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Random variation in rectal position during radiotherapy for prostate cancer is two to three times greater than that predicted from prostate motion.

Published version
Peer-reviewed

Repository DOI


Type

Article

Change log

Authors

Scaife, J 
Harrison, K 
Romanchikova, M 

Abstract

OBJECTIVE: Radiotherapy for prostate cancer does not explicitly take into account daily variation in the position of the rectum. It is important to accurately assess accumulated dose (DA) to the rectum in order to understand the relationship between dose and toxicity. The primary objective of this work was to quantify systematic (Σ) and random (σ) variation in the position of the rectum during a course of prostate radiotherapy. METHODS: The rectum was manually outlined on the kilo-voltage planning scan and 37 daily mega-voltage image guidance scans for 10 participants recruited to the VoxTox study. The femoral heads were used to produce a fixed point to which all rectal contours were referenced. RESULTS: Σ [standard deviation (SD) of means] between planning and treatment was 4.2 mm in the anteroposterior (AP) direction and 1.3 mm left-right (LR). σ (root mean square of SDs) was 5.2 mm AP and 2.7 mm LR. Superior-inferior variation was less than one slice above and below the planning position. CONCLUSION: Our results for Σ are in line with published data for prostate motion. σ, however, was approximately twice as great as that seen for prostate motion. This suggests that DA may differ from planned dose in some patients treated with radiotherapy for prostate cancer. ADVANCES IN KNOWLEDGE: This work is the first to use daily imaging to quantify Σ and σ of the rectum in prostate cancer. σ was found to be greater than published data, providing strong rationale for further investigation of individual DA.

Description

Keywords

Aged, Humans, Male, Movement, Prostatic Neoplasms, Radiotherapy Planning, Computer-Assisted, Rectum, Reproducibility of Results, Tomography, X-Ray Computed

Journal Title

Br J Radiol

Conference Name

Journal ISSN

0007-1285
1748-880X

Volume Title

87

Publisher

Oxford University Press (OUP)
Sponsorship
Science and Technology Facilities Council (ST/K003917/1)
Cancer Research Uk (None)
JS is supported by Cancer Research UK through the Cambridge Cancer Centre. NGB is supported by the NIHR Cambridge Biomedical Research Centre. VoxTox is funded by Cancer Research UK.