PT - JOURNAL ARTICLE AU - Lars Kurch AU - Andreas Hüttmann AU - Thomas W. Georgi AU - Jan Rekowski AU - Osama Sabri AU - Christine Schmitz AU - Regine Kluge AU - Ulrich Dührsen AU - Dirk Hasenclever TI - Interim PET in Diffuse Large B-Cell Lymphoma AID - 10.2967/jnumed.120.255034 DP - 2021 Aug 01 TA - Journal of Nuclear Medicine PG - 1068--1074 VI - 62 IP - 8 4099 - http://jnm.snmjournals.org/content/62/8/1068.short 4100 - http://jnm.snmjournals.org/content/62/8/1068.full SO - J Nucl Med2021 Aug 01; 62 AB - In diffuse large B-cell lymphoma, early assessment of treatment response by 18F-FDG PET may trigger treatment modification. Reliable identification of good and poor responders is important. We compared 3 competing methods of interim PET evaluation. Methods: Images from 449 patients participating in the “PET-Guided Therapy of Aggressive Non-Hodgkin Lymphomas” trial were reanalyzed by applying the visual Deauville score and the SUV-based qPET (q = quantitative) and ΔSUVmax scales to interim PET scans performed after 2 cycles of chemotherapy. qPET relates residual lymphoma 18F-FDG uptake to physiologic liver uptake, converting the ordinal Deauville scale into a continuous scale and permitting a direct comparison with the continuous ΔSUVmax scale, which is based on SUVmax changes between baseline and interim scans. Positive and negative predictive values were calculated for progression-free survival. Results: When established thresholds were used to distinguish between good and poor responders (visual Deauville score 1–3 vs. 4–5; ΔSUVmax > 66% vs. ≤ 66%), the positive predictive value was significantly lower with Deauville than ΔSUVmax (38.4% vs. 56.6%; P = 0.03). qPET and ΔSUVmax were strongly correlated on the log scale (Pearson r = 0.75). When plotted along corresponding percentiles, the positive predictive value curves for qPET and ΔSUVmax were superimposable, with low values up to the 85th percentile and a steep rise thereafter. The recommended threshold of 66% SUVmax reduction for the identification of poor responders was equivalent to qPET = 2.26, corresponding to score 5 on the visual Deauville scale. The negative predictive value curves were also superimposable but remained flat between 80% and 70%. Conclusion: Continuous scales are better suited for interim PET–based outcome prediction than the ordinal Deauville scale. qPET and ΔSUVmax essentially carry the same information. The proportion of poor-risk patients identified is less than 15%.