Early detection of relapse by whole-body positron emission tomography in the follow-up of patients with Hodgkin's disease

Background: Relapse after treatment of Hodgkin's disease (HD) is usually identified as a result of the investigation of symptoms. We undertook this study to examine the value of whole-body positron emission tomography (PET) for the detection of preclinical relapse. Patients and methods: Thirty-six patients underwent 2-[fluorine-18]fluoro-2-deoxy-D-glucose (F-18-FDG) PET at the end of treatment and than every 4-6 months for 2-3 years after the end of polychemotherapy and/or radiotherapy. In those cases of abnormal F-18-FDG accumulation a confirmatory study was performed 4-6 weeks later. Results: One patient had residual tumor and four patients relapsed during a follow-up of 5-24 months. All five events were correctly identified early by F-18-FDG PET. Residual tumor or relapse was never first diagnosed based on clinical examination, laboratory findings or computed tomography (CT) studies. Two patients presented B symptoms and the three others were asymptomatic at the time of residual disease or relapse. Confirmation of residual disease or relapse was obtained by biopsy in four patients 1, 1, 5 and 9 months after PET and by unequivocal clinical symptoms and CT studies in one patient 3 months after PET. False-positive F-18-FDG PET studies incorrectly suggested possible relapse in six other patients, but the confirmatory PET was always negative. Our study also provides important information about physiological F-18-FDG uptake in the thymus. Conclusions: Our data suggest the potential of F-18-FDG PET to detect preclinical relapse in patients with HD. This could help identify patients requiring salvage chemotherapy at the time of minimal disease rather than at the time of clinically overt relapse. Further studies are warranted to determine the impact of PET on treatment management and outcome. In fact, the aim of follow-up procedures is not only to detect preclinical relapse but mainly to obtain better results by starting salvage treatment earlier. A cost-benefit analysis will also be necessary before F-18-FDG PET can be used routinely in the follow-up of patients with HD.