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Spatial rectal dose/volume metrics predict patient-reported gastro-intestinal symptoms after radiotherapy for prostate cancer

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Version 4 2019-12-09, 11:24
Version 3 2019-10-25, 13:43
Version 2 2019-10-24, 12:16
Version 1 2017-09-08, 12:44
journal contribution
posted on 2019-12-09, 11:24 authored by Oscar Casares-Magaz, Ludvig Paul Muren, Vitali Moiseenko, Stine E. Petersen, Niclas Johan Pettersson, Morten Høyer, Joseph O. Deasy, Maria Thor

Background: Gastro-intestinal (GI) toxicity after radiotherapy (RT) for prostate cancer reduces patient’s quality of life. In this study, we explored associations between spatial rectal dose/volume metrics and patient-reported GI symptoms after RT for localized prostate cancer, and compared these with those of dose–surface/volume histogram (DSH/DVH) metrics.

Material and methods: Dose distributions and six GI symptoms (defecation urgency/emptying difficulties/fecal leakage, ≥Grade 2, median follow-up: 3.6 y) were extracted for 200 patients treated with image-guided RT in 2005–2007. Three hundred and nine metrics assessed from 2D rectal dose maps or DSHs/DVHs were subject to 50-times iterated five-fold cross-validated univariate and multivariate logistic regression analysis (UVA, MVA). Performance of the most frequently selected MVA models was evaluated by the area under the receiving–operating characteristics curve (AUC).

Results: The AUC increased for dose-map compared to DSH/DVH-based models (mean SD: 0.64 ± 0.03 vs. 0.61 ± 0.01), and significant relations were found for six versus four symptoms. Defecation urgency and faecal leakage were explained by high doses at the central/upper and central areas, respectively; while emptying difficulties were explained by longitudinal extensions of intermediate doses.

Conclusions: Predictability of patient-reported GI toxicity increased using spatial metrics compared to DSH/DVH metrics. Novel associations were particularly identified for emptying difficulties using both approaches in which intermediate doses were emphasized.

Funding

This work has been partially supported by the European Commission under the project “The Digital Radiation Therapy Patient” (Dr. Therapat Project).

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