Role of radiotherapy in brain tumours

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