Stereotactic radiosurgery: a meta-analysis of current therapeutic applications in neuro-oncologic disease

Neurosurgical treatment and outcome patterns in patients with meningioma in South Moravian region-a population-based study

INTRODUCTION

Meningiomas are usually slow-growing tumours, constituting about one third of all primary intracranial tumours. They occur more frequently in women. Clinical manifestation of meningiomas depends on their location, tumour size and growth rate. In most cases, surgical treatment is the procedure of choice. The success of this treatment is, however, associated with the radicality of the resection. Radiotherapy represents an additional or alternative treatment modality. Gamma knife surgery is another notable treatment method, especially in small and/or slow-growing tumours in eloquent areas or in elderly patients.

MATERIAL AND METHODS

Authors describe their experience with the diagnosis, treatment and outcome of the patients with meningioma (n = 857). Furthermore, they also assess the postoperative morbidity/mortality and recurrence rate.

RESULTS AND CONCLUSIONS

In view of the benign histology of meningiomas, the success of the treatment largely depends (besides the tumour grading) on the radicality of the resection. The emphasis is also put on appropriate follow-up of the patients. In certain patients, the watch and wait strategy should be also considered as a suitable treatment method.

Assessing the long-term safety and efficacy of gamma knife and linear accelerator radiosurgery for vestibular schwannoma: A systematic review and meta-analysis

Background

Differences in long-term outcomes of single-fraction stereotactic radiosurgery (SRS) between gamma knife (GK) and linear accelerator (LINAC) systems for vestibular schwannoma (VS) management remain unclear. To investigate differences in safety and efficacy between modalities, we conducted a meta-analysis of studies over the past decade.

Methods

MEDLINE, EMBASE, and Cochrane databases were queried for studies with the following inclusion criteria: English language, published between January 2010 and April 2020, cohort size ≥30, and mean/median follow-up ≥5 years. Odds ratios (OR) compared rates of tumor control, hearing preservation, and cranial nerve toxicities before and after SRS.

Results

Thirty-nine studies were included (29 GK, 10 LINAC) with 6516 total patients. Tumor control rates were 93% (95% CI 91-94%) and 94% (95% CI 91-97%) for GK and LINAC, respectively. Both GK (OR 0.06, 95% CI 0.02-0.13) and LINAC (OR 0.47, 95% CI 0.29-0.76) reduced odds of serviceable hearing. Neither GK (OR 0.71, 95% CI 0.41-1.22) nor LINAC (OR 1.13, 95% CI 0.64-2.00) impacted facial nerve function. GK decreased odds of trigeminal nerve (TN) impairment (OR 0.55, 95% CI 0.32-0.94) while LINAC did not impact TN function (OR 1.45, 95% CI 0.81-2.61). Lastly, LINAC offered decreased odds of tinnitus (OR 0.15, 95% CI 0.03-0.87) not observed with GK (OR 0.70, 95% CI 0.48-1.01).

Conclusions

VS tumor control and hearing preservation rates are comparable between GK and LINAC SRS. GK may better preserve TN function, while LINAC decreases tinnitus rates. Future studies are warranted to investigate the efficacy of GK and LINAC SRS more directly.

Efficacy and comorbidities of hypofractionated and single-dose radiosurgery for vestibular schwannomas: a systematic review and meta-analysis

Background

Vestibular schwannomas (VS) are tumors of the cerebellopontine angle with significant morbidity, causing hearing loss, tinnitus, and trigeminal and facial nerve compromise. An effective alternative to microsurgical resection is stereotactic radiosurgery (SRS), which can be delivered in either single-fraction (SRS) or hypofractionated stereotactic radiotherapy (hSRT) (3-5 treatments) regimens. It remains unclear which fractionation regimen provides superior outcomes.

Methods

Ovid MEDLINE, EMBASE, CINAHL, and Cochrane Reviews were searched for studies either comparing hSRT with SRS or focusing on hSRT alone in treating VS. Primary endpoints included tumor control, serviceable hearing, tinnitus, and cranial nerve V and VII symptoms. A random-effects analysis was employed to compare pre- and post-treatment effects (hSRT alone) or SRS and hSRT outcomes (two-arm studies).

