Parameters On Interim F-18-Fdg Pet Are Strong Predictors Of Survival, Independent Of Clinical Prognostic Indexes And Biological Markers, In Patients With Diffuse Large B Cell Lymphoma

176 Aim: The prognostic value of interim 18F-FDG PET (iPET) in diffuse large B cell lymphoma (DLBCL) remains unclear. The optimal timing and PET parameters of SUVmax, Deauville score, and total metabolic tumour volume (TMTV) have not been established.1-4 The aim is to explore which PET parameter on iPET is the best predictor of survival outcomes compared to the accepted clinicopathological prognostic scores.\n Methods: In this retrospective study, all de novo DLBCL cases since 2012 treated with R-CHOP and staged with a baseline PET, with at least one iPET and 12 months of follow-up were included. Baseline PET scans were assessed for TMTV. iPET parameters assessed were Deauville scores (1-3 vs. 4-5) and reduction in SUVmax from baseline PET (iPET2 ΔSUVmax \u003e66% vs. ≤66% and iPET4 ΔSUVmax \u003e73% vs. ≤73%).1-3 Response criteria were assigned using Lugano 2014 criteria.Clinicopathological data including NCCN-IPI, IHC expression of MYC/BCL2 (DE) and cell-of-origin (COO) by Hans algorithm was also collected. Cox regression analysis was used to determine factors associated with a poor prognosis.\n Results: 152 patients were included for analysis, who had 196 iPET scans (140 iPET2 and 56 iPET4). Median follow up duration was 30.4 months. Estimated 2-year PFS and OS for the whole cohort were 67.1% and 82.5% respectively. At baseline, NCCN-IPI ≥ 4 and TMTV ≥ 298ml (cohort’s median) but not DE or COO, were prognostically significant on univariate analysis for PFS and OS. In contrast, both Deauville scores ≥ 4 and lower ΔSUVmax at iPET2 and iPET4 were prognostically significant. Patients with residual disease on iPET2 who subsequently achieved complete remission (CR) on iPET4 (n=10) had an estimated 2-year PFS of 100%. Those patients failing to achieve CR by iPET4 (n=29) had 2 year PFS and OS of 41.9% and 52.2% respectively. Baseline TMTV ≥ 298ml and iPET4 ΔSUVmax \u003c73% were independent prognostic factors on multivariate analysis for PFS and OS (p-value \u003c0.05 for both PFS and OS).\n Conclusions: ΔSUVmax at iPET4 was independently prognostic for both PFS and OS in DLBCL treated with RCHOP. Patients with residual disease at iPET2 who subsequently achieve CR by iPET4 have excellent outcomes.\nReferences: 1. Duhrsen U, Muller S, Hertenstein B, Thomssen H, Kotzerke J, Mesters R et al. Positron Emission Tomography-Guided Therapy of Aggressive Non-Hodgkin Lymphomas (PETAL): A Multicenter, Randomized Phase III Trial. Journal of Clinical Oncology. 2018;36(20):2024-2034. 2. Lin C, Itti E, Haioun C, Petegnief Y, Luciani A, Dupuis J et al. Early 18F-FDG PET for Prediction of Prognosis in Patients with Diffuse Large B-Cell Lymphoma: SUV-Based Assessment Versus Visual Analysis. Journal of Nuclear Medicine. 2007;48(10):1626-1632. 3. Itti E, Lin C, Dupuis J, Paone G, Capacchione D, Rahmouni A et al. Prognostic Value of Interim 18F-FDG PET in Patients with Diffuse Large B-Cell Lymphoma: SUV-Based Assessment at 4 Cycles of Chemotherapy. Journal of Nuclear Medicine. 2009;50(4):527-533.\n4. Pregno P, Chiappella A, Bello M, Botto B, Ferrero S, Franceschetti S et al. Interim 18-FDG-PET/CT failed to predict the outcome in diffuse large B-cell lymphoma patients treated at the diagnosis with rituximab-CHOP. Blood. 2012;119(9):2066-2073.