Advantage of protons compared to IMRT in the treatment of medulloblastoma
James Metz, MD
OncoLink Associate Editor
Last Modified: October 24, 2000
Presenter: W. H. St. Clair
Affiliation: Massachusetts General Hospital
There is continued interest in finding ways to
reduce the radiation related toxicity associated
with the treatment of medulloblastoma. Both
proton radiotherapy and intensity modulated
radiation therapy (IMRT) have been shown to
reduce the amount of normal tissue that receives
a high dose of radiation. This study was
performed to compare conventional photons,
proton radiotherapy, and IMRT for the treatment of
Materials and Methods:
- Conventional photon, proton, and IMRT plans
were compared for the treatment of a single
patient with a diagnosis of medulloblatoma.
- The target volume was the entire craniospinal
axis followed by a boost to the posterior fossa.
- Dose volume histograms (DVH) were compared for
a variety of normal tissues for each of the
- There was substantial normal tissue dose
sparing for both the IMRT and proton plans when
compared to the conventional photon plan
- Protons were clearly superior to both IMRT and
- Treatment with IMRT resulted in more exposure to
normal tissues when the low dose region was
evaluated for some DVH's, although there was
sparing at the high dose regions when compared to
- There was a continuous improvement in dose
deposition with improvements in technology
(photons-->IMRT-->protons), with protons showing
the best results.
- Because of the better dose distribution of
protons, there may be significant decreases in
late toxicity when using this modality compared to
- This is a small study with only one patient
analyzed, thus the results must be taken with
- Because IMRT uses multiple field arrangements
to decrease the amount of normal tissue receiving
a high dose of radiation, there may be exposure
of more normal tissues to a low dose of radiation
then with conventional photons.
- Other reports have previously supported the use
of protons over conventional photons in the
treatment of medulloblastoma.
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