Effect of bladder filling protocols on bladder volume variation in the age of adaptive radiotherapy
Joseph, N. Elumalai, Thiraviyam Cree, A. Hoskin, Peter J McWilliam, Alan Song, Yee Pei
Joseph, N.
Elumalai, Thiraviyam
Cree, A.
Hoskin, Peter J
McWilliam, Alan
Song, Yee Pei
Citations
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Abstract
Purpose or Objective
Drinking protocols are increasingly used in pelvic radiotherapy to optimise bladder volume reproducibility.
However, there is no data to show their efficacy. This study assesses the effect of a standardised bladder
filling protocol on bladder volumes during each fraction and across the radiotherapy schedule.
Materials and Methods
Twenty patients undergoing radiotherapy for cancers of the cervix or bladder at a tertiary centre were
included. All patients were instructed to void prior to drinking 300mls of water. They were imaged using 1.5T
Siemens Aera MRI scanner after 30min. Two T2 sequences were taken 20min apart. This process was repeated
weekly throughout treatment. Bladders were contoured at both time points on Raystation 7R by a single
oncologist. Two patients were excluded due to poor image quality. Factors affecting bladder filling were investigated in models using multiple measures analysis of variation and mixed linear regression.
Results
Complete data was available in 8 bladder and 10 cervical cancer patients. Mean bladder volume was 143ml
(95% CI, 137-150ml), and the volume range was large (35-645ml). There was no significant difference in
bladder volume between bladder cancer and cervical cancer patients (median volume 120ml vs 90ml; p=0.2).
When adjusting for intra-patient variability using the mixed linear model, there was no trend with tumour site
or at any measured time point (Figure 1). However, bladder volume in the whole cohort was significantly
higher in the secConclusion
Given that the bladder collects urine inflow, the significant increase in bladder volume between scan 1 and 2
each week was expected. Our data demonstrates significant variation between patients and across time points
despite a standardised bladder filling protocol. Whilst it seems that for some patients the filling protocol
produced consistent bladder volumes, we could not identify any variables allowing us to predict for this. We
acknowledge that the sample size was low, but we believe this study adds weight to the adoption of adaptive
radiotherapy with a “plan of the day” rather than relying on a drinking protocol to achieve an optimal target
coverage throughout treatment.ond scan each week (122ml vs 108ml, p<0.001). The coefficient of variability (CV) for intra-patient variability was 0.47 (95% CI, 0.32-0.62) while that of inter-patient variability was 0.41 (95% CI, 0.28-
0.54).
Description
Date
2021
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Sanderson B, Joseph N, Elumalai T, Cree A, van Herk M, Hoskin P, et al. Effect of bladder filling protocols on bladder volume variation in the age of adaptive radiotherapy. Radiotherapy and Oncology. 2021;161:S1243-S4.