Dual-point FDG-PET/CT for treatment response assessment in Hodgkin lymphoma, when an FDG-avid lesion persists after treatment.

FDG-PET/CT (PET) is now considered the standard imaging tool for Hodgkin Lymphoma (HL) staging and restaging. However a CT-detected residual mass at the end of therapy (EoT) is still a challenge for PET interpretation. The aim of our study was to improve the overall accuracy of EoT PET/CT by using a dynamic dual-point scanning at 60 and 120 after FDG injection (2P-PET/CT). Fifty-one HL patients showing a single residual FDG-avid mass (SFAM) at EoT PET/CT were included in the study in Italy and Poland. Treatment was ABVD, ABVD followed by BEACOPP or ABVD plus radiotherapy. Only patients with a SFAM and a Deauville score (DS) > 2 in EoT PET/CT were included in the study. Two independent nuclear medicine reviewed images with a semi-quantitative analysis (SUVMax and retention index, RI) and a visual scoring according to DS. Compared to standard PET, 2P-PET/CT showed only a modest increase in NPV and PPV, from 0.87 to 0.89 and of the PPV from 0.67 to 0.71, respectively. Increase of the overall accuracy became substantial upon including in the analysis only patients whose images were acquired in strict adhesion to original protocol of 2P-PET/CT scanning: (t 120'-6040 min): the sensitivity increased from 0.60 to 1.00, PPV from 0.75 to 0.83 and NPV from 0.89 to 1. This study, with caution for the small number of patients included, seems to suggest that 2P-PET/CT could increase the overall accuracy of EoT PET/CT in correctly classifying treatment response in HL with a persisting SFAM at EoT.