Quality assurance of contouring and dosimetric consistency in the GETUG-AFU 31 salvage prostate stereotactic reirradiation trial
Abstract
Background and purpose: Salvage stereotactic body radiotherapy (SBRT) represents a promising approach for managing intraprostatic recurrence following radiotherapy. The multicenter phase I/II GETUG-AFU 31 trial evaluated 6 × 6 Gy SBRT, with delineation and dosimetric dummy runs performed to ensure consistent target and organ-at-risk (OAR) delineation and treatment plan quality across centers. We report the outcomes of this pre-accrual quality reassurance process.
Materials and methods: Eighteen centers received CT, PET, and multiparametric prostate MRI (mpMRI) datasets of recurrent lesions and contoured the gross target volume (GTV), clinical target volume (CTV), prostate, bladder/rectum (whole and wall), penile bulb, and urethra + 3 mm. The Dice similarity coefficient (DSC) and average Hausdorff distance (HD avg) were calculated against an expert reference. Each center subsequently generated a 6 × 6-Gy plan on another anonymized dataset. Dose-volume indices were compared with the protocol limits. Major deviations were subsequently revised.
Results: Of the 18 centers, 5 (28 %) required resubmission. Variability was high for the GTV (median DSC: 0.63 [interquartile range {IQR}: 0.45-0.70; HD avg: >1.8 mm), CTV: (0.79 [0.71-0.82]; HDavg: >1.8 mm), and urethra: (0.10 [0.05-0.26]; HD avg: >3.6 mm). Larger structures showed higher agreement: bladder, 0.93; rectum, 0.85; prostate, 0.85. All revised plans satisfied constraints: CTV Dmedian > 38.1 ± 1.4 Gy; rectal-wall V27Gy…
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Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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