Exploring liverSUVmax% as a practical alternative to ΔSUVmax for interim PET/CT assessment in DLBCL: a validation cohort study and a single-centre retrospective exploratory analysis

Introduction PET-guided strategies are central to the management of diffuse large B-cell lymphoma (DLBCL), with quantitative ΔSUVmax emerging as a prognostic tool in trials. However, its routine use is limited by technical constraints, such as standardised imaging protocols and baseline PET/CT requirements. Methods In this single-centre retrospective study of 144 DLBCL patients treated with R-CHOP, we evaluated the real-world applicability of ΔSUVmax and liverSUVmax% as alternative PET interpretation methods. Results Only 47.9% (69/144) of our patients were assessed using ΔSUVmax in a real-time workflow, mostly due to logistical constraints or physician discretion, while the remainder were assessed using the Deauville score (DS). We then externally validated the prognostic role of the 160% liverSUVmax threshold at interim PET after 2 cycles (iPET2) for PFS and OS. After 4 cycles (iPET4), the 140% threshold showed a better balance between sensitivity and specificity for predicting progression than the 160% threshold, though results were less clear. Exploratory ROC analyses identified liverSUVmax% cut-offs at iPET2 (160%) and iPET4 (120%) with favourable prognostic performance. LiverSUVmax% showed moderate agreement with both ΔSUVmax and the Deauville score at iPET2 ( κ =0.59 and κ =0.52, respectively), while agreement with the Deauville score was almost perfect at iPET4 using the 120% threshold ( κ =0.91). Discussion This study, like previous research, highlights the potential of liverSUVmax% as a practical, semi-quantitative metric to address the limitations of ΔSUVmax in routine practice. Further prospective validation is warranted to refine thresholds and optimize iPET-based strategies in DLBCL using additional metrics.