title: Comparison of three-dimensional (3D) conformal proton radiotherapy (RT), 3D conformal photon RT, and intensity-modulated RT for retroperitoneal and intra-abdominal sarcomas.
abstract: OBJECTIVE
  To compare three-dimensional conformal proton radiotherapy (3DCPT), intensity-modulated photon radiotherapy (IMRT), and 3D conformal photon radiotherapy (3DCRT) to predict the optimal RT technique for retroperitoneal sarcomas.
  
  
  METHODS
  3DCRT, IMRT, and 3DCPT plans were created for treating eight patients with retroperitoneal or intra-abdominal sarcomas. The clinical target volume (CTV) included the gross tumor plus a 2-cm margin, limited by bone and intact fascial planes. For photon plans, the planning target volume (PTV) included a uniform expansion of 5 mm. For the proton plans, the PTV was nonuniform and beam-specific. The prescription dose was 50.4 Gy/Cobalt gray equivalent CGE. Plans were normalized so that >95% of the CTV received 100% of the dose.
  
  
  RESULTS
  The CTV was covered adequately by all techniques. The median conformity index was 0.69 for 3DCPT, 0.75 for IMRT, and 0.51 for 3DCRT. The median inhomogeneity coefficient was 0.062 for 3DCPT, 0.066 for IMRT, and 0.073 for 3DCRT. The bowel median volume receiving 15 Gy (V15) was 16.4% for 3DCPT, 52.2% for IMRT, and 66.1% for 3DCRT. The bowel median V45 was 6.3% for 3DCPT, 4.7% for IMRT, and 15.6% for 3DCRT. The median ipsilateral mean kidney dose was 22.5 CGE for 3DCPT, 34.1 Gy for IMRT, and 37.8 Gy for 3DCRT. The median contralateral mean kidney dose was 0 CGE for 3DCPT, 6.4 Gy for IMRT, and 11 Gy for 3DCRT. The median contralateral kidney V5 was 0% for 3DCPT, 49.9% for IMRT, and 99.7% for 3DCRT. Regardless of technique, the median mean liver dose was <30 Gy, and the median cord V50 was 0%. The median integral dose was 126 J for 3DCPT, 400 J for IMRT, and 432 J for 3DCRT.
  
  
  CONCLUSIONS
  IMRT and 3DCPT result in plans that are more conformal and homogenous than 3DCRT. Based on Quantitative Analysis of Normal Tissue Effects in Clinic benchmarks, the dosimetric advantage of proton therapy may be less gastrointestinal and genitourinary toxicity.
authors.affiliation: Department of Radiation Oncology, University of Florida, Gainesville, Florida, USA.
authors.forename: Erika L
authors.initials: EL
authors.lastname: Swanson
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Indelicato
authors.forename: Debbie
authors.initials: D
authors.lastname: Louis
authors.forename: Stella
authors.initials: S
authors.lastname: Flampouri
authors.forename: Zuofeng
authors.initials: Z
authors.lastname: Li
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Morris
authors.forename: Nitesh
authors.initials: N
authors.lastname: Paryani
authors.forename: Roelf
authors.initials: R
authors.lastname: Slopsema
mesh_terms: D000008:Abdominal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D000368:Aged; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use*; D061766:Proton Therapy; D011522:Protons / Q000009:adverse effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods; D012186:Retroperitoneal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D012509:Sarcoma / Q000473:pathology / Q000532:radiotherapy*; D047368:Tumor Burden
chemical_list: D011522:Protons