with high-dose radiotherapy in patients with symptomatic COVID-19 should be considered.

Bevacizumab Treatment of Radiation-Induced Brain Necrosis: A Systematic Review

BACKGROUND

Radiation brain necrosis (RBN) is a serious complication in patients receiving radiotherapy for intracranial disease. Many studies have investigated the efficacy and safety of bevacizumab in patients with RBN. In the present study, we systematically reviewed the medical literature for studies reporting the efficacy and safety of bevacizumab, as well as for studies comparing bevacizumab with corticosteroids.

MATERIALS AND METHODS

We searched PubMed, Cochrane library, EMBASE, and ClinicalTrials.gov from their inception through 1 March, 2020 for studies that evaluated the efficacy and safety of bevacizumab in patients with RBN. Two investigators independently performed the study selection, data extraction, and data synthesis.

RESULTS

Overall, the present systematic review included 12 studies (eight retrospective, two prospective, and two randomized control trials [RCTs]) involving 236 patients with RBN treated who were treated with bevacizumab. The two RCTs also had control arms comprising patients with RBN who were treated with corticosteroids/placebo (n=57). Radiographic responses were recorded in 84.7% (200/236) of patients, and radiographic progression was observed in 15.3% (36/236). Clinical improvement was observed in 91% (n=127) of responding patients among seven studies (n=113). All 12 studies reported volume reduction on T1 gadolinium enhancement MRI (median: 50%, range: 26%-80%) and/or T2 FLAIR MRI images (median: 59%, range: 48%-74%). In total, 46 responding patients (34%) had recurrence. The two RCTs revealed significantly improved radiographic response in patients treated with bevacizumab (Levin et al.: p = 0.0013; Xu et al.: p < 0.001). Both also showed clinical improvement (Levin et al.: NA; Xu et al.: p = 0.039) and significant reduction in edema volume on both T1 gadolinium enhancement MRI (Levin et al.: p=0.0058; Xu et al.: p=0.027) and T2 FLAIR MRI (Levin et al.: p=0.0149; Xu et al.: p < 0.001). Neurocognitive improvement was significantly better after 2 months of treatment in patients receiving bevacizumab than in those given corticosteroids, as assessed by the MoCA scale (p = 0.028). The recurrence rate and side effects of the treatments showed no significant differences.

CONCLUSIONS

Patients with RBN respond to bevacizumab, which can improve clinical outcomes and cognitive function. Bevacizumab appears to be more efficacious than corticosteroid-based treatment. The safety profile was comparable to that of the corticosteroids.