The quantitative impact of joint peer review with a specialist radiologist in head and neck cancer radiotherapy planning

Abstract

Objectives: Radiologist input in peer review of head and neck radiotherapy has been introduced as a routine departmental approach. The aim was to evaluate this practice and to quantitatively analyse the changes made. Methods: Patients treated with radical-dose radiotherapy between August and November 2020 were reviewed. The incidence of major and minor changes, as defined by The Royal College of Radiologists guidance, was prospectively recorded. The amended radiotherapy volumes were compared with the original volumes using Jaccard Index (JI) to assess conformity; Geographical Miss Index (GMI) for undercontouring; and Hausdorff Distance (HD) between the volumes. Results: In total, 73 out of 87 (84%) patients were discussed. Changes were recommended in 38 (52%) patients: 30 had ≥1 major change, eight had minor changes only. There were 99 amended volumes: The overall median JI, GMI and HD was 0.91 (interquartile range [IQR]=0.80–0.97), 0.06 (IQR = 0.02–0.18) and 0.42 cm (IQR = 0.20–1.17 cm), respectively. The nodal gross-tumour-volume (GTVn) and therapeutic high-dose nodal clinical-target-volume (CTVn) had the biggest magnitude of changes: The median JI, GMI and HD of GTVn was 0.89 (IQR = 0.44–0.95), 0.11 (IQR = 0.05–0.51), 3.71 cm (IQR = 0.31–6.93 cm); high-dose CTVn was 0.78 (IQR = 0.59–0.90), 0.20 (IQR = 0.07–0.31) and 3.28 cm (IQR = 1.22–6.18 cm), respectively. There was no observed difference in the quantitative indices of the 85 ‘major’ and 14 ‘minor’ volumes (p = 0.5). Conclusions: Routine head and neck radiologist input in radiotherapy peer review is feasible and can help avoid gross error in contouring. Advances in knowledge: The major and minor classifications may benefit from differentiation with quantitative indices but requires correlation from clinical outcomes.