End-of-treatment positron emission tomography after uniform first-line therapy of B cell posttransplant lymphoproliferative disorder identifies patients at low risk of relapse in the prospective German PTLD registry

Background Fluorine-18 fluorodeoxyglucose (18F-FDG) - positron-emission tomography (PET) is a recommended standard in the staging and response assessment of 18F-FDG-avid lymphoma. Posttransplant lymphoproliferative disorder (PTLD) can be detected by 18F-FDG-PET at diagnosis with high sensitivity and specificity. However, the role of response assessment by end of treatment (EOT)-PET has only been addressed in small case series. Methods We performed a retrospective, multi-center study of 37 patients with CD20-positive posttransplant lymphoproliferative disorder (PTLD) after solid organ transplantation (SOT) treated with uniform, up-to-date first-line protocols in the prospective German PTLD registry who had received EOT-18F-FDG-PET between 2006 and 2014. Median follow-up was 5.0 years. Any nonphysiological 18F-FDG uptake (Deauville score greater 2) was interpreted as PET-positive. Results By computed tomography (CT) final staging, 18 out of 37 patients had a complete response (CR), 18 had a partial response and 1 patient had stable disease. EOT PET was negative in 24/37 patients and positive in 13/37. The positive predictive value of EOT PET for PTLD relapse was 38% and the negative predictive value 92%. Time to progression (TTP) and progression-free-survival (PFS) were significantly longer in the PET negative group (p=0.019 and p=0.013). In the 18 patients in a partial response by CT staging, we noted highly significant differences in overall survival (p=0.001), TTP (p=0.007), and PFS (p

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