Predictors of individual tumor local control after stereotactic radiosurgery for non-small cell lung cancer brain metastases

Factors associated with the local control of brain metastases: a systematic search and machine learning application

BACKGROUND

Enhancing Local Control (LC) of brain metastases is pivotal for improving overall survival, which makes the prediction of local treatment failure a crucial aspect of treatment planning. Understanding the factors that influence LC of brain metastases is imperative for optimizing treatment strategies and subsequently extending overall survival. Machine learning algorithms may help to identify factors that predict outcomes.

METHODS

This paper systematically reviews these factors associated with LC to select candidate predictor features for a practical application of predictive modeling. A systematic literature search was conducted to identify studies in which the LC of brain metastases is assessed for adult patients. EMBASE, PubMed, Web-of-Science, and the Cochrane Database were searched up to December 24, 2020. All studies investigating the LC of brain metastases as one of the endpoints were included, regardless of primary tumor type or treatment type. We first grouped studies based on primary tumor types resulting in lung, breast, and melanoma groups. Studies that did not focus on a specific primary cancer type were grouped based on treatment types resulting in surgery, SRT, and whole-brain radiotherapy groups. For each group, significant factors associated with LC were identified and discussed. As a second project, we assessed the practical importance of selected features in predicting LC after Stereotactic Radiotherapy (SRT) with a Random Forest machine learning model. Accuracy and Area Under the Curve (AUC) of the Random Forest model, trained with the list of factors that were found to be associated with LC for the SRT treatment group, were reported.

RESULTS

The systematic literature search identified 6270 unique records. After screening titles and abstracts, 410 full texts were considered, and ultimately 159 studies were included for review. Most of the studies focused on the LC of the brain metastases for a specific primary tumor type or after a specific treatment type. Higher SRT radiation dose was found to be associated with better LC in lung cancer, breast cancer, and melanoma groups. Also, a higher dose was associated with better LC in the SRT group, while higher tumor volume was associated with worse LC in this group. The Random Forest model predicted the LC of brain metastases with an accuracy of 80% and an AUC of 0.84.

CONCLUSION

This paper thoroughly examines factors associated with LC in brain metastases and highlights the translational value of our findings for selecting variables to predict LC in a sample of patients who underwent SRT. The prediction model holds great promise for clinicians, offering a valuable tool to predict personalized treatment outcomes and foresee the impact of changes in treatment characteristics such as radiation dose.

Prognostic analysis of stereotactic radiosurgery for brain metastases: a single-center retrospective study

OBJECTIVES

Brain metastasis (BM) is a common event during the development of many cancers, and is also one of the main causes of death of patients. Stereotactic radiosurgery (SRS) is an effective treatment for BM. The prognostic effects of various clinical factors on local control (LC) and overall survival (OS) after SRS treatment are still unclear. The purpose of this study is to retrospectively analyze the intracranial progression free survival (iPFS) and OS of patients receiving SRS treatment, and explore the relationship between various clinical characteristics and patient prognosis.

MATERIALS AND METHODS

We collected the clinical information of patients who were diagnosed with BM and received SRS treatment in our center between 2018 and 2021. Univariate and multivariate Cox regression analysis and KM analysis for iPFS and OS were conducted in R software to investigate the prognostic effects of clinical characteristics.

RESULTS

In total, 183 patients that received SRS in our center were enrolled in the cohort. The median iPFS for all patients was 8.87 months (95% CI 6.9-10.6), and the median OS was 16.5 months (95% CI 12.9-20.7). BM number >  = 5 (HR 1.965 [95% CI 1.381-2.796], p < 0.001, FDR-corrected p < 0.001) was found to be strong predictor for shorter iPFS and OS. Subgroup analysis showed that patients with cumulative intracranial tumor volume (CITV) >  = 2.14 cm3 and number >  = 5 had shortest iPFS (P < 0.001) and OS (P = 0.007), compared with other subgroups. For patients with more than 5 BMs, SRS plus whole brain radiotherapy (WBRT) could achieve better local control, compared with SRS alone group (P = 0.0357). Peripheral blood inflammation indicators were associated with the prognosis of BM patients in univariate Cox analysis, but not in multivariate Cox analysis.

CONCLUSIONS

BM number is an independent prognostic factor for BM patients. The prognosis of patients in the subgroup with larger CITV and more BM is the worst. For patients with more than 5 BM, the combination of SRS and WBRT can improve the local control, but cannot prolong the OS.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Retrospective non-inferiority study of stereotactic radiosurgery for more than ten brain metastases

AIM

This study aimed to investigate the clinical benefits of stereotactic radiosurgery (SRS) in patients with > 10 brain metastases (BM) compared to patients with 2-10 BM.

