Staged Stereotactic Radiosurgery for Large Brain Metastases: Local Control and Clinical Outcomes of a One-Two Punch Technique

Novel radiotherapeutic strategies in the management of brain metastases: Challenging the dogma

The role of radiation therapy in the management of brain metastasis is evolving. Advancements in machine learning techniques have improved our ability to both detect brain metastasis and our ability to contour substructures of the brain as critical organs at risk. Advanced imaging with PET tracers and magnetic resonance imaging-based artificial intelligence models can now predict tumor control and differentiate tumor progression from radiation necrosis. These advancements will help to optimize dose and fractionation for each patient's lesion based on tumor size, histology, systemic therapy, medical comorbidities/patient genetics, and tumor molecular features. This review will discuss the current state of brain directed radiation for brain metastasis. We will also discuss future directions to improve the precision of stereotactic radiosurgery and optimize whole brain radiation techniques to improve local tumor control and prevent cognitive decline without forming necrosis.

Rate of pachymeningeal failure following adjuvant WBRT vs SRS in patients with brain metastases

Background

Stereotactic radiosurgery (SRS) has supplanted whole brain radiotherapy (WBRT) as standard-of-care adjuvant treatment following surgery for brain metastasis (BrM). Concomitant with the adoption of adjuvant SRS, a new pattern of failure termed "Pachymeningeal failure" (PMF) has emerged.

Methods

We reviewed a prospective registry of 264 BrM patients; 145 and 119 were treated adjuvantly with WBRT and SRS, respectively. The Cox proportional hazards model was used to identify variables correlating to outcomes. Outcomes were calculated using the cumulative incidence (CI) method. Univariate (UVA) and multivariate analyses (MVA) were done to identify factors associated with PMF.

Results

CI of PMF was 2 % and 18 % at 12 months, and 2 % and 23 % at 24 months for WRBT and SRS, respectively (p < 0.001). The CI of classic leptomeningeal disease (LMD) was 3 % and 4 % at 12 months, and 6 % and 6 % at 24 months for WBRT and SRS, respectively (P = 0.67). On UVA, adjuvant SRS [HR 9.75 (3.43-27.68) (P < 0.001)]; preoperative dural contact (PDC) [HR 6.78 (1.64-28.10) (P = 0.008)]; GPA score [HR 1.64 (1.11-2.42) (P = 0.012)]; and lung EGFR/ALK status [HR 3.11 (1.02-9.45) (P = 0.045)]; were associated with PMF risk. On MVA, adjuvant SRS [HR 8.15 (2.69-24.7) (P < 0.001)]; and PDC [HR 6.28 (1.51-26.1) (P = 0.012)] remained associated with PMF.

Conclusions

Preoperative dural contact and adjuvant SRS instead of adjuvant WBRT were associated with an increased risk of PMF. Strategies to improve pachymeningeal radiation coverage to sterilize at risk pachymeninges should be investigated.

Is two-staged gamma knife surgery a reasonable management option for very large cerebellar metastases? A case series of three patients

OBJECTIVE

Two-staged gamma knife surgery (GKS) is a method that may extend the upper tumor volume limit for using GKS in the management of brain metastases. However, the safety of treating very large posterior fossa lesions with this technique has not been well demonstrated. Therefore, we analyzed our experience in treating cerebellar metastases larger than 12 cm3 with two-staged GKS.

METHODS

Four consecutive patients harboring 12 to 30 cm3 cerebellar metastases scheduled two-staged GKS were included in the study, and all but one patient completed the treatment. The treatment doses were 10-13 Gy. All patients were followed with regular MR imaging and clinical assessments, and the tumor volumes were measured on all treatment and follow-up images.

RESULTS

Tumor progression was not demonstrated in any of the patients. Tumor volumes decreased by, on average, more than half between the two stages. The median survival was 22 months, and no patient died due to intracranial tumor progression. Peritumoral edema at the first GKS resolved in all patients, replaced by asymptomatic mild T2 changes in two of them not requiring any treatment. No radiation-induced complication has developed thus far.

CONCLUSION

Staged GKS seems to be a feasible management option for very large cerebellar metastases.

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

OBJECTIVE

Imaging changes after stereotactic radiosurgery (SRS) can occur for years after treatment, although the available data on the incidence of tumor progression and adverse radiation effects (ARE) are generally limited to the first 2 years after treatment.

METHODS

A single-institution retrospective review was conducted of patients who had >18 months of imaging follow-up available. Patients who had ≥1 metastatic brain lesions treated with Gamma Knife SRS were assessed for the time to radiographic progression. Those with progression ≥18 months after the initial treatment were included in the present study. The lesions that progressed were characterized as either ARE or tumor progression based on the tissue diagnosis or imaging characteristics over time.

RESULTS

The cumulative incidence of delayed imaging radiographic progression was 35% at 5 years after the initial SRS. The cumulative incidence curves of the time to radiographic progression for lesions determined to be ARE and lesions determined to be tumor progression were not significantly different statistically. The cumulative incidence of delayed ARE and delayed tumor progression was 17% and 16% at 5 years, respectively. Multivariate analysis indicated that the number of metastatic brain lesions present at the initial SRS was the only factor associated with late radiographic progression.

CONCLUSIONS

The timing of late radiographic progression does not differ between ARE and tumor progression. The number of metastatic brain lesions at the initial SRS is a risk factor for late radiographic progression.

Two fractions staged Gammaknife radiosurgery for "large" cerebral metastases

BACKGROUND

Gammaknife radiosurgery (GKRS) is a valuable option to control cerebral metastases. However, the risk (adverse radiation effect (ARE))-benefit (local control (LC)) ratio switches when the target is too large.

OBJECTIVE

In order to balance this ratio, two fractions staged GKRS protocol was conducted for "large" cerebral metastases. The aim of this study is to evaluate the outcome (LC, ARE).

METHODS

A total of 39 large cerebral metastases in 35 patients were treated. The initial mean tumor volume was 14.6 cc [6.1; 35.8]. The prescription margin dose was 12 Gy on the 50% isodose line, with 2 weeks between them. A majority of primary cancer were from lung (43%), melanoma (20%) or breast (17%) origin. The mean age was 63 years old (31-89). Mean Graded Prognostic Assessment (GPA) was 2.

RESULTS

At the second fraction, mean tumor volume was 10.3 cc [1.9-27.4]. The mean percentage of volume variation for decreasing lesions was 29%. At last follow-up, mean tumor volume was 7.4 cc [0-25.2]; 34 lesions decreased volume (mean 35%). A decreased volume of more than 45% after first stage GKRS was able to predict a long-term local response to staged GKRS treatment. Local control rate at 6 months and 1 year was 87.3% and 75% respectively. The rate of ARE was 7.7%. No predictive factor of local control or ARE was found in a univariate analysis.

CONCLUSION

The new 2-fractions-dose-staged GKRS concept seems to be a well-tolerated and effective treatment option for large cerebral metastases.

Efficacy and safety of a "sandwich therapy" based on staged stereotactic radiosurgery and bevacizumab for large brainstem metastases

OBJECTIVE

Gamma Knife stereotactic radiosurgery (SRS) is an effective therapeutic option for unresectable brainstem metastases. Currently, staged stereotactic radiosurgery (SSRS) has become available for large brainstem metastases（≥ 1 cm3） despite the limitation of peritumoral edema. The authors developed the so-called "sandwich therapy" which integrated 2-stage stereotactic radiosurgery (2-SSRS) with bevacizumab for peritumoral edema reduction and local control of large brainstem metastases.

