Is the bladder filling protocol for prostate cancer patients undergoing radiotherapy fit for purpose?

Abstract

Introduction: Conventional radiotherapy has been planned with a full bladder based on the rationale that it will move the small bowel out of the treatment field and result in greater sparing of the bladder itself[1]. Our department has moved from a ‘comfortably full’ bladder to a strict drinking protocol of emptying the bladder, drinking three cups of water and waiting 30 minutes prior to treatment for our prostate cancer patients. A service evaluation was carried out to determine if this change in practice results in a more consistent bladder volume from CT panning to treatment. Method and Materials: Based on 233 prostate patients treated per year a sample size of 146 was determined to result in a 95% confidence level with a 5% margin of error[2]. The last 73 patients on the comfortably full protocol and the first 73 patients on the new bladder protocol were compared. Their bladder volume from CT and on their CBCT fraction one was outlined by one observer to ascertain the difference in bladder volume and assess consistency. Results: The bladder filling protocol does not result in a statistically significant difference in bladder volume from CT to CBCT fraction one compared to comfortably full; the results prove that there is statistically no benefit from moving from comfortably full to the strict drinking protocol in terms of consistency of bladder volume achieved. Conclusion and Discussion: In the UK there are currently no official guidelines on what is the optimal volume of bladder for prostate cancer patients[3]. To attend a busy regional cancer centre patients may have had to travel a long distance. This coupled with any unintended delays can result in patients having to empty or be taken of the treatment couch, therefore a strict drinking protocol may not be feasible .The results of this well powered study that there is no statistically significant difference in consistency gained from employing a strict drinking protocol compared to maintaining a comfortably full bladder.