title: Dosimetric comparison of combined intensity-modulated radiotherapy (IMRT) and proton therapy versus IMRT alone for pelvic and para-aortic radiotherapy in gynecologic malignancies.
abstract: OBJECTIVE
  To perform a dosimetric comparison of intensity-modulated radiotherapy (IMRT), passive scattering proton therapy (PSPT), and intensity-modulated proton therapy (IMPT) to the para-aortic (PA) nodal region in women with locally advanced gynecologic malignancies.
  
  
  METHODS
  The CT treatment planning scans of 10 consecutive patients treated with IMRT to the pelvis and PA nodes were identified. The clinical target volume was defined by the primary tumor for patients with cervical cancer and by the vagina and paravaginal tissues for patients with endometrial cancer, in addition to the regional lymph nodes. The IMRT, PSPT, and IMPT plans were generated using the Eclipse Treatment Planning System and were analyzed for various dosimetric endpoints. Two groups of treatment plans including proton radiotherapy were created: IMRT to pelvic nodes with PSPT to PA nodes (PSPT/IMRT), and IMRT to pelvic nodes with IMPT to PA nodes (IMPT/IMRT). The IMRT and proton RT plans were optimized to deliver 50.4 Gy or Gy (relative biologic effectiveness [RBE)), respectively. Dose-volume histograms were analyzed for all of the organs at risk. The paired t test was used for all statistical comparison.
  
  
  RESULTS
  The small-bowel V(20), V(30), V(35), andV(40) were reduced in PSPT/IMRT by 11%, 18%, 27%, and 43%, respectively (p < 0.01). Treatment with IMPT/IMRT demonstrated a 32% decrease in the small-bowel V(20). Treatment with PSPT/IMRT showed statistically significant reductions in the body V(5-20); IMPT/IMRT showed reductions in the body V(5-15). The dose received by half of both kidneys was reduced by PSPT/IMRT and by IMPT/IMRT. All plans maintained excellent coverage of the planning target volume.
  
  
  CONCLUSIONS
  Compared with IMRT alone, PSPT/IMRT and IMPT/IMRT had a statistically significant decrease in dose to the small and large bowel and kidneys, while maintaining excellent planning target volume coverage. Further studies should be done to correlate the clinical significance of these findings.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Abigail Berman
authors.initials: AB
authors.lastname: Milby
authors.forename: Stefan
authors.initials: S
authors.lastname: Both
authors.forename: Mark
authors.initials: M
authors.lastname: Ingram
authors.forename: Lilie L
authors.initials: LL
authors.lastname: Lin
mesh_terms: D001012:Aorta, Abdominal; D016889:Endometrial Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007668:Kidney / Q000528:radiation effects; D015182:Lymphatic Irradiation / Q000379:methods*; D058958:Organs at Risk; D010388:Pelvis; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012062:Relative Biological Effectiveness; D012542:Scattering, Radiation; D013116:Spinal Cord / Q000528:radiation effects; D047368:Tumor Burden; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011522:Protons
chemical_list: D011522:Protons