METHODS

42 patients with large brainstem metastases ≥1 cm3 who received 2-SSRS simultaneously with bevacizumab were screened from 2019 to 2021 retrospectively. The first SRS margin doses were 13 Gy (range 11-15) and the second SRS margin doses were 12 Gy (range 11-13), one-time vascular endothelial growth factor (VEGF) inhibitor (bevacizumab) of 3.5-5 mg/kg was administrated intravenously the next day after the first SRS. The median interval between the two sessions of SRS was 6 days. Baseline demographics, clinical and radiology imaging follow-ups were recorded to determine symptomatic improvement, peritumoral edema reduction, local control, and disease progression. Median survival was calculated using Kaplan-Meier analysis. Multivariate analysis was performed to identify prognostic factors.

RESULTS

The "sandwich therapy" was applied to 42 lesions. Significant reductions of tumor volume (p < 0.05) and peritumoral edema volume (p < 0.01) were achieved at the second SRS in comparison to those at the first SRS. The proportion of favorable Karnofsky performance scale (KPS) (≥80 %) increased significantly at early follow-up time points and reached the highest value of 85.7 %. The median survival time was 9.7 months, the median local control duration was 11.3 months. 8 acute adverse events of CTCAE grade 2 and 3 were observed in 6 patients and resolved with palliative treatment. Tyrosine kinase inhibitor (TKI) treatment was identified as a predictive factor for longer survival.

CONCLUSION

The "sandwich therapy" which integrates 2-SSRS with bevacizumab is a safe and effective option for large brainstem metastases.

'Sandwich treatment' for posterior fossa brain metastases with volume larger than 4cm3: a multicentric retrospective study

Single stereotactic radiosurgery (SRS) for posterior fossa brain metastases (BM) larger than 4cm3 is dangerous. 'Sandwich treatment' strategy was developed for these BMs. The strategy was one week treatment course which includes 2-stage SRS and using Bevacizumab once during SRS gap. Patients from four gamma knife center were retrospectively analyzed. The changes of tumor and peri-tumor edema volume were studied. The Dizziness Handicap Inventory (DHI) Vomiting Score (VS) and Glasgow Coma Scale (GCS) were used to evaluate patients' clinical symptom changes. Karnofsky performance scale (KPS) and Barthel Index (BI) were used to evaluate patients' overall fitness status and physical activity rehabilitation. Tumor local control (TLC) and patients' overall survival (OS) rate were also calculated. Forty patients with 45 LBMs received 'Sandwich treatment'. The mean edema volume reduced remarkably at the course of therapy and 3 months later (P < 0.01). The mean tumor volume greatly decreased 3 months later (P < 0.01). Patients' clinical symptoms that reflected by median score of DHI, VS, GCS were improved dramatically at the course of therapy and 3 months later (P < 0.01). Similar changes happened in median score of KPS and BI that reflected patients' overall fitness status and physical activity rehabilitation (P < 0.01). Patients' median OS was 14.3 months, with 95.4%, 76.2%, and 26.3% survival rate at 6, 12, 24 months. The TLC rate at 6, 12, 24 months was 97.5%, 86.0% and 62.2%.The 'Sandwich treatment' is safe and effective for patients with LBM over 4cm3 in the posterior fossa. The strategy could quickly improve patients' symptoms, well control tumor growth, prolong patient's OS, and has controllable side effects.

Modern Stereotactic Radiotherapy for Brain Metastases from Lung Cancer: Current Trends and Future Perspectives Based on Integrated Translational Approaches

Brain metastases (BMs) represent the most frequent metastatic event in the course of lung cancer patients, occurring in approximately 50% of patients with non-small-cell lung cancer (NSCLC) and in up to 70% in patients with small-cell lung cancer (SCLC). Thus far, many advances have been made in the diagnostic and therapeutic procedures, allowing improvements in the prognosis of these patients. The modern approach relies on the integration of several factors, such as accurate histological and molecular profiling, comprehensive assessment of clinical parameters and precise definition of the extent of intracranial and extracranial disease involvement. The combination of these factors is pivotal to guide the multidisciplinary discussion and to offer the most appropriate treatment to these patients based on a personalized approach. Focal radiotherapy (RT), in all its modalities (radiosurgery (SRS), fractionated stereotactic radiotherapy (SRT), adjuvant stereotactic radiotherapy (aSRT)), is the cornerstone of BM management, either alone or in combination with surgery and systemic therapies. We review the modern therapeutic strategies available to treat lung cancer patients with brain involvement. This includes an accurate review of the different technical solutions which can be exploited to provide a "state-of-art" focal RT and also a detailed description of the systemic agents available as effective alternatives to SRS/SRT when a targetable molecular driver is present. In addition to the validated treatment options, we also discuss the future perspective for focal RT, based on emerging clinical reports (e.g., SRS for patients with many BMs from NSCLC or SRS for BMs from SCLC), together with a presentation of innovative and promising findings in translational research and the combination of novel targeted agents with SRS/SRT.

Fractionated versus staged gamma knife radiosurgery for mid-to-large brain metastases: a propensity score-matched analysis

PURPOSE

To compare treatment results between fractionated gamma knife radiosurgery (f-GKRS) and staged gamma knife radiosurgery (s-GKRS) for mid-to-large brain metastases (BMs).

METHODS

We retrospectively analyzed data of patients with medium (4-10 mL) to large (> 10 mL) BMs who underwent s-GKRS or f-GKRS between March 2008 and September 2022. Patients were treated with (i) s-GKRS before May 2018 and (ii) f-GKRS after May 2018. Patients who underwent follow-up magnetic resonance imaging at least once were enrolled. Case-matched studies were conducted by applying propensity score matching to minimize treatment selection bias and potential confounding. Local control (LC) was set as the primary endpoint and overall survival (OS) as the secondary endpoint.

RESULTS

This study included 129 patients with 136 lesions and 70 patients with 78 lesions who underwent s-GKRS and f-GKRS, respectively. Overall, 124 lesions (62 lesions in each group) were selected in the case-matched group. No differences were observed in the 6-month and 1-year cumulative incidences of LC failure between the s-GKRS and f-GKRS groups (15.6% vs. 15.9% at 6 months and 25.6% vs. 25.6% at 1 year; p = 0.617). One-year OS rates were 62.6% (95% confidence interval [CI]: 45.4-75.7%) and 73.9% (95% CI: 58.8-84.2%) in the s-GKRS and f-GKRS groups, respectively. The post-GKRS median survival time was shorter in the s-GKRS group than in the f-GKRS group (17 vs. 36 months), without significance (p = 0.202).

CONCLUSIONS

This is the first study to compare f-GKRS and s-GKRS in large BMs. Fractionation is as effective as staged GKRS for treating mid-to-large BMs.

An exploratory analysis of MR-guided fractionated stereotactic radiotherapy in patients with brain metastases

Purpose

To assess the feasibility and potential benefits of online adaptive MR-guided fractionated stereotatic radiotherapy (FSRT) in patients with brain metastases (BMs).

