The implementation of an empty bladder filling protocol for localised prostate volumetric modulated arctherapy (VMAT): early results of a single institution service evaluation.

Abstract

To examine the impact of an empty bladder filling protocol on patients receiving radical RT for localised prostate cancer on post RT toxicity and biochemical progression free survival (bPFS). Records of patients receiving radical external beam RT (EBRT) for localised prostate cancer with a full or empty bladder were reviewed. These included the bladder size on planning CT, daily online image guided RT (IGRT) setup data, treatment time and post treatment follow up data.These included bPFS, gastrointestinal(GI) and genitourinary(GU) toxicity scoring post RT using the CTCAE v4.0 scoring system. All patients included in the study were planned and treated under the same departmental clinical protocol with VMAT and daily online IGRT corrections. 90 patients were treated with 60 Gy in 20 fractions with a median follow up of 48 months. At 4 years bPFS in the empty bladder group was 100 and 98% in the full bladder group (p = 0.27). There were no statistically significant differences in cumulative ≥Grade 2GU (p = 0.10) and GI (p = 0.27) toxicity rates between the two bladder filling protocols. No statistically significant differences in the IGRT setup between the two groups of patients. Although the median treatment times per fraction were not statistically different between the two groups (p = 0.47), patients in the full bladder filling group were required to spend a longer time in the RT department per treatment session for bladder filling. An empty bladder filling protocol has non-inferior bPFS, GI and GU toxicities at 4 years in patients with localised prostate cancer using advanced RT techniques in comparison to a full bladder filling protocol. A longer follow up with a larger sample size is required to validate this approach. This study suggests that an empty bladder filling protocol can be used in external beam EBRT for localised prostate cancer with non-inferior treatment outcomes.