Results

This analysis included 21 studies focusing on hSRT alone and 13 studies comparing SRS and hSRT. Significant heterogeneity was observed. Overall, when hSRT was analyzed alone, crude tumor control was achieved in 94% (95% CI: 88%, 99%) of 1571 patients. There was no difference between pre- and post-treatment odds ratios (OR) of tinnitus, facial, or trigeminal impairment. Serviceable hearing was diminished following hSRT (OR = 0.60, 95% CI: 0.44, 0.83). Comparison with SRS showed no difference with respect to tumor control, serviceable hearing, trigeminal or facial nerve impairment.

Conclusions

hSRT achieved excellent tumor control and, with the exception of serviceable hearing, did not result in worse post-treatment cranial nerve symptomatology. Analysis of comparative studies between hSRT and SRS did not reveal any significant difference in either tumor control or treatment morbidities.

Evolutionary basis of a new gene- and immune-therapeutic approach for the treatment of malignant brain tumors: from mice to clinical trials for glioma patients

Glioma cells are one of the most aggressive and malignant tumors. Following initial surgery, and radio-chemotherapy they progress rapidly, so that patients' median survival remains under two years. They invade throughout the brain, which makes them difficult to treat, and are universally lethal. Though total resection is always attempted it is not curative. Standard of care in 2016 comprises surgical resection, radiotherapy and chemotherapy (temozolomide). Median survival is currently ~14-20months post-diagnosis though it can be higher in high complexity medical university centers, or during clinical trials. Why the immune system fails to recognize the growing brain tumor is not completely understood. We believe that one reason for this failure is that the brain lacks cells that perform the role that dendritic cells serve in other organs. The lack of functional dendritic cells from the brain causes the brain to be deficient in priming systemic immune responses to glioma antigens. To overcome this drawback we reconstituted the brain immune system for it to initiate and prime anti-glioma immune responses from within the brain. To achieve brain immune reconstitution adenoviral vectors are injected into the resection cavity or remaining tumor. One adenoviral vector expresses the HSV-1 derived thymidine kinase which converts ganciclovir into phospho-ganciclovir which becomes cytotoxic to dividing cells. The second adenovirus expresses the cytokine fms-like tyrosine kinase 3 ligand (Flt3L). Flt3L differentiates precursors into dendritic cells and acts as a chemokine for dendritic cells. This results in HSV-1/ganciclovir killing of tumor cells, and the release of tumor antigens, which are then taken up by dendritic cells recruited to the brain tumor microenvironment by Flt3L. Concomitant release of HMGB1, a TLR2 agonist that activates dendritic cells, stimulates dendritic cells loaded with glioma antigens to migrate to the cervical lymph nodes to prime a systemic CD8+ T cytotoxic killing of brain tumor cells. This induced immune response causes glioma-specific cytotoxicity, induces immunological memory, and does not cause brain toxicity or autoimmunity. A Phase I Clinical Trial, to test our hypothesis in human patients, was opened in December 2013 (see: NCT01811992, Combined Cytotoxic and Immune-Stimulatory Therapy for Glioma, at ClinicalTrials.gov). This trial is a first in human trial to test whether the re-engineering of the brain immune system can serve to treat malignant brain tumors. The long and winding road from the laboratory to the clinical trial follows below.

The Long and Winding Road: From the High-Affinity Choline Uptake Site to Clinical Trials for Malignant Brain Tumors

Malignant brain tumors are one of the most lethal cancers. They originate from glial cells which infiltrate throughout the brain. Current standard of care involves surgical resection, radiotherapy, and chemotherapy; median survival is currently ~14-20 months postdiagnosis. Given that the brain immune system is deficient in priming systemic immune responses to glioma antigens, we proposed to reconstitute the brain immune system to achieve immunological priming from within the brain. Two adenoviral vectors are injected into the resection cavity or remaining tumor. One adenoviral vector expresses the HSV-1-derived thymidine kinase which converts ganciclovir into a compound only cytotoxic to dividing glioma cells. The second adenovirus expresses the cytokine fms-like tyrosine kinase 3 ligand (Flt3L). Flt3L differentiates precursors into dendritic cells and acts as a chemokine that attracts dendritic cells to the brain. HSV-1/ganciclovir killing of tumor cells releases tumor antigens that are taken up by dendritic cells within the brain tumor microenvironment. Tumor killing also releases HMGB1, an endogenous TLR2 agonist that activates dendritic cells. HMGB1-activated dendritic cells, loaded with glioma antigens, migrate to cervical lymph nodes to stimulate a systemic CD8+ T cells cytotoxic immune response against glioma. This immune response is specific to glioma tumors, induces immunological memory, and does neither cause brain toxicity nor autoimmune responses. An IND was granted by the FDA on 4/7/2011. A Phase I, first in person trial, to test whether reengineering the brain immune system is potentially therapeutic is ongoing.

