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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 4  |  Issue : 2  |  Page : 92-101

Step by step stereotactic planning of meningioma: A guide to radiation oncologists—the ROSE case [radiation oncology from simulation to execution]


1 Department of Radiation Oncology, Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam, India
2 Department of Radiation Oncology, Acharya Harihar Post Graduate Institute of Cancer, Cuttack, Odisha, India
3 Department of Neurosurgery, Medicover Hospital, Visakhapatnam, India
4 Department of Medical Physics, Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam, Andhra Pradesh, India

Date of Submission25-Oct-2021
Date of Acceptance09-Dec-2021
Date of Web Publication23-Feb-2022

Correspondence Address:
Dr. Kanhu Charan Patro
Department of Radiation Oncology, Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jco.jco_36_21

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  Abstract 

Background: Intracranial meningiomas account for 33% of all primary tumors of the brain. One of the main modalities of the treatment is stereotactic radiosurgery (SRS). Here, we describe the procedural steps for radiation planning of stereotactic radiotherapy (SRT) of meningioma. Methods: The step-by-step procedure for stereotactic planning of meningioma has been described using a clinical scenario of meningioma. Results: The stereotactic radiation planning of meningioma starts with the basic history and relevant clinical evaluation of various signs and symptoms of the patient followed by imaging and grading of meningioma. Magnetic resonance imaging (MRI) of the brain is the imaging modality of choice. Evaluation of surgical notes and postoperative histopathology confirmation of diagnosis should also be done. Radiation is indicated in postoperative residual or recurrent disease and in unresectable settings. The radiation planning of meningioma starts with computed tomography (CT) simulation and MRI of the brain that should be performed in prescribed format to achieve uniformity in radiation planning. After CT and MRI fusion, contouring of target, organs at risk (OAR), and radiation planning should be performed. The plan evaluation includes target and OAR coverage index, conformity, homogeneity and gradient index, and beam arrangement. After radiation plan evaluation, the treatment is delivered after quality assurance and dry run. Conclusion: The article highlights the sequential process of radiation planning for SRT of meningioma—starting from simulation to planning, evaluation of plan, and treatment.

Keywords: Meningioma, radiation planning, SRS


How to cite this article:
Patro KC, Avinash A, Pradhan A, Tatineni S, Kundu C, Bhattacharyya PS, Pilaka VK, Rao MM, Prabu AC, Kumar AA, Aketi S, Prasad P, Damodara VN, Avidi VS, Atchaiyalingam M, Karthikeyan K, Muralikrishna V. Step by step stereotactic planning of meningioma: A guide to radiation oncologists—the ROSE case [radiation oncology from simulation to execution]. J Curr Oncol 2021;4:92-101

How to cite this URL:
Patro KC, Avinash A, Pradhan A, Tatineni S, Kundu C, Bhattacharyya PS, Pilaka VK, Rao MM, Prabu AC, Kumar AA, Aketi S, Prasad P, Damodara VN, Avidi VS, Atchaiyalingam M, Karthikeyan K, Muralikrishna V. Step by step stereotactic planning of meningioma: A guide to radiation oncologists—the ROSE case [radiation oncology from simulation to execution]. J Curr Oncol [serial online] 2021 [cited 2022 Sep 25];4:92-101. Available from: http://www.https://journalofcurrentoncology.org//text.asp?2021/4/2/92/338060




  Introduction Top


Intracranial meningiomas have an incidence of 6 in 1 lakh annually.[1] World Health Organization (WHO) classification has divided meningioma into benign, atypical, and malignant as grade 1, 2, and 3, respectively.[2] The primary modality of treatment is surgery. Radiation is considered in post-operative residual or recurrent disease and unresectable benign tumors. Post-operative radiation is a must for atypical and malignant meningioma following surgery regardless of residual disease.[3] Here, we describe a sequential procedure for stereotactic radiation therapy (SRT) planning for meningioma.


  Methods Top


In this paper, the various steps of radiation planning for SRT have been illustrated in an easy way for the beginners who are planning for SRT in a case of meningioma with the help of a clinical case as described below.

A 41-year-old female presented with the chief complaints of headache for 4 months which was intermittent stabbing type. She had a history of pain in the left eye, no history of vomiting, head reeling sensation, blurring of vision, no history of limb weakness, or seizure episodes.

