role of radiotherapy in brain tumours
TRANSCRIPT
ROLE OF RADIOTHERAPY IN BRAIN TUMORS
Dr. Abhilash G JR-3
SEER STATISTICS Brain tumors account for 1.4% of all
cancers Median age of diagnosis is 58 years. Incidence is 6.4 per 100,000 men and
women per year The 5-year survival for localized brain
and other nervous system cancer is 36.3%.
Brain tumors account for 2.6% of all cancer deaths
INTRODUCTION Sixty percent of all primary brain
tumours are glial tumours, and two-thirds of these are clinically aggressive, high-grade tumours.
COBALT 60 LINAC
INDICATIONS OF RADIOTHERAPY
High Grade Gliomas Residual Disease Recurrent Disease Benign Tumors Brachytherapy (selected cases)
BENIGN BRAIN TUMORS Meningioma Pituitary tumors Craniopharyngioma Arteriovenous Malformations Hemangioblastoma and Hemangiopericytoma Glomus Jugulare Tumor Pineocytoma Chordoma Vestibular Schwannoma Ganglioglioma Central Neurocytoma
TYPES OF RADIOTHERAPY TECHNIQUES
Conventional 2D approach 3 dimensional conformal radiotherapy
(3DCRT) Stereotactic Radiosurgery and Stereotactic
Radiotherapy Brachytherapy Proton Beam Therapy
Two Dimensional planning for Brain
Tumors
CONTOUR TARGET OUTLINE
PLACE A FIELD
Immobilization• Head Rest• Thermoplastic mask• Base plate
2-D BEAM ARRANGEMENTS
CONVENTIONAL PLANNING Disadvantages
Irradiation of large volumes of brain
with normal tissue also
Higher toxicity and side effects
Lack of 3D visualization of tumor
2D planning of 3D tumor
3D CRT
Plan Evaluation
Biological dose
Immobilization
3D Imaging
Delineation of Target & critical organs
Beam Shaping
Block , MLC
Dose computation
Plan Evaluation
Physical dose
Plan
Implementation
Pre tre
atmen
t
verifi
catio
n
Treatm
ent
deliv
ery Repo
rting
Steps of 3DCRT
TAKING PLANNING CT SLICES IN NEUROONCOLOGY
Different from diagnostic imaging Use appropriate immobilization
device Image the patient in treatment
position
Planning MRI
• Position
Ideally in treatment position with
orfit & base plate.
• Transfer images to planning system
Imaging• CT• CT-MR Fusion• PET Scan – limited but emerging role
TARGET DELIENATION
BEAM SHAPING
Multileaf collimators (MLC)
TumorOAR
OAR
PLAN EVALUATION
3-D PLANNING Advantages
Ideal for all cases Conformal Maximum sparing of normal tissue Lower toxicity
Stereotactic Radiosurgery and
Stereotactic Radiotherapy
“Stereo”: Greek: Solid or 3 dimensional “tact” Latin: To touch: Greek “taxic” an arrangement
Stereotactic: 3 dimensional arrangement to touch
Stereotactic Radiosurgery (SRS): Stereotactically directed conformal radiation in a single fraction
Stereotactic Radiation Therapy (SRT): Stereotactically directed conformal radiation in multiple fractions
Fractionated Stereotactic Radiosurgery (FSR): Stereotactically directed conformal radiation in 2-5 fractions
Advantages of SRS and SRT over 3DCRT High conformity To treat small lesions not amenable to
3D CRT Higher tumor dose Save larger amount of normal tissue
STEREOTACTIC RADIOSURGERY
STEREOTACTIC RADIOTHERAPY
Dose per Fraction High Low
Number of Fractions 1 Multiple
Targeting accuracy <1 mm 3-20 mm
INDICATIONS SRS Benign and malignant brain tumors Arteriovenous malformations Well circumscribed targets < 4 cm diameter
SRT Lesions > 4cm Lesions located near critical structures
Leksell Frame
Brain Lab Non invasive head ring for SRT
GAMMA KNIFE (SRS & SRT)
ADVANTAGES• Over 30 years of clinical use and a large clinical
experience • Very high targeting precision • Multiple targets treated during a single
treatment session
DISADVANTAGES • Use in the brain only • Painful stereotactic head frame • Difficult to treat lesions located in the periphery
of the brain • Co sources decay, increasing treatment time and
cost to replace after 5 years
LINAC BASED (SRS & SRT)
ADVANTAGES
• More commonplace technology in hospitals• No invasive stereotactic frame • Can be used for extracranial tumors also
DISADVANTAGES
• Painful head frame• Less targeting accuracy and treatment accuracy when
treating extracranial tumors
TRUE BEAM
Linear Accelerator
Manipulator
ImageDetectors
X-ray Sources
IMAGINGSYSTEM
ROBOTICDELIVERYSYSTEM
TARGETING SOFTWARE
Cyber knife
Gamma Knife Cyber Knife
Immobilization Invasive Frame Frameless
Patient Comfort Moderate Very Good
Issue of radioactivity Replacement & Disposal
None
BRACHYTHERAPY bis-Chloronitrosourea (BCNU)-
impregnated biodegradable polymer (GLIADEL wafer) may be considered for intraoperative placement if frozen section reveals high grade glioma.
I-125 liquid soaked wafers also used
FUTURISTIC RADIOTHERAPY IN
BRAIN TUMORS
PROTON BEAM THERAPY
Low entrance dose (plateau) Maximum dose at depth (Bragg peak) Rapid distal dose fall-off
Photons Protons
PROTONS IN CNS TRIALS• Low grade & High grade glioma• Benign brain tumors:
– Vestibular Schwannomas/Acoustic Neuromas– Meningioma– Pituitary adenoma– AVM
• Skull base tumors: Chordoma/Chondrosarcomas• Pediatric brain tumors: Medulloblastoma,
Ependymoma, Pilocytic astrocytoma, Germ cell tumors
EXAMPLE – CASE OF PITUITARY ADENOMA
TWO DIMENSIONAL PLAN
THREE DIMENSIONAL PLAN
CYBER KNIFE PLAN
SUMMARY Multiple options and techniques available for
treating brain tumors. Need to use the optimum technique Decision to be based on need of patient and
available technique.
THANK YOU