Dose-response mapping of bladder and rectum in prostate cancer patients undergoing radiotherapy with and without baseline toxicity correction

Dose-response mapping of bladder and rectum in prostate cancer patients undergoing radiotherapy with and without baseline toxicity correction

Background and purpose: Radiotherapy dose–response maps (DRM) combine dose-surface maps (DSM) and toxicity outcomes to identify high-risk subregions in organ-at-risk. This study assesses the impact of baseline toxicity correction on the identification of high-risk subregions in dose–response modelin...

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Main Authors: Tanuj Puri, Tiziana Rancati, Petra Seibold, Adam Webb, Eliana Vasquez Osorio, Andrew Green, Eliana Gioscio, David Azria, Marie-Pierre Farcy-Jacquet, Jenny Chang-Claude, Alison Dunning, Maarten Lambrecht, Barbara Avuzzi, Dirk de Ruysscher, Elena Sperk, Ana Vega, Liv Veldeman, Barry Rosenstein, Jane Shortall, Sarah Kerns, Christopher Talbot, Andrew P. Morris, Alan McWilliam, Peter Hoskin, Ananya Choudhury, Catharine West, Marcel van Herk
Format: Article
Language:English
Published: Elsevier 2025-07-01
Series:Physics and Imaging in Radiation Oncology
Subjects:
Prostate cancer
Radiotherapy
VBA
IBDM
Dose-toxicity modeling
Organ-at-risk
Online Access:http://www.sciencedirect.com/science/article/pii/S2405631625001101
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Summary:Background and purpose: Radiotherapy dose–response maps (DRM) combine dose-surface maps (DSM) and toxicity outcomes to identify high-risk subregions in organ-at-risk. This study assesses the impact of baseline toxicity correction on the identification of high-risk subregions in dose–response modeling for prostate cancer patients undergoing radiotherapy. Materials and methods: The analysis included 1808 datasets, with 589 exclusions before toxicity-specific data removal. Bladder/rectum were automatically segmented on planning computed tomography scans, DSMs unwrapped into 91x90 voxel grids, and converted to equivalent doses in 2 Gy fractions (EQD2; α/β = 1 Gy). Seventeen late toxicities were assessed with two methods: (i) baseline toxicity subtracted from the maximum of 12- and 24-months toxicity scores, dichotomized at grade 1, and (ii) maximum of 12- and 24-months toxicity scores dichotomized at grade 1. DSMs were split accordingly, and voxel-wise t-values computed using Welch’s t-equation. Statistically significant voxels were identified via the 95th percentile of maximum of t-value (Tmax) distribution. Results: Event counts with baseline correction were 82/82/286/226 for urinary tract obstruction/retention/urgency/incontinence, respectively; without baseline correction, they were 93/104/465/361. For bladder DSMs, urinary incontinence, obstruction, retention, and urgency had 1143/186, 1768/1848, 516/0, and 33/0 significant voxels without/with baseline correction. For rectum DSMs, urinary incontinence and tract obstruction had 604/0 and 1980/889 significant voxels without/with baseline correction. However, no significant associations between rectal DSMs and rectum-related toxicities were found. Conclusions: DRM without baseline correction appears more sensitive to high-risk subregions due to higher event counts. Non-linear toxicity grading and multivariable analysis may enhance DRM reliability.
ISSN:2405-6316

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