title: Whole abdomen radiation therapy in ovarian cancers: a comparison between fixed beam and volumetric arc based intensity modulation.
abstract: OBJECTIVE
  A study was performed to assess dosimetric characteristics of volumetric modulated arcs (RapidArc, RA) and fixed field intensity modulated therapy (IMRT) for Whole Abdomen Radiotherapy (WAR) after ovarian cancer.
  
  
  METHODS
  Plans for IMRT and RA were optimised for 5 patients prescribing 25 Gy to the whole abdomen (PTV_WAR) and 45 Gy to the pelvis and pelvic nodes (PTV_Pelvis) with Simultaneous Integrated Boost (SIB) technique. Plans were investigated for 6 MV (RA6, IMRT6) and 15 MV (RA15, IMRT15) photons. Objectives were: for both PTVs V90% > 95%, for PTV_Pelvis: Dmax < 105%; for organs at risk, maximal sparing was required. The MU and delivery time measured treatment efficiency. Pre-treatment Quality assurance was scored with Gamma Agreement Index (GAI) with 3% and 3 mm thresholds.
  
  
  RESULTS
  IMRT and RapidArc resulted comparable for target coverage. For PTV_WAR, V90% was 99.8 ± 0.2% and 93.4 ± 7.3% for IMRT6 and IMRT15, and 98.4 ± 1.7 and 98.6 ± 0.9% for RA6 and RA15. Target coverage resulted improved for PTV_Pelvis. Dose homogeneity resulted slightly improved by RA (Uniformity was defined as U5-95% = D5%-D95%/Dmean). U5-95% for PTV_WAR was 0.34 ± 0.05 and 0.32 ± 0.06 (IMRT6 and IMRT15), 0.30 ± 0.03 and 0.26 ± 0.04 (RA6 and RA15); for PTV_Pelvis, it resulted equal to 0.1 for all techniques. For organs at risk, small differences were observed between the techniques. MU resulted 3130 ± 221 (IMRT6), 2841 ± 318 (IMRT15), 538 ± 29 (RA6), 635 ± 139 (RA15); the average measured treatment time was 18.0 ± 0.8 and 17.4 ± 2.2 minutes (IMRT6 and IMRT15) and 4.8 ± 0.2 (RA6 and RA15). GAIIMRT6 = 97.3 ± 2.6%, GAIIMRT15 = 94.4 ± 2.1%, GAIRA6 = 98.7 ± 1.0% and GAIRA15 = 95.7 ± 3.7%.
  
  
  CONCLUSIONS
  RapidArc showed to be a solution to WAR treatments offering good dosimetric features with significant logistic improvements compared to IMRT.
authors.affiliation: Radiation Oncology Department, Oncology Institute of Southern Switzerland, Bellinzona, Switzerland.
authors.forename: Umesh
authors.initials: U
authors.lastname: Mahantshetty
authors.forename: Swamidas
authors.initials: S
authors.lastname: Jamema
authors.forename: Reena
authors.initials: R
authors.lastname: Engineer
authors.forename: Deepak
authors.initials: D
authors.lastname: Deshpande
authors.forename: Rajiv
authors.initials: R
authors.lastname: Sarin
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.forename: Giorgia
authors.initials: G
authors.lastname: Nicolini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Clivio
authors.forename: Eugenio
authors.initials: E
authors.lastname: Vanetti
authors.forename: Shyamkishore
authors.initials: S
authors.lastname: Shrivastava
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D000005:Abdomen / Q000528:radiation effects*; D000465:Algorithms; D002277:Carcinoma / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D058958:Organs at Risk / Q000528:radiation effects; D010051:Ovarian Neoplasms / Q000532:radiotherapy*; D010388:Pelvis / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*