METHODS

The study included multiple BM patients who underwent SRS between 2014 and 2022, excluding patients who underwent whole brain radiotherapy, had a Karnofsky Performance Status score < 60, suspected leptomeningeal disease, or a single BM lesion. Patients were divided into two groups (2-10 and > 10 BM groups) and matched 2:1 based on propensity scores. The primary endpoint was overall survival (OS) in the matched dataset, with intracranial progression-free survival (PFS) as the secondary endpoint. Non-inferiority was established if the upper limit of the 95% confidence interval (CI) of the adjusted hazard ratio was below 1.3.

RESULTS

Of the 1042 patients identified, 434 met eligibility criteria. After propensity score matching, 240 patients were analyzed (160 in the BM 2-10 group and 80 in the > 10 BM group). The median OS was 18.2 months in the 2-10 BM group and 19.4 months in the > 10 BM group (P = 0.60). The adjusted hazard ratio was 0.86 (95% CI: 0.59-1.24), indicating non-inferiority. PFS was not significantly different between the groups (4.8 months vs. 4.8 months, P = 0.94). The number of BM did not significantly impact OS or PFS.

CONCLUSIONS

SRS for selected patients with > 10 BM was non-inferior in terms of OS compared to those with 2-10 BM in a propensity score-matched dataset.

Comparison of dosimetric parameters and robustness for rotational errors in fractionated stereotactic irradiation using automated noncoplanar volumetric modulated arc therapy for patients with brain metastases: single- versus multi-isocentric technique

To compare the dosimetric parameters of automated noncoplanar volumetric modulated arc therapy plans using single-isocentric (SIC) and multi-isocentric (MIC) techniques for patients with two brain metastases (BMs) in stereotactic irradiation and to evaluate the robustness of rotational errors. The SIC and MIC plans were retrospectively generated (35 Gy/five fractions) for 58 patients. Subsequently, a receiver operating characteristic curve analysis between the tumor surface distance (TSD) and V_25Gy was performed to determine the thresholds for the brain tissue. The SIC and MIC plans were recalculated based on the rotational images to evaluate the dosimetric impact of rotational error. The MIC plans showed better brain tissue sparing for TSD > 6.6 cm. The SIC plans provided a significantly better conformity index for TSD ≤ 6.6 cm, while significantly lower gradient index was obtained (3.22 ± 0.56vs. 3.30 ± 0.57, p < 0.05) in the MIC plans with TSD > 6.6 cm. For organs at risk (OARs) (brainstem, chiasm, lens, optic nerves, and retinas), D_0.1 cc was significantly lower (p < 0.05) in the MIC plans than in the SIC plans. The prescription dose could be delivered (D_99%) to the gross tumor volume (GTV) for patients with TSD ≤ 6.6 cm when the rotational error was < 1°, whereas 31% of the D_99% of GTV fell below the prescription dose with TSD > 6.6 cm. MIC plans can be an optimal approach for reducing doses to OARs and providing robustness against rotational errors in BMs with TSD > 6.6 cm.

Novel Mechanisms and Future Opportunities for the Management of Radiation Necrosis in Patients Treated for Brain Metastases in the Era of Immunotherapy

Radiation necrosis, also known as treatment-induced necrosis, has emerged as an important adverse effect following stereotactic radiotherapy (SRS) for brain metastases. The improved survival of patients with brain metastases and increased use of combined systemic therapy and SRS have contributed to a growing incidence of necrosis. The cyclic GMP-AMP (cGAMP) synthase (cGAS) and stimulator of interferon genes (STING) pathway (cGAS-STING) represents a key biological mechanism linking radiation-induced DNA damage to pro-inflammatory effects and innate immunity. By recognizing cytosolic double-stranded DNA, cGAS induces a signaling cascade that results in the upregulation of type 1 interferons and dendritic cell activation. This pathway could play a key role in the pathogenesis of necrosis and provides attractive targets for therapeutic development. Immunotherapy and other novel systemic agents may potentiate activation of cGAS-STING signaling following radiotherapy and increase necrosis risk. Advancements in dosimetric strategies, novel imaging modalities, artificial intelligence, and circulating biomarkers could improve the management of necrosis. This review provides new insights into the pathophysiology of necrosis and synthesizes our current understanding regarding the diagnosis, risk factors, and management options of necrosis while highlighting novel avenues for discovery.

