Impact of FDG PET-CT in the staging and management of follicular lymphoma

Learning Objectives This pictorial and literature review aims to demonstrate the utility of PET-CT in the staging and management of follicular lymphoma (FL), including its impact on therapy planning.

Follicular lymphoma accounts for 20-25% of adult non Hodgkin lymphomas worldwide. It has a variable course, usually indolent, with some patients experiencing a complete response to therapy while others relapse or transform to aggressive lymphoma. Up to 23% may spontaneously regress (1). Treatment varies depending on stage and clinical presentation. Durable remissions have been attained in 30-35% of patients with early (stage I-II) FL treated with radiotherapy alone (2), however more extensive disease in the absence of B symptoms would be better managed with watchful waiting. Therefore accurate staging is crucial for appropriate management. Although the impact of PET-CT on the staging and assessment of treatment response in potentially curable/ high grade lymphomas is well established (3), its role in indolent disease such as FL is more controversial. Studies have shown that FL is almost always FDG avid (4), and may identify further findings in 18-29% of cases (5,6). Given the importance of appropriate staging, PET may improve patient selection for therapy. Previous studies and a recent meta-analysis (7-9) have suggested that PET-based response criteria may alter patient management in FL, although the impact on long-term survival remains unclear. In this pictorial review we will present the available evidence in the literature for the use of PET-CT in FL and will provide multiple case examples illustrating the significant impact of PET-CT findings on therapy planning and patient management.