Increased survival using delayed gamma knife radiosurgery for recurrent high-grade glioma: a feasibility study

OBJECTIVE

The current study retrospectively assessed delayed gamma knife radiosurgery (GKRS) in the management of high-grade glioma recurrences.

METHODS

A total of 55 consecutive patients with high-grade glioma comprising 68 World Health Organization (WHO) III and WHO IV were treated with GKRS for local recurrences between 2001 and 2007. All patients had undergone microsurgery and radiochemotherapy, considered as standard therapy for high-grade glioma. Complete follow-up was available in all patients; median follow-up was 17.2 months (2.5-114.2 months). Median tumor volume was 5.2 mL, prescription dose was 20 Gy (14-22 Gy), and median max dose was 45 Gy (30-77.3 Gy).

RESULTS

The patients with WHO III tumors showed a median survival of 49.6 months with and a 2-year survival of 90%. After GKRS of the recurrences, these patients showed a median survival of 24.2 months and a 2-year survival of 50%. The patients with WHO IV tumors had a median survival of 24.5 months with a 2-year survival of 51.4%. After the recurrence was treated with GKRS, the median survival was 11.3 months and a 2-year survival: 22.9% for the WHO IV patients.

CONCLUSION

The current study shows a survival benefit for high-grade glioma recurrences when GKRS was administered after standard therapy. This is a relevant improvement compared with earlier studies that had had not been able to provide a beneficial effect timing radiosurgery in close vicinity to EBRT.

Image-guided stereotactic radiotherapy for patients with vestibular schwannoma. A clinical study

INTRODUCTION

Local tumor control and functional outcome after linac-based stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) for vestibular schwannoma (VS) were assessed.

METHODS

In all, 250 patients with VS were treated: 190 patients with tumors < 2 cm diameter underwent SRS and 60 patients with tumors >2 to 3.5 cm underwent FSRT. Dose prescription for all cases with SRS (n = 190, 76 %) was 13.5 Gy. For FSRT, mainly two hypofractionated schedules (n = 60, 24 %) with either 7 fractions of 5 Gy (total dose: 35 Gy; n = 35) or 11 fractions of 3.8 Gy (total dose: 41.8 Gy; n = 16) were used. The primary endpoint was local tumor control. Secondary endpoints were symptomatic control and morbidity.

RESULTS

The median follow-up was 33.8 months. The 3-year local tumor control was 88.9 %. Local control for SRS and FSRT was 88 and 92 %, respectively. For FSRT with 35 and 41.8 Gy, local control was 90 and 100 %, respectively. There were no acute reactions exceeding grade I. In 61 cases (24.4 % of the entire cohort), trigeminal neuralgia was reported prior to treatment. At last follow-up, 16.3 % (10/61) of those patients reported relief of pain. Regarding facial nerve dysfunction, 45 patients (18 %) presented with symptoms prior to RT. At the last follow-up, 13.3% (6/45) of those patients reported a relief of dysesthesia.

CONCLUSION

Using SRS to treat small VS results in good local control rates. FSRT for larger lesions also seems effective. Severe treatment-related complications are not frequent. Therefore, image-guided stereotactic radiotherapy is an appropriate alternative to microsurgery for patients with VS.

Results for local control and functional outcome after linac-based image-guided stereotactic radiosurgery in 190 patients with vestibular schwannoma

BACKGROUND

We assessed local control (LC) and functional outcome after linac-based stereotactic radiosurgery (SRS) for vestibular schwannoma (VS).

METHODS

Between 1998 and 2008, 190 patients with VS were treated with SRS. All patients had tumors <2 cm diameter. Patients received 13.5 Gy prescribed to the 80th isodose at the tumor margin. The primary endpoint was LC. Secondary endpoints were symptomatic control and morbidity.