Hair Dye Ingredients and Potential Health Risks from Exposure to Hair Dyeing

Given the worldwide popularity of hair dyeing, there is an urgent need to understand the toxicities and risks associated with exposure to chemicals found in hair dye formulations. Hair dyes are categorized as oxidative and nonoxidative in terms of their chemical composition and ingredients. For several decades, the expert panel's Cosmetic Ingredient Review (CIR) has assessed the safety of many of the chemicals used in hair dyes; however, a comprehensive review of hair dye ingredients and the risk of exposure to hair dyeing has not been documented. Herein, we review the safety of the various chemicals in oxidative and nonoxidative hair dyes, toxicities associated with hair dyeing, and the carcinogenic risks related to hair dyeing. While many compounds are considered safe for users at the concentrations in hair dyes, there are conflicting data about a large number of hair dye formulations. The CIR expert panel has ratified a number of coloring ingredients for hair dyes and banned a series of chemicals as carcinogenic to animals and unsafe for this application. The use of these chemicals as raw materials for producing hair dyes may result in the synthesis of other contaminants with potential toxicities and increased risk of carcinogenesis. It is an open question whether personal or occupational hair dyeing increases the risk of cancer; however, in specific subpopulations, a positive association between hair dye use and cancer occurrence has been reported. To address this question, a better understanding of the chemical and mechanistic basis of the reported toxicities of hair dye mixtures and individual hair dye ingredients is needed. It is anticipated that in-depth chemical and systems toxicology studies harnessing modern and emerging techniques can shed light on this public health concern in the future.

Local control and radionecrosis of brain metastases from non– small-cell lung cancer treated by hypofractionated stereotactic radiotherapy: Evaluation of predictive factors

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First study on brain metastases 3-fraction SRT from a homogeneous population of NSCLC, according to French MF-SRT recommendations.

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MF-SRT with 3x7.7 Gy on the 70% isodose line and PTV = GTV + 2 mm leads to high local control rates in this population, with acceptable rates of radionecrosis.

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GTV Dmin ≥ 27.4 Gy leads to higher local control.

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Dyslipidemia could be involved in radionecrosis appearance.

Background

The objective of our study was to report predictive factors of local control (LC) and radionecrosis (RN) of brain metastases (BM) of non-small cell lung carcinoma (NSCLC) treated by multifractionated stereotactic radiotherapy (MF-SRT) according to French recommendations.

Method

From 2012 to 2020, 87 patients with 101 BM were retrospectively included. The median age was 63 years (37–85). GTV was defined using contrast-enhanced T1w MRI and was isotropically extended by 2 mm to form PTV. Mean maximum BM diameter was 24.5 mm (10–46). Patients were treated with dynamic arctherapy from May 2012 to February 2016 and then with VMAT. The total prescribed dose was 23.1 Gy prescribed to the encompassing 70% isodose, in 3 fractions.

Results

LC rates at 6 months, 1 year and 2 years was 95.7%, 90.7% and 87.9% respectively. In multivariate analysis, high GTV Dmin (HR = 0.822, p = 0.012) was in favor of better LC whereas a large maximum diameter was predictive of poor LC (HR = 1.124, p = 0.02). GTV Dmin of 27.4 Gy was identified as a discriminant threshold of LC. In case of GTV Dmin ≥ 27.4 Gy, LC at 1 year was 95.3% versus 75.1% with GTV Dmin < 27.4 Gy. Cumulative incidence of RN at 6 months, 1 year and 2 years was 6.3%, 15.4% and 18.1%, respectively. In multivariate analysis, only dyslipidemia was predictive of RN (HR = 2.69, p = 0.03). No dosimetric predictive factor of RN was found in our study.

Conclusion

MF-SRT (3x7.7 Gy on 70% isodose line, with PTV = GTV + 2 mm; according to French recommendations) of BM from NSCLC gives high LC rates with acceptable RN rate. A GTV Dmin of at least 27.4 Gy could be proposed to optimize dosimetric objectives. No dosimetric predictive factors of RN were found in this study. However, dyslipidemia was identified as a potential predictive factor of RN.

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.

Performance assessment of two motion management systems for frameless stereotactic radiosurgery

BACKGROUND/PURPOSE

Frameless stereotactic radiosurgery (SRS) requires dedicated systems to monitor patient motion in order to avoid inaccurate radiation delivery due to involuntary shifts. The purpose of this study is to assess the accuracy and sensitivity of two distinct motion monitoring systems used for frameless SRS.

METHODS

A surface image-guided system known as optical surface monitoring system (OSMS), and a fiducial marker-based system known as high definition motion management (HDMM) as part of the latest Gamma Knife Icon® were compared. A 3D printer-based cranial motion phantom was developed to evaluate the accuracy and sensitivity of these two systems in terms of: (1) the capability to recognize predefined shifts up to 3 cm, and (2) the capability to recognize predefined speeds up to 3 cm/s. The performance of OSMS, in terms of different reference surfaces, was also evaluated.

