|
|
Intensity modulated
radiotherapy in high grade gliomas: Clinical and dosimetric results
A. Narayana, J. Yamada, M. Hunt, P. Shah, P. Gutin, S. A. Leibel
Memorial Sloan Kettering Cancer Center, New York, NY
Background. Intensity Modulated Radiotherapy (IMRT) is an emerging
treatment for brain tumors, but there is very little clinical or dosimetric data
on doses and outcomes from IMRT treatment for malignant gliomas.
This study reports the preliminary data with IMRT in these tumors.
Methods.
Sixty six consecutive high grade gliomas were treated between
January 2001 and December 2003 with dynamic multileaf collimator IMRT with
inverse planning.
A dose of 59.4-60Gy using 1.8-2.0 Gy per fraction was delivered. 3-5
non-coplanar beams were used for the IMRT plan to cover at least 95% of the
target volume with the prescription isodose line.
Glioblastoma accounted for 62% of the cases and oligodendroglioma histology
(pure or mixed) was seen in 16.7% of the cases.
Surgery was restricted to biopsy only in 26% of the patients.
80% of the patients received adjuvant chemotherapy.
Results.
With a median follow-up of 18 months, 85% of the patients have
relapsed.
The median disease free survival for anaplastic glioma and glioblastoma were 5.6
and 2.5 months.
The median overall survival for the anaplastic glioma and glioblastoma
histologies were 16.5 and 10.6 months respectively.
96% of the recurrences were local.
No grade IV delayed neurological toxicities were noted.
A comparative dosimetric analysis revealed that regardless of tumor location,
IMRT did not improve target coverage compared to conventional 3-dimensional
treatment planning.
However, the use of IMRT resulted in a decreased dose to spinal cord, optic
chiasm and brain stem by 19%, 4.5% and 8% respectively due to its improved dose
conformality.
Use of IMRT did not result in an increase of the dose received by the normal
brain.
Conclusions.
Use of IMRT did not increase either the disease free
survival or the overall survival in patients with malignant gliomas when
compared to historical controls.
It is unlikely that IMRT will improve the local control in high grade gliomas
without further dose escalation.
However, it may result in decreased late toxicities associated with radiation
therapy.
Copyright 2004 American Society of Clinical Oncology All rights
reserved worldwide.
Source: http://www.asco.org/ac/1,1003,_12-002636-00_18-0026-00_19-003463,00.asp
|
