BACKGROUND AND PURPOSE: In radiotherapy (RT) of prostate cancer the key organs at risk (ORs) - the rectum and the bladder - display considerable motion, which may influence the dose/volume parameters predicting for morbidity.
In this study we compare motion-inclusive doses to planned doses for the rectum and bladder and explore their associations with prospectively recorded morbidity.
MATERIALS AND METHODS: The study included 38 prostate cancer patients treated with hypo-fractionated image-guided intensity-modulated RT that had an average of nine repeat CT scans acquired during treatment. These scans were registered to the respective treatment planning CT (pCT) followed by a new dose calculation from which motion-inclusive dose distributions were derived. The pCT volumes, the treatment course averaged volumes as well as the planned and motion-inclusive doses were associated with acute and late morbidity (morbidity cut-off: ⩾Grade 2).
RESULTS: Acute rectal morbidity (observed in 29% of cases) was significantly associated with both smaller treatment course averaged rectal volumes (population median: 75 vs. 94cm3) and the motion-inclusive volume receiving doses close to the prescription dose (2Gy-equivalent dose of 76Gy).
CONCLUSION: Variation in rectum and bladder volumes leads to deviations between planned and delivered dose/volume parameters that should be accounted for to improve the ability to predict morbidity following RT.
Written by:
Thor M, Bentzen L, Hysing LB, Ekanger C, Helle SI, Karlsdóttir A, Muren LP. Are you the author?
Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark; Department of Oncology, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
Reference: Radiother Oncol. 2013 May;107(2):147-52.
doi: 10.1016/j.radonc.2013.03.029
PubMed Abstract
PMID: 23684586
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