Contribution of PET imaging to the initial staging and prognosis of patients with Hodgkin's disease

Background: Positron emission tomographic (PET) scanning utilizing [F-18]fluorodeoxyglucose (FDG) is a new method of tumor imaging based on the increased glucose metabolic activity of malignant tumors. In Hodgkin's disease (HD), PET has proven value for the evaluation of residual masses following treatment and for the early diagnosis of relapse. In the initial staging of HD, PET frequently shows a higher stage than conventional methods (upstaging by PET). In the present study, we evaluated the frequency of stage changes by PET in a multicenter setting and determined its prognostic relevance. Patients and methods: A total of 73 patients with newly diagnosed HD were staged with both conventional methods and whole-body PET scanning. All histological types and stages were represented. The median time of follow-up after the initial diagnosis was 25 months (range 1 month to 5 years). The response to treatment was determined by standard clinical and diagnostic criteria. For the purpose of this analysis, data from a PET center associated with a university medical center and a PET center associated with a group oncology practice were combined. Results: A total of 21 patients (28.8%) were upstaged by PET compared with conventional methods. In two cases (2.7%), a lower stage was suggested by PET scanning. With one possible exception, the upstaging had no obvious clinical or biological correlate. Among 12 patients in stage I (A+B) by conventional methods, seven were upstaged by PET (58.3%), four to stage II, one to stage III and two to stage IV. Among 42 patients in stage II, eight were upstaged by PET (19.0%), six to stage III and two to stage IV. Among 12 patients in stage III, six (50%) were upstaged to stage IV by PET. If only early-stage patients and major changes are considered (stages IA-IIB to III or IV), among 49, 10 were upstaged to III or IV, whereas in 39 staging was unchanged following PET. In the former group, three relapsed or were refractory compared with none in the latter group (P<0.006). In advanced stage patients (IIIA or IIIB) a trend toward treatment failure was apparent in patients who were upstaged by PET. Conclusions: PET scanning is an interesting new modality for the accurate staging of patients with HD and frequently shows a higher stage than conventional methods. PET should be performed at initial diagnosis and should be included in prospective studies of patients with HD. Upstaging by PET may represent a risk factor for a more advanced stage or a biologically more aggressive tumor. Patients with early-stage disease as identified by conventional methods have a significant risk of treatment failure if a more advanced stage is indicated by PET. At present, major stage changes suggested by PET imaging should be confirmed by an independent diagnostic method.