05.11.2019 1 Dr. med. Rami El Shafie Heidelberg Institute for Radiation Oncology(HIRO) Heidelberg University Hospital Stereotactic Radiosurgery for intracerebral arteriovenous malformations Agenda Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie|Dr. med. Rami El Shafie • Indications for Radiosurgery – Guideline recommentations • Radiosurgery Techniques – CyberKnife – Proton Therapy • Practical aspects of Radiosurgery – Target Definition – Dosimetric Evaluation – Examples INDICATIONS FOR STEREOTACTIC RADIOSURGERY Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie|Dr. med. Rami El Shafie Interdisciplinary guidelines – interdisciplinary AVM board – consisting of neurosurgeons, neurointerventionalists, radiosurgeons, and neurologists experienced in the diagnosis and treatment of brain AVM – primary strategy should be defined by the multidisciplinary team prior to the beginning of the treatment and should aim at complete eradication of AVM – Balancing the risk of hemorrhage against the risks of treatment Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie|Dr. med. Rami El Shafie Interdisciplinary guidelines Frequent indications for stereotactic radiosurgery (SRS) – risk factors for rupturing (e.g. history, deep location, deep venous drainage,…) – symptoms, deficits – unresectable, resection risky, patient wish – embolization not possible – complementing incomplete embolization Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie|Dr. med. Rami El Shafie Efficacy of SRS – Obliteration rates in literature: 40‐90% – strongly influence by prognostic factors – average time to obliteration: 18 months – 90% chance of obliteration with a margin dose ≥ 20 Gy1 – between 12 and 22 Gy: approx. 25% increase in obliteration probability per Gy2 – larger nidus / larger margin dose = dose to healthy brain ↑ = complication risk ↑ favorable prognostic factors: • S‐M‐grade (I‐III) ↓ • nidus size ↓ • margin dose ↑ • (previous embolization)* • age ↓ • recent treatment *complications ↑ unfavorable prognostic factors: • S‐M grade ↑ • age ↑ • nidus size ↑ • ruptured AVM • eloquent location largest published meta‐analysis: – 142 cohors, 13.698 patients, of those 9.436 treated with SRS – median FU: 30 months 1Lunsford LD, Kondziolka D, Flickinger JC, et al. Stereotactic radiosurgery for arteriovenous malformations of the brain. J Neurosurg. 1991;75(4):512‐524. doi:10.3171/jns.1991.75.4.0512. Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie|Dr. med. Rami El Shafie 2Milker‐Zabel S et al. Proposal for a new prognostic score for linac‐based radiosurgery in cerebral arteriovenous malformations. IJROBP. 2012;83(2):525‐532. 1 2 3 4 5 6
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ElShafie Handout SRS AVM for cAVM.pdf · MRA‐contour CBCT‐contour smaller than MRA‐contour lowsimilarity ... AVM, leading to obliteration rates of up to 90%. • Precision is
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05.11.2019
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Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Dr. med. Rami El Shafie
Heidelberg Institute for Radiation Oncology(HIRO) Heidelberg University Hospital
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
• Indications for Radiosurgery
– Guideline recommentations
• Radiosurgery Techniques
– CyberKnife
– Proton Therapy
• Practical aspects of Radiosurgery
– Target Definition
– Dosimetric Evaluation
– Examples
INDICATIONS FOR STEREOTACTIC RADIOSURGERY
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Interdisciplinary guidelines
– interdisciplinary AVM board
– consisting of neurosurgeons, neurointerventionalists, radiosurgeons, and neurologists experienced in the diagnosis and treatment of brain AVM
– primary strategy should be defined by the multidisciplinary team prior to the beginning of the treatment and should aim at complete eradication of AVM
– Balancing the risk of hemorrhage against the risks of treatment
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Interdisciplinary guidelines
Frequent indications for stereotactic radiosurgery (SRS)
– risk factors for rupturing (e.g. history, deep location, deep venous drainage,…)
– symptoms, deficits
– unresectable, resection risky, patient wish
– embolization not possible
– complementing incomplete embolization
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Efficacy of SRS
– Obliteration rates in literature:40‐90%
– strongly influence by prognostic factors
– average time to obliteration: 18months
– 90% chance of obliteration with a margin dose≥ 20Gy1
– between 12 and 22 Gy: approx. 25% increasein obliteration probability per Gy2
largest publishedmeta‐analysis:– 142 cohors, 13.698 patients, of those 9.436 treated with SRS– median FU: 30 months
1 Lunsford LD, Kondziolka D, Flickinger JC, et al. Stereotactic radiosurgery for arteriovenous malformations of the brain. J Neurosurg. 1991;75(4):512‐524. doi:10.3171/jns.1991.75.4.0512.