RESULTS

Translational motion could be accurately detected by both systems, with an accuracy of 0.3 mm for displacement up to 1 cm, and 0.5 mm for larger displacements. The reference surface selection had an impact on OSMS performance, with flat surface resulting in less accuracy. HDMM was in general more sensitive when compared with OSMS in capturing the motion, due to its faster frame rate, but a delay in response was observed with faster speeds. Both systems were less sensitive in detection of superior-inferior motion when compared to lateral or vertical displacement directions.

CONCLUSION

Translational motion can be accurately and sensitively detected by OSMS and HDMM real-time monitoring systems. However, performance variations were observed along different motion directions, as well as amongst the selection of reference images. Caution is needed when using real-time monitoring systems for frameless SRS treatment.

Tumor Control Probability of Radiosurgery and Fractionated Stereotactic Radiosurgery for Brain Metastases

PURPOSE

As part of the American Association of Physicists in Medicine Working Group on Stereotactic Body Radiotherapy, tumor control probability (TCP) after stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) for brain metastases was modeled based on pooled dosimetric and clinical data from published English-language literature.

METHODS AND MATERIALS

PubMed-indexed studies published between January 1995 and September 2017 were used to evaluate dosimetric and clinical predictors of TCP after SRS or fSRS for brain metastases. Eligible studies had ≥10 patients and included detailed dose-fractionation data with corresponding ≥1-year local control (LC) data, typically evaluated as a >20% increase in diameter of the targeted lesion using the pre-SRS diameter as a reference.

RESULTS

Of 2951 potentially eligible manuscripts, 56 included sufficient dose-volume data for analyses. Accepting that necrosis and pseudoprogression can complicate the assessment of LC, for tumors ≤20 mm, single-fraction doses of 18 and 24 Gy corresponded with >85% and 95% 1-year LC rates, respectively. For tumors 21 to 30 mm, an 18 Gy single-fraction dose was associated with 75% LC. For tumors 31 to 40 mm, a 15 Gy single-fraction dose yielded ∼69% LC. For 3- to 5-fraction fSRS using doses in the range of 27 to 35 Gy, 80% 1-year LC has been achieved for tumors of 21 to 40 mm in diameter.

CONCLUSIONS

TCP for SRS and fSRS are presented. For small lesions ≤20 mm, single doses of ≈18 Gy appear generally associated with excellent rates of LC; for melanoma, higher doses seem warranted. For larger lesions >20 mm, local control rates appear to be ≈ 70% to 75% with usual doses of 15 to 18 Gy, and in this setting, fSRS regimens should be considered. Greater consistency in reporting of dosimetric and LC data is needed to facilitate future pooled analyses. As systemic and biologic therapies evolve, updated analyses will be needed to further assess the necessity, efficacy, and toxicity of SRS and fSRS.

Stereotactic radiosurgery combined with targeted/ immunotherapy in patients with melanoma brain metastasis

BACKGROUND

There is limited data on the use of targeted or immunotherapy (TT/IT) in combination with single fraction stereotactic radiosurgery (SRS) in patients with melanoma brain metastasis (MBM). Therefore, we analyzed the outcome and toxicity of SRS alone compared to SRS in combination with TT/IT.

METHODS

Patients with MBM treated with single session SRS at our department between 2014 and 2017 with a minimum follow-up of 3 months after first SRS were included. The primary endpoint of this study was local control (LC). Secondary endpoints were distant intracranial control, radiation necrosis-free survival (RNFS), and overall survival (OS). The local/ distant intracranial control rates, RNFS and OS were analyzed using the Kaplan-Meier method. The log-rank test was used to test differences between groups. Cox proportional hazard model was performed for univariate continuous variables and multivariate analyses.

RESULTS

Twenty-eight patients (17 male and 11 female) with 52 SRS-lesions were included. The median follow-up was 19 months (range 14-24 months) after first SRS. Thirty-six lesions (69.2%) were treated with TT/IT simultaneously (4 weeks before and 4 weeks after SRS), while 16 lesions (30.8%) were treated with SRS alone or with sequential TT/IT. The 1-year local control rate was 100 and 83.3% for SRS with TT/IT and SRS alone (p = 0.023), respectively. The estimated 1-year RNFS was 90.0 and 82.1% for SRS in combination with TT/IT and SRS alone (p = 0.935). The distant intracranial control rate after 1 year was 47.7 and 50% for SRS in combination with TT/IT and SRS alone (p = 0.933). On univariate analysis, the diagnosis-specific Graded Prognostic Assessment including the BRAF status (Melanoma-molGPA) was associated with a significantly improved LC. Neither gender nor SRS-PTV margin had a prognostic impact on LC. V10 and V12 were significantly associated with RNFS (p < 0.001 and p = 0.004).