RESULTS

Median follow-up was 40 months. LC was achieved in 88% of patients. There were no acute reactions exceeding Grade I. Trigeminal nerve dysfunction was present in 21.6% (n = 41) prior to SRS. After treatment, 85% (n = 155) had no change, 4.4,% (n = 8) had a relief of symptoms, 10.4% (n = 19) had new symptoms. Facial nerve dysfunction was present in some patients prior to treatment, e.g. paresis (12.6%; n = 24) and dysgeusia (0.5%; n = 1). After treatment 1.1% (n = 2) reported improvement and 6.1% (n = 11) experienced new symptoms. Hearing problems before SRS were present in 69.5% of patients (n = 132). After treatment, 62.6% (n = 144) had no change, 10.4% (n = 19) experienced improvement and 26.9% (n = 49) became hearing impaired.

CONCLUSION

This series of SRS for small VS provided similar LC rates to microsurgery; thus, it is effective as a non-invasive, image-guided procedure. The functional outcomes observed indicate the safety and effectiveness of linac-based SRS. Patients may now be informed of the clinical equivalence of SRS to microsurgery.

The prognostic value of tumor necrosis in patients undergoing stereotactic radiosurgery of brain metastases

Background

This retrospective study investigated the outcome of patients with brain metastases after radiosurgery with special emphasis on prognostic impact of visible intratumoral necrosis on survival and local control.

Methods

From 1998 through 2008, 149 patients with brain metastases from solid tumors were treated with stereotactic radiotherapy at Luebeck University. Median age was 58.4 years with 11%, 78%, 10% in recursive partitioning analysis (RPA) classes I, II, III, respectively. 70% had 1 metastasis, 29% 2-3 metastases, 2 patients more than 3 metastases, 71% active extracranial disease. Median volume of metastatic lesions was 4.7 cm³, median radiosurgery dose 22 Gy (single fraction). 71% of patients received additional whole-brain irradiation (WBI). All patients were analyzed regarding survival, local, distant failure and prognostic factors, side effects and changes in neurologic symptoms after radiotherapy. The type of contrast-enhancement in MR imaging was also analyzed; metastatic lesions were classified as containing necrosis if they appeared as ring-enhancing with central areas of no or minimal contrast enhancement.

Results

Median survival was 7.0 months with 1-year and 5-year survival rates of 33% and 0.4%, respectively. Tumor necrosis (ring-enhancement) was visible on pretreatment MRI scans in 56% of all lesions and lesions with necrosis were larger than non-necrotic lesions (6.7 cm³ vs. 3.2 cm³, p = 0.01). Patients with tumor necrosis had a median survival of 5.4 months, patients without tumor necrosis 7.2 months. Local control rate in the irradiated volume was 70%, median survival without local failure 17.8 months. Control in the brain outside the irradiated volume was 60%, median survival without distant failure 14.0 months. Significant prognostic factors for overall survival were KPS (p = 0.001), presence of tumor necrosis on pretreatment MRI (p = 0.001) with RPA-class and WBI reaching marginal significance (each p = 0.05). Prognostic impact of tumor necrosis remained significant if only smaller tumors with a volume below 3.5 cm³ (p = 0.03). Side effects were rare, only one patient suffered from serious acute side effects.

Conclusions

Results of this retrospective study support that stereotactic radiotherapy is an effective treatment option for patients with metastatic brain lesions. The prognostic impact of visible tumor necrosis (ring-enhancement) on pretreatment MRI scans should be further investigated.

Gamma knife surgery for a hemangioma of the cavernous sinus in a child

Cavernous sinus (CS) hemangiomas are rare vascular abnormalities that constitute 0.4%-2% of all lesions within the CS. Cavernous sinus hemangiomas are high-flow vascular tumors that tend to hemorrhage profusely during resection, leading to incomplete resection and high morbidity and mortality. While Gamma Knife surgery (GKS) has proven to be an effective treatment of CS hemangiomas in the adult population, few reports of GKS for treatment of CS hemangiomas exist in the pediatric literature. Here, the authors present the first case of a 15-year-old girl with a biopsy-proven CS hemangioma who achieved complete resolution of her symptoms and a complete imaging-defined response following GKS. If suspicion for a CS hemangioma is high in a pediatric patient, GKS may be considered as an effective treatment modality, thus avoiding the morbidities of open resection.

Fractionated stereotactic radiotherapy for acoustic neuromas: a prospective monocenter study of about 158 cases

PURPOSE

To evaluate long-term outcomes and efficacy of fractionated stereotactic radiotherapy in the treatment of acoustic neuromas.

