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 cm3 (CI 143-223 cm3) reduction in PTV-ART compared to the non-adaptive PTV (R2 = 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.
Written by:
Vestergaard A, Muren LP, Lindberg H, Jakobsen KL, Petersen JB, Elstrøm UV, Agerbæk M, Høyer M. Are you the author?
Department of Medical Physics, Aarhus University Hospital/Aarhus University, Aarhus, Denmark.
Reference: Acta Oncol. 2014 Jun 24:1-8.
doi: 10.3109/0284186X.2014.928419
PubMed Abstract
PMID: 24957559
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