Methods and materials

Twenty-eight consecutive patients with BMs were treated with FSRT of 30 Gy in 5 fractions on the 1.5 T MR-Linac. The FSRT fractions employed daily MR scans and the contours were utilized to create each adapted plan. The brain lesions and perilesional edema were delineated on MR images of pre-treatment simulation (Fx0) and all fractions (Fx1, Fx2, Fx3, Fx4 and Fx5) to evaluate the inter-fractional changes. These changes were quantified using absolute/relative volume, Dice similarity coefficient (DSC) and Hausdorff distance (HD) metrics. Planning target volume (PTV) coverage and organ at risk (OAR) constraints were used to compare non-adaptive and adaptive plans.

Results

A total of 28 patients with 88 lesions were evaluated, and 23 patients (23/28, 82.1%) had primary lung adenocarcinoma. Significant tumor volume reduction had been found during FSRT compared to Fx0 for all 88 lesions (median -0.75%, -5.33%, -9.32%, -17.96% and -27.73% at Fx1, Fx2, Fx3, Fx4 and Fx5, p < 0.05). There were 47 (47/88, 53.4%) lesions being accompanied by perilesional edema and the inter-fractional changes were significantly different compared to those without perilesional edema (p < 0.001). Patients with multiple lesions (13/28, 46.4%) had more significant inter-fractional tumor changes than those with single lesion (15/28, 53.6%), including tumor volume reduction and anatomical shift (p < 0.001). PTV coverage of non-adaptive plans was below the prescribed coverage in 26/140 fractions (19%), with 12 (9%) failing by more than 10%. All 140 adaptive fractions met prescribed target coverage. The adaptive plans also had lower dose to whole brain than non-adaptive plans (p < 0.001).

Conclusions

Significant inter-fractional tumor changes could be found during FSRT in patients with BMs treated on the 1.5 T MR-Linac. Daily MR-guided re-optimization of treatment plans showed dosimetric benefit in patients with perilesional edema or multiple lesions.

Stereotactic Radiation Therapy for Brain Metastases: Factors Affecting Outcomes and Radiation Necrosis

Stereotactic radiation therapy (SRT) is a proven effective treatment for brain metastases (BM); however, symptomatic radiation necrosis (RN) is a late effect that may impact on patient’s quality of life. The aim of our study was to retrospectively evaluate survival outcomes and characterize the occurrence of RN in a cohort of BM patients treated with ablative SRT at Federico II University Hospital. Clinical and dosimetric factors of 87 patients bearing a total of 220 BMs treated with SRT from 2016 to 2022 were analyzed. Among them, 46 patients with 127 BMs having clinical and MRI follow-up (FUP) ≥ 6 months were selected for RN evaluation. Dosimetric parameters of the uninvolved brain (brain without GTV) were extracted. The crude local control was 91% with neither clinical factors nor prescription dose correlating with local failure (LF). At a median FUP of 9 (1–68) months, the estimated median overall survival (OS), progression-free survival (PFS), and brain progression-free survival (bPFS) were 16, 6, and 9 months, respectively. The estimated OS rates at 1 and 3 years were 59.8% and 18.3%, respectively; bPFS at 1 and 3 years was 29.9% and 13.5%, respectively; PFS at 1 and 3 years was 15.7% and 0%, respectively; and local failure-free survival (LFFS) at 1 and 3 years was 87.2% and 83.8%, respectively. Extracranial disease status was an independent factor related to OS. Fourteen (30%) patients manifested RN. At multivariate analysis, adenocarcinoma histology, left location, and absence of chemotherapy were confirmed as independent risk factors for any-grade RN. Nine (20%) patients developed symptomatic (G2) RN, which improved or stabilized after 1–16 months of steroid therapy. With prompt recognition and, when necessary, medical therapy, RN radiological and clinical amelioration can be obtained.

Dose-staged Gamma Knife radiosurgery for meningiomas: A retrospective study in a single center

Objective

This study aimed to study the efficiency and safety of a dose-staged Gamma Knife radiosurgery strategy for large meningiomas or meningiomas close to important nerve structures.

Methods

This study evaluates the outcome of a prospectively accrued series of 71 consecutive patients with meningiomas treated with staged dose-fractionated Gamma Knife radiosurgery. The average peripheral doses for the first and second fractions were 9.0 ± 0.9 Gy (8–12 Gy) and 8.6 ± 0.7 Gy (range, 7–10 Gy), respectively. The interval between fractions was 6.1 ± 1.9 months (range, 3–12 months). The median follow-up time was 36 months (12–96 months).

Results

During the follow-up period after the second fraction, 97.2% achieved tumor control in our series. A total of 2 patients exhibited local recurrence at 30 and 60 months after the second fraction, respectively. No treatment-related complications or new long-term neurological dysfunctions were reported. MRIs observed slightly or moderately increased peritumoral edema in six patients, but no specific neurological complaints are attributed to this finding.

Conclusion

This study investigates the efficiency and safety of dose-staged Gamma Knife radiosurgery as an alternative option for meningiomas that were large in volume, adjacent to crucial structures, or in patients with contraindications to craniotomy.

Volume prediction for large brain metastases after hypofractionated gamma knife radiosurgery through artificial neural network

The effectiveness of single-session gamma knife radiosurgery (GKRS) for small metastatic brain tumors has been proven, but hypofractionated GKRS (hfGKRS) for large brain metastases (BM) from the linear quadratic (LQ) model is uncertain. The purpose of this study was to investigate volume changes large BM after hfGKRS from the LQ model and predict volume changes using artificial neural network (ANN). We retrospectively investigated the clinical findings of 28 patients who underwent hfGKRS with large BM (diameter >3 cm or volume >10 cc). A total of 44 tumors were extracted from 28 patients with features. We randomly divided 30 large brain tumors as training set and 14 large brain tumors as test set. To predict the volume changes after hfGKRS, we used ANN models (single-layer perceptron (SLP) and multi-layer perceptron (MLP)). The volume reduction was 96% after hfGKRS for large BM from the LQ model. ANN model predicted volume changes with 70% and 80% accuracy for SLP and MLP, respectively. Even in large BM, hfGKRS from the LQ model could be a good treatment option. Additionally, the MLP model could predict volume changes with 80% accuracy after hfGKRS for large BM.

Staged radiosurgery alone versus postoperative cavity radiosurgery for patients with midsize-to-large brain metastases: a propensity score matching analysis

OBJECTIVE

The authors investigated and compared the results of staged stereotactic radiosurgery (S-SRS) alone and those of postoperative cavity SRS (C-SRS) for patients with midsize-to-large brain metastases (BMs).

METHODS

Patients with BMs who had undergone S-SRS or C-SRS during the period from 2010 to 2020 were retrospectively identified from an institutional database. The two treatment groups were generated by propensity score matching (PSM; match ratio 2:1) based on 13 potential prognostic covariates: sex, age, Karnofsky Performance Status, type of primary cancer, timing of BM diagnosis, extracranial disease status, driver mutations, molecular target therapy, neurological symptoms, number of BMs, location of BMs treated with S-SRS or C-SRS, maximal tumor or cavity volume, and cumulative intracranial tumor volume. Patient survival and control of intracranial disease were compared between the S-SRS and C-SRS groups using time-dependent analyses taking into account competing events.

