Dose-volume analysis of planned versus accumulated dose as a predictor for late gastrointestinal toxicity in men receiving radiotherapy for high-risk prostate cancer (original) (raw)
Physics and Imaging in Radiation Oncology
Background and purpose: Significant dose deviations have been reported between planned (D P) and accumulated (D A) dose in prostate radiotherapy. This study aimed to develop multivariate analysis (MVA) models associating Grade 1 and 2 gastrointestinal (GI) toxicity with clinical and D P or D A dosimetric variables separately. Materials and methods: Dose volume (DV) metrics were compared between D A and D P for 150 high-risk prostate cancer patients. MV models were generated from significant clinical and dosimetric variables (p < 0.05) at univariate level. Dose-based-region of interest (DB-ROI) metrics were included. Model performance was measured, and additional subgroup analysis were performed. Results: Rectal D A demonstrated a higher intermediate-high dose (V 30-65 Gy and DB-ROI at 15-50 mm) compared to D P. Conversely, at the very high dose region, rectal D A (V 75 Gy and DB-ROI at 5-10 mm) were significantly lower. In MVA, rectal DB-ROI at 10 mm was predictive for Grade ≥ 1 GI toxicity for D A and D P. Age, rectal D A for D 0.03 cc , and rectal D P for DB-ROI 10 mm were predictors for Grade 2 GI toxicity. Subgroup analysis revealed that patients ≥ 72 years old and a rectal D A of ≥ 78.2 Gy were highly predictive of Grade 2 GI toxicity. Conclusions: The dosimetric impact of a higher dose rectal dose in D A due to volumetric changes was minimal and was not predictive of detrimental clinical toxicity apart from rectal D 0.03 cc ≥ 78.2 Gy for Grade 2 GI toxicity. The use of the DB-ROI method can provide equivalent predictive power as the DV method in toxicity prediction.
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