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Published online by Cambridge University Press: 12 January 2016
The purpose of this study was to audit positioning errors during bladder image-guided radiotherapy (IGRT) and quantify survival outcomes.
We carried out a retrospective review of 141 patients treated between March 2007 and July 2010 with three-dimensional conformal radiotherapy. An offline imaging protocol using kV cone beam computed tomography (CBCT) was used. Positioning errors, clinical interventions and re-planning rates were quantified. Cancer outcomes and survival were collected by review of patient notes and a registry search.
Among all, 43% of the patients required no intervention. Isocentre corrections were used for systematic bony set-up error in 13% and to improve bladder coverage in 28%. Clinical interventions to improve bladder coverage were required in 16% of the patients and repeat computed tomography planning in a further 16%. Overall, 44% of the patients demonstrated some form of organ deformation that would have resulted in inadequate dose to the bladder or significant overdose to an organ at risk if not corrected for. Post-treatment check cystoscopy was undertaken in 107 patients (76%) with 72 noted to have a complete response. Overall survival was 47·8% at 3 years.
Organ deformation during radiotherapy for bladder cancer is a significant problem for over 40% of patients. Strategies to compensate are essential to ensure optimal plan delivery.