The value of semiquantitative analysis in identifying diffuse bone marrow involvement in follicular lymphoma

The aim of the study was to investigate the value of fluorine-18-fluorodeoxyglucose ((18)F-FDG)-PET/computed tomography (CT) in identifying diffuse bone marrow (BM) involvement in follicular lymphoma using semiquantitative assessment.

This is a retrospective analysis of 41 patients with grade 1-3a follicular lymphoma who underwent (18)F-FDG-PET/CT, contrast-enhanced CT and bone marrow trephine biopsy (BMB) as part of staging. BM involvement on PET/CT was assessed by visual and semiquantitative analysis. Standardized uptake values (SUVmax) were measured at the sternum, at both iliac blades and at the T12 vertebra. An average of these four measurements was recorded as SUVav. The single highest overall SUVmax for the four bone sites, the SUVav and the ratios SUVav/mediastinal blood pool (MBP) and SUVav/liver were compared with the BMB result.

Focal bone uptake was identified on (18)F-FDG-PET/CT by visual analysis in six patients, including two cases in which the BMB was negative. Assessment of diffuse BM involvement on (18)F-FDG-PET/CT by visual analysis had a sensitivity and specificity of 31 and 92%, respectively. Semiquantitative analysis resulted in an improved sensitivity and specificity of 58 and 96%, respectively, when using SUVav greater than or equal to 2 as the cutoff. Using the ratio SUVav/MBP greater than or equal to 1 the sensitivity of (18)F-FDG-PET/CT to detect BM involvement improved to 83%.

Visual analysis is useful in determining focal bone involvement, whereas semiquantitative analysis using SUVav/MBP has a high sensitivity and specificity for predicting BM involvement in patients lacking focal bone lesions.