Every patient with complaints of pain should be evaluated by the Barrow Neurological Institute pain score and Brief Pain Inventory Facial tool to be used for evaluation of trigeminal pain. On evaluation, the patient had a pain score of III using the Barrow Neurological Institute pain score depicted in [Table 1]. While using the Brief Pain Inventory Facial tool for evaluation of trigeminal pain, the patient had average pain intensity in last week, and she had interference in normal work and face-specific activities.
Table 1: Describing the barrow neurological institute pain score and brief pain inventory for trigeminal pain

Click here to view



  Imaging Top


Magnetic resonance imaging (MRI) of brain revealed a well-defined intensely enhancing extra-axial mass of size 2.3 cm × 2.2 cm × 1.9 cm which was hypo-intense on T2 weighted images [Figure 1] and iso-intense on T1. The mass was present posterior to left cavernous sinus indenting on pons with the probable invasion of Meckel cave and V cranial nerve on the left side.
Figure 1: Showing the lesion as hypo-intense on MRI T2 weighted image

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  Surgery Top


Patient underwent surgery in the form of near-total excision of the lesion by Kawase Approach.


  Histopathology Top


The post-operative histopathology examination revealed 3 cm × 3 cm × 1 cm, firm, whorled, and myxoid spindle-shaped tumor cells in fascicles whorls with intersecting psammoma bodies confirming the diagnosis to be Grade I transitional meningioma. The bilateral hearing and vision were normal. With the above features, a final diagnosis of left-sided Petro-Clival meningioma with trigeminal pain and facial palsy with residual lesion was made.


  Tumor Board Decision Top


The case detail was discussed in the tumor board among neurosurgeons and radiation oncologists, and the board decided on SRT.


  Patient Discussion Top


The patient was explained about the procedure, complications, and the outcome.


  Dose Selection Top


For appropriate dose selection, we need to focus on the location of the target and tolerance dose of the surrounding critical structures. As per Tishler et al.,[4] a stereotactic radiosurgery (SRS) dose of 40 Gy can be delivered safely to the tumors located near the cavernous sinus with relatively few complications to the cranial nerves within the sinus. According to Correa et al.,[5] inoperable and symptomatic cavernous sinus meningioma can be treated with SRS or SRT with equal efficacy and safety. The normal tissues dose constraints and toxicity rate is given in [Table 1] as per European Society for Radiotherapy and Oncology (ESTRO) Advisory Committee for Radiation Oncology Practice (ACROP) guidelines.[1] Minniti et al.[6] in their article have stated that while treating a patient with SRS and in order to decrease the occurrence of pituitary deficits, the mean dose should be limited to 12–15 Gy and 7–10 Gy to the pituitary gland and stalk, respectively. As per Zhang et al.,[7] in SRS, the maximum dose to the hippocampus should be limited to 6.6 Gy, or the dose to 40% of the hippocampus should be limited to 4.5 Gy to decrease neurocognitive deficits.

ESTRO ACROP guidelines stated that for benign meningioma, a dose of 13–15 Gy is favored for single-fraction SRS, whereas 21–25 Gy in 3–5 fractions is advocated for SRT.[1] The systematic review and meta-analysis by Fatima et al.[8] have shown that local tumor control and symptomatic edema are less with SRT as compared to SRS. Unger et al.[9] have stated in their article that larger volume tumors and single-fraction SRS are the risk factors associated with increased risk of post-radiation edema as compared to fractionated SRS. Meniai-Merzouki et al.,[10] in their scientific report, have compared the efficacy and tolerance of hypofractionated SRT for intracranial meningioma in primary setting as compared to salvage hypofractionated SRT for recurrent disease post radiation. They found that the 2-year local control was significantly higher in primary hypofractionated SRT as compared to salvage hypofractionated SRT for recurrent disease. Also, the incidence of radionecrosis at 2 years was significantly lower in primary hypofractionated SRT versus to salvage hypofractionated SRT for recurrent disease. Onodera et al.,[11] in their article, have stated that treatment of intracranial meningioma with fractionated SRT is safe and effective for tumor volume less than 9 cc with or without surgery. Prasad et al.[12] have advocated the use of fractionated SRS at a dose of 25–30 Gy in 5 fractions for meningiomas with high risk for peritumoral edema with single-fraction SRS due to large tumor volume, prior exposure to radiation, or close proximity to critical structures. As per International Stereotactic Radiosurgery Society (ISRS) recommendations, single-fraction SRS with a dose of 12–15 Gy is advocated in intracranial meningioma. But fractionated SRT with a dose of 25 Gy in 5 fractions is to be considered while treating large meningioma or critically located tumors.[13]


  Final Decision of Tumor Board on Dose Selection Top


The tumor board decided that the current case of meningioma is to be treated with a dose of 25 Gy in 5 fractions taking into account the following points.