CONCLUSION

SRS with simultaneous TT/IT significantly improved LC with no significant difference in radiation necrosis rate. The therapy combination appears to be effective and safe. However, prospective studies on SRS with simultaneous TT/IT are necessary and ongoing.

TRIAL REGISTRATION

The institutional review board approved this analysis on 10th of February 2015 and all patients signed informed consent (UE nr. 128-14).

Tumor volume and sphericity as predictors of local control after stereotactic radiosurgery for limited number (1-4) brain metastases from nonsmall cell lung cancer

AIM

This study aims to evaluate the usage of brain metastases (BM) tumor volume and sphericity as prognostic factors in local control (LC) after stereotactic radiosurgery (SRS) for limited number (1-4) BM from nonsmall cell lung cancer (NSCLC).

METHODS

We retrospectively reviewed 80 patients, with 141 BM, who were treated with SRS from 2012 to 2017. Local failure was defined as an increase in lesion size after SRS. LC and overall survival (OS) were estimated using Kaplan-Meier method. The Cox proportional hazards model was used for univariate and multivariate analysis.

RESULTS

The median clinical and radiographic follow-up was 11.2 and 9.0 months, respectively. The median BM tumor volume was 0.31 cm³ (0.01-21.64 cm³ ) and the median tumor sphericity was 0.76 (0.39-0.95). The median LC of the entire cohort was 28.8 months. LC rate at last follow-up was achieved in 84.4% of patients (35.5% CR, 35.5% PR, and 13.5% SD). LC was 83.8% at 1 year and 56.3% at 2 years. On multivariate analysis, only sphericity (P < .001) and volume (P = .004) were found to be a strong predictor for LC. The median OS of the entire cohort was 24.1 months. On multivariate analysis, only GPA score was found to be a predictor for OS.

CONCLUSION

BM tumor sphericity and volume were found to be strong predictors for LC. Tumor sphericity and volume should be taken into consideration when treating patients with BM and when designing future prospective studies and developing prognostic indices.

The effect of brain metastasis location on clinical outcomes: A review of the literature

It is common clinical practice to consider the location of a brain metastasis when making decisions regarding local therapies and, in some scenarios, estimating clinical outcomes, such as local disease control and patient survival. However, the location of a brain metastasis is not included in any validated prognostic nomogram and it is unclear if this is due to a lack of a relationship or a lack of support from published data. We performed a comprehensive review of the literature focusing on studies that have investigated a relationship between brain metastasis location and clinical outcomes, including patient survival. The vast majority of reports anatomically categorized brain metastases as supratentorial or infratentorial whereas some reports also considered other subdivisions of the brain, including different lobes or with particular areas defined as eloquent cortex. Results were variable across studies, with some finding a relationship between metastasis location and survival, but the majority finding either no relationship or a weak correlation that was not significant in the context of multivariable analysis. Here, we highlight the key findings and limitations of many studies, including how neurosurgical resection might influence the relative importance of metastasis location and in what ways future analyses may improve anatomical categorization and resection status.

Single-Fraction Radiosurgery Using Conservative Doses for Brain Metastases: Durable Responses in Select Primaries With Limited Toxicity

BACKGROUND

Optimal doses for single-fraction stereotactic radiosurgery (SRS) in the treatment of brain metastases are not well established. Our institution utilized conservative dosing compared to maximum-tolerated doses from the Radiation Therapy Oncology Group 90-05 Phase I study.

OBJECTIVE

To report individual lesion control (LC) from conservative single-fraction doses and determine factors affecting LC.

METHODS

From 2003 to 2015, patients who underwent linear accelerator-based single-fraction SRS for cerebral/cerebellar metastases and receiving at least 1 follow-up magnetic resonance imaging (MRI) were identified. Lesion response was assessed by a size-based rating system and modified "Response Assessment in Neuro-Oncology Brain Metastases" (RANO-BM) criteria.

RESULTS

Among 188 patients with 519 lesions, median survival was 13.1 mo; median follow-up time with MRI was 9.6 mo per course. Median tumor-periphery dose was 15 Gy (range: 7.5-20.7). Median lesion volume was 0.5 cc and diameter was 9 mm (range: 2-45). Concordance between RANO-BM and size-based system was 93%. Crude 1-yr LC was 80%, 73%, 56%, and 38% for lesions 1 to 10, 11 to 20, 21 to 30, >31 mm, respectively. On multivariate analysis, increased size, melanoma and colorectal histology, and progression after whole brain radiation therapy predicted worse LC. When excluding lesions treated as a boost, dose was a significant predictor of LC in multivariate models (hazard ratio 0.89, P = .01). Symptomatic radiation necrosis occurred in 10 lesions in 10 patients.

