[Delineation variation of lung cancer in conformal radiotherapy among radiation oncology residents after an educational course: a prospective study]

Abstract

Purpose: During the French national course of radiotherapy, delineation stations were at disposition for the residents. A comparative study of delineation and doses prescribed for a clinical case of lung carcinoma is reported before and after the completion of a theoretical education.

Methods: For this comparative study, 120 residents divided in 30 groups, have delineated the case before and after a lecture of radio-anatomy and a presentation of volumes and doses. The software Artiview (Aquilab SAS) was used to calculate the volume ratio (VR), common volume (CV), additional volume (AV), kappa (K) and overlap (OV) between the different volumes of interest. The expansion margins and the prescribed doses were noticed. A comparative study by a test of Student for paired series was performed.

Results: The GTV was 89.1cm(3) for the expert. It was 103.4 cm(3) (59.9-215.2 cm(3)) before versus 99.5 cm(3) (39.7-202.3 cm(3)) after the teaching intervention for participants. For GTV, comparison index were respectively before and after the intervention 1.16 cm(3) (0.7-2.4 cm(3)) and 1.1 cm(3)(0.5-2.3 cm(3)) for the VR (p=0.53), 78.4 cm(3) (58.9-91.8 cm(3)) and 76.4 cm(3) (40.2-92.1cm(3)) for the CV (p=0.27), 28.8 cm(3) (7.1-62 cm(3)) and 27.8 cm(3) (9.1-59.6 cm(3)) for the AV (p=0.7). OV and K were respectively 0.58 and 0.73 cm(3) before and after education. The median margin prescribed to obtain CTV from GTV was 6mm (5-10mm), no change was noticed after the course. The expert prescribed a 6mm margin. The median margin prescribed by the participants to obtain PTV from CTV was 7 mm (3-15 mm) before the course and 5mm (3-15 mm) afterwards, versus 5mm for the expert. The dose prescribed by the expert was 66 Gy on PTV. The dose was 66.2 Gy (60-70 Gy) before and 66.5 Gy (64-70 Gy) after course for residents.

Conclusion: No significant volume modification was found after the educational course. We noticed however an adaptation of the margins and a tendency to increase the prescribed dose as well as a reduction of the delineated volume. Good quality of the initial delineation could explain the absence of significant progress after education.