Stereotactic Radiosurgery:A Noninvasive Brain Tumor Treatment Option
Susan C. Pannullo, MD
Director of Neuro-OncologyDepartment of Neurological Surgery
New York-Presbyterian Hospital/ Weill Cornell Medical College
Director of Neurosurgical RadiosurgeryNew York Presbyterian Hospital
Associate Professor of Clinical Neurological SurgeryWeill Cornell Medical College
Adjunct Professor of Biomedical Engineering Cornell University
Stereotactic Radiosurgery (SRS)
• Non-invasive technique for delivery of highly focused radiation with extreme precision
• Creates a desired response (e.g. tumor cell death)• Minimal effect on normal surrounding structures• Uses high resolution imaging for “stereotactic” (3-D)
treatment planning• Generally single session, can be multiple (< 5)• Multidisciplinary team: Neurosurgeon, Radiation
Oncologist, Medical Physicist
Stereotactic Radiosurgery: Indications
• Brain tumors– Benign– Malignant
• Primary brain tumors• Brain metastases
• Arteriovenous malformations• Functional disorders/ Pain
– Trigeminal neuralgia– Epilepsy– Psychiatric illness (e.g. obsessive compulsive disorder)
• Spine and other body cancers
Stereotactic Radiosurgery: Brief History
• 1950s: Neurosurgeon Lars Leksell develops Stereotactic Radiosurgery technique at Karolinska Hospital –Stockholm
• 1960s: “Gamma Knife”– Pituitary (sella visualized on xrays)– AVMs (angiogram)
• Mid-1970s: expanded applications of Gamma Knife due to CT
Stereotactic Radiosurgery: Brief History
• 1980s: – Linear accelerator modified SRS for brain tumors– 1987- Stereotactic Radiosurgery approved by FDA
• 1990s: MRI better targeting• 2000 +:
– higher resolution imaging– clinical trials/data collection increased use of SRS for variety of brain tumors
Stereotactic Radiosurgery for Brain Tumors
• Stereotactic Radiosurgery is used alone or in addition to other brain tumor therapies such as surgery, “conventional” radiation, and chemotherapy.
Stereotactic Radiosurgery: Some Devices Used
Stereotactic Radiosurgery: 3 Types of Devices
• Gamma Knife
• LINAC
• Proton Beam
Stereotactic Radiosurgery: Technologies
• Gamma Knife– 201 beams of Co-60
(photons from decay) pass through various sized holes (“collimators”) in “helmet”
– Target is placed in the center of the converging beams
Stereotactic Radiosurgery: Technologies
• Linear Accelerator (LINAC)– Most widely available
• Majority are modified multi-use LINACs
– Special software – Special hardware
• Some are specially designed for SRS
– Accelerated photons– Multiple convergent arcs or
beams of radiation
Stereotactic Radiosurgery: Technologies
• Proton Beam– Protons– Few active units in US– Expensive– Protons drop off their
energy at one point (“Bragg Peak Effect”)Minimizes entry/exit
dose
Stereotactic Radiosurgery: How Treatment May Be Done
Patient selection
• Tumor considerations:– Tumor type– Size (< 3 cm)– Location (“critical” structures)
• Patient considerations:– Motivated, cooperative– Body shape (for Gamma Knife)– Can lie flat– Poor surgical risk ok– Anticoagulation ok
Patient Preparation
• Same day surgery
• Pre-op medications:• Edema steroids• Seizures anticonvulsants
• Pre-op explanation/ consent
Frame Application
• Gamma Radiosurgery requires solid fixation of the patient’s head in a metal head frame
• Patient comfort:– Mild oral sedation– Local anaesthetic– Comforting
environment
Frame Placement
• Optimal frame placement- critical for frame based radiosurgery– Avoid cranial defects– Place target(s) in the
center of the frame– Anticipate collisions– Consider patient
positioning and body shape limitations
• “Bubble” measurements
Imaging and Treatment Planning
• Imaging– MRI, CT in head frame– Image transfer to planning
workstation
• Treatment planning– Radiation oncologist,
neurosurgeon, physicist, computer
– Target and critical structures identification
– Dose– Positioning in the machine
Treatment Planning
Treatment Set Up
• Collimator helmet chosen for identified “shot”
• x, y, z stereotactic coordinates “Gamma Angle” set
• Helmet/frame/patient docked into machine
• Exposure time set
Treatment Delivery
LINAC Stereotactic Radiosurgery Techniques
• LINAC Radiosurgery can be frame-based or frameless
