Clinical Implementation of Adaptive Hypofractionated Bladder Radiotherapy for Improvement in Normal Tissue Irradiation

Abstract Aims Adaptive bladder radiotherapy, with plan of the day selection and plan library development based on individual filling patterns, has been previously modelled in patients receiving weekly hypofractionated treatment and improved geometric accuracy has been shown. The aim of this study was to assess the clinical implementation of the technique. Materials and methods Conformal plans (with small, intermediate and large planning target volumes) were developed for 25 patients. After pre-treatment cone-beam computed tomography, the optimal plan of the day was selected and delivered by two trained observers. Independent off-line plan selection was also carried out. Concordance between the on-line and off-line selections, frequency of plan usage, target coverage and normal tissue sparing were assessed. Results Plan selection concordance was 91%. Fifty-five per cent of fractions were delivered using small or large plans. The mean coverage of the clinical target volume by the 95% isodose was 99%. The mean reduction in the volume of normal tissue treated to 95% of the prescription dose was 219 cm3 compared with the previous institutional standard approach. Conclusions Good concordance in plan selection is shown with clinical implementation of the adaptive strategy. Adequate target coverage was achieved with reduction in the volume of normal tissue irradiated to a high dose compared with the previous standard approach.