Characteristics and treatments of large cystic brain metastasis: radiosurgery and stereotactic aspiration.

Brain metastasis represents one of the most common causes of intracranial tumors in adults, and the incidence of brain metastasis continues to rise due to the increasing survival of cancer patients. Yet, the development of cystic brain metastasis remains a relatively rare occurrence. In this review, we describe the characteristics of cystic brain metastasis and evaluate the combined use of stereotactic aspiration and radiosurgery in treating large cystic brain metastasis. The results of several studies show that stereotactic radiosurgery produces comparable local tumor control and survival rates as other surgery protocols. When the size of the tumor interferes with radiosurgery, stereotactic aspiration of the metastasis should be considered to reduce the target volume as well as decreasing the chance of radiation induced necrosis and providing symptomatic relief from mass effect. The combined use of stereotactic aspiration and radiosurgery has strong implications in improving patient outcomes

The role of stereotactic radiosurgery in the multimodal management of growth hormone–secreting pituitary adenomas

Growth hormone (GH)–secreting pituitary adenomas represent a common source of GH excess in patients with acromegaly. Whereas surgical extirpation of the culprit lesion is considered first-line treatment, as many as 19% of patients develop recurrent symptoms due to regrowth of previously resected adenomatous tissue or to continued growth of the surgically inaccessible tumor. Although medical therapies that suppress GH production can be effective in the management of primary and recurrent acromegaly, these therapies are not curative, and lifelong treatment is required for hormonal control. Stereotactic radiosurgery has emerged as an effective adjunctive treatment modality, and is an appealing alternative to conventional fractionated radiation therapy. The authors reviewed the growing body of literature concerning the role of radiosurgical procedures in the treatment armamentarium of acromegaly, and identified more than 1350 patients across 45 case series. In this review, the authors report that radiosurgery offers true hormonal normalization in 17% to 82% of patients and tumor growth control in 37% to 100% of cases across all series, while minimizing adverse complications. As a result, stereotactic radiosurgery represents a safe and effective treatment option in the multimodal management of primary or recurrent acromegaly secondary to GH-secreting pituitary adenomas

Brainstem metastases treated with Gamma Knife stereotactic radiosurgery: the Indiana University Health experience

Brainstem metastases offer a unique challenge in cancer treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. This report discusses the clinical outcomes of patients with brainstem metastases treated at Indiana University with Gamma Knife (GK) radiosurgery from 2008 to 2016. 19 brainstem metastases from 14 patients who had follow-up brain imaging were identified. Median tumor volume was 0.04 cc (range: 0.01-2.0 cc). Median prescribed dose was 17.5 Gy to the 50% isodose line (range: 14-22 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range: 2.8-45.6 months). The experience at Indiana University confirms the safety and efficacy of range of GK SRS prescription doses (14-22 Gy) to brainstem metastases

Stereotactic Radiosurgery Practice Patterns for Brain Metastases in the United States: A National Survey

Background: Stereotactic radiosurgery (SRS) has emerged as an important modality for the treatment of intracranial metastases. There are currently few established guidelines delineating indications for SRS use and fewer still regarding plan evaluation in the treat- ment of multiple brain metastases. Methods: An 18 question electronic survey was distributed to radiation oncologists at National Cancer Institute (NCI) designated cancer centers in the US (60). Centers without radiation oncologists were excluded. Physicians who indicated that they do not prescribe SRS were excluded from the remaining survey questions. Sign test and Chi-square test were used to determine if responses differed significantly from random distribution. Results: 116 of the 697 radiation oncologists surveyed completed the questionnaire, representing 51 institutions. 62% reported treating patients with brain metastases using SRS. Radiation oncologists prescribing SRS most commonly treat CNS (66.2%) and lung (49.3%) malignancies. SRS was used more frequently for \u3c10 brain metastases (73.7%; p\u3c.0001) and whole brain radiation therapy (WBRT) for \u3e10 brain metastases (82.5%; p\u3c.0001). The maximum number of lesions physicians were willing to treat with SRS without WBRT was 1-4 (40.4%) and 5-10 (42.4%) (p\u3c.0001 compared to 11-15, 16-20 and no limit). The most important criteria for choosing SRS or WBRT were number of lesions (p\u3c.0001) and performance status (p=.016). The most common margin for SRS was 0 mm (49.1%; p=.0021). The most common dose constraints other than critical structure was conformity index (84.2%) and brain V12 (61.4%). The LINAC was the most common treatment modality (54.4%) and mono-isocenter technique for multiple brain metastases was commonly used (43.9%; p=.23). Most departments do not have a policy for brain metastases treatment (64.9%; p=.024). Conclusions: This is one of the first national surveys assessing the use of SRS for brain metastases in clinical practice. These data highlight some clinical considerations for physicians treating brain metastases with SRS. Summary: This is among the first national surveys to assess the use of SRS for brain metastases in clinical practice. Specifically, radiation oncologist reported increasingly using SRS instead of WBRT for treating \u3c10 metastases, with the LINAC being the most common modality. Further, treatment parameters considered the most important included 0 mm margins, conformity index, brain V12, and mono- isocenter technique for multiple brain metastases. These results may provide context regarding the use of SRS for brain metastases in clinical practice

Systematic Analysis of Clinical Outcomes Following Stereotactic Radiosurgery for Central Neurocytoma.

