[Usefulness of FDG-PET in monitoring effects of the modality therapy for central nervous system malignant lymphoma: report of three cases].

We have reported three cases of central nervous system malignant lymphoma in which FDG-PET was useful in monitoring therapeutic effects. Case 1: A 53-year-old man complained of gait and memory disturbance. An MRI of the patient's brain showed enhanced mass lesions in the bifrontal lobe. An FDG-PET showed markedly high uptake of the tracer, which means a higher metabolism of glucose. The tumor was biopsied and the histological diagnosis was diffuse B cell lymphoma. The patient received chemotherapy and external irradiation therapy. Case 2: A 64-year-old woman suffered memory disturbance and left hemiparesis. An MRI showed a right frontal mass lesion, and FDG-PET showed high uptake of glucose. After the histological diagnosis was determined as diffuse large B cell lymphoma, the patient received the same therapy as case 1. Case 3: A 55-year-old woman suffered right hemianopsia. An MRI showed an enhanced lesion in the right basal ganglia and an FDG-PET showed high uptake of glucose. After the histological diagnosis was determined as diffuse large B cell lymphoma, the patient received the same therapy as case 1 and 2. In all cases, high uptake of glucose disappeared on the PET after initial chemotherapy, although an enhanced lesion continued on MRI even after radiation. FDG-PET was useful in monitoring the therapeutic effects of malignant lymphoma. These results indicate that we were able to confirm the effectiveness of the therapy in the early stage.