This study evaluates whether adaptive stereotactic body radiotherapy (SBRT) provides dosimetric advantages compared to non-adaptive SBRT in localized prostate cancer. Five low-dose CT scans are performed before each SBRT session to assess anatomical variations (bladder filling, rectal volume) and determine if a dosimetric recalculation would have been required. The study also evaluates cumulative dose to organs at risk, patient-reported quality of life over 24 months, and overall and recurrence-free survival.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
100
Five low-dose, non-contrast CT scans performed immediately before each SBRT session (≈10 min before treatment) to assess anatomical variations impacting target volume and organ-at-risk dosimetry.
Clinique Sainte Clotilde
Saint-Denis, Reunion
RECRUITINGProportion of patients requiring dosimetric recalculation due to anatomical variations
Percentage of patients for whom at least one stereotactic body radiotherapy (SBRT) fraction would have required a dosimetric recalculation due to anatomical variations (bladder filling and/or rectal emptying), based on comparison between the initial treatment plan and pre-treatment low-dose CT scans acquired before each SBRT fraction (5). This outcome reflects the potential benefit of an adaptive radiotherapy approach compared to a non-adaptive strategy.
Time frame: At each of the 5 SBRT sessions (10 days max) Based on scanners low-dose comparison.
Cumulative delivered dose to Organs at Risk (OARs)
Definition: Quantitative assessment of the dose actually delivered to each OAR across all fractions, based on dose-volume parameters derived from the low-dose CTs and DVH (Dose-Volume Histogram) analyses. OARs and parameters include: Rectum Maximum dose (0.03 cc) Dose to 3 cc Dose to 10%, 20%, and 50% of the volume Bladder Maximum dose (0.03 cc) Dose to 10% and 50% of the volume Penile bulb Maximum dose Dose to 3 cc Femoral heads Dose to 10 cc (combined left and right) Maximum dose Bowel (GETUG-14 constraints) D5cc D1cc Urethra Maximum dose
Time frame: From baseline CT + all 5 fraction low-dose CT scans. (up to 10 days)
Change from baseline in global quality of life (EORTC QLQ-C30)
Change from baseline in global quality of life assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). Score range: 0-100 Higher scores indicate better quality of life.
Time frame: Time Frame: Baseline (pre-radiotherapy) 1 month 3 months 6 months 12 months 18 months 24 months post-radiotherapy
Survival outcomes
Overall Survival (OS): Death from any cause.
Time frame: 1, 3, 6, 12, 18, 24 months post-radiotherapy
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Recurrence-Free Survival (RFS)
Clinical, biochemical, or radiological recurrence.
Time frame: 1, 3, 6, 12, 18, 24 months post-radiotherapy
Change from baseline in prostate cancer-specific quality of life (EORTC QLQ-PR25)
Change from baseline in prostate cancer-specific quality of life domains assessed using the EORTC QLQ-PR25 questionnaire. Score range: 0-100 Higher scores indicate worse symptoms.
Time frame: Baseline, 1, 3, 6, 12, 18, and 24 months post-radiotherapy
Change from baseline in urinary symptoms (IPSS)
Change from baseline in urinary symptoms assessed using the International Prostate Symptom Score (IPSS). Score range: 0-35 Higher scores indicate worse urinary symptoms.
Time frame: Baseline, 1, 3, 6, 12, 18, and 24 months post-radiotherapy