Does PDG-PET Add Additional Prognostic Information to CT Staging in Lymphoma Patients?

BACKGROUND: 18-Fluoro-deoxyglucose positron emission tomography (FDG-PET) is a noninvasive imaging tool for initial staging and evaluation of treatment response in Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphoma (NHL). PET imaging can provide additional information to conventional imaging as computer tomography (CT).

AIM: The aim of this study was to evaluate the role of PET in improving the staging and if this fact could have an impact in prognosis, in compared to CT.

METHODS: From February 2005 to January 2008, one hundred ten consecutive patients with NHL (49 aggressive, 32 indolent and 3 unclassifficated) and HL (26 patients) were staged according to the Ann Arbor classification with CT and bone marrow biopsy (BMb). As well, all patients underwent to FDG-PET body before treatment. International Prognostic Index (IPI) was calculated following standard staging (IPI-st) and with standard staging plus FDG-PET (IPI-PET) in NHL.

RESULTS: CT and FDG-PET were concordant in 84 patients (66%). In 37 patients (34%) discordance was observed: in 7 patients FDG-PET was negative, in 11 patients FDG-PET detected more bone lesions, in 11 patients FDGPET uptake in other lymph nodes, including spleen infiltration, and in 8 patients FDGPET detected less lymph nodes or organ involvement. However, additional information of FDG-PET changed in staging in 21 out of 37 patients with discordant findings but the IPI risk changed in only 5 patients. Discrepancies CT and FDG-PET were seen in similar proportion in all lymphoma subtypes. Overall survival curves at two years showed no differences between IPI-st and IPI-PET (IPI-st 0–1: 97%, 2–3: 89%, 4–5: 48%; IPI-PET 0–1: 96%, 2–3: 89%, 4–5: 48% ).

CONCLUSIONS: FDG-PET can provide additional information to CT in both aggressive or indolent non-Hodgkin lymphoma and Hodgkin lymphoma. CT and FDG-PET were discordant in 30 % of the patients but only half of them showed change of stage. IPI risk was modified in few patients with NHL. Inclusion of patients is ongoing.