Routine use of PET scans after completion of therapy in pediatric Hodgkin disease results in a high false positive rate.

PURPOSE: Fluoro-2-deoxy-D-glucose positron emission tomography scans are becoming standard of care in the evaluation of Hodgkin disease (HD). The frequency of false positive (FP) PET scans in pediatric HD after completion of therapy has not been well studied. PATIENTS AND METHODS: All PET scan reports on pediatric HD patients at our institution between February 2000 and February 2005 were retrospectively reviewed. Scans were considered positive if the interpretation was most consistent with malignancy. FP results were determined by pathologic evaluation, resolution on scan, or absence of disease progression over at least 1 year without intervention.
RESULTS: We reviewed 255 PET scans on 47 patients, including 156 posttherapy scans on 34 patients. Positive predictive value for scans obtained during routine follow-up was 11%, with an FP rate of 16%. Identifiable etiologies of FP scans included: fibrosis, progressive transformation of germinal centers, abdominal wall hernia, appendicitis, thymus and HIV associated lymphadenopathy.
CONCLUSIONS: Routine PET scans after completion of therapy in pediatric HD patients have a low positive predictive value and a high FP rate. Prospective studies are needed to reduce the ambiguity of positive results. In the interim, positive PET scans after treatment should be interpreted cautiously and therapeutic decisions should not be made without histologic confirmation.