Exploring extended [18F]FDG kinetics in lymphoma with ultra-late LAFOV-PET/CT.

PURPOSE: This prospective trial investigated extended [18F]FDG kinetics in lymphoma to provide in-vivo insights into glucose metabolism with potential relevance for staging and risk stratification.

METHODS

Fifteen consecutive, treatment- naïve lymphoma patients (4 Hodgkin, 11 non-Hodgkin) underwent routine whole-body [18F]FDG-PET/CT at 1 h post injection (p.i., injected activity 3.02 ± 0.34 MBq/kg) followed by additional Long Axial Field-Of-View (LAFOV)-PET/CT scans at 3 h and 6 h p.i. (Biograph Vision Quadra®, Siemens Healthineers; acquisition 5/15/30 min). Standardised uptake values (SUV) of lymphoma, benign lymph nodes, organs and reference tissues were quantified and multi time-point kinetics were described using Retention Indices (RI) and linear/quadratic trajectory analyses. Image quality was rated by two blinded readers on a 5-point Likert scale.

RESULTS

Image quality remained diagnostic in all datasets. Median Tumour-to-Background Ratio (TBR) increased significantly from 4.1 (1 h p.i.) to 12.5 (3 h p.i.) and 23.9 (6 h p.i.), p < 0.001. High-grade lymphoma exhibited an almost linear SUV rise, whereas low-grade entities followed a parabolic course, peaking at 3 h p.i. Benign lymph nodes demonstrated constant uptake (1 h: 0.9 ± 0.3, 3 h: 0.8 ± 0.5, 6 h: 0.8 ± 0.4). RIs showed a significant increase in [18F]FDG uptake over time in lymphoma, compared with a decline in benign lymph nodes (1-3 h p.i.: 19.4% vs. -14.4%, p < 0.001).

CONCLUSION

The LAFOV scanner enables high-quality [18F]FDG PET imaging for up to 6 h p.i., with a six-fold increase of TBR in ultra-late scans 6 h p.i. Extended [18F]FDG kinetic analysis differentiates high- and low-grade lymphomas from benign lymph nodes and reveals a significant decline in tracer uptake in low-grade lymphomas between 3 and 6 h p.i.

TRIAL REGISTRATION: DRKS00027307. Registered 26 November 2021.