The role of serial pre-transplantation positron emission tomography in predicting progressive disease in relapsed lymphoma

Background and Objectives. F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) appears to be an excellent tool for evaluating early response to chemotherapy in lymphoma patients. As only chemosensitive patients with relapsed lymphoma may benefit from ablative therapy and autologous stem cell transplantation (ASCT), PET may be used to select patients for ASCT. A prospective study was performed to investigate the optimal time point of pre-transplantation PET, using different PET-parameters.Design and Methods. Three serial whole-body attenuation-corrected FDG-PET scans were performed in 39 consecutive patients with relapsed lymphoma (28 with aggressive non-Hodgkin's lymphoma and 11 with Hodgkin's disease) eligible for second-line chemotherapy followed by ASCT: PET1 before treatment, PET2 after two cycles of induction chemotherapy and PET3 after a third cycle of chemotherapy just before ASCT in cases with an abnormal PET2. Visual analysis and standardized uptake value (SUV) parameters were obtained for each scan. The follow-up lasted a minimun of 6 months after ASCT.Results. PET2 normalized in 43% (17/39) of the patients, and PET3 normalized in 27% (6/22). Persistent abnormal FDG-uptake was observed in 41% of the patients: 15% showed partial remission and 26% stable or even progressive abnormalities. With a median follow-up of 22 months (range 6-55) 54% of all patients relapsed after ASCI The results demonstrated that those patients who showed a complete response after the second and third cycles of chemotherapy had a 2-year progression-free survival of 71% and 58%, respectively, while those who showed no response, all relapsed shortly after ASCT Analysis of the SUV parameters did not reveal additional information compared to that yielded by the visual assessment.Interpretation and Conclusions. Two serial PET scans predict outcome after ASCT more precisely than one interim PET in patients with relapsed lymphoma.