PET/CT Assessment of Follicular Lymphoma and High Grade B Cell Lymphoma - Good Correlation with Clinical and Histological Features at Diagnosis.

BACKGROUND: Follicular lymphoma is a common type of non-Hodgkin's lymphoma observed in Western countries. The diagnosis of this disease is based primarily on morphological and immunohistochemical assessment. The proliferative index Ki67 correlates with histological grading and clinical aggressiveness. Currently, positron emission tomography/computed tomography scanning are not applied for standard staging at diagnosis of follicular lymphoma and its use is limited to those patients for whom the identification of residual disease is crucial for therapeutic decisions and only when transformation to a high-grade lymphoma is suspected. OBJECTIVES: Our aim was to assess whether a correlation exists between the maximal standardized uptake value (SUVmax) at the biopsy site as detected via positron emission tomography/computed tomography and pathological (Ki67 and FL histological grade) and clinico-biological features (e.g. LDH, beta-2-microglobulin, Ann Arbor stage and FL International Prognostic Index--FLIPI) at diagnosis. MATERIAL AND METHODS: We retrospectively identified 16 patients during the previous 3.5 years in whom node biopsies were guided, taking into account the SUVmax as detected upon PET/CT scan at diagnosis. The results of these biopsies were diagnostic of follicular lymphoma. We also included 6 patients with high grade B cell lymphoma: 5 diffuse large B cell lymphoma (DLBCL) and 1 FL 3b histological grade. A 2-tailed non-parametric Spearman's correlation analysis of the SUVmax with Ki67, histological grade, LDH and b-2-microglobuline was performed. RESULTS: The Ki67 (r=0.73) and follicular lymphoma histological grade (r=0.75) at the biopsy displayed a significant correlation with the SUVmax at diagnosis (p<0.01). CONCLUSIONS: Our results suggest that SUV detected by positron emission tomography/computed tomography correlates with histological grade in follicular lymphoma/high grade B cell lymphoma, Ki67 and LDH. Positron emission tomography/computed tomography should be considered for guiding lymph node biopsy when transformation to a high-grade B cell lymphoma is suspected.