• CyberKnife: frameless LINAC radiosurgery– Patient comfort– Permits fractionation– Allows treatment of
extracranial sites (spine)
CyberKnife Stereotactic Radiosurgery
• Mask fixation• Robot constantly
adjusts beam trajectory using x-rays performed during treatment to track patient position
CyberKnife Stereotactic Radiosurgery
Stereotactic Radiosurgery: Some Tumor Types Treated
Stereotactic Radiosurgery:Some Tumor Applications
• Acoustic neuromas• Meningiomas• Brain metastases• Pituitary adenomas • Glioblastoma Multiforme• Craniopharyngiomas • Trigeminal and other cranial nerve schwannomas• Glomus Jugulare tumors• Hemangiopericytomas• Ependymomas• Recurrent medulloblastomas
Stereotactic Radiosurgery for Acoustic Neuroma
• Disease stabilization > 90%
• Hearing preservation 60 %– Possibly improved with fractionated stereotactic
radiosurgery – Facial weakness 2-3 % – Face numbness 2-3 %
• Other complications 6 %
• Minimal improvement of tinnitus (17 %)
Stereotactic Radiosurgery for Acoustic Neuroma
• Avoids hearing loss associated with some surgical approaches
• Minimizes risk of facial weakness
• Avoids anaesthesia complications, CSF leak, infection
• May complicate future surgery, if needed
Stereotactic Radiosurgery for Acoustic Neuroma
Stereotactic Radiosurgery for Meningioma
• Inaccessible, recurrent, residual meningiomas
• Disease stabilization 90 %
• Complication rate 7 %
• Higher control rate, fewer complications with smaller tumors
Stereotactic Radiosurgery for Meningioma
Stereotactic Radiosurgery for Brain Metastases
• Newly diagnosed, recurrent, residual brain metastases or sometimes to an area around a tumor after surgery
• Control of treated tumors ranges 60 - 97 %
• Can treat multiple metastases at one time
• Single session therapy allows proceeding with treatment of systemic cancer
Stereotactic Radiosurgery for Brain Metastases
• Need known cancer diagnosis
• Large tumors generally need an operation
• May be used with or without additional radiation treatments
Stereotactic Radiosurgery for Brain Metastases
Stereotactic Radiosurgery for Brain Metastases
Stereotactic Radiosurgery for Pituitary Adenomas
• Radiosurgery can be used for residual, recurrent or occasionally for newly diagnosed pituitary adenomas
• Secreting and nonsecreting pituitary adenomas– Stable/decreased size = 92-100%– Sometimes the goal of treatment is to control tumor
hormone secretion
• If tumor is near visual structures, fractionation may be used
Radiosurgery for Pituitary Adenomas
Stereotactic Radiosurgery for Glioblastoma Multiforme
• Potential indications for radiosurgery for GBM– “boost” following initial conformal radiation
therapy– salvage at time of recurrence– upfront therapy
• Use of stereotactic radiosurgery for GBM is controversial
• Possibly appropriate for use in localized GBM to achieve local control
Stereotactic Radiosurgery for Glioblastoma Multiforme
Stereotactic Radiosurgery: Risks and Benefits
Radiosurgery for Brain Tumors:
General Risks• Time of presentation:
– Acute (hours to days)– Early (weeks to months)– Late (months to years)
• Complications determined by various factors– Tumor type, size, location– Prior radiation– Radiation dose given
Radiosurgery for Brain Tumors:
General Risks• Necrosis/inflammation
– edema– mass effect– seizures
• Late radiation effects on normal structures– Cranial nerves– Optic chiasm– Brainstem
• ? Radiation-induced secondary tumors
Stereotactic Radiosurgery for Brain Tumors: Potential Benefits• Minimally/ Non-Invasive
– Well tolerated– Outpatient procedure– Immediate return to normal activities
• Single (or few) treatments sustained effect• Treats a wide variety of tumors• Can treat multiple tumors at one sitting• Avoids systemic toxicity• May be combined with other therapies
Stereotactic Radiosurgery for Brain Tumors: Conclusions
Stereotactic Radiosurgery for Brain Tumors: Conclusions
• Treats a wide range of brain tumor types
• Single or few sessions • Minimally/ Non-invasive• Safe• Effective
Stereotactic Radiosurgery for Brain Tumors: Conclusions
• A powerful tool in the treatment of brain (and spine) tumors…
New York Presbyterian Hospital
Weill Cornell Medical College