  1. Radionecrosis was lower with fractionated SRS.


  2. Post radiation edema is lower with fractionated SRS.


  3. Equal tumor control with fractionated SRS as compared to single-fraction SRS.


  4. Cranial nerve symptoms were better tolerated with fractionated SRS.


  5. Lesions located near critical structures were better with fractionated SRS.



  RT Technique Top


Radiation planning can be done using any of the RT techniques, i.e., Volumetric Modulated Arc Therapy (VMAT), Dynamic Conformal Arc Therapy (DCARC), 3-Dimensional Conformal Radiotherapy (3DCRT), or Intensity Modulated Radiotherapy (IMRT).

In this case, VMAT technique was used for radiation planning.


  Patient Counselling Top


The patient was explained about the follow-up, response rate, repeat SRS, and post-radiotherapy raised intracranial tension.

RT planning

Here, we describe the radiation planning of the meningioma in the following steps.

Step 1—Computed tomography simulation

The patient was simulated in supine position with neutral neck position, immobilization was done with FRAXION thermoplastic mask and a stereotactic frame, and fiducials were placed on the thermoplastic mask after proper alignment with the lasers [Figure 2]A. Intravenous contrast was given at a dose of 1 mg per kg body weight. The computed tomography (CT) scan was taken just after contrast injection from vertex to neck with a CT slice thickness of 1 mm [Figure 2]B. After simulation, the Digital Imaging and Communications in Medicine (DICOM) CT images were sent to our Treatment Planning System (TPS) and were imported for delineation of target and organs at risk.
Figure 2: Showing the CT and MRI images taken as per simulation protocol. (A) Immobilization using stereotactic mask. (B) CT scan taken during the simulation. (C) T2 weighted image. (D) FSPGR sequence

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Step 2-Imaging protocol

MRI protocol

It includes usual T1, T2 [Figure 2C], FLAIR, and Three Dimensional-Fast Spoiled Gradient Echo (3D-FSPGR) sequences [Figure 2D] for normal anatomy. It included 512 × 512 matrix, 1 mm slice thickness, no gap, no tilt, and neutral neck position. The field of vision includes body contour, nose, eyes, and skull.

PET CT protocol

If the tumor is involving the para-pharyngeal soft tissues or is difficult to visualize on MRI or CT scan due to location near the bone, then Ga 68 DOTATOC or Ga 68 DOTANOC PET scan can be done.[1] The whole-body PET CT scan is done in the same position as the CT simulation, from vertex to mid-thigh after injecting 5 mCi of 68 Ga DOTATOC intravenously. The scan is taken 45 minutes post-injection in 3D mode. The axial, coronal, and sagittal PET and CT images were fused.

Step 3-Image fusion

These acquired MRI sequences were fused with the planning CT scan by contouring the eyes, lens, basilar artery, sinuses, and calcification, and matching was done using an auto-fusion technique to help in target and organ at risk (OAR) delineation [Figure 3].
Figure 3: Showing fusion of the planning CT scan with the MRI

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Step 4-Target delineation

The delineation of the target is done as per the ESTRO ACROP guidelines.[1] The gross tumor volume (GTV) was contoured as the visible contrast-enhancing lesion on CT [Figure 4]A–C that was fused with MRI. Also thickened dural tail is included but not the linearly enhanced dura or non-enhancing thickened dura in the GTV. There is no necessity of clinical target volume (CTV) margin in case of benign meningioma. For fixed frame SRS, no additional planning target volume (PTV) margin is required, but for frameless SRS, a margin of 1–3 mm is usually given to GTV to get the PTV. The delineation of the GTV for the present case is shown in [Figure 4]D–F. The PTV contour is then smoothened which is not a necessary step, and it depends upon the algorithm being used for planning [Figure 5]A.
Figure 4: Showing the delineation of GTV in all the three planes—axial (A), coronal (B), and sagittal (C) and PTV in all the three planes- axial (D), coronal (E), and sagittal (F).

