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

Abstract

Aim The aim of the study was to investigate the value of fluorine-18-fluorodeoxyglucose (¹⁸F-FDG)-PET/computed tomography (CT) in identifying diffuse bone marrow (BM) involvement in follicular lymphoma using semiquantitative assessment. Methods This is a retrospective analysis of 41 patients with grade 1–3a follicular lymphoma who underwent ¹⁸F-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 (SUV_max) were measured at the sternum, at both iliac blades and at the T₁₂ vertebra. An average of these four measurements was recorded as SUV_av. The single highest overall SUV_max for the four bone sites, the SUV_av and the ratios SUV_av/mediastinal blood pool (MBP) and SUV_av/liver were compared with the BMB result. Results Focal bone uptake was identified on ¹⁸F-FDG-PET/CT by visual analysis in six patients, including two cases in which the BMB was negative. Assessment of diffuse BM involvement on ¹⁸F-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 SUV_av greater than or equal to 2 as the cutoff. Using the ratio SUV_av/MBP greater than or equal to 1 the sensitivity of ¹⁸F-FDG-PET/CT to detect BM involvement improved to 83%. Conclusion Visual analysis is useful in determining focal bone involvement, whereas semiquantitative analysis using SUV_av/MBP has a high sensitivity and specificity for predicting BM involvement in patients lacking focal bone lesions.