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Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy

Shelley, LEA and Scaife, JE and Romanchikova, M and Harrison, K and Forman, JR and Bates, AM and Noble, DJ and Jena, R and Parker, MA and Sutcliffe, MPF and Thomas, SJ and Burnet, NG (2017) Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy. Radiotherapy and Oncology, 123. pp. 466-471.

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$\textbf{BACKGROUND AND PURPOSE}$: For the first time, delivered dose to the rectum has been calculated and accumulated throughout the course of prostate radiotherapy using megavoltage computed tomography (MVCT) image guidance scans. Dosimetric parameters were linked with toxicity to test the hypothesis that delivered dose is a stronger predictor of toxicity than planned dose. $\textbf{MATERIAL AND METHODS}$: Dose-surface maps (DSMs) of the rectal wall were automatically generated from daily MVCT scans for 109 patients within the VoxTox research programme. Accumulated-DSMs, representing total delivered dose, and planned-DSMs, from planning CT data, were parametrised using Equivalent Uniform Dose (EUD) and 'DSM dose-width', the lateral dimension of an ellipse fitted to a discrete isodose cluster. Associations with 6 toxicity endpoints were assessed using receiver operator characteristic curve analysis. $\textbf{RESULTS}$: For rectal bleeding, the area under the curve (AUC) was greater for accumulated dose than planned dose for DSM dose-widths up to 70Gy. Accumulated 65Gy DSM dose-width produced the strongest spatial correlation (AUC 0.664), while accumulated EUD generated the largest AUC overall (0.682). For proctitis, accumulated EUD was the only reportable predictor (AUC 0.673). Accumulated EUD was systematically lower than planned EUD. $\textbf{CONCLUSIONS}$: Dosimetric parameters extracted from accumulated DSMs have demonstrated stronger correlations with rectal bleeding and proctitis, than planned DSMs.

Item Type: Article
Uncontrolled Keywords: delivered dose dose–surface maps prostate radiotherapy rectal toxicity VoxTox
Divisions: Div C > Biomechanics
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:10
Last Modified: 15 Apr 2021 05:04
DOI: 10.1016/j.radonc.2017.04.008