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Figure 5: Showing the smoothening of the PTV contour in (A) and distance between the PTV (white) and the optic chiasma (green) is 0.45 cm in (B)

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Step 5-OAR delineation

Optic apparatus, pituitary gland and stalk, (Brain-PTV), brainstem, hippocampus, and cochlea are the OARs that are delineated as per the ESTRO ACROP guidelines.[1] The distance between the PTV and optic chiasma was calculated to be 0.45 cm [Figure 5B]. The dose constraints and toxicity rate of individual organ at risk structures are shown in [Table 2].
Table 2: Showing CT simulation and MRI Protocol to be followed for Meningioma

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Step 6-Plan evaluation

RT Planning

As discussed above, RT planning was done using the VMAT technique and Monte Carlo algorithm. After the planning is done by the physicist, the following indices need to be followed for evaluation of the treatment plan.

PTV coverage index

Following the beam arrangement, we need to see the PTV coverage. The prescription isodose level is usually not 100% of the prescribed dose covering 100% of the PTV. Often the 95% of the prescription dose should cover 95% or higher percentage of the PTV, or 100% of the prescription dose should cover 95% or higher percentage of the PTV.[14]

In the present case, 95% of the prescription dose covers 99.7% of the PTV, and 100% of the prescription dose cover 97.06% of the PTV which meets the above-mentioned parameter for the PTV coverage and is depicted in [Table 3].
Table 3: Depicting the dose constraints and toxicity rate of individual organ at risk structures

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OAR index

Keeping in mind the desirable dose constraints to the OAR, we need to check the dose to individual OARs.[15]

The dose desirable and dose achieved for all the OARs in the present case are depicted in Table 5.

Conformity index

To note the conformity index of the SRS, here, we used 2 types of conformity indices, i.e., the RTOG conformity index, and the Paddick conformity index.[14],[16] If a plan is unable to achieve these parameters, then replanning has to be done.

RTOG conformity index (CIRTOG) is calculated using the following formula.

CIRTOG = volume of prescription isodose / PTV volume

Paddick conformity index (CIPaddick) was calculated using the following formula.

CIPaddick = (volume of prescription isodose in the area of interest, i.e., PTV)2 / PTV volume × volume of prescription isodose

In the current case, the Radiation Therapy Oncology Group (RTOG) conformity index was 1.26, and the Paddick conformity index was 0.913 [Table 4].
Table 4: Depicting the PTV coverage of meningioma in the current case

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  Homogeneity Index Top


It is calculated using the formula

Homogeneity index = maximum dose / prescription dose

In this case, the Homogeneity index was 1.28 [Table 4].


  Dose Fall Off Top


The dose fall-off observation is very much needed in the plan evaluation under the heading of gradient index. For this, we need to calculate the difference between various isodose lines. To calculate the difference between the isodose lines, we need to calculate the equivalent radius.


  Equivalent Radius Calculation Top


To evaluate the dose gradient, we have to find out the difference between the radius of various isodose lines. But none of the isodose is spherical. So, we use the following formula to calculate the equivalent radius.

First: Find out the specified isodose volume.

Second: Calculate the radius of the isodose volume by using the formula:

V = 4/3 π r3

r = (3V/4 π)1/3

The calculation of volume and radius of various isodose lines in the present case is shown in [Table 5].
Table 5: Showing the individual OARs with its desirable dose and dose achieved in the current case of meningioma

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  Gradient Index Top


The formula for calculating gradient index is as given below.

Gradient index = equivalent radius of 50% isodose−equivalent radius of prescription isodose. Ideally, the gradient index should be between 0.3 and 0.9 mm.

In the current case, the gradient index is 1.96 mm–1.21 mm = 0.75 mm which is close to the ideal gradient index.


  Distance Between Various Isodose Lines Top


The various isodose lines are depicted in [Figure 6]A.
Figure 6: Showing the isodose lines—100% (red), 80% (orange), 60% (yellow), 50% (pink), and 40% (blue) in (A) and beam arrangement in axial (B), coronal (C) and sagittal view (D) for the current case of meningioma in (B) with the PTV (green)

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The ideal difference between 80% and 60% isodose lines should be <2 mm.[17]

In the current case, it is 0.28 mm [Table 4].

The ideal difference between 80% and 40% isodose lines should be <8 mm.

