Shannon M MacDonald1, Salahuddin Ahmad2, Stefanos Kachris3, Betty J Vogds2, Melissa DeRouen3, Alicia E Gitttleman3, Keith DeWyngaert3,

Maria T Vlachaki4

1 Massachusetts General Hospital 2 University of Oklahoma Health Sciences Center

3 New York University Medical Center4 Wayne State University

INTENSITY MODULATED RADIATION THERAPY VERSUS THREE DIMENSIONAL CONFORMAL

RADIATION THERAPY FOR THE TREATMENT OF HIGH GRADE GLIOMA: A DOSIMETRIC COMPARISON

STUDY DESIGN

•Dosimetric comparison of IMRT versus 3DCRT in twenty patients with high-grade glioma. •Prescribed Dose: 59.4 Gy, 33 fractions, 4-10 MV

•Dose constraints for brainstem: 55-60 Gy

•Dose constraints for optic chiasm & nerves: 50-54 Gy

•DVHs for target, brain, brainstem and optic nerves/chiasm were generated and compared

•TCP and NTCP were also calculated and compared

p=0.004

Brainstem

0

10

20

30

40

50

% > 45Gy % > 54Gy

Pe

rce

nt

Org

an

Vo

lum

e

IMRT

3DCRT

p=0.004

0

10

20

30

40

50

60

70

min PTV max PTV mean PTV min PTVcd max PTVcd mean PTVcd

Dos

e (G

y) IMRT

3DCRT

p=0.023

p=0.006p=0.01

p=0.003 p≤0.0001

Optic Chiasm

0

10

20

30

40

50

60

% > 45Gy % > 50.4Gy

Perc

ent O

rgan

Vol

ume

IMRT

3DCRT

p=0.047

p=0.047

Brain

0

10

20

30

40

50

60

% > 18Gy % > 24Gy % > 45Gy

Dos

e (G

y)

IMRT

3DCRT

p=0.06 p=0

.01

p<0.0001

p=0.059

p=0.015

p≤0.0001

COMPARISON OF TARGET AND NORMAL TISSUE DOSIMETRY:

IMRT v. 3DCRT

Brainstem

Brain

Optic ChiasmPTVcd

Target and Normal Tissue DVHs for one patient with L temporal lobe tumor

0

0.2

0.4

0.6

0.8

1

1.2

10M/cc 5M/cc 1M/cc O.5M/cc 0.1M/cc

Clonogen Cell Density (CCD)

TCP IMRT

3DCRT

p≤0.001

p≤0.001p=0.015

p=0.091

p≤0.001

0

0.005

0.01

0.015

0.02

0.025

0.03

Brain Brainstem Optic Chiasm

NT

CP IMRT

3DCRT

p=0.003

TCP as a function of clonogen cell density

NTCP

CONCLUSIONS

• IMRT improved target coverage and tumor control probability.

• IMRT also improved sparing of normal brain, brainstem and optic chiasm.

• Combining IMRT with new more accurate tumor imaging tools and more effective systemic agents may allow us to increase tumor doses while minimizing toxicity and, therefore, improve outcomes in high grade glioma patients.

CONCLUSIONS

• IMRT improved target coverage and tumor control probability.

• IMRT also improved sparing of normal brain, brainstem and optic chiasm.

• Combining IMRT with new more accurate tumor imaging tools and more effective systemic agents may allow us to increase tumor doses while minimizing toxicity and, therefore, improve outcomes in high grade glioma patients.