18FDG-positron emission tomography in post treatment evaluation of residual mass in Hodgkin's lymphoma: Long-term results

In patients with Hodgkin's lymphoma (HL) at the end of first line therapy an accurate imaging technique with high prognostic value is needed to assess response to treatment and predict those patients who will suffer disease relapse. This technique and its results permit the quick initiation of a second line therapy in patients suffering from a progressive disease or those unresponsive to treatment avoid over-treatment of patients in complete remission or those having a non-active residual disease. We included a 18FDG-positron emission tomography (PET) scan to the diagnostic set-up to investigate 28 patients following the end of their treatment. Fifteen patients out of the 28 (54%) had positive CT scans while 13 (46%) had negative ones. Eleven patients out of the 15 CT positive (73%) had negative PET scans and no relapse. The remaining four patients (27%) had positive PET scans with only one relapse (25%). With respect to the 13 patients who had negative CT scans, 9 patients (69%) had negative PET scans and no relapse. The remaining 4 patients (31%) had positive PET scans with 3 relapse cases (75%). In our final assessment after a median follow-up period of 45 months, starting from PET execution to the last follow-up, overall sensitivity of the CT and the PET were 25 and 100% respectively, specificity 42 and 83% respectively, positive predictive value (PPV) 7 and 50% respectively, negative predictive value (NPV) 77 and 100% respectively, and accuracy 39 and 86% respectively. In our experience, FDG-PET performed in patients after induction therapy appears to offer important additional information: FDG-PET results are predictors of prognosis giving 100% DFS in PET negative patients and 54% DSF in PET positive patients.