Evaluation of clinical target volume expansion required for involved site neck radiotherapy for lymphoma to account for the absence of a pre-chemotherapy PET-CT in the radiotherapy treatment position

Publication date: Available online 6 June 2017
Source:Radiotherapy and Oncology
Author(s): David Bird, Chirag Patel, Andrew F. Scarsbrook, Viv Cosgrove, Emma Thomas, Di Gilson, Robin J.D. Prestwich
Background and purposeInvolved site radiotherapy clinical target volume (CTV) for lymphoma requires an expansion to account for the absence of radiotherapy treatment-position pre-chemotherapy imaging, which is not widely implemented. This prospective imaging study aims to quantify CTV expansion required for neck radiotherapy.Materials and methods10 patients from a prospective single centre imaging study underwent a pre-chemotherapy FDG-PET-CT in both the diagnostic and radiotherapy treatment position, and subsequently received neck radiotherapy post-chemotherapy. CTVINRT and CTVdiagPET were delineated on the planning CT, following co-registration of the radiotherapy position PET-CT and side-by-side assessment of diagnostic PET-CT respectively.ResultsIntra-observer variability was limited, with delineation of CTVINRT highly reproducible and slightly lower for CTVdiagPET (mean DICE 0.88 and 0.8 respectively). Superiorly, CTVdiagPET varied by −10 to +15mm from CTVINRT. Inferiorly, CTVdiagPET varied by −18 to +6mm from CTVINRT. Comparing CTVINRT and CTVdiagPET in the axial plane, the mean DICE was 0.74. Mean sensitivity index was 0.75 (range 0.59–0.91), showing that on average 75% of the CTVINRT was encompassed by the CTVdiagPET.ConclusionsIn the absence of treatment-position PET-CT, CTV expansion cranially and caudally by 10mm and 18mm respectively, along with generous contouring in the axial plane, was required to encompass pre-chemotherapy disease.



http://ift.tt/2r29Qb0