Intensity-modulated radiotherapy in high-grade gliomas: clinical and dosimetric results.
OBJECTIVE
To report preliminary clinical and dosimetric data from intensity-modulated radiotherapy (IMRT) for malignant gliomas.


METHODS
Fifty-eight consecutive high-grade gliomas were treated between January 2001 and December 2003 with dynamic multileaf collimator IMRT, planned with the inverse approach. A dose of 59.4-60 Gy at 1.8-2.0 Gy per fraction was delivered. A total of three to five noncoplanar beams were used to cover at least 95% of the target volume with the prescription isodose line. Glioblastoma accounted for 70% of the cases, and anaplastic oligodendroglioma histology (pure or mixed) was seen in 15% of the cases. Surgery consisted of biopsy only in 26% of the patients, and 80% received adjuvant chemotherapy.


RESULTS
With a median follow-up of 24 months, 85% of the patients have relapsed. The median progression-free survival time for anaplastic astrocytoma and glioblastoma histology was 5.6 and 2.5 months, respectively. The overall survival time for anaplastic glioma and glioblastoma was 36 and 9 months, respectively. Ninety-six percent of the recurrences were local. No Grade IV/V late neurologic toxicities were noted. A comparative dosimetric analysis revealed that regardless of tumor location, IMRT did not significantly improve target coverage compared with three-dimensional planning. However, IMRT resulted in a decreased maximum dose to the spinal cord, optic nerves, and eye by 16%, 7%, and 15%, respectively, owing to its improved dose conformality. The mean brainstem dose also decreased by 7%. Intensity-modulated radiotherapy delivered with a limited number of beams did not result in an increased dose to the normal brain.


CONCLUSIONS
It is unlikely that IMRT will improve local control in high-grade gliomas without further dose escalation compared with conventional radiotherapy. However, it might result in decreased late toxicities associated with radiotherapy.
Narayana
Ashwatha
A
Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. narayana@mskcc.org
Yamada
Josh
J
Berry
Sean
S
Shah
Priti
P
Hunt
Margie
M
Gutin
Philip H
PH
Leibel
Steven A
SA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000528:radiation effects; D001932:Brain Neoplasms / Q000532:radiotherapy*; D018450:Disease Progression; D005260:Female; D005909:Glioblastoma / Q000532:radiotherapy; D005910:Glioma / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009837:Oligodendroglioma / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects; D012189:Retrospective Studies