ProCaLung – Peer review in stage III, mediastinal node-positive, non-small-cell lung cancer: How to benchmark clinical practice of nodal target volume definition and delineation in Belgium☆

•Nodal definition and delineation for lung cancer is variable in clinical practice.•Knowledge of anatomy and strict guidelines are crucial for high contouring quality.•A qualitative review is essential to understanding interobserver variability.•Quantitative evaluations are more robust if performed after a qualitative review.•Standardization and peer review of clinical practice at country level is feasible.