LOCALLY INCREASED UPTAKE OF FLUORINE-19-FLUORODEOXYGLUCOSE AFTER INTRACAVITARY ADMINISTRATION OF IODINE-131-LABELED ANTIBODY FOR PRIMARY BRAIN-TUMORS

After the intracavitary administration of I-131-labeled monoclonal ant ibody for treatment of primary brain tumors after surgical resection, a persistent rim of F-18-fluouodeoxyglucose (FDG) accumulation surroun ding the cavity can be observed on PET, This rim, although it accumula tes more FDG than adjacent normal brain tissue, is not necessarily ass ociated with tumor. In our study, we examine the characteristics of th e rim that indicate persistent tumor and tumor progression. Methods: S equential PET studies obtained after treatment in 10 patients were rev iewed and the results correlated with dosimetry and post-treatment his tologic diagnoses. Results: The rim of FDG accumulation was seen on th e first post-treatment scan obtained 1-3 mo after therapy and persiste d unchanged over the 2-26 mo follow-up period. Pathologically, the non malignant rim was associated with marked increase of macrophage infilt rates, Nodularity of the rim was associated with tumor. Conclusion: Ou r study demonstrates that a rim of FDG accumulation is seen after intr acavitary administration of I-131-labeled monoclonal antibody therapy independent of the presence of malignant disease. Malignant recurrence is suggested by the development of new nodularity in the rim of FDG a ccumulation.