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