Quality assessment of delineation and dose planning of early breast cancer patients included in the randomized Skagen Trial 1.

Background and Purpose: To report on a Quality assessment (QA) of Skagen Trial 1, exploring hypofractionation for breast cancer patients with indication for regional nodal radiotherapy.
Material and Methods: Deviations from protocol regarding target volume delineations and dose parameters (Dmin, Dmax, D98%, D95% and D2%) from randomly selected dose plans were assessed. Target volume delineation according to ESTRO guidelines was obtained through atlas based automated segmentation and centrally approved as gold standard (GS). Dice similarity scores (DSC) with original delineations were measured. Dose parameters measured in the two delineations were reported to assess their dosimetric outcome.
Results: Assessment included 88 plans from 12 centres in 4 countries. DSC showed high agreement in contouring, 99% and 96% of the patients had a complete delineation of target volumes and organs at risk. No deviations in the dosimetric outcome were found in 76% of the patients, 82% and 95% of the patients had successful coverage of breast/chestwall and CTVn_L2-4-interpectoral. Dosimetric outcomes of original delineation and GS were comparable.
Conclusions: QA showed high protocol compliance and adequate dose coverage in most patients. Inter-observer variability in contouring was low. Dose parameters were in harmony with protocol regardless original or GS segmentation.
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