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

Introduction: Interfraction bladder motion is substantial and therefore many different adaptive radiotherapy approaches have been developed to accommodate that motion. Previous studies comparing the efficacy of those adaptive strategies have demonstrated that reoptimization (ReOpt) was dosimetrically superior when compared to Plan of the Day (POD) and Patient-specific PTV (PS-PTV). However, the feasibility of clinical implementation is dependent upon assessment of the resource burden. This study assessed and compared the resource burden of three adaptive strategies.

Methods: Using the planning CT and all daily CBCTs of 10 bladder patients, the following adaptive strategies were simulated offline to deliver 46 Gy in 23 fractions: POD, PS-PTV and ReOpt. Additional activities required to execute these strategies compared to a nonadaptive approach were identified and categorized. Time consumed for the execution of each strategy was measured for a single, experienced observer.

Results: The time (minutes) consumed to execute the additional activities for PS-PTV, POD and ReOpt was 14.4, 49.1 and 248.5, respectively. In addition to a significantly shorter time spent, all activities associated with PS-PTV were categorized as those that could be performed without the presence of the patient or a treatment room. On the other hand, ReOpt was the most time intensive and all activities were categorized as those that could lead to increasing patient's time in the treatment room and decreasing capacity.

Conclusions: Although ReOpt was preferred with respect to improving dosimetry, the heavy resource burden it incurred could be a deterrent for clinical implementation. PS-PTV was the least resource-intensive strategy.