Assessing the level of agreement in tumour alignment, correction and tumour delineation for Lung Cancer Radiotherapy on kilo-voltage Cone Beam Computed Tomography

Abstract

Soft tissue matching using Cone Beam Computed Tomography (CBCT) is in many centres the preferred treatment verification method for lung cancer. However radiations Therapists (RTs) are trained in bony matching and not soft tissue matching. The purpose of this study was to determine whether RTs were equivalent to a Radiation Oncologist (RO) and Radiologist (RD) in alignment of the treatment CBCT with the gross tumour volume (GTV) defined at planning and in delineating the GTV on the treatment CBCT as may be necessary for adaptive radiotherapy. Materials & Methods: Ten RTs, a RO and RD each performed a manual tumour alignment and correction of the planning GTV to a treatment CBCT to generate an isocentre correction distance for fifteen patient datasets. Participants also contoured the GTV on the same datasets. The isocentre correction distance and the contoured GTVs from the RTs were compared with the RD and RO. Results: The mean difference in isocentre correction distances was 0.40cm between the RO and RD, 0.51cm between the RTs and RO and 0.42cm between the RTs and RD. The 95% confidence intervals were smaller than the equivalence limit of 0.5 cm, indicating that the RTs were equivalent to the RO and RD. For GTV delineation comparisons, the RTs were not found to be equivalent to the RD or RO. Conclusion: The alignment of the planning defined GTV and treatment CBCT using soft tissue matching by the RTs has been shown to be equivalent to the RO and RD. Tumour delineation by the RTs on the treatment CBCT however was not equivalent to that of the RO and RD. Thus it may be appropriate for RTs to undertake soft tissue alignment based on CBCT, however further investigation may be necessary before RTs undertake delineation for adaptive radiotherapy purposes.