title: Planning study to compare dynamic and rapid arc techniques for postprostatectomy radiotherapy of prostate cancer.
abstract: OBJECTIVE
  To compare our standard technique for postprostatectomy radiotherapy of prostate cancer, i.e. using two lateral conformal dynamic arcs with volumetric-modulated arc therapy (VMAT) performed with the RapidArc(®) (Varian Medical Systems, Palo Alto, CA, USA). The plans were referred to as DA and RA, respectively.
  
  
  METHODS
  The treatment plans of 44 patients receiving adjuvant/salvage radiotherapy in the first months of 2010 were compared. In all cases, the prescribed total dose was 66-68.2 Gy (2.2 Gy per fraction). Both DA and RA plans were optimized in terms of dose coverage and constraints.
  
  
  RESULTS
  Small differences between the techniques were observed for planning target volume (PTV) dose distribution, whereas significant differences in sparing of organs at risk (OARs) were recorded (p < 0.0001). The OAR values (median; 95 % confidence interval, CI) were: rectum: D30 % = 60.7 Gy (59.40-62.04 Gy) and 48.2 Gy (46.40-52.72 Gy), D60 % = 34.1 Gy (28.50-38.92 Gy) and 27.7 Gy (21.80-31.51 Gy); bladder: D30 % = 57.3 Gy (45.83-64.53 Gy) and 46.4 Gy (33.23-61.48 Gy), D50 % = 16.4 Gy (11.89-42.38 Gy) and 17.2 Gy (10.97-27.90 Gy), for DA and RA, respectively. Treatment times were very similar, whereas the monitor units (MU) were 550 ± 29 versus 277 ± 3 for RA and DA, respectively.
  
  
  CONCLUSIONS
  Dose-volume histograms (DVHs) show improvements in OAR sparing with RA. However, the RA technique is associated with almost double the number of MUs compared to DA. Regarding the PTV, DA is slightly superior in terms of D2 % and dose homogeneity. On the whole, the results suggest that RA be the favorable technique.
authors.affiliation: Department of Medical Physics, Istituto Europeo di Oncologia, via Ripamonti 435, 20141, Milan, Italy, raffaella.cambria@ieo.it.
authors.forename: R
authors.initials: R
authors.lastname: Cambria
authors.forename: F
authors.initials: F
authors.lastname: Cattani
authors.forename: B A
authors.initials: BA
authors.lastname: Jereczek-Fossa
authors.forename: F
authors.initials: F
authors.lastname: Pansini
authors.forename: D
authors.initials: D
authors.lastname: Ciardo
authors.forename: S
authors.initials: S
authors.lastname: Vigorito
authors.forename: S
authors.initials: S
authors.lastname: Russo
authors.forename: D
authors.initials: D
authors.lastname: Zerini
authors.forename: L
authors.initials: L
authors.lastname: Cozzi
authors.forename: R
authors.initials: R
authors.lastname: Orecchia
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003131:Combined Modality Therapy; D003198:Computer Simulation; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D016879:Salvage Therapy