In present case, it is 0.7 mm [Table 4].

Beam arrangement

The arrangement of the beams was done such that there is adequate coverage of the target while giving less dose to the OARs [Figure 6B–D]. It should be noted that the beams should not pass through the ipsilateral eyes.

Step 7—Quality assurance

Mechanical isocentre check was done using the Winston Lutz test. Point dose verification was done keeping the tolerance as 1 mm.[18]

Step 8—Dry run

Treatment verification consists of setup reproduction, isocentre verification, and clinically mode up each treatment fieldcheck beam clearance, check any interlockmultileaf collimator (MLC) interlock and potential Monitor Unit (MU) problems. Then clearly mark the immobilization devices after successful dry run.

Step 9—Pre-medication protocol

Prior to start of treatment, pre-medication was delivered in the form of tablets as described below—all starting the day before start of RT treatment.

Tablet dexamethasone 8 mg thrice daily

Tablet ondansetron 8 mg thrice daily

Tablet pantoprazole 40 mg once daily

If the patient is diabetic, proper diabetic care needs to be done.

Step 10—Set up verification and treatment delivery

It includes cone-beam CT correction and hexapod corrections as depicted in the [Figure 7]A and B, respectively. After all the corrections were done, treatment is delivered.
Figure 7: Showing the setup verification by Cone Beam Computed Tomography (CBCT) in (A) and hexapod correction in (B)

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Step 11—Post medication

It is an optional protocol that usually includes anti-emetics, proton pump inhibitors, and tapering the dose of steroid over a week.

Step 12—Advice

After the completion of the treatment, the patient is usually advised to follow after 6 months for imaging.

Step 13—Follow-up protocol

All of the patients were followed prospectively after the treatment. The protocol included medical evaluations for neurological symptoms and cranial MRI. A first follow-up visit was scheduled 40 days after completion of radiation, and at 3-month intervals thereafter for the first year. From the second year on, follow-up intervals were extended to 6–12-month intervals or as requested clinically. At least 3 years of follow-up was required. Progression-free survival was determined based on the Response Evaluation Criteria in Solid Tumours (RECIST) criteria that evaluate two orthogonal diameters of the tumor. Radiological response was defined as the disappearance of the enhancement of the tumor mass or shrinkage of initial volume by at least 20 mm on MRI. Clinical response was defined as regression in signs or symptoms of up to 80% based on pre-treatment levels.[1


  Response Evaluation Top


Evaluation of response to treatment was done as per the Response Assessment in Neuro Oncology (RANO) criteria for meningioma.[19]

Supplementary File

Here, we also provide the Meningioma SRS Plan Evaluation sheet as a supplementary file that will help in proper and accurate plan evaluation for every SRS case of Meningioma


Click here to view



  Conclusion Top


This article conceptualizes and acts as an easy guide for the beginners for stereotactic radiation planning for meningioma.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Combs SE, Baumert BG, Bendszus M, Bozzao A, Brada M, Fariselli L, et al. ESTRO ACROP guideline for target volume delineation of skull base tumors. Radiother Oncol 2021;156: 80-94.  Back to cited text no. 1
    
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Louis DN, Perry A, Reifenberger G, von Deimling A, Figarella-Branger D, Cavenee WK, et al. The 2016 world health organization classification of tumors of the central nervous system: A summary. Acta Neuropathol 2016;131:803-20.  Back to cited text no. 2
    
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Goldbrunner R, Minniti G, Preusser M, Jenkinson MD, Sallabanda K, Houdart E, et al. EANO guidelines for the diagnosis and treatment of meningiomas. Lancet Oncol 2016;17: e383-91.  Back to cited text no. 3
    
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Tishler RB, Loeffler JS, Lunsford LD, Duma C, Alexander E 3rd, Kooy HM, et al. Tolerance of cranial nerves of the cavernous sinus to radiosurgery. Int J Radiat Oncol Biol Phys 1993;27:215-21.  Back to cited text no. 4
    
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Correa SF, Marta GN, Teixeira MJ Neurosymptomatic carvenous sinus meningioma: A 15-years experience with fractionated stereotactic radiotherapy and radiosurgery. Radiat Oncol 2014;9:27.  Back to cited text no. 5
    
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Minniti G, Osti MF, Niyazi M Target delineation and optimal radiosurgical dose for pituitary tumors. Radiat Oncol 2016;11:135.  Back to cited text no. 6
    
