How to Improve the Implementation of New Radiotherapy Guidelines? Interests and Llimits of a National Training Workshop

Objectives

The Inter-Ewing-1 trial is currently implemented in several countries with two randomized questions regarding radiotherapy: (1) dose escalation in definitive radiotherapy and (2) dose optimisation in post-operative radiotherapy. A prospective radiotherapy quality assurance (Quartet RTQA) is an essential part of the trial. Before opening the trial, the French Radiotherapy Group Society organised a delineation workshop to train the participants and evaluate the benefit on the delineation quality.

Methods

Before the workshop, all the participants were asked to delineate the target volumes of a benchmark case as recommended in the guidelines. During the workshop, the case and delineations were reviewed. A second delineation round was asked after the workshop.

Quantitative volume (Dice coefficient (DC)), dimension (Hausdorff distance (HD)), concordance and discordance index comparisons with the reference contours were made for GTVp_Pre, GTVp_Post, CTVp_Pre and CTVp_Post, before and after workshop.

Results

Eight centers provided both pre- and post-workshop delineations. Before the workshop, the median [Q25; Q75] DC for CTVp_Pre and CTVp_Post were 0.670 [0.629; 0.723] and 0.552 [0.428. 0.579] respectively versus 0.673 [0.656; 0.752] (Paired T-Test Welch, p=0.06) and 0.686 [0.574. 0.756] (Paired T-Test Welch, p=0.015) after the training.

Before the workshop, the median [Q25; Q75] HD for CTVp_Pre and CTVp_Post were 24.4 [19.0; 27.5] and 33.5 [27.1; 49.0] respectively versus 24.7 [19.8; 27.5] (Wilcoxon Signed Rank Test, p=0,830) and 22.8 [20.9; 35.6] (Wilcoxon Signed Rank Test, p=0.110) after the training. The results were similar for the GTVp_Pre and GTVp_Post and will be detailed at the congress.

Conclusion

The delineation of target volumes in ES remains difficult despite guidelines. These results confirm that training makes it possible to improve practices but this remains insufficient. This result highlights the importance of developing prospective RTQA to improve the quality of treatments.