title: Is volumetric modulated arc therapy (RapidArc) better than intensity modulated radiotherapy for gynecological malignancies? A dosimetric comparison.
abstract: OBJECTIVE
  Evaluation of the dosimetric advantage, if any, of RapidArc (double arc and triple arc [DA and TA]) over standard fixed field intensity-modulated radiation therapy (IMRT) in gynecologic malignancies.
  
  
  METHODS
  A total of 20 cases of gynecologic malignancies were included. Static IMRT sliding window, single arc (SA), DA and TA plans were generated with eclipse planning system. The prescribed dose was 50.4 Gy/28# to the planning target volumes.
  
  
  RESULTS
  IMRT provided target coverage equivalent to DA and inferior to TA (D95% [in Gy]--49.94, 49.58, 49.96, 50.17 for IMRT, SA, DA and TA respectively--all observations in the same sequence). Conformity index 90 (CI 90 (0.964, 0.927, 0.918, 0.822) and homogeneity index (0.0683, 0.119, 0.098, 0.097) of IMRT were superior. TA was superior to other arcs in all parameters except CI 90 (P=0.805) and bladder dose (lower in DA). Rectal, bladder and bowel sparing was best achieved with IMRT followed by TA; bilateral femur dose was lower in arcs. The total monitor units and treatment time of arcs were significantly lower than IMRT, reduced by a factor of 2.41-2.59 and 3.2-3.5 respectively (All P values significant).
  
  
  CONCLUSIONS
  IMRT provided better overall plan for gynecologic malignancies with lower organs at risk dose and target coverage equivalent to DA and TA. Treatment delivery efficiency was higher with RapidArc. The TA plan is dosimetrically superior to DA, but the gain is small. The decision whether or not to add a third arc for a small gain should be individualized.
authors.affiliation: Department of Radiation Oncology, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi - 110 085, India.
authors.forename: Manoj Kumar
authors.initials: MK
authors.lastname: Sharma
authors.forename: Swarupa
authors.initials: S
authors.lastname: Mitra
authors.forename: Upasna
authors.initials: U
authors.lastname: Saxena
authors.forename: Manindra
authors.initials: M
authors.lastname: Bhushan
authors.forename: Himanshu
authors.initials: H
authors.lastname: Shrivastava
authors.forename: David K
authors.initials: DK
authors.lastname: Simson
authors.forename: Abhinav
authors.initials: A
authors.lastname: Dewan
authors.forename: Deepika
authors.initials: D
authors.lastname: Chauhan
mesh_terms: D000465:Algorithms; D016889:Endometrial Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D016896:Treatment Outcome; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*