Comparison of FDG-PET and Ga-67 Scintigraphy in the Evaluation of Lymphoma and Its Relationship to the Pathologic Diagnosis Using WHO Classification System.

Abstract In the management of lymphoma patients, 18fluoro-2-deoxyglucose positron emission tomography (FDG-PET) has emerged as an important tool. However there are conflicting results that have been reported concerning its usefulness in different histological subtypes, especially in indolent lymphomas. The aim of this study was to retrospectively assess and compare the sensitivity of FDG-PET with gallium-67 citrate scintigraphy (Ga-67) with regard to the capacity for identification of disease involvement in patients with malignant lymphoma, and to investigate the relationship with the World Health Organization’s (WHO) classification system for pathological diagnosis of such cases. We contemporaneously performed 100 cases of FDG-PET and Ga-67 in addition to CT scans and/or MRIs prior to the treatment. Histological diagnoses included diffuse large B-cell lymphoma (DLBCL; n=38), MALT lymphoma (MALT; n=29), follicular lymphoma (FL; n=14), Hodgkin lymphoma (HL; n=8), NK lymphoma (NK; n=2), mantle cell lymphoma (MCL; n=2), Burkitt lymphoma (Burkitt; n=2), splenic marginal zone lymphoma (SMZL; n=2), and one case each with anaplastic large cell lymphoma (ALCL), peripheral T cell lymphoma (PTCL) and small lymphocytic lymphoma (SLL). In the 100 lymphoma cases, FDG-PET was unable to detect at least one of the disease involvement sites for 2/38 in DLBCL, 3/14 in FL, 1/8 in HD, 11/29 in MALT, 2/2 in SMZL, and 1/1 in SLL. FDG-PET detected more involvement sites than Ga-67 with 11/38 in DLBCL, 6/14 in FL, 4/8 in HL, 7/29 in MALT, 2/2 in MCL, and 1/2 in NK. In contrast, Ga-67 was more informative in two cases of MALT and in one case of SMZL, in which the regions included the eyelid, pleura and spleen. During the lymphoma imaging that was done before therapy, FDG-PET was highly sensitive in aggressive and high-grade lymphoma patients as compared to seen for Ga-67. In contrast, FDG-PET seemed to be more informative in FL with regard to indolent lymphomas, but was especially less reliable in MALT and SMZL. Anatomical imaging from CT scans and MRIs were useful in that they provided additional helpful information for the FDG-PET results in the lymphoma subgroups. Result of FDG-PET and Ga scintigraphy CT positive CT positive Histology No. of cases PET negative Ga negative ALCL 1 0 0 Burkitt 2 0 1 DLBCL 38 2 13 FL 14 3 8 HL 8 1 5 MALT 29 11 14 MCL 2 0 2 NK 2 0 1 peripheral T 1 0 0 SLL 1 1 1 SMZL 2 2 1