Marked Improvement in Detecting the Number of Involved Nodal Areas in Lymphoma, Using ¹⁸ F- FDG - PET and CT Scan.

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 non- Hodgkin’s lymphoma (NHL). However, the degree of concordance of PET and TAC scanning for each nodal and extra nodal site are not well defined. The number of nodal areas involved is a new prognostic factor in follicular lymphomas as was demonstrated in the Follicular Lymphoma (FL) International prognostic index (FLIPI), and their use may be useful for the LNH and HL. In this study, we examined the performance of CT versus FDG-PET scanning, comparing each one of the nodal and extra nodal areas, as it is described in the FLIPI, in a retrospective cohort of lymphoma patients (pts) with HL and NHL. We reviewed the charts of 56 patients with diagnosis of HL and NHL in the initial and relapse staging, in a single tertiary care center. All patients had FDG-PET imaging study, clinical examination and CT scans. The Ann Arbor stage, each nodal site (cervical, mediastinal, axillary, mesenteric, para aortic, inguinal), and extra nodal sites were evaluated on the basis of FDG-PET scanning and were compared with the findings derived from CT. Bone marrow biopsy results were excluded from this initial analysis. The histopathological diagnoses included diffuse large B-cell Lymphomas in 20/56 pts (36%), HL 15/56 pts (27%), anaplastic large cell lymphoma 8/56 pts (14%), FL 5/56 pts (9%), peripheral T-cell Lymphoma 4/56 (7%) and others 7%. Among the 56 pts, 22 (39%) had discordant results between FDG-PET scanning and CT scanning, that lead to a change in stage assignment. Among the discordant cases FDG-PET resulted in upstaging in 18/56 pts (32%), and down staging in 4/56 pts (7%). Forty for pts (79%) had discordant results in the number of nodal areas, among the discordant cases FDG-PET detected more nodal areas in 36/56 pts (64%) and CT in 8/56 pts (14%). The discordant cases were distributed as it is shown in the table.

In conclusion Pet and CT in combination detects more involved nodal areas than each method by itself.