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
2 Milker‐Zabel S et al. Proposal for a new prognostic score for linac‐based radiosurgery in cerebral arteriovenous malformations. IJROBP. 2012;83(2):525‐532.doi:10.1016/j.ijrobp.2011.07.008.
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RADIOSURGICAL TECHNIQUES / MODALITIES
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
A look at what‘s available…
CyberKnife+ robotic precision↑+ frameless
‐ treatment time↑‐ low dose↑
GammaKnife+ precision↑+ longestexperience
‐ frame‐based‐ treatment time↑‐ low dose↑
AdaptedLINAC+ availability↑+ cost↓
‐ frame‐based‐ precision↓‐ low dose↑
Protontherapy+ low dose↓+ large lesions
‐ availability ↓‐ cost↑‐ experience↓
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
robotic
patientcouch
stereoscopicX‐rays
(image guidance)
linearaccelerator
X‐ray detectors
Cyberknife M6 – stereotactic radiosurgery (SRS)
robot
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
The robotic approach
• Automated irradiation from multiple different angles “nodes” on a virtual sphere around the target.
• typically 200‐400 beams per session (vs. 10‐15 at conventional linac)
Images courtesy of Accuray Inc.
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
protons
photons
Why use protons?• inverted depth dose profile
• max. dose deposition at predefined depth „Bragg peak“
• less dose in entry‐ and exit trajectories
• problems:
– lateral scattering unsuitable for small lesions
– range uncertainties for matter with ↑↑or ↓↓ HU(e.g. air, metal, embolisate)1
.5cm
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Proton SRS
– largest analyzed collective– n = 248, median FU = 35 mo– AVM‐volume (median) = 3.5 ml– Dose (median) = 15 GyRBE– Outcome: 64.6% CO, median time to CO = 31mo
depending on size and location• prescription to the PTV
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Zielvolumendefinition
Gross Target Volume (GTV) = green line
Planning Target Volume (PTV) = red line
margin dose = yellow line
PTV volume = 0.37ml
Gross Target Volume (GTV) = not visible
Planning Target Volume (PTV) = red line
margin dose = yellow line
PTV volume = 1.9ml
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
DOSIMETRIC EVALUATION
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
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Prospective treatment plan comparisonHeidelbergWorkflow:treatment planning for all AVM patients by prospective dosimetric comparison
target definition
structure set export
treatment plan calculation for CyberKnife and
protons
comparisonconsideringall
relevant aspects
decision ontreatmenttechnique
Decision criteria:
dosimetric criteria• conformity and dose gradient – High‐dose „spill“ surrounding targetvolume?• coverage – entire target covered? relevant for complex shapes andgeometries• mid‐ and low‐dose distribution – Comparison of V10Gy and V12Gy volumes• organs at risk –Which technique achieves better sparing of critical adjoining organs at risk?• beam trajectories – Are there relevant limitations? (e.g.embolisate,artefacts)
clinical criteria• treatment time – relevant for pa ents with clinical performance ↓, clasutrophobic patients• location – periventricular lesion? higher risk for necrosis with protons
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Individual dosimetric comparison
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Individual dosimetric comparison
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Individual dosimetric comparison
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Individual dosimetric comparison
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
Take home
Universitätsklinikum Heidelberg | RadioOnkologie und Strahlentherapie| Dr. med. Rami ElShafie
• Stereotactic radiosurgery is an effective means of treating AVM, leading to obliteration rates of up to 90%.
• Precision is paramount to lower dose exposure of surrounding healthy brain and reduce risk of complications
• Choice of ideal treatment modality (e.g. CyberKnife, proton SRS) is influenced by different factors (size, shape, location,...) and done individually for each case.