PET/CT for Lymphoma Post-therapy Response Assessment in Other Lymphomas, Response Assessment for Autologous Stem Cell Transplant, and Lymphoma Follow-up

FDG-PET/CT is an established first-line diagnostic imaging tool used in the staging of most lymphomas and for post-therapy response assessment in Hodgkin lymphoma (HL) and diffuse large B-cell lymphoma (DLBCL). Many of the subtypes of lymphoid neoplasms classified by the World Health Organization demonstrate significant FDG-avidity or uptake; however, many guidelines and Lugano classification do not recommend the use of FDG-PET/CT in assessing response to therapy for these non-HL, non-DLBCL subtypes as a first-line diagnostic tool. This article reviews the role of FDG-PET/CT in the evaluation of the other most common “FDG-avid” lymphomas than HL and DLBCL, the role of FDG-PET/CT before autologous stem cell transplant, and for post-treatment follow-up. Follicular lymphoma is most commonly FDG-avid with a wide range of uptake that generally correlates with the histologic grade, a major determinant of aggressiveness and prognosis. FDG-PET/CT is more sensitive and specific than CT for detecting residual disease post therapy for both aggressive and indolent follicular lymphoma. Post-treatment FDG-PET/CT for follicular lymphoma has significant prognostic value, that is, better predicts progression-free and overall survival than does conventional post-treatment assessment with CT. FDG-PET/CT is useful in the staging of mantle cell lymphoma, a very aggressive, incurable subtype of lymphoma; however, data show mixed results on the benefits of FDG-PET/CT over conventional CT assessment in post-therapy response evaluation. Peripheral T-cell lymphomas, a rare aggressive group of T-cell lymphomas, are often FDG-avid. Post-therapy FDG-PET/CT results have major prognostic value and therapeutic implications in many subtypes of peripheral T-cell lymphomas. Post-treatment FDG-PET/CT is superior to conventional CT for determining chemosensitivity of lymphoma, and therefore is better able to predict which patients will have a greater benefit or outcome with autologous stem cell transplant. There are mixed data on the value of FDG-PET/CT for surveillance after treatment because of high reported false-positive rates and accuracy that depends on the duration or timing of surveillance and the subtype of lymphoma.