CONCLUSION

Histology predicts LC after conservative SRS doses with evidence of a dose-response relationship. Conservative single-fraction SRS doses confer minimal toxicity and acceptable control in certain subgroups (breast cancer, <5 mm), with suboptimal control in larger lesions and in combination with whole brain radiation therapy.

Dosimetric effect of rotational setup errors in stereotactic radiosurgery with HyperArc for single and multiple brain metastases

Purpose

In stereotactic radiosurgery (SRS) with single‐isocentric treatments for brain metastases, rotational setup errors may cause considerable dosimetric effects. We assessed the dosimetric effects on HyperArc plans for single and multiple metastases.

Methods

For 29 patients (1–8 brain metastases), HyperArc plans with a prescription dose of 20–24 Gy for a dose that covers 95% (D_95%) of the planning target volume (PTV) were retrospectively generated (Ref‐plan). Subsequently, the computed tomography (CT) used for the Ref‐plan and cone‐beam CT acquired during treatments (Rot‐CT) were registered. The HyperArc plans involving rotational setup errors (Rot‐plan) were generated by re‐calculating doses based on the Rot‐CT. The dosimetric parameters between the two plans were compared.

Results

The dosimetric parameters [D_99%, D_95%, D_1%, homogeneity index, and conformity index (CI)] for the single‐metastasis cases were comparable (P > 0.05), whereas the D_95% for each PTV of the Rot‐plan decreased 10.8% on average, and the CI of the Rot‐plan was also significantly lower than that of the Ref‐plan (Ref‐plan vs Rot‐plan, 0.93 ± 0.02 vs 0.75 ± 0.14, P < 0.01) for the multiple‐metastases cases. In addition, for the multiple‐metastases cases, the Rot‐plan resulted in significantly higher V_10Gy (P = 0.01), V_12Gy (P = 0.02), V_14Gy (P = 0.02), and V_16Gy (P < 0.01) than those in the Ref‐plan.

Conclusion

The rotational setup errors for multiple brain metastases cases caused non‐negligible underdosage for PTV and significant increases of V_10Gy to V_16Gy in SRS with HyperArc.

Retrospective dosimetric analysis of brain lesions planned in Pinnacle 9.8 via a HDMLC linac

The University of Toledo Medical Center's Eleanor N. Dana Cancer Center located in northwest Ohio currently utilizes the Edge Radiosurgery System (Varian Medical Systems Inc., Palo Alto, CA) to deliver stereotactic radiosurgery for the treatment of brain lesions. The purpose of this study is to determine the quality of conformal arc radiotherapy in treating patients with brain lesions at The University of Toledo Medical Center and to provide more data for conformity and gradient indices (due to a lack of current data) to hopefully improve national standards by allowing centers to compare among each other. Treatment plans were assessed using the Pinnacle³ v9.8 Radiation Therapy Planning System (Philips Healthcare, Amsterdam, Netherlands). For patients (n = 41) presenting with small brain lesions (n = 82) and treated with conformal arc radiotherapy via the Edge Radiosurgery System, the RTOG conformity index, Paddick conformity index, conformity gradient index, gradient index, and dose gradient index were determined for each plan. This study additionally provides data to suggest the more accurate method of volume derivation provided by the Pinnacle³ v9.8 software. Using this method, average values for each of the following indices were calculated: RTOG conformity index = 1.36 ± 0.29; Paddick conformity index = 0.72 ± 0.12; conformity gradient index = 214.67 ± 12.35; gradient index = 3.64 ± 1.09; dose gradient index = -0.11 ± 0.16. Thus, The University of Toledo Medical Center provides favorable conformity of dose to intracranial target lesions.

HyperArc VMAT planning for single and multiple brain metastases stereotactic radiosurgery: a new treatment planning approach

Purpose

The HyperArc VMAT (HA-VMAT) planning approach was newly developed to fulfill the demands of dose delivery for brain metastases stereotactic radiosurgery. We compared the dosimetric parameters of the HA-VMAT plan with those of the conventional VMAT (C-VMAT).

Material and methods

For 23 patients (1–4 brain metastases), C-VMAT and HA-VMAT plans with a prescription dose of 20–24 Gy were retrospectively generated, and dosimetric parameters for PTV (homogeneity index, HI; conformity index, CI; gradient index, GI) and brain tissue (V_2Gy-V_16Gy) were evaluated. Subsequently, the physical characteristics (modulation complexity score for VMAT, MCSV; Monitor unit, MU) of both treatment approaches were compared.

