The use of a proposed updated EARL harmonization of ¹⁸F-FDG PET-CT in patients with lymphoma yields significant differences in Deauville score compared with current EARL recommendations

The Deauville score (DS) is a clinical tool, based on the comparison between lesion and reference organ uptake of ¹⁸F-fluorodeoxyglucose (FDG), used to stratify patients with lymphoma into categories reflecting their disease status. With a plethora of positron emission tomography with computed tomography (PET-CT) hard- and software algorithms, standard uptake value (SUV) in lesions and reference organs may differ which affects DS classification and therefore medical treatment. The EANM Research Ltd. (EARL) harmonization program from the European Association of Nuclear Medicine (EANM) partly mitigates this issue, but local preferences are common in clinical practice. We have investigated the discordance in DS calculated from patients with lymphoma referred for ¹⁸F-FDG PET-CT reconstructed with three different algorithms: the newly introduced block-sequential regularization expectation-maximization algorithm commercially sold as Q. Clear (QC, GE Healthcare, Milwaukee, WI, USA), compliant with the newly proposed updated EARL recommendations, and two settings compliant with the current EARL recommendations (EARL_lower and EARL_upper, representing the lower and upper limit of the EARL recommendations).

Fifty-two patients with non-Hodgkin and Hodgkin lymphoma were included (18 females and 34 males). Segmentation of mediastinal blood pool and liver were semi-automatically performed, whereas segmentation of lesions was done manually. From these segmentations, SUV_max and SUV_peak were obtained and DS calculated.

There was a significant difference in DS between the QC algorithm and EARL_lower/EARL_upper (p < 0.0001 for both) but not between EARL_lower and EARL_upper (p = 0.102) when SUV_max was used. For SUV_peak, there was a significant difference between QC and EARL_lower (p = 0.001), but not for QC vs EARL_upper (p = 0.071) or EARL_lower vs EARL_upper (p = 0.102). Five non-responders (DS 4–5) for QC were classified as responders (DS 1–3) when EARL_lower/EARL_upper was used, both when SUV_max and SUV_peak were investigated.

Using the proposed updated EARL recommendations compared with the current recommendations will significantly change DS classification. In select cases, the discordance would affect the choice of medical treatment. Specifically, the current EARL recommendations were more often prone to classify patients as responders.