An adaptive radiotherapy planning strategy for bladder cancer using deformation vector fields

Comparison of 3 image-guided adaptive strategies for bladder locoregional radiotherapy

“…7,8 Different adaptive strategies, such as "plan of the day" (POD), [9][10][11][12][13][14][15][16][17][18][19] "patient-specific planning target volume (PTV)" (PS-PTV), [20][21][22] and daily reoptimization (ReOpt) 23 have been proposed and investigated for bladder radiotherapy to compensate for the large interfraction and interpatient variations observed. However, most studies have evaluated the efficacy based on geometric coverage, 9,12,15,[17][18][19][20][21]24 per-fraction comparison, 13,22 or direct summation of dose-volume histogram. 10,11 Moreover, previous studies have primarily compared the different methods of generating the multiple PTVs for the POD strategy 10,15,19 or between 2 adaptive strategies.…”

“…However, most studies have evaluated the efficacy based on geometric coverage, 9,12,15,[17][18][19][20][21]24 per-fraction comparison, 13,22 or direct summation of dose-volume histogram. 10,11 Moreover, previous studies have primarily compared the different methods of generating the multiple PTVs for the POD strategy 10,15,19 or between 2 adaptive strategies. 23 Because deformable image registration (DIR) enables the accumulation of delivered dose to the target and the normal tissue onto a reference image by tracking the corresponding voxels between multiple image datasets, [25][26][27] it was applied in the present study to conduct a dosimetric comparison of 3 adaptive strategies against a standard population marginbased PTV in assessing their efficacy in reducing the irradiated volume for locoregional radiotherapy for bladder cancer.…”

Evaluation of resource burden for bladder adaptive strategies: A timing study

“…This study chose the simplest method in generating the POD library by applying different margin expansion on the bladder delineated on a single planning CT. The time reported herein could therefore underestimate the time required when compared to methods that incorporate multiple planning CT datasets 2,3,5,8,9 or CBCTs 6,7,[9][10][11]13 in the POD library construction. Using a semi-automated workflow, Meijer et al 8 reported an average of 30 minutes to generate a POD library consisting of six distributions.…”

“…Due to the substantial variation of bladder volume observed throughout the course of treatment, large margins in the range of 20–30 mm have been used, irradiating large volumes of normal tissue . With the capability of visualizing soft tissue with cone beam computerized tomography (CBCT), various adaptive radiotherapy strategies have been developed and are reported as being effective at reducing the irradiated volume …”

“…1 With the capability of visualizing soft tissue with cone beam computerized tomography (CBCT), various adaptive radiotherapy strategies have been developed and are reported as being effective at reducing the irradiated volume. [2][3][4][5][6][7][8][9][10][11][12][13] A dosimetric comparison among the three most widely published adaptive strategies (Plan of the Day (POD), Patient-Specific PTV (PS-PTV) and daily reoptimization (ReOpt)) demonstrated that ReOpt was the most effective at reducing normal tissue irradiation. 14 However, the need to modify the initial treatment plan frequently during the course of radiotherapy demands additional time, personnel and equipment, with some strategies entailing more resources than the others do.…”