Results

HA-VMAT provided higher HI (1.41 ± 0.07 vs. 1.24 ± 0.07, p < 0.01), CI (0.93 ± 0.02 vs. 0.90 ± 0.05, p = 0.01) and lower GI (3.06 ± 0.42 vs. 3.91 ± 0.55, p < 0.01) values. Moderate-to-low dose spreads (V_4Gy-V_16Gy) were significantly reduced (p < 0.01) in the HA-VMAT plan over that of C-VMAT. HA-VMAT plans resulted in more complex MLC patterns (lower MCSV, p < 0.01) and higher MU (p < 0.01).

Conclusions

HA-VMAT plans provided significantly higher conformity and rapid dose falloff with respect to the C-VMAT plans.

Stereotactic Radiosurgery for Treatment of Brain Metastases

Brain metastases are the most common intracranial malignancy. Incidence of brain metastases has risen as systemic therapies have improved and patients with metastatic disease live longer. Whole-brain radiation therapy, for many years, has been the standard treatment approach. Stereotactic radiosurgery has become an increasingly popular option because of its relatively short, convenient, and noninvasive treatment course. Although recently published data have renewed interest in use of whole-brain radiation therapy or systemic therapies for control of micrometastatic disease, stereotactic radiosurgery continues to be an important modality, capable of delivering ablative doses of radiation for long-term control of macroscopic disease. The purpose of this review is to explore the different paradigms for incorporation of stereotactic radiosurgery into management of brain metastases. Current uses for stereotactic radiosurgery include delivery as a boost with whole-brain radiation therapy; alone for patients with a limited number of brain metastases; in pre- or postoperative settings; and in combination with systemic, targeted, and immune-based therapies. Mature prospective data on use of stereotactic radiosurgery in combination with whole-brain radiation therapy is available; however, prospective, randomized data on stereotactic radiosurgery for patients with a greater number of brain metastases, its use in pre- and postoperative settings, and its use in combination with systemic therapies are limited. Data from ongoing and future studies are needed to define the appropriate use of stereotactic radiosurgery in these settings.

Distant intracranial failure in melanoma brain metastases treated with stereotactic radiosurgery in the era of immunotherapy and targeted agents

Purpose

Stereotactic radiosurgery (SRS) in combination with immunotherapy (IMT) or targeted therapy is increasingly being used in the setting of melanoma brain metastases (MBMs). The synergistic properties of combination therapy are not well understood. We compared the distant intracranial failure rates of intact MBMs treated with SRS, SRS + IMT, and SRS + targeted therapy.

Methods and materials

Combination therapy was defined as delivery of SRS within 3 months of IMT (anti-CTLA-4 /anti-PD-1 therapy) or targeted therapy (BRAF/MEK inhibitors). The primary endpoint was distant intracranial failure after SRS, which was defined as any new MBM identified on brain magnetic resonance imaging. Outcomes were evaluated using the Kaplan Meier method and Cox proportional hazards.

Results

A total of 72 patients with melanoma with 233 MBMs were treated between April 2006 and April 2016. The number of MBMs within each treatment group was as follows: SRS: 121; SRS + IMT: 48; and SRS + targeted therapy: 64. The median follow-up was 8.9 months. One-year distant intracranial control rates for SRS, SRS + IMT, and SRS + targeted therapy were 11.5%, 60%, and 10%, respectively (P < .001). On multivariate analysis, after adjusting for steroid use and number of MBMs, SRS + IMT remained associated with a significant reduction in distant intracranial failure compared with SRS (hazard ratio [HR], 0.48; 95% confidence interval [CI], 0.29-0.80; P = .003) and compared with SRS + targeted therapy (HR, 0.41; 95% CI, 0.25-0.68; P = .001).One-year local control for SRS, SRS + IMT, and SRS + targeted therapy was 66%, 85%, and 72%, respectively (P = .044). On multivariate analysis, after adjusting for dose, SRS + IMT remained associated with a significant reduction in local failure compared with SRS alone (HR, 0.37; 95% CI, 0.14-0.95; P = .04).

Conclusions

SRS with immunotherapy is associated with decreased distant and local intracranial failure compared with SRS alone. Prospective studies are warranted to validate this result.

Role of Gamma Knife® Radiosurgery for the Treatment of Brain Metastases from Gynecological Cancers

Objective: Gamma Knife^® (GK) (Elekta Instruments, Stockholm, Sweden) radiosurgery is well established for treatment of brain metastases. There are limited data on patients treated with GK from gynecological cancers. The authors sought to determine the effectiveness of the GK in patients with brain metastases from gynecological cancers.

