PET/CT combines functional and morphologic data and increases diagnostic accuracy in a variety of malignancies. Positron emission tomography (PET) imaging with 18-fluoro-2- deoxiglucose (FDG) is used increasingly for the initial evaluation and staging of patients with Hodgkin's lymphoma (HL) and nonHodgkin's lymphoma (NHL). The number of nodal areas involved is a new prognostic factor as demonstrated in the Follicular Lymphoma (FL) International prognostic index (FLIPI), and their use may be useful for the NHL and HL(21 ). The aim of this study is to compare the value of PET/CT over conventional CT in the evaluation of patients with lymphoma for staging or restaging after treatment. Patients
and Methods: 60 patients with diagnosis of HL (42 patients) and NHL (18 patients) in the initial and follow up staging were reviewed in a single tertiary care center to investigate the potential impact of positron emission tomography (PET)/computed tomography (CT) as compared to conventional enhanced CT on the staging of patients with lymphoma. All patients had FDG-PET/CT imaging study, clinical examination and CT scans. The Ann Arbor stage, each nodal site (cervical, axillary, thoracic, abdominal and inguinal), and extranodal sites were evaluated on the basis of FDGPET/CT scanning and were compared with the findings derived from conventional CT.
Results: PET/CT diagnosed 96 nodal regions as positive for lymphomatous involvement and 384 as disease free the same number was also diagnosed by enhanced CT. Staging concordance between FDG-PET/CT and enhanced CT was found in 50 % of cases, false upstaging by CT was found in 18 (30%) of cases, and false down staging was found in 10% of cases. All cases of disconcordance between PET-CT and enhanced conventional CT were examined for post treatment restaging. The respective sensitivities, specificities, and accuracies were 99%, 100%, and 99.8% for PET/CT, and 70%, 100%, and 94.7% for CT. PET/CT performed significantly better than CT (p<0.001 for sensitivity and accuracy). PET/CT and enhanced CT correctly identified similar extra-nodal lesions.
Conclusion: PET/CT has a higher sensitivity and accuracy in patients with HL and NHL provides significantly more accurate information compared to conventional enhanced CT for the staging and restaging of patients with lymphoma. Specificity is comparative. Disease occurring in normal appearing lymph nodes or extra-nodal sites can be picked up by PET. or CT.