Negative predictive value of F-18-FDG coincidence PET in patients with Hodgkin's disease and a residual mass after therapy: a retrospective diagnostic test study

Background. The aim of the study was to asses the negative predictive value (NPV) of FDG-PET performed with triple-head coincidence gamma camera after the first-line therapy or salvage therapy in patients with Hodgkin's disease (HD) compared by a long-term follow-up as a reference standard. Methods. This retrospective diagnostic test study was done at the University Hospital Centre Zagreb between June 2001 and February 2008. The charts of 131 consecutive patients with Hodgkin's disease were reviewed. Seventy-three consecutive PET-negative patients (median age 28 years; range 12-80 years) with primary or recurrent biopsy confirmed lymphoma after the first-line therapy or salvage therapy were followed-up at least 12 months (median 23 months; range 12-69 months). All already performed F-18-FDG PET scans (using hybrid PET camera with triple head coincidence imaging capability within a few months after the completion of the therapy) were again visually interpreted by two board-certified nuclear medicine physicians who were blinded to any clinical or CT data. The negative predictive value of FDG-PET performed with triple-head coincidence gamma camera (Index test) was compared with a long-term follow-up as a reference standard. Results. Out of 131 patients 73 turned-out to be PET-negative. Of those 73 PET-negative patients, 61 have been scanned after the first-line chemotherapy/radiotherapy, and only 3 of them relapsed in a follow-up (negative predictive value 0.95). Twelve patients with resistant disease have been scanned after the repeated therapy, and 4 of them relapsed in a follow-up period (negative predictive value 0.66). Conclusions. This methodology with a triple-head coincidence gamma camera has a high negative predictive value. A negative PET scan can reassure patients and their doctors that the disease is not active.