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An Orthotopic Bladder Tumor Model and the Evaluation of Intravesical saRNA Treatment
Published on: July 28, 2012
Online adaptive radiotherapy for muscle-invasive bladder cancer: results of a pilot study
Farshad Foroudi1, Jacky Wong, Tomas Kron
1Division of Radiation Oncology, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia. farshad.foroudi@petermac.org
Purpose:
To determine the advantages and disadvantages of daily online adaptive image-guided radiotherapy (RT) compared with conventional RT for muscle-invasive bladder cancer.
Methods And Materials:
Twenty-seven patients with T2-T4 transitional cell carcinoma of the bladder were treated with daily online adaptive image-guided RT using cone-beam computed tomography (CBCT). From day 1 daily soft tissue-based isocenter positioning was performed using CBCT images acquired before treatment. Using a composite of the initial planning CT and the first five daily CBCT scans, small, medium, and large adaptive plans were created. Each of these adaptive plans used a 0.5-cm clinical target volume (CTV) to planning target volume expansion. For Fractions 8-32, treatment involved daily soft tissue-based isocenter positioning and selection of suitable adaptive plan of the day. Treating radiation therapists completed a credentialing program, and one radiation oncologist performed all the contouring. Comparisons were made between adaptive and conventional treatment on the basis of CTV coverage and normal tissue sparing.
Results:
All 27 patients completed treatment per protocol. Bladder volume decreased with time or fraction number (p < 0.0001). For the adaptive component (Fractions 8-32) the small, medium, large, and conventional plans were used in 9.8%, 49.2%, 39.5%, and 1.5% of fractions, respectively. For the adaptive strategy, 2.7% of occasions resulted in a CTV V95 <99%, compared with 4.8% of occasions for the conventional approach (p = 0.42). Mean volume of normal tissue receiving a dose >45 Gy was 29% (95% confidence interval, 24-35%) less with adaptive RT compared with conventional RT. The mean volume of normal tissue receiving >5 Gy was 15% (95% confidence interval, 11-18%) less with adaptive RT compared with conventional RT.
Conclusions:
Online adaptive radiotherapy is feasible in an academic radiotherapy center. The volume of normal tissue irradiated can be significantly smaller without reducing CTV coverage.
