ESTRO 2024 - Abstract Book

S5525

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

1212

Proffered Paper

Assessing a unique bladder preparation protocol for patients undergoing prostate cancer radiotherapy

Shabanaz Boodhoo 1 , Sophie Alexander 2,1 , Helen Barnes 1 , Greta Bucinskaite 2,1 , Robert Huddart 2,1 , Trina Herbert 1 , Babusha Kalra 1 , Rebekah Lawes 1 , Kian Morrison 1 , Hosna Mohammad 1 , Jayde Nartey 1 , Alison Tree 2,1 , Victoria Tawiah 1 , Bethany Williams 1 , Rosalyne Westley 2,1 , Helen McNair 2,1 1 Royal Marsden NHS Foundation Trust, Radiotherapy, Sutton, United Kingdom. 2 Institute of Cancer Research, Radiotherapy, Sutton, United Kingdom

Purpose/Objective:

Conventionally, patients undergoing prostate cancer radiotherapy follow a rigid bladder filling preparation protocol. Although an empty bladder protocol can result in a more consistent bladder volume (1) and greater patient tolerability, there are concerns regarding the potential increase in bladder dose and resulting GI toxicity (2) . A full bladder regime has been shown to reduce interfraction setup error compared to an empty bladder, although difficulty maintaining a consistent bladder volume is reported (3,4) . Patient anxiety can also be escalated with bladder filling (5) . In our hospital, patients are asked to empty their bladder, then drink 350 ml of water one hour before conventional linac and 30 minutes prior to MR-Linac (MRL) (Unity Elekta AB, Stockholm, Sweden) treatment, to achieve a desired bladder volume greater than 200 cm 3 . Previous inhouse work demonstrated that mandatory dose constraints can be achieved on the MRL despite varying bladder volumes and variable adherence to the standard bladder filling protocol (5) , suggesting that strict adherence to the protocol is not essential to meet clinical dose constraints. However, whilst the current protocol enables dose constraints to be achieved, significant bladder filling between session Magnetic Resonance Imaging (MRI) and verification MRI is common. Bladder filling during this period (approx. 25 minutes) increases the probability of prostate motion, sufficient to require position adjustment prior to treatment, thereby increasing overall time on the MRL couch. We developed and investigated a novel flexible bladder filling protocol which emphasises the importance of hydration throughout the day and removes the need for well-hydrated patients to follow a specific bladder filling regime. The aim of the novel protocol was to:

• Achieve a bladder volume of approximately 200 cm 3 at time of treatment. • Reduce bladder filling rate and prostate motion. • Be acceptable to patients.

Material/Methods:

Patients receiving 60 Gy in 20-fractions of radiotherapy to the prostate on a conventional linac, were approached at their pre-treatment appointment to assess suitability. Participant exclusion criteria included contraindications to