Staging, Response to Therapy, and Restaging of Lymphomas with18 F-FDG PET

Background We undertook this study to determine the diagnostic accuracy of18 FDG after three cycles and at the end of chemotherapy in non-Hodgkin's lymphoma (NHL) or Hodgkin's lymphoma (HL). We also evaluated the role of67 Ga, bone marrow aspiration (BMA), and computed tomography (CT) in monitoring lymphoma treatment. Methods18 FDG,67 Ga, BMA, and CT were performed before chemotherapy on 40 untreated patients.18 FDG and CT data were also obtained in 28/40 patients after 3 cycles of chemotherapy and at the end of chemotherapy. Patients had a median follow-up of 18 months, 21 had NHL, 7 had HL. Age range was from 15 to 74 years. Histopathology considered the standard reference at the initial stage. Follow-up was a comparative study of all exam results. Results Initial staging for PET and CT was as follows: sensitivity (Se) was 100%, specificity (Sp) 100%, positive predictive value (PPV) 100%, negative predictive value (NPV) 0%, and accuracy (Ac) 100%.67 Ga was Se, 64%; Sp, 0%, PPV, 100 %; and Ac, 64%. After the third cycle of chemotherapy and at the end of chemotherapy, Se, Sp, PPV, NPV, and Ac were always higher with PET than with CT. Eighteen patients had complete response, and seven had partial or no response. Conclusions18 FDG had greater prognostic values than CT after the third and last cycle of chemotherapy. PET after three cycles of chemotherapy is predictive of 18-month outcome in patients with intermediate and aggressive NHL and HL and may help in the identification of patients who would benefit from more intensive treatment or from a change in chemotherapy.