RESULTS

In total, 110 patients in the S-SRS group and 62 in the C-SRS group were selected by PSM. In the S-SRS group, the median interval between the two radiosurgical sessions was 21 days, and the median total prescription dose was 28 Gy at 50%. In the C-SRS group, the median time from surgery to C-SRS was 16 days, and the median prescription dose delivered to the surgical cavity was 15 Gy at 55%. At the time point of data set fixation, 129 patients had died, 43 were alive, and none had been lost to follow-up. The 2-year survival rates for the S-SRS and C-SRS groups after the initial intervention were 33% and 37% and the median survival times were 14.8 and 17.5 months, respectively (p = 0.33). The 2-year cumulative neurological mortality rates were 11% and 9%, respectively (p = 0.65). The 2-year local failure rates were 32% and 12% (p = 0.036) and the 2-year distant recurrence rates were 55% and 58%, respectively (p = 0.53). The 2-year leptomeningeal disease development rates were 9% and 25%, respectively (p = 0.007).

CONCLUSIONS

The present study revealed no significant difference in overall survival or cumulative neurological mortality between the S-SRS and C-SRS groups. The local control failure rate was significantly higher in the S-SRS group, whereas the incidence of leptomeningeal disease development was significantly higher in the C-SRS group.

Metastatic Neoplasm Volume Kinetics Following Two-Staged Stereotactic Radiosurgery

INTRODUCTION

Multisession staged stereotactic radiosurgery (2-SSRS) represents an alternative approach for management of large brain metastases (LBMs), with potential advantages over fractionated SRS. We investigated the clinical efficacy and safety of 2-SSRS in patients with LBMs.

METHODS

LBMs patients treated with 2-SSRS between 2014-2020 were evaluated. Demographic, clinical, and radiologic information was obtained. Volumetric measurements at first SSRS, second SSRS, and follow-up imaging studies were obtained. Characteristics that might predict response to 2-SSRS were evaluated through Fischer-exact or Mann-Whitney U test.

RESULTS

Twenty-four patients with 26 LBMs were included in the study. Median marginal doses for first and second SSRS were 15 Gy (14-18 Gy) and 15 Gy (12-16 Gy), respectively. Median tumor volumes at first SSRS, second SSRS, and 3-month follow-up were 8.1 cm³ (1.5-28.5 cm³), 3.3 cm³ (0.8-26.1 cm³), and 2.2 cm³ (0.2-10.1 cm³), respectively. Overall, 24/26 lesions (92%) demonstrated early local control following the first SSRS with 17 lesions (71%) demonstrating a decrease of >30% in the T1 post-contrast MRI volume before the second SSRS and 3 lesions (12%) remaining stable. Eventually, four lesions showed disease progression after 2-SSRS. The median time to local progression was not reached and the median time to intracranial progression was 9.1 months.

CONCLUSIONS

Our study supports the effectiveness and safety of 2-SSRS as a treatment modality for patients with large, symptomatic brain metastases, especially in poor surgical candidates. The local failure rate and low occurrence of adverse effects are comparable to other staged radiosurgery studies.

Cerebral metastases

Brain metastases are common and deadly. Over the last 25 years GKNS has been established as an invaluable treatment. It may be used as a primary treatment or after either surgery or WBRT. Patients are assessed using one of a number of available scales. GKNS may be repeated for new metastases and for unresponsive tumors. Prescription doses are usually between 18 and 20Gy. The use of advanced MR techniques to highlight sensitive structures like the hippocampi have extended the efficacy of the treatment. More recently GKNS has been used with different target therapies with improved results. More recently frameless treatments have become more popular in this group of very sick patients. GKNS controls tumors in between 80% and over 95% of cases and may even be used for brainstem tumors.

A multidisciplinary management algorithm for brain metastases

The incidence of brain metastases continues to present a management issue despite the advent of improved systemic control and overall survival. While the management of oligometastatic disease (ie, 1-4 brain metastases) with surgery and radiation has become fairly straightforward in the era of radiosurgery, the management of patients with multiple metastatic brain lesions can be challenging. Here we review the available evidence and provide a multidisciplinary management algorithm for brain metastases that incorporates the latest advances in surgery, radiation therapy, and systemic therapy while taking into account the latest in precision medicine-guided therapies. In particular, we argue that whole-brain radiation therapy can likely be omitted in most patients as up-front therapy.

Brain metastases: An update on the multi-disciplinary approach of clinical management

IMPORTANCE

Brain metastasis (BM) is the most common malignant intracranial neoplasm in adults with over 100,000 new cases annually in the United States and outnumbering primary brain tumors 10:1.

OBSERVATIONS

The incidence of BM in adult cancer patients ranges from 10-40%, and is increasing with improved surveillance, effective systemic therapy, and an aging population. The overall prognosis of cancer patients is largely dependent on the presence or absence of brain metastasis, and therefore, a timely and accurate diagnosis is crucial for improving long-term outcomes, especially in the current era of significantly improved systemic therapy for many common cancers. BM should be suspected in any cancer patient who develops new neurological deficits or behavioral abnormalities. Gadolinium enhanced MRI is the preferred imaging technique and BM must be distinguished from other pathologies. Large, symptomatic lesion(s) in patients with good functional status are best treated with surgery and stereotactic radiosurgery (SRS). Due to neurocognitive side effects and improved overall survival of cancer patients, whole brain radiotherapy (WBRT) is reserved as salvage therapy for patients with multiple lesions or as palliation. Newer approaches including multi-lesion stereotactic surgery, targeted therapy, and immunotherapy are also being investigated to improve outcomes while preserving quality of life.

CONCLUSION

With the significant advancements in the systemic treatment for cancer patients, addressing BM effectively is critical for overall survival. In addition to patient's performance status, therapeutic approach should be based on the type of primary tumor and associated molecular profile as well as the size, number, and location of metastatic lesion(s).

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. 

Volumetric Response of Limited Brain Metastatic Disease to Focal Hypofractionated Radiation Therapy

Background: This is a retrospective study aimed at assessing the volumetric response, morbidity and failure rates of hypofractionated radiation therapy (HFRT) for definitive focal management of limited brain metastasis. Methods: Patients managed with HFRT for unresected limited metastatic (≤10 lesions) brain disease were entered into an ethics-approved database. Included patients had been deemed unsuitable for surgical resection, and lesions managed with prior radiation therapy were excluded. HFRT was delivered using IMRT or VMAT with 25 Gy or 30 Gy in five fractions. Individual lesions had volumetric assessment performed at three timepoints. The primary endpoint was the change of volume from baseline (GTV0) to one month post-HFRT (GTV1) and to seven months post-HFRT (GTV7). Secondary endpoints were local failure, survival and rates of radiation necrosis. Results: One hundred and twenty-four patients with 233 lesions were managed with HFRT. Median follow-up was 23.5 months with 32 (25.8%) patients alive at censure. Median overall survival was 7.3 months with 36.3% survival at 12 months. Superior survival was predicted by smaller GTV0 (p = 0.003) and increased percentage of volumetric response (p < 0.001). Systemic therapy was delivered to 81.5% of patients. At one month post-HFRT, 206 metastases (88.4%) were available for assessment and at seven months post-HFRT, 118 metastases (50.6%) were available. Median metastasis volume at GTV0 was 1.6 cm³ (range: 0.1–19.1). At GTV1 and GTV7, this reduced to 0.7 cm³ (p < 0.001) and 0.3 cm³ (p < 0.001), respectively, correlating to percentage reductions of 54.9% and 83.3%. No significant predictors of volumetric response following HFRT were identified. Local failure was identified in 4.3% of lesions and radiation necrosis in 3.9%. Conclusion: HFRT is an effective therapy for limited metastatic disease in the brain to maximise initial volumetric response whilst minimising toxicity.

