title: A dosimetric comparison of proton and intensity-modulated photon radiotherapy for pediatric parameningeal rhabdomyosarcomas.
abstract: OBJECTIVE
  We compared tumor and normal tissue dosimetry of proton radiation therapy with intensity-modulated radiation therapy (IMRT) for pediatric parameningeal rhabdomyosarcomas (PRMS).
  
  
  METHODS
  To quantify dosimetric differences between contemporary proton and photon treatment for pediatric PRMS, proton beam plans were compared with IMRT plans. Ten patients treated with proton radiation therapy at Massachusetts General Hospital had IMRT plans generated. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing.
  
  
  RESULTS
  Proton and IMRT plans provided acceptable and comparable target volume coverage, with at least 99% of the CTV receiving 95% of the prescribed dose in all cases. Improved dose conformality provided by proton therapy resulted in significant sparing of all examined normal tissues except for ipsilateral cochlea and mastoid; ipsilateral parotid gland sparing was of borderline statistical significance (p = 0.05). More profound sparing of contralateral structures by protons resulted in greater dose asymmetry between ipsilateral and contralateral retina, optic nerves, cochlea, and mastoids; dose asymmetry between ipsilateral and contralateral parotids was of borderline statistical significance (p = 0.05).
  
  
  CONCLUSIONS
  For pediatric PRMS, superior normal tissue sparing is achieved with proton radiation therapy compared with IMRT. Because of enhanced conformality, proton plans also demonstrate greater normal tissue dose distribution asymmetry. Longitudinal studies assessing the impact of proton radiotherapy and IMRT on normal tissue function and growth symmetry are necessary to define the clinical consequences of these differences.
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Kozak
authors.forename: Judith
authors.initials: J
authors.lastname: Adams
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Krejcarek
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Tarbell
authors.forename: Torunn I
authors.initials: TI
authors.lastname: Yock
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated; D012208:Rhabdomyosarcoma / Q000473:pathology / Q000532:radiotherapy*; D047368:Tumor Burden; D011522:Protons
chemical_list: D011522:Protons