1. Shannon M MacDonald 1, Salahuddin Ahmad 2, Stefanos Kachris 3, Betty J Vogds 2, Melissa DeRouen 3, Alicia E Gitttleman 3, Keith DeWyngaert 3, Maria T Vlachaki 4 1 Massachusetts General Hospital 2 University of Oklahoma Health Sciences Center 3 New York University Medical Center 4 Wayne State University INTENSITY MODULATED RADIATION THERAPY VERSUS THREE DIMENSIONAL CONFORMAL RADIATION THERAPY FOR THE TREATMENT OF HIGH GRADE GLIOMA: A DOSIMETRIC COMPARISON

2. 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

3. p=0.0 04 Brainstem 0 10 20 30 40 50 % > 45Gy% > 54Gy Percent Organ Volume IMRT 3DCRT p=0.004 p=0.023 p=0.006 p=0.01 p=0.003 p≤0.0001 p=0. 047 p=0.06 p=0. 01 p<0.00 01 p=0.059 p=0.015 p≤0.0001 COMPARISON OF TARGET AND NORMAL TISSUE DOSIMETRY: IMRT v. 3DCRT

4. Brainstem Brain Optic Chiasm PTVcd Target and Normal Tissue DVHs for one patient with L temporal lobe tumor

5. p≤0.001 p=0.015 p=0.091 p≤0.001 p=0.003 TCP as a function of clonogen cell density NTCP

6. 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.