Clinical assessment of a biophysical model for distinguishing tumor progression from radiation necrosis

PURPOSE

The efficacy of an imaging-driven mechanistic biophysical model of tumor growth for distinguishing radiation necrosis from tumor progression in patients with enhancing lesions following stereotactic radiosurgery (SRS) for brain metastasis is validated.

METHODS

We retrospectively assessed the model using 73 patients with 78 lesions and histologically confirmed radiation necrosis or tumor progression. Postcontrast T1-weighted MRI images were used to extract parameters for a mechanistic reaction-diffusion logistic growth model mechanically coupled to the surrounding tissue. The resulting model was then used to estimate mechanical stress fields, which were then compared with edema visualized on FLAIR imaging using DICE similarity coefficients. DICE, model, and standard radiographic morphometric analysis parameters were evaluated using a receiver operating characteristic (ROC) curve for prediction of radiation necrosis or tumor progression. Multivariate logistic regression models were then constructed using mechanistic model parameters or advanced radiomic features. An independent validation was performed to evaluate predictive performance.

RESULTS

Tumor cell proliferation rate resulted in ROC AUC = 0.86, 95% CI: 0.76-0.95, P < 0.0001, 74% sensitivity and 95% specificity) and DICE similarity coefficient associated with high stresses demonstrated an ROC AUC = 0.93, 95% CI: 0.86-0.99, P < 0.0001, 81% sensitivity and 95% specificity. In a multivariate logistic regression model using an independent validation dataset, mechanistic modeling parameters had an ROC AUC of 0.95, with 94% sensitivity and 96% specificity.

CONCLUSIONS

Imaging-driven biophysical modeling of tumor growth represents a novel method for accurately predicting clinically significant tumor behavior.

Multidisciplinary treatment of primary intracranial yolk sac tumor: A case report and literature review

RATIONALE

Intracranial yolk sac tumors (YSTs) are rare malignancies with limited treatment options and a dismal prognosis. They are usually managed with surgical resection and chemoradiotherapy.

PATIENT CONCERNS

Here, we report a patient with primary YST in the pineal region who achieved long term survival. Despite undergoing treatment, he experienced several recurrences over a 15-year period.

DIAGNOSIS

Brain magnetic resonance imaging (MRI) demonstrated the presence of space-occupying lesions in the pineal region and the medial tail of the left lateral ventricle. The tumors were excised, and the histological diagnosis suggested an intracranial YST.

INTERVENTIONS

The patient achieved long term survival after combined modality therapy including surgery, stereotactic radiosurgery (SRS)/intensity modulated radiation therapy (IMRT), chemotherapy, and targeted therapy.

OUTCOMES

The disease remained stable. However, the patient gave up treatment and passed away in October 2020, with a total survival of about 15 years.

LESSONS

To the best of our knowledge, this patient with intracranial YST had received a longer survival compared with other published reports. We summarize previously published reports of intracranial YST and discuss the importance of multidisciplinary treatment. SRS may have a role, as a focal boost to residual tumor after resection or in case of recurrence after conventional radiotherapy, in the multimodality management of intracranial YSTs.

Expanded Radiosurgery Capabilities Utilizing Gamma Knife Icon™

The indications and techniques for the treatment of intracranial lesions continue to evolve with the advent of novel technologies. The Gamma Knife Icon™ (GK Icon™) is the most recent model available from Elekta, providing a frameless solution for stereotactic radiosurgery. At our institution, 382 patients with 3,213 separate intracranial lesions have been treated with frameless stereotactic radiotherapy using the GK Icon. The wide range of diagnoses include brain metastases, meningiomas, arteriovenous malformations, acoustic neuromas, pituitary adenomas, and several other histologies. The ability to perform both frame and frameless treatments on the GK Icon has significantly increased our daily volume by almost 50% on a single machine. Although the frameless approach allows one to take advantage of the precision in radiosurgery, the intricacies regarding treatment with this frameless system are not well established. Our initial experience will help to serve as a guide to those wishing to implement this novel technology in their practice.

Hypofractionated frameless gamma knife radiosurgery for large metastatic brain tumors

Hypofractionated stereotactic radiosurgery has become an alternative for metastatic brain tumors (METs). We aimed to analyze the efficacy and safety of frameless hypofractionated Gamma Knife radiosurgery (hfGKRS) in the management of unresected, large METs. All patients who were managed with hfGKRS for unresected, large METs (> 4 cm³) between June 2017 and June 2020 at a single center were reviewed in this retrospective study. Local control (LC), progression-free survival (PFS), overall survival (OS), and toxicities were investigated. A total of 58 patients and 76 METs with regular follow-up were analyzed. LC rate was 98.5% at six months, 96.0% at one year, and 90.6% at 2 years during a median follow-up of 12 months (range, 2-37). The log-rank test indicated no difference in the distribution of LC for any clinical or treatment variable. PFS was 86.7% at 6 months, 66.6% at 1 year, and 58.5% at 2 years. OS was 81% at 6 months, 63.6% at one year, and 50.7% at 2 years. On the log-rank test, clinical parameters such as control status of primary cancer, presence of extracranial metastases, RTOG-RPA class, GPA group, and ds-GPA group were significantly associated with PFS and OS. Patients presented with grade 1 (19.0%), grade 2 (3.5%) and grade 3 (5.2%) side effects. Radiation necrosis was not observed in any patients. Our current results suggest that frameless hfGKRS for unresected, large METs is a rational alternative in selected patients with promising results.

Single- and Multifraction Stereotactic Radiosurgery Dose/Volume Tolerances of the Brain

PURPOSE

As part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy investigating normal tissue complication probability (NTCP) after hypofractionated radiation therapy, data from published reports (PubMed indexed 1995-2018) were pooled to identify dosimetric and clinical predictors of radiation-induced brain toxicity after single-fraction stereotactic radiosurgery (SRS) or fractionated stereotactic radiosurgery (fSRS).

METHODS AND MATERIALS

Eligible studies provided NTCPs for the endpoints of radionecrosis, edema, or symptoms after cranial SRS/fSRS and quantitative dose-volume metrics. Studies of patients with only glioma, meningioma, vestibular schwannoma, or brainstem targets were excluded. The data summary and analyses focused on arteriovenous malformations (AVM) and brain metastases.

RESULTS

Data from 51 reports are summarized. There was wide variability in reported rates of radionecrosis. Available data for SRS/fSRS for brain metastases were more amenable to NTCP modeling than AVM data. In the setting of brain metastases, SRS/fSRS-associated radionecrosis can be difficult to differentiate from tumor progression. For single-fraction SRS to brain metastases, tissue volumes (including target volumes) receiving 12 Gy (V12) of 5 cm³, 10 cm³, or >15 cm³ were associated with risks of symptomatic radionecrosis of approximately 10%, 15%, and 20%, respectively. SRS for AVM was associated with modestly lower rates of symptomatic radionecrosis for equivalent V12. For brain metastases, brain plus target volume V20 (3-fractions) or V24 (5-fractions) <20 cm³ was associated with <10% risk of any necrosis or edema, and <4% risk of radionecrosis requiring resection.

