Prognostic value of interim fluorodeoxyglucose and fluorothymidine PET/CT in diffuse large B cell lymphoma.

Objective: To examine the prognostic value of fluoro-deoxyglucose (FDG) and fluorothymidine (FLT) interim positron emission tomography/CT (PET/CT) for diffuse large B-cell lymphoma (DLBCL). Methods: 44 patients with newly diagnosed DLBCL underwent both fluorine 18 FDG (F-18-FDG) and F-18-FLT PET/CT scans at baseline and after two cycles of a rituximab-containing chemotherapy regimen. Maximum standard uptake values (SUVmax) and changes in SUV (Delta SUV) were calculated for both tracers for the predominant lesion of each patient, for prediction of progression-free survival (PFS) and overall survival (OS). Results: The median follow-up period was 71 months. Receiver operating characteristic (ROC) analysis indicated that the best Delta SUV cut-off values for FDG (Delta SUVFDG) and FLT (Delta SUVFLT) were 79 and 76%, respectively. A ASUV FLT cut-off of 76% had the highest significance for prediction of PFS (p = 0.003) and OS (p = 0009), with sensitivity, specificity, and accuracy of 80.0, 85/, and 81.8% respectively in response assessment. Conclusion: Interim FLT PET/CT had higher specificity and accuracy than standard FDG PET/CT-based interpretation. Advances in knowledge: This study demonstrated that interim FLT PET/CT had higher accuracy than standardized FDG-based interpretation for therapeutic response assessment in DLBCL. FLT had the advantage of potentially reducing false positive of interim FDG PET/CT.