title: Normal tissue sparing in a phase II trial on daily adaptive plan selection in radiotherapy for urinary bladder cancer.
abstract: Background: Patients with urinary bladder cancer often display large changes in the shape and size of their bladder target during a course of radiotherapy (RT), making adaptive RT (ART) appealing for this tumour site. We are conducting a clinical phase II trial of daily plan selection-based ART for bladder cancer and here report dose-volume data from the first 20 patients treated in the trial.
  
  
  METHODS
  All patients received 60 Gy in 30 fractions to the bladder; in 13 of the patients the pelvic lymph nodes were simultaneously treated to 48 Gy. Daily patient set-up was by use of cone beam computed tomography (CBCT) guidance. The first 5 fractions were delivered with large, population-based (non-adaptive) margins. The bladder contours from the CBCTs acquired in the first 4 fractions were used to create a patient-specific library of three plans, corresponding to a small, medium and large size bladder. From fraction 6, daily online plan selection was performed, where the smallest plan covering the bladder was selected prior to each treatment delivery. A total of 600 treatment fractions in the 20 patients were evaluated.
  
  
  RESULTS
  Small, medium and large size plans were used almost equally often, with an average of 10, 9 and 11 fractions, respectively. The median volume ratio of the course-averaged PTV (PTV-ART) relative to the non-adaptive PTV was 0.70 (range: 0.46-0.89). A linear regression analysis showed a 183 cm(3) (CI 143-223 cm(3)) reduction in PTV-ART compared to the non-adaptive PTV (R(2) = 0.94).
  
  
  CONCLUSIONS
  Daily adaptive plan selection in RT of bladder cancer results in a considerable normal tissue sparing, of a magnitude that we expect will translate into a clinically significant reduction of the treatment-related morbidity.
authors: Department of Medical Physics, Aarhus University Hospital/Aarhus University , Aarhus , Denmark.
authors: Anne
authors: A
authors: Vestergaard
authors: Ludvig P
authors: LP
authors: Muren
authors: Henriette
authors: H
authors: Lindberg
authors: Kirsten L
authors: KL
authors: Jakobsen
authors: Jørgen B B
authors: JB
authors: Petersen
authors: Ulrik V
authors: UV
authors: Elstrøm
authors: Mads
authors: M
authors: Agerbæk
authors: Morten
authors: M
authors: Høyer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D015182:Lymphatic Irradiation / Q000379:methods; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009929:Organ Size; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D012044:Regression Analysis; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D001749:Urinary Bladder Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*