CONCLUSIONS

The risk of radionecrosis after SRS and fSRS can be modeled as a function of dose and volume treated. The use of fSRS appears to reduce risks of radionecrosis for larger treatment volumes relative to SRS. More standardized dosimetric and toxicity reporting is needed to facilitate future pooled analyses that can refine predictive models of brain toxicity risks.

Two-Session Radiosurgery for Large Primary Tumors Affecting the Brain

Introduction Surgery is an option for patients with large, symptomatic primary tumors affecting the brain. However, surgery might not be suitable for all tumors, especially those located in sensitive areas such as the pineal region and the hypothalamus. Single-session stereotactic radiosurgery (SRS) might not provide an adequate dose for long-term local control due to the initial tumor volume and the involvement of radiation sensitive organs at risk (OARs). Two-session radiosurgery has been described as a feasible strategy for dose escalation in large secondary brain tumors. This report describes a series of patients treated upfront with two-session radiosurgery for primary tumors affecting the brain. Materials and methods From May 2017 to January 2020, eight patients with primary tumors affecting the brain were treated with two-session radiosurgery due to either an initial large tumor volume or tumor localization and the involvement of OARs. The response was assessed by imaging and clinical evaluations. Results A total of eight patients were treated, nine tumors were treated with two-session radiosurgery, four patients had tumors in the pineal region (50%), and the rest were in the hypothalamic region (25%) or elsewhere. The mean tumor volume for the first SRS session was 15 mL (range 5.2 to 51.6 mL), the mean prescription dose was 13 Gy, and the timespan between both sessions was 30 days (range, 30 to 42 days). During the second session, tumor volume was reduced to 73.6% (range, -20% to 98.7%) of the original dimension, mean tumor volume was 5 mL (range, 0.1 to 17.8 ml), mean prescription dose for the second session was 16.2 Gy estimated by time, dose, and fractionation and by bioequivalent dose under alpha-beta values often to be equivalent to a single dose of 15.8 Gy. Doses to the OARs for the optic pathway were equivalent to a single maximum dose of 9.75 Gy (range, 7.12 to 10.92), and to the brainstem, the equivalent was a maximum dose of 12.3 Gy (range, 5.6 to 15.07). At last follow-up, at a mean of 336.5 days (range, 65 to 962 days), seven patients were alive, five tumors had a partial response (PR), and three had stable disease in accordance to Response Evaluation Criteria in Solid Tumors (RECIST) criteria. One patient died 435 days after treatment, the Karnofsky Performance Status (KPS) was 90 at the first session, 90 at the second session, and was maintained at last follow-up. No adverse radiation effects were reported. Conclusions Two-stage SRS proved to be a safe method to escalate dose in proportionately large volume primary brain tumors whose histology is expected to have a quick biological response to radiation. Longer follow-up is needed to determine the long-term effectiveness by tumor subtypes of two-stage SRS in the same manner as it has been proven in single session SRS series in smaller tumor volumes.

Two-staged stereotactic radiosurgery for the treatment of large brain metastases: Single institution experience and review of literature

Introduction: Two-staged stereotactic radiosurgery (SRS) has been shown as an effective treatment for brain metastases that are too large for single fraction SRS. Methods: Patients with large brain metastases (>4 cm³) treated with two-staged SRS from January 2017 to December 2019 at our institution were retrospectively identified. Results: There were 23 brain metastases treated. The normal brain volume receiving equivalent 12Gy-in-single-fraction was defined as V_12E. The V_12E for original single-fraction GKS plan (mean of 41.4 cm³, range 5.6-146.1 cm³) was significantly higher compared to that of the second stage (mean of 23.7 cm³, range 2.8-92.7 cm³). The median tumor volume measured at the second stage (4.30 cm³) was reduced by an average of 52.2% compared to the first stage (9.58 cm³). Three patients (27.3%) showed local tumor progression in 4 tumors (20%). The median time to progression was 152 days. Conclusions: Two-staged SRS is an effective treatment technique for large brain metastasis that results in significant reduction of tumor volume at the second stage SRS. Optimal treatment dose has not yet been defined.

Single- versus 2-session Gamma Knife surgery for symptomatic midsize brain metastases: a propensity score-matched analysis

OBJECTIVE

Two-session Gamma Knife surgery (GKS) has recently been demonstrated to be an effective and less-invasive alternative for large brain metastases not treatable by microsurgical resection. This raises the clinical question of whether the 2-session GKS strategy further improves treatment outcomes for patients with symptomatic midsize brain metastases (2-10 cm3) as compared to single-session GKS. The present study aimed to compare the local therapeutic effects and toxicities of single-session and 2-session GKS for treating these lesions.

METHODS

Patients with focal neurological deficits attributable to midsize brain metastases who underwent upfront GKS during the period from 2010 to 2018 were retrospectively identified from an institutional database. Patients for whom both post-GKS imaging studies and neurological evaluations from outpatient visits were available were eligible. Using propensity score-matching (PSM) analysis, unique matched pairs which had a similar likelihood of receiving 2-session GKS were generated. The main outcome measure was a composite of imaging and/or neurological worsening of the lesion of interest. Functional improvement and overall survival (OS) were also compared between the 2 treatment arms.

RESULTS

In total, 219 cancer patients with 252 symptomatic midsize brain metastases were eligible. Of these 252 tumors, 176 and 76 were treated with single- and 2-session GKS, respectively. After PSM, 68 pairs of tumors were obtained. The Gray test showed that 2-session GKS achieved a longer local progression-free interval than single-session GKS (1-year local control rate: 84% vs 53%; HR 0.31, 95% CI 0.16-0.63, p = 0.001). Two-session GKS was also associated with greater functional improvement in KPS scores (mean 18.3 ± 14.6 vs 12.8 ± 14.1, p = 0.040). The median OS did not differ significantly between single- and 2-session GKS (15.6 vs 24.7 months; HR 0.69, 95% CI 0.44-1.10, p = 0.11).

CONCLUSIONS

Two-session GKS achieved more durable local tumor control and greater functional improvement than single-session GKS for patients with symptomatic midsize brain metastases, although there was no OS advantage.

MRI appearance change during stereotactic radiotherapy for large brain metastases and importance of treatment plan modification during treatment period

Purpose

We aimed to evaluate the magnetic resonance imaging (MRI) appearance changes during stereotactic radiotherapy (SRT) for large sized brain metastases, and analyze the lesions necessitating treatment plan modification.

Materials and methods

A total of 23 patients (27 lesions, >2 cm in tumor diameter) underwent SRT and all lesions were evaluated the appearance changes which had the necessity of the treatment plan modification. The appearance change of tumor during SRT was evaluated using gadolinium-enhanced MRI. The reasons of the modification were classified into tumor reduction, tumor enlargement, displacement, and shape change.

Results

Among the 27 lesions, 55.6% required the treatment plan modification. The reasons were tumor reduction in six lesions, tumor enlargement in three lesions, displacement in three lesions, and shape change in three lesions. The planning target volume (PTV) size changed up to 43.0% and the shift of center of PTV was a maximum of 1.7 mm. The pathological status (adenocarcinoma vs others) and timing of steroid administration (prior vs after SRT start) were the predictive factors of tumor changes required the modification.