Methods: An IRB-approved database was queried for patients with gynecologic cancers treated with GK between June 1996 and May 2016. Imaging studies were reviewed post-SRS (stereotactic radiosurgery) to evaluate local control (LC) and distant brain control (DC). Overall survival (OS), local control, and distant brain control were calculated using the Kaplan-Meier (KM) method and log-rank test. 

Results: Thirty-three patients underwent SRS for 73 separate cranial lesions. The median age was ­58.5 years, and 17 (52%) also had extracranial metastases. Ten (30%) patients had previously received whole brain radiotherapy (WBRT), and 11 (33%) underwent concurrent WBRT. The median tumor volume was 0.96 cm³. Median radiographic follow-up was 11 months. At the time of treatment, 39% of patients were categorized as recursive partitioning analysis (RPA) Class I, 55% as RPA Class II, and 6% as RPA Class III. The local failure rate was 8%. Five patients (15%) developed new brain lesions outside the radiation field with a median progression-free survival (PFS) of seven (range: 3-9) months. Median OS was 15 months from GK treatment. One-year OS was 72.9% from GK treatment. Primary cancer histology was a significant predictor of OS, favoring ovarian and endometrial cancer (p = 0.03).

Conclusions: Gamma Knife stereotactic radiosurgery for gynecologic brain metastases leads to excellent control rates of treated lesions. Primary histology may have a significant impact on OS following GK, with improved survival seen with ovarian and cervical cancer following Gamma Knife radiosurgery (p = 0.03).

Hypofractionated stereotactic radiotherapy for brain metastases from lung cancer : Evaluation of indications and predictors of local control

AIM

To evaluate the efficacy and toxicity of hypofractionated stereotactic radiotherapy (HSRT) for brain metastases (BMs) from lung cancer, and to explore prognostic factors associated with local control (LC) and indication.

PATIENTS AND METHODS

We evaluated patients who were treated with linac-based HSRT for BMs from lung cancer. Lesions treated with stereotactic radiosurgery (SRS) in the same patients during the same periods were analysed and compared with HSRT in terms of LC or toxicity. There were 53 patients with 214 lesions selected for this analysis (HSRT: 76 lesions, SRS: 138 lesions). For HSRT, the median prescribed dose was 35 Gy in 5 fractions.

RESULTS

The 1‑year LC rate was 83.6 % in HSRT; on multivariate analysis, a planning target volume (PTV) of <4 cm(3), biologically effective dose (BED10) of ≥51 Gy, and adenocarcinoma were significantly associated with better LC. Moreover, in PTVs ≥ 4 cm(3), there was a significant difference in LC between BED10 < 51 Gy and ≥ 51 Gy (p = 0.024). On the other hand, in PTVs < 4 cm(3), both HSRT and SRS had good LC with no significant difference (p = 0.195). Radiation necrosis emerged in 5 of 76 lesions (6.6 %) treated with HSRT and 21 of 138 (15.2 %) lesions treated with SRS (p = 0.064).

CONCLUSION

Linac-based HSRT was safe and effective for BMs from lung cancer, and hence might be particularly useful in or near an eloquent area. PTV, BED10, and pathological type were significant prognostic factors. Furthermore, in BMs ≥ 4 cm(3), a dose of BED ≥ 51 Gy should be considered.

Single fraction volumetric modulated arc radiosurgery of brain metastases

PURPOSE

To show the clinical results of the treatment of brain metastases via radiosurgery using Volumetric Modulated Arc Therapy (VMAT).

MATERIALS AND METHODS

52 patients having lung (62 %), breast (17 %), colorectal (8 %) and other cancers (13 %) with one to three brain metastases were treated with 5 non-coplanar VMAT arcs. The treatment dose varied from 12 to 20 Gy, administered in one single session. The volume of metastases ranged from 0.04 to 24.92 cc. Radiosurgery alone was used for 54 % of cases, while 19 % received whole brain radiotherapy due to relapse. Patients were classified according to the Disease-specific graded prognostic assessment (DS-GPA) index and survival was assessed via the Kaplan-Meier model.

RESULTS

The median survival time was 7.2 months from the date of radiosurgery. The Karnofsky and DS-GPA indices were the most significant with regard to survival. Patients with a Karnofsky performance status (KPS) over 70 had a longer survival time of 9.2 months, as opposed to those with a KPS below 70 of 3.5 months. No significant differences were found with regard to the type of cancer or the number of lesions. Local tumour control was achieved for 42 metastases (82 %), of which a complete response was achieved for 7 lesions, a partial response for 21; 15 lesions were stabilized. Local progression was observed in 8 lesions (15 %). The median treatment time per patient was 29 min.

CONCLUSIONS

The VMAT technique proves to be safe and effective for treating brain metastases via radiosurgery.