Impact of FDG-PET on lung cancer delineation for radiotherapy

Purpose: The purpose of this study is to assess the impact of fused diagnostic F‐18 2‐fluoro‐2‐deoxy‐D‐glucose (FDG) positron emission tomography (PET)/computed tomography (CT) and planning FDG‐PET/CT scans on voluming of lung cancer for radiotherapy. Methods: Five radiation oncologists (ROs), five radiation oncology trainees and a radiologist contoured five cases of non‐small cell lung cancer. The CT alone, the diagnostic FDG‐PET/CT and planning FDG‐PET/CT each registered to the CT, were used to contour three volumes. The concordance index (CI) was used to compare each volume with a reference RO. Results: Although there was considerable inter‐observer variability in CT contouring, there was no significant difference between mean volumes of the gross tumour volume for the RO and radiation oncology trainees using any technique. There was no increase in CI with the addition of PET/CT, either diagnostic or planning, for the RO. However, the volumes of the radiation oncology trainees showed a significant increase in CI from 65.8% with CT alone to 68.0% and 72.3% with diagnostic PET/CT and planning PET/CT, respectively (P = 0.028). Mean variation at the tumour/mediastinum interface was significantly reduced with addition of registered PET/CT. Conclusions: The concordance of RO with the reference RO did not significantly increase with use of integrated FDG PET/CT images. However, the contouring of radiation oncology trainees' became more concordant with the reference.