Central neurocytoma (CN) typically presents as an intraventricular mass causing obstructive hydrocephalus. The first line of treatment is surgical resection with adjuvant conventional radiotherapy. Stereotactic radiosurgery (SRS) was proposed as an alternative therapy for CN because of its lower risk profile. The objective of this systematic analysis is to assess the efficacy of SRS for CN. A systematic analysis for CN treated with SRS was conducted in PubMed. Baseline patient characteristics and outcomes data were extracted. Heterogeneity and publication bias were also assessed. Univariate and multivariate linear regressions were used to test for correlations to the primary outcome: local control (LC). The estimated cumulative rate of LC was 92.2% (95% confidence interval: 86.5-95.7%, p<0.001). Mean follow-up time was 62.4 months (range 3-149 months). Heterogeneity and publication bias were insignificant. The univariate linear regression models for both mean tumor volume and mean dose were significantly correlated with improved LC (p<0.001). Our data suggests that SRS may be an effective and safe therapy for CN. However, the rarity of CN still limits the efficacy of a quantitative analysis. Future multi-institutional, randomized trials of CN patients should be considered to further elucidate this therapy

Quality assurance in stereotactic radiosurgery/radiotherapy according to DIN 6875-1

The new DIN (' Deutsche Industrie- Norm') 6875- 1, which is currently being finalised, deals with quality assurance ( QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/ radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4- mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in- house, the use of commercially available tools facilitated the QA according to the DIN 6875- 1 with which our results complied. Copyright (C) 2004 S. Karger AG, Basel

Intensity-modulated stereotactic radiosurgery for arteriovenous malformations: guidance for treatment planning.

BackgroundStereotactic Radiosurgery (SRS) is a common tool used to treat Arteriovenous Malformations (AVMs) in anatomical locations associated with a risk of surgical complications. Despite high rates of clinical effectiveness, SRS carries a risk of toxicity as a result of radiation injury to brain tissue. The use of intensity-modulated radiotherapy (IMRT) has increased because it may lead to improved PTV conformity and better Normal Tissue (NT) sparing compared to 3D Conformal Radiotherapy (3DCRT). The aim of this study was twofold: 1) to develop simple patient stratification rules for the recommendation of IMRT planning strategies over 3DCRT in the treatment of AVMs with SRS; and 2) to estimate the impact of IMRT in terms of toxicity reduction using retrospectively reported data for symptomatic radiation injury following SRS.MethodsThirty-one AVM patients previously treated with 3DCRT were replanned in a commercial treatment planning system using 3DCRT and static gantry IMRT with identical beam arrangements. The radiotherapy planning metrics analyzed included AVM volume, diameter, and volume to surface area ratio. The dosimetric endpoints analyzed included conformity index improvements and NT sparing measured by the maximum NT dose, and the volume of surrounding tissue that received 7Gy and 12Gy.ResultsOur analysis revealed stratified subsets of patients for IMRT that were associated with improved conformity, and those that were associated with decreased doses to normal tissue. The stratified patients experienced an improvement in conformity index by -6-68%, a reduction in the maximum NT dose by -0.5-12.3%, a reduction in the volume of NT receiving 7Gy by 1-8 cc, and a reduction in the volume of NT receiving 12Gy by 0-3.7 cc. The reduction in NT receiving 12Gy translated to a theoretical decrease in the probability of symptomatic injury by 0-9.3%.ConclusionsThis work indicates the potential for significant patient improvements when treating AVMs and provides rules to predict which patients are likely to benefit from IMRT

Dosimetric Analysis of Neural and Vascular Structures in Skull Base Tumors Treated with Stereotactic Radiosurgery.

Objective To examine the relationship between the prescribed target dose and the dose to healthy neurovascular structures in patients with vestibular schwannomas treated with stereotactic radiosurgery (SRS). Study Design Case series with chart review. Setting SRS center from 2011 to 2013. Subjects Twenty patients with vestibular schwannomas treated at the center from 2011 to 2013. Methods Twenty patients with vestibular schwannomas were included. The average radiation dose delivered to healthy neurovascular structures (eg, carotid artery, basilar artery, facial nerve, trigeminal nerve, and cochlea) was analyzed. Results Twenty patients with vestibular schwannomas who were treated with fused computed tomography/magnetic resonance imaging-guided SRS were included in the study. The prescribed dose ranged from 10.58 to 17.40 Gy over 1 to 3 hypofractions to cover 95% of the target tumor volume. The mean dose to the carotid artery was 5.66 Gy (95% confidence interval [CI], 4.53-6.80 Gy), anterior inferior cerebellar artery was 8.70 Gy (95% CI, 4.54-12.86 Gy), intratemporal facial nerve was 3.76 Gy (95% CI, 3.04-4.08 Gy), trigeminal nerve was 5.21 Gy (95% CI, 3.31-7.11 Gy), and the cochlea was 8.70 Gy (95% CI, 7.81-9.59 Gy). Conclusions SRS for certain vestibular schwannomas can expose the anterior inferior cerebellar artery (AICA) and carotid artery to radiation doses that can potentially initiate atherosclerotic processes. The higher doses to the AICA and carotid artery correlated with increasing tumor volume. The dose delivered to other structures such as the cochlea and intratemporal facial nerve appears to be lower and much less likely to cause immediate complications when shielded

Stereotactic radiosurgery for vestibular schwannomas.

Stereotactic radiosurgery (SRS) maintains an important role in managing vestibular schwannoma (VS). Long-term clinical data have clearly established the safety and efficacy of the procedure for managing Koos low grade to intermediate grade VS. Historically, the procedure was developed via a multidisciplinary approach that involves physicians (eg, neurosurgeons and radiation oncologists) as well as clinical specialists (eg, radiation physicists). In this paper, we have reviewed current technical and clinical practices of SRS for VS from a procedural specialist's perspective and from a clinician's perspective