Clinical impact of FDG-PET/CT in the planning of radiotherapy for early-stage Hodgkin lymphoma

Background: Early-stage Hodgkin lymphoma (HL) has excellent survival rates but carries a high risk of late treatment-related adverse effects. Modern, individualised therapeutic strategies require an accurate determination of the extent of the disease. This study investigated the potential impact of 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography/computerised tomogrpahy (FDG-PET/CT) in the planning of involved field radiotherapy (IFRT). Patients and methods: Thirty patients received staging FDG-PET/CT before therapy, and IFRT after a short course of ABVD (adriamycin, bleomycin, vinblastine, dacarbazine) chemotherapy. IFRT planning was performed using only the CT data from the FDG-PET/CT scan. Later, the IFRT planning was performed anew using the FDG-PET/CT data as basis for contouring. Results: In 20 out of 30 patients, the radiotherapy (RT) course was unaffected by the addition of FDG-PET/CT. FDG-PET/CT would have increased the irradiated volume in seven patients where the volume receiving a minimum of 90% of the target dose was increased by 8-87%. FDG-PET/CT decreased the volume in two patients where the volume was reduced by 18% and 30%. Conclusions: When used for RT planning, FDG-PET/CT results in larger IFRT treatment volumes. If FDG-PET/CT is introduced to RT planning, the method should be accompanied by a change in RT treatment strategy, aiming at more targeted therapy in order to best avoid radiation to normal tissues.