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Zhang I, Antone J, Li J, Saha S, Riegel AC, Vijeh L, et al. Hippocampal-sparing and target volume coverage in treating 3 to 10 brain metastases: A comparison of gamma knife, single-isocenter VMAT, cyberknife, and tomotherapy stereotactic radiosurgery. Pract Radiat Oncol 2017;7:183-9.  Back to cited text no. 7
    
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Fatima N, Meola A, Pollom EL, Soltys SG, Chang SD Stereotactic radiosurgery versus stereotactic radiotherapy in the management of intracranial meningiomas: A systematic review and meta-analysis. Neurosurg Focus 2019;46:E2.  Back to cited text no. 8
    
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Unger KR, Lominska CE, Chanyasulkit J, Randolph-Jackson P, White RL, Aulisi E, et al. Risk factors for posttreatment edema in patients treated with stereotactic radiosurgery for meningiomas. Neurosurgery 2012;70:639-45.  Back to cited text no. 9
    
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Meniai-Merzouki F, Bernier-Chastagner V, Geffrelot J, Tresch E, Lacornerie T, Coche-Dequeant B, et al. Hypofractionated stereotactic radiotherapy for patients with intracranial meningiomas: Impact of radiotherapy regimen on local control. Sci Rep 2018;8:13666.  Back to cited text no. 10
    
11.
Onodera S, Aoyama H, Katoh N, Taguchi H, Yasuda K, Yoshida D, et al. Long-term outcomes of fractionated stereotactic radiotherapy for intracranial skull base benign meningiomas in single institution. Japanese J Clin Oncol 2011;41:462-8.  Back to cited text no. 11
    
12.
Prasad RN, Breneman JC, Struve T, Warnick RE, Pater LE Linac-based fractionated stereotactic radiosurgery for high-risk meningioma. J Radiosurg SBRT 2018;5:269-76.  Back to cited text no. 12
    
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Marchetti M, Sahgal A, De Salles AAF, Levivier M, Ma L, Paddick I, et al. Stereotactic radiosurgery for intracranial noncavernous sinus benign meningioma: International stereotactic radiosurgery society systematic review, meta-analysis and practice guideline. Neurosurgery 2020;87:879-90.  Back to cited text no. 13
    
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Torrens M, Chung C, Chung H, Hanssens P, Jaffray D, Kemeny A et al,Standardization of terminology in stereotactic radiosurgery: Report from the Standardization Committee of the International Leksell Gamma Knife Society. J N S 2014;121(suppl 2):2-15.  Back to cited text no. 14
    
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Hanna GG, Murray L, Patel R, Jain S, Aitken KL, Franks KN, et al. UK consensus on normal tissue dose constraints for stereotactic radiotherapy. Clin Oncol (R Coll Radiol) 2018;30:5-14.  Back to cited text no. 15
    
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Petkovska S, Tolevska C, Kraleva S, Petreska E Conformity index for brain cancer patients. Proceedings of the second conference on medical physics and biomedical engineering of R Macedonia. 2010;43:111.  Back to cited text no. 16
    
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Kocher M, Soffietti R, Abacioglu U, Villà S, Fauchon F, Baumert BG, et al. Adjuvant whole-brain radiotherapy versus observation after radiosurgery or surgical resection of one to three cerebral metastases: Results of the EORTC 22952-26001 study. J Clin Oncol 2011;29:134-41.  Back to cited text no. 17
    
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Denton TR, Shields LB, Howe JN, Spalding AC Quantifying isocenter measurements to establish clinically meaningful thresholds. J Appl Clin Med Phys 2015;16:5183.  Back to cited text no. 18
    
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Raymond YH, Wenya LB, Michael W, Thomas K, Jaishri B, Ian D, et al. Proposed response assessment and endpoints for meningioma clinical trials: Report from the Response Assessment in Neuro-Oncology Working Group, Neuro-Oncology 2019;21:26-36.  Back to cited text no. 19
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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  In this article
Abstract
Introduction
Methods
Imaging
Surgery
Histopathology
Tumor Board Decision
Patient Discussion
Dose Selection
Final Decision o...
RT Technique
Patient Counselling
Homogeneity Index
Dose Fall Off
Equivalent Radiu...
Gradient Index
Distance Between...
Response Evaluation
Conclusion
References
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