Conclusions

As tumor changes might occur even during short period of SRT, the treatment plan evaluation and modification were important in SRT for large brain metastases.

Three-stage Gamma Knife treatment for metastatic brain tumors larger than 10 cm3: a 2-institute study including re-analyses of earlier results using competing risk analysis

OBJECTIVEThe results of 3-stage Gamma Knife treatment (3-st-GK-Tx) for relatively large brain metastases have previously been reported for a series of patients in Chiba, Japan (referred to in this study as the C-series). In the current study, the authors reappraised, using a competing risk analysis, the efficacy and safety of 3-st-GK-Tx by comparing their experience with that of the C-series.METHODSThis was a retrospective cohort study. Among 1767 patients undergoing GK radiosurgery for brain metastases at Mito Gamma House during the 2005-2015 period, 78 (34 female, 44 male; mean age 65 years, range 35-86 years) whose largest tumor was > 10 cm3, treated with 3-st-GK-Tx, were studied (referred to in this study as the M-series). The target volumes were covered with a 50% isodose gradient and irradiated with a peripheral dose of 10 Gy at each procedure. The interval between procedures was 2 weeks. Because competing risk analysis had not been employed in the published C-series, the authors reanalyzed the previously published data using this method.RESULTSThe overall median survival time after 3-st-GK-Tx was 8.3 months (95% CI 5.6-12.0 months) in the M-series and 8.6 months (95% CI 5.5-10.6 months) in the C-series (p = 0.41). Actuarial survival rates at the 6th and 12th post-3-st-GK-Tx months were, respectively, 55.1% and 35.2% in the M-series and 62.5% and 26.4% in the C-series (HR 1.175, 95% CI 0.790-1.728, p = 0.42). Cumulative incidences at the 12th post-3-st-GK-Tx, determined by competing risk analyses, of neurological deterioration (14.2% in C-series vs 12.8% in M-series), neurological death (7.2% vs 7.7%), local recurrence (4.8% vs 6.2%), repeat SRS (25.9% vs 18.0%), and SRS-related complications (2.3% vs 5.1%) did not differ significantly between the 2 series.CONCLUSIONSThere were no significant differences in post-3-st-GK-Tx results between the 2 series in terms of overall survival times, neurological death, maintained neurological status, local control, repeat SRS, and SRS-related complications. The previously published results (C-series) are considered to be validated by the M-series results.

Outcome of three-fraction gamma knife radiosurgery for brain metastases according to fractionation scheme: preliminary results

PURPOSE

The optimal interfraction intervals for fractionated radiosurgery has yet to be established. We investigated the outcome of fractionated gamma knife radiosurgery (FGKRS) for large brain metastases (BMs) according to different interfraction intervals.

METHODS

Between September 2016 and May 2018, a total of 45 patients who underwent FGKRS for BMs were enrolled in this study. They were divided into two groups (standard fractionation over 3 consecutive days with a 24-h interfraction interval versus prolonged fractionation over 4 or 5 days with an interfraction interval of at least 48-h). BMs with ≥ 2 cm in maximum diameter or ≥ 5 cm³ in volume were included in analysis.

RESULTS

Among 52 BMs treated with 3-fraction GKRS, 25 (48.1%) were treated with standard fractionation scheme, and 27 (51.9%) with prolonged fractionation scheme. The median follow-up period was 10.5 months (range 5-25). Local tumor control rates of the standard group were 88.9% at 6 months and 77.8% at 12 months, whereas those of the prolonged group were 100% at 6 and 12 months (p = 0.023, log-rank test). In multivariate analysis, fractionation scheme (hazard ratio [HR] 0.294, 95% CI 0.099-0.873; p = 0.027) and tumor volume (HR 0.200, 95% CI 0.051-0.781; p = 0.021) were revealed as the only significant factors affecting the local tumor control after 3-fraction GKRS.

CONCLUSIONS

Our preliminary tumor control results suggest a promising role of 3-fraction GKRS with an interfraction interval of at least 48-h. This fractionation regimen could be an effective and safe treatment option in the management of large BMs.

Two-session Radiosurgery as Initial Treatment for Newly Diagnosed Large, Symptomatic Brain Metastases from Breast and Lung Histology

Introduction

Surgery is considered the treatment of choice for patients with large, symptomatic brain metastases. This report describes a series of patients treated with upfront two-session radiosurgery rather than surgery for large brain metastases from breast and lung histology.

Methods

From October 2016 to January 2019, 10 consecutive patients with neurologic symptoms from large brain metastases producing mass effects underwent two sessions of radiosurgical treatments 30 days apart. The response was assessed by imaging and clinical evaluations. 

Results

Ten patients had a total of 36 tumors; of these, 22 lesions with a mean volume of 12.3 ml (range, 7-78.4 ml) underwent two-session radiosurgery. The mean prescription dose for the first treatment was 13 Gy (range, 9-18 Gy) to the 50% isodose line, and the intratumoral mean dose was 17.9 Gy (12-22.9). All 10 patients had neurological symptoms, with a mean Karnofsky physical score (KPS) of 60 (range, 50-70) on the day of treatment. None of these patients required neurosurgical or emergency consultation related to worsening of neurological symptoms between the first and second treatments. At 30 days, the mean KPS was 80 and maintained at 80 at the last follow-up (range, 60-100; P=0.002), and mean lesion volume was 4.1 ml (range, 1.3-70 ml). The mean prescription dose for the second treatment was 12 Gy (range, 9-18 Gy) to the 50% isodose line, and the intratumoral mean dose was 17.9 Gy (11-22.4). The mean overall survival was 24 months (range, 3-32 months). At last follow-up, three patients (30%) had died, two of systemic progression and one of tumor progression, and at one year, local tumor control was 91% and 19 (86%) lesions showed documented local control at last follow up. In those tumors that progressed, the mean time to progression was eight months (range, 5-20 months), and the mean time to surgery was nine months (range, 5-32 months).

Conclusion

Two-session radiosurgery proved to be a safe treatment for patients with large, symptomatic metastases in this series. Neurological worsening after radiosurgery for large lesions of breast and lung histology may be an infrequent event. This strategy in radiosurgery may have neurological benefits for these patients providing adequate local tumor control while reducing the need of upfront surgery at diagnosis.

Cerebral Radiation Necrosis: Incidence, Pathogenesis, Diagnostic Challenges, and Future Opportunities

PURPOSE OF REVIEW

Cerebral radiation necrosis (CRN) is a major dose-limiting adverse event of radiotherapy. The incidence rate of RN varies with the radiotherapy modality, total dose, dose fractionation, and the nature of the lesion being targeted. In addition to these known and controllable features, there is a stochastic component to the occurrence of CRN-the genetic profile of the host or the lesion and their role in the development of CRN.

RECENT FINDINGS

Recent studies provide some insight into the genetic mechanisms underlying radiation-induced brain injury. In addition to these incompletely understood host factors, the diagnostic criteria for CRN using structural and functional imaging are also not clear, though multiple structural and functional imaging modalities exist, a combination of which may prove to be the ideal diagnostic imaging approach. As the utilization of novel molecular therapies and immunotherapy increases, the incidence of CNR is expected to increase and its diagnosis will become more challenging. Tissue biopsies can be insensitive and suffer from sampling biases and procedural risks. Liquid biopsies represent a promising, accurate, and non-invasive diagnostic strategy, though this modality is currently in its infancy. A better understanding of the pathogenesis of CRN will expand and optimize the diagnosis and management of CRN by better utilizing existing treatment options including bevacizumab, pentoxifylline, hyperbaric oxygen therapy, and laser interstitial thermal therapy.

