Role of FDG-PET/CT in the Staging of Patients with Follicular Lymphoma
Authors: Yuda Sayako , Maruyama Dai , Kurihara Hiroaki , Maeshima Akiko Miyagi , Toyoda Kosuke , Nobuhiko Yamauchi , Makita Shin-ichi , Fukuhara Suguru , Munakata Wataru , Kobayashi Yukio , Taniguchi Hirokazu , Tobinai Kensei 
Published: November 2019

Abstract
Introduction
The Lugano Classification incorporating recommendations of 18-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography/computed tomography (PET/CT) in the staging and response assessment of FDG-avid lymphomas was published. This classification is based on plenty of reports that suggested that evaluation with FDG-PET/CT improved the accuracy of the staging and response assessment of FDG-avid lymphomas, especially of diffuse large B-cell lymphoma and Hodgkin lymphoma. However, we are not sure of the role of FDG-PET/CT in indolent B-cell lymphomas, such as follicular lymphoma (FL).
Patients and Methods
Patients who were initially diagnosed as having FL of grade 1 to 3a at our institution between 2010 and 2012 were included in this study. We analyzed the number of nodal areas and the location of extranodal diseases identified by FDG-PET/CT added to the conventional evaluation consisting of CT, bone marrow examination and upper gastrointestinal endoscopy. The clinical stage by the conventional evaluation was compared to that by the Lugano Classification using FDG-PET/CT. It was also investigated whether adding PET/CT to the conventional evaluation might have had any influence on the decision regarding the initial treatment for patients with FL.
Results
A total of 67 patients with a median age of 62 years (range: 39-85) were included in this analysis. In comparison with CT, FDG-PET/CT identified a higher number of nodal areas in 11 patients (16%). Most of the extranodal sites except bone marrow and gastrointestinal tract were more frequently detected by PET-CT. Bone marrow examination detected 22 patients (33%) with bone marrow involvement, while PET-CT detected only 4 patients (6%). Gastrointestinal lesions were identified in 15 patients (22%) with conventional evaluation and in 4 patients (6%) by PET-CT (Table 1). In one of these 4 patients, endoscopic biopsy revealed that the PET-CT positive lesion was adenoma. In seven patients (10%), upstaging occurred through conventional evaluation plus PET-CT: 3 patients were upstaged from stage I to II, 2 from stage II to IV, 1 from stage II to III, and 1 from stage III to IV (Table 2). International Prognostic Index (IPI) and Follicular Lymphoma International Prognostic Index (FLIPI) were revised upward in 9 patients (13%) and 12 patients (18%), respectively. However, the change of stage, IPI, or FLIPI did not affect the decision regarding the initial treatment.
Conclusion
Our data suggest that FDG-PET/CT cannot take the place of the conventional evaluation, especially in patients with FL, because of the low sensitivity of involvements in bone marrow and gastrointestinal tract, although it may be helpful to use FDG-PET/CT in the staging of FL. Moreover, FDG-PET/CT might not have had any impact on the decision regarding the treatment strategy in FL. That may be partly because the lesions detected only by FDG-PET/CT did not affect the judgment of tumor burden. Prospective evaluation of the influence of FDG-PET/CT on the clinical outcomes is needed to establish an appropriate evaluation in the staging of patients with FL.

Disclosures
Maruyama: Takeda Pharmaceutical Company Limited: Honoraria; Eisai Co., Ltd.: Honoraria. Kobayashi:Nippon Shinyaku: Honoraria; Pfizer: Research Funding. Tobinai:Gilead Sciences: Research Funding.