MATERIAL AND METHODS

Between January 1996 and December 2009, 158 acoustic neuromas were treated by FSR in 155 patients. They received a dose of 50.4 Gy, with a safety margin of 1-2mm with a median tumor volume at 2.45 mL (range: 0.17-12.5 mL) and a median follow-up duration at 60 months (range: 24-192).

RESULTS

FSR was well tolerated in all patients with mild sequelae consisting in radiation-induced trigeminal nerve impairments (3.2%), Grade 2 facial neuropathies (2.5%), new or aggravated tinnitus (2.1%) and VP shunting (2.5%). The treatment failed in four patients (2.5%) who had subsequent surgery respectively at 20, 38, 45 and 84 months post-FSR. The local tumor control rates were respectively 99.3%, 97.5% and 95.2% at 3, 5 and >7-year of follow-up. For initial Gardner-Robertson Grade 1 and 2 ANs, the preservation of useful hearing was possible in 54% of the cases; only Grade 1 ANs had stabilized during the course of the follow-up with 71% >7 years. However, hearing preservation was not correlated to the initial Koos Stage and to the radiation dose delivered to the cochlea. Tinnitus (70%), vertigo (59%), imbalance (46%) and ear mastoid pain (43%) had greatly improved post-FRS in most patients. Tumor control, hearing preservation and FRS toxicity were quite similar in patients with NF2, cystic acoustic neuroma, prior surgical resection and Koos Stage 4 AN. No secondary tumors were observed.

CONCLUSION

FSR is a safe and effective therapeutic for acoustic neuromas and could be an alternative to microsurgery. Compared to radiosurgery, there are no contraindications for fractioned doses of stereotactic radiotherapy especially for Stage-4 tumors and patients at high risk of hearing loss.

Chemotherapy: What is its role in meningioma?

While strong evidence exists for the standard therapy for meningiomas, inclusive of surgery and/or radiation therapy, for those tumors which recur, progress or are inoperable, the optimal medical therapies are yet to be elucidated. This article reviews the current literature for chemotherapeutic options for this subset of tumors, including cytotoxic agents, biologic agents, targeted molecular agents and hormonal agents. At this point in time, the most data is with hydroxyurea and somatostatin, although further trials with combination and targeted molecular therapies are still underway.

Management of intracranial meningiomas in Enugu, Nigeria

Background:

Meningiomas may range on presentation from incidentally identified small lesions to large symptomatic tumors in eloquent areas of the brain. Management options correspondingly vary and include careful observation, surgical excision, and palliative application of very limited therapeutic maneuvers in select cases. This paper discusses the options and difficulties in the management of meningiomas in a developing country.

Methods:

This study is a retrospective analysis of prospectively recorded data of patients managed for intracranial meningioma between January 2006 and September 2011 at Memfys Hospital for Neurosurgery, Enugu. Radiographic diagnosis of meningioma was based on computed tomography (CT) and or magnetic resonance imaging (MRI) criteria in all cases, but only patients who had surgery and a histological diagnosis were analyzed.

Results:

Seventy-four patients were radiographically diagnosed with intracranial meningioma over the period under review. Fifty-five patients were operated upon and 52 (70.3%) with histological diagnosis of meningioma were further analyzed. Histological diagnosis was complete in 42 (56.8%) patients and in 10 (13.5%) patients the subtype of meningioma was not determined. The male to female ratio was 1:1.08. The peak age range for females was in the 6th decade and for males in the 5th decade. The locations were olfactory groove (26.9%), convexity (21.2%), parasagittal/falx (19.2%), sphenoid ridge (15.4%), tuberculum sellae (7.7%), tentorial (3.8%), and posterior fossa (5.8%). The most common clinical presentation was headaches in 67.3% followed by seizures (40.4%) and visual impairment (38.5%). Histology was benign (World Health Organization [WHO] grade 1) in 39 patients. One patient harbored an atypical and two had anaplastic tumors. Gross total resection of the tumor was achieved in 41 patients. Surgical mortality was 3.9%.

Conclusion:

Effective management of meningioma depends largely on adequate and complete surgical resection and results in good outcomes. Adequate preoperative assessment, including visual assessment, and hormonal assessment in olfactory groove and sphenoid region meningiomas, is necessary.