Unexpected Daily Changes in Tumor Volume during Fractionated Gamma Knife Radiosurgery for Solitary Intraventricular Metastatic Renal Cell Carcinoma: A Case Report

For most fractionated stereotactic radiosurgery treatment plans, daily imaging is not routinely performed, because there is little expectation that lesions will change significantly in the short term. However, here, we present the case of an abrupt increase and decrease in tumor volume during fractionated gamma knife radiosurgery (GKRS) for metastatic brain cancer. A 65-year-old man with a history of nephrectomy due to renal cell carcinoma was admitted to our hospital because of mild cognitive disorder and gait disturbance. An initial MRI of the brain demonstrated a 5 × 3 × 4.5 cm-sized, heterogeneously well-enhanced tumor with a large cystic component compressing the left thalamus and corpus callosum near the lateral ventricle. Owing to its large size and proximity to critical structures, we decided to perform 3 fractionated GKRSs over 3 consecutive days. After the first fraction of 9 Gy with 50% isodose, follow-up MRI the next day revealed an unexpected increase in tumor volume up to 30%. Therefore, the radiosurgical plan was adjusted, and GKRS was performed again using the same dose for the second fraction. The image taken on the third day showed rapid shrinkage of the tumor volume. This case shows that a tumor may change its shape and volume unexpectedly even during the short period of a fractionated GKRS session. Hence, for optimal fractionated GKRS treatment of tumors with the likelihood of an abrupt change in the short term, interval imaging should be considered.

Single versus Multifraction Stereotactic Radiosurgery for Large Brain Metastases: An International Meta-analysis of 24 Trials

PURPOSE

Multifraction (MF) stereotactic radiosurgery (SRS) purportedly reduces radionecrosis risk over single-fraction (SF) SRS in the treatment of large brain metastases. The purpose of the current work is to compare local control (LC) and radionecrosis rates of SF-SRS and MF-SRS in the definitive (SF-SRS_D and MF-SRS_D) and postoperative (SF-SRS_P and MF-SRS_P) settings.

METHODS AND MATERIALS

Population, Intervention, Control, Outcomes, Study Design/Preferred Reporting Items for Systematic Reviews and Meta-analyses and Meta-analysis of Observational Studies in Epidemiology guidelines were used to select articles in which patients had "large" brain metastases (Group A: 4-14 cm³, or about 2-3 cm in diameter; Group B: >14 cm³, or about >3 cm in diameter); 1-year LC and/or rates of radionecrosis were reported; radiosurgery was administered definitively or postoperatively. Random effects meta-analyses using fractionation scheme and size as covariates were conducted. Meta-regression and Wald-type tests were used to determine the effect of increasing tumor size and fractionation on the summary estimate, where the null hypothesis was rejected for P < .05.

RESULTS

Twenty-four studies were included, published between 2008 and 2017, with 1887 brain metastases. LC random effects estimate at 1 year was 77.6% for Group A/SF-SRS_D and 92.9% for Group A/MF-SRS_D (P = .18). LC random effects estimate at 1 year was 77.1% for Group B/SF-SRS_D and 79.2% for Group B/MF-SRS_D (P = .76). LC random effects estimate at 1 year was 62.4% for Group B/SF-SRS_P and 85.7% for Group B/MF-SRS_P (P = .13). Radionecrosis incidence random effects estimate was 23.1% for Group A/SF-SRS_D and 7.3% for Group A/MF-SRS_D (P = .003). Radionecrosis incidence random effects estimate was 11.7% for Group B/SF-SRS_D and 6.5% for Group B/MF-SRS_D (P = .29). Radionecrosis incidence random effects estimate was 7.3% for Group B/SF-SRS_P and 7.5% for Group B/MF-SRS_P (P = .85). Metaregression assessing 1-year LC and radionecrosis as a continuous function of increasing tumor volume was not statistically significant.

CONCLUSIONS

Treatment for large brain metastases with MF-SRS regimens may offer a relative reduction of radionecrosis while maintaining or improving relative rates of 1-year LC compared with SF-SRS. These findings are hypothesis-generating and require validation by ongoing and planned prospective clinical trials.

Surgical resection and postoperative radiosurgery versus staged radiosurgery for large brain metastases

PURPOSE

The purpose of this study was to retrospectively evaluate the new treatment paradigm of staged stereotactic radiosurgery (SRS) for the treatment of large brain metastases (BM) compared to the standard of surgical resection followed by SRS.

METHODS

We evaluated 78 patients with large BM treated 2012-2017 with surgical resection and postoperative SRS (surgery + SRS) or staged SRS separated by 1 month. Overall survival (OS) was estimated using the Kaplan Meier method and compared across groups using the log-rank test. Cumulative incidence of neurologic death and local and distant brain failure (LF, DBF) were estimated using competing risk methodology.

RESULTS

Forty patients were treated with surgery + SRS and 38 patients were treated with staged SRS. Median follow-up was 23.2 months (95% CI 20.5-39.3). Median OS was 13.2 months for staged SRS compared to surgery + SRS 9.7 months (p = 0.53). Cumulative incidence of neurologic death at 1 year was 23% after surgery + SRS, 27% after staged SRS (p = 0.69); cumulative incidence of LF at 1 year was 6% and 8% (p = 0.65) and 1-year DBF was 59% and 21% (p ≤ 0.01). Overall rates of leptomeningeal failure and radiation necrosis were similar between the groups (p = 0.63 and p = 1.0).

CONCLUSIONS

Though surgery and postoperative SRS is the standard, staged SRS represents an attractive treatment paradigm for treating large BM without sacrificing LC or survival, and potentially decreases DBF. Prospective studies are needed to validate these findings.

Hypofractionated Radiation Therapy for Large Brain Metastases

Single fraction radiosurgery (SRS) treatment is an effective and recognized alternative to whole brain radiation for brain metastasis. However, SRS is not always possible, especially in tumors of a larger diameter where the administration of high dose in a single fraction is limited by the possibility of acute and late side effects and the dose to the surrounding organs at risk. Hypofractionated radiation therapy allows the delivery of high doses of radiation per fraction while minimizing adverse events, all the while maintaining good local control of lesions. The optimal dose fractionation has however not been established. This overwiew presents available evidence and rationale supporting usage of hypofractionated radiation therapy in the treatment of large brain metastases.

Modern management for brain metastasis patients using stereotactic radiosurgery: literature review and the authors' gamma knife treatment experiences

Historically, whole brain radiotherapy was administered to most patients with brain metastases. However, over the past three decades, stereotactic radiosurgery (SRS), targeted at individual cranial lesions, has been accepted widely. In this study, based on the authors' experiences along with published data, recent trends in SRS for brain metastases are discussed. This article focuses on the following issues: 1) How many tumors can or should be treated with SRS? 2) Two-/three-staged SRS for relatively large tumors, 3) post- or preoperative SRS, and 4) repeat SRS.