Normal tissue sparing in a phase II trial on daily adaptive plan selection in radiotherapy for urinary bladder cancer

Acta Oncol. 2014 Aug;53(8):997-1004. doi: 10.3109/0284186X.2014.928419. Epub 2014 Jun 24.


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.

Material and 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).

Conclusion: 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.

Publication types

  • Clinical Trial, Phase II

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anatomic Landmarks
  • Cone-Beam Computed Tomography
  • Dose Fractionation, Radiation
  • Female
  • Humans
  • Lymphatic Irradiation / methods
  • Male
  • Middle Aged
  • Neoplasm Invasiveness
  • Organ Size
  • Organ Sparing Treatments / methods*
  • Organs at Risk / diagnostic imaging
  • Prostatic Neoplasms / diagnostic imaging
  • Prostatic Neoplasms / pathology
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Radiotherapy, Image-Guided / methods*
  • Rectum / diagnostic imaging
  • Regression Analysis
  • Urinary Bladder / anatomy & histology
  • Urinary Bladder / diagnostic imaging
  • Urinary Bladder Neoplasms / diagnostic imaging
  • Urinary Bladder Neoplasms / pathology
  • Urinary Bladder Neoplasms / radiotherapy*