[Stereotactic radiotherapy of intracranial benign tumors]

Stereotactic radiotherapy can be delivered in one fraction or in multiple fractions schedule. It is used in benign tumours such as meningiomas, mainly localized in the base of the skull, for acoustic schwannoma and pituitary tumours. Whatever the tumour, results with the Gamma Knife(®) are the most numerous, but those obtained by linear accelerators, adapted or dedicated, are comparable. The peripheral dose is preferred to the dose delivered to the isocentre. One fraction stereotactic irradiation should be proposed in small lesions and fractionated treatment for tumours larger. Whatever the tumour, the results are satisfactory with a control rate of 90%. However, this value reflects a disparity assessment, radiological stability for meningiomas, radiological stability and preservation of useful hearing in schwannoma and radiological stability and a decrease in hormonal secretions for pituitary adenomas. Overall complication rates are low. In total, the treatment of benign lesions with stereotactic irradiation gives satisfactory results with few complications.

γ knife surgery versus reoperation for recurrent glioblastoma multiforme

BACKGROUND

The optimal management of patients with recurrent glioblastoma multiforme (GBM) is a subject of controversy. These patients may be candidates for both reoperation and/or gamma knife surgery (GKS). Few studies have addressed the role of GKS for relapsing gliomas, and the results have not been compared with reoperation. To validate the efficacy and safety of GKS, we compared the survival and complication rates of GKS and reoperation for recurrent GBMs.

METHODS

This study retrospectively reviewed 77 consecutive patients with histopathologically confirmed GBMs retreated for recurrent GBM between 1996 and 2007. Thirty-two patients underwent GKS, 26 reoperation and 19 both procedures.

RESULTS

The median time from the second intervention to tumor progression was longer after GKS than after resection, P = 0.009. Median survival after retreatment was 12 months for the 51 patients receiving GKS compared with 6 months for reoperation only (P = 0.001, hazard ratio [HR] 2.4), and 19 months versus 16 months from the time of primary diagnosis (P = 0.021, HR 1.8). A multivariate analysis adjusted for possible confounding factors (tumor volume, recursive partitioning analysis class, neurological deficits, time to recurrence, adjuvant therapy, and tumor location) showed significantly longer survival for patients treated with GKS, both from retreatment (P = 0.013, HR 4.1) and from primary diagnosis (P = 0.002, HR 5.8). The adjusted results were still significant after separate analysis according to tumor volume <5 mL, 5 to 20 mL, and >20 mL. The complications rate was 9.8% after GKS and 25.2% after reoperation.

CONCLUSIONS

GKS may be an alternative to open surgery for small GBMs at the time of recurrences, with a significantly lower complication rate and a possible survival benefit compared with reoperation.

Gamma Knife, CyberKnife, TomoTherapy: gadgets or useful tools?

PURPOSE OF REVIEW

This review provides information and an update on stereotactic radiosurgery (SRS) equipment, with a focus on intracranial lesions and brain neoplasms.

RECENT FINDINGS

Gamma Knife radiosurgery represents the gold standard for intracranial radiosurgery, using a dedicated equipment, and has recently evolved with a newly designed technology, Leksell Gamma Knife Perfexion. Linear accelerator-based radiosurgery is more recent, and originally based on existing systems, either adapted or dedicated to radiosurgery. Equipment incorporating specific technologies, such as the robotic CyberKnife system, has been developed. Novel concepts in radiation therapy delivery techniques, such as intensity-modulated radiotherapy, were also developed; their integration with computed tomography imaging and helical delivery has led to the TomoTherapy system. Recent data on the management of intracranial tumors with radiosurgery illustrate the trend toward a larger use and acceptance of this therapeutic modality.

SUMMARY

SRS has become an important alternative treatment for a variety of lesions. Each radiosurgery system has its advantages and limitations. The 'perfect' and ubiquitous system does not exist. The choice of a radiosurgery system may vary with the strategy and needs of specific radiosurgery programs. No center can afford to acquire every technology, and strategic choices have to be made. Institutions with large neurosurgery and radiation oncology programs usually have more than one system, allowing optimization of the management of patients with a choice of open neurosurgery, radiosurgery, and radiotherapy. Given its minimally invasive nature and increasing clinical acceptance, SRS will continue to progress and offer new advances as a therapeutic tool in neurosurgery and radiotherapy.