PURPOSE: To calculate treatment plans and compare the dose distributions and 
dose-volume histograms (DVHs) for photon three-dimensional conformal radiation 
therapy (3D-CRT), electron therapy, intensity-modulated radiation therapy 
(IMRT), and standard (nonintensity modulated) proton therapy in three pediatric 
disease sites.
METHODS AND MATERIALS: The tumor volumes from 8 patients (3 retinoblastomas, 2 
medulloblastomas, and 3 pelvic sarcomas) were studied retrospectively to compare 
DVHs from proton therapy with 3D-CRT, electron therapy, and IMRT. In 
retinoblastoma, several planning techniques were analyzed: A single electron 
appositional beam was compared with a single 3D-CRT lateral beam, a 3D-CRT 
anterior beam paired with a lateral beam, IMRT, and protons. In medulloblastoma, 
three posterior fossa irradiation techniques were analyzed: 3D-CRT, IMRT, and 
protons. Craniospinal irradiation (which consisted of composite plans of both 
the posterior fossa and craniospinal components) was also evaluated, primarily 
comparing spinal irradiation using 3D-CRT electrons, 3D-CRT photons, and 
protons. Lastly, in pelvic sarcoma, 3D-CRT, IMRT, and proton plans were 
assessed.
RESULTS: In retinoblastoma, protons resulted in the best target coverage 
combined with the most orbital bone sparing (10% was the mean orbital bone 
volume irradiated at > or =5 Gy for protons vs. 25% for 3D-CRT electrons, 69% 
for IMRT, 41% for a single 3D lateral beam, 51% for a 3D anterolateral beam with 
a lens block, and 65% for a 3D anterolateral beam without a lens block). A 
single appositional electron field was the next best technique followed by other 
planning approaches. In medulloblastoma, for posterior fossa and craniospinal 
irradiation, protons resulted in the least dose to the cochlea (for only 
posterior fossa irradiation at > or =20 Gy, 34% was the mean cochlear volume 
irradiated for protons, 87% for IMRT, 89% for 3D-CRT) and hypothalamus-pituitary 
axis (for only posterior fossa irradiation at > or =10 Gy, 21% was the mean 
hypothalamus-pituitary volume irradiated for protons, 81% for IMRT, 91% for 
3D-CRT); additional dose reductions to the optic chiasm, eyes, vertebrae, 
mandible, thyroid, lung, kidneys, heart, and liver were seen. 
Intensity-modulated radiotherapy appeared to be the second best technique for 
posterior fossa irradiation. For spinal irradiation 3D-CRT electrons were better 
than 3D-CRT photons in sparing dose to the thyroid, heart, lung, kidney, and 
liver. With pelvic sarcoma, protons were superior in eliminating any dose to the 
ovaries (0% of mean ovarian volume was irradiated at > or =2 Gy with protons) 
and to some extent, the pelvic bones and vertebrae. Intensity-modulated 
radiotherapy did show more bladder dose reduction than the other techniques in 
pelvic sarcoma irradiation.
CONCLUSIONS: In the diseases studied, using various techniques of 3D-CRT, 
electrons, IMRT, and protons, protons are most optimal in treating 
retinoblastomas, medulloblastomas (posterior fossa and craniospinal), and pelvic 
sarcomas. Protons delivered superior target dose coverage and sparing of normal 
structures. As dose-volume parameters are expected to correlate with acute and 
late toxicity, proton therapy should receive serious consideration as the 
preferred technique for the treatment of pediatric tumors.