Prognostic Significance of Interim 18f-FDG PET/CT for the Treatment of Diffuse Large B-Cell Lymphoma In the Post-Rituximab Era.

Abstract 1799 18F-fluoro-2-dexoy-D-glucose-positron emission tomography (FDG-PET)/computerized tomography (CT) has been used for staging and monitoring responses to treatment in patients with diffuse large B cell lymphoma (DLBCL). The sequential interim PET/CT was prospectively investigated to determine whether it provided additional prognostic information and could be a positive predictable value within patients with the same international prognostic index (IPI) after the use of rituximab in DLBCL. Patients and methods: One hundred and sixty-one patients with newly diagnosed DLBCL were enrolled between August 2004 and December 2009 at a single institution. The assessment of the PET/CT was performed at the time of diagnosis and mid-treatment of R-CHOP chemotherapy. The clinical stage and response of the patients were assessed according to revised response criteria for aggressive lymphomas (Cheson, J Clin Oncol, 2007). The positivity of interim PET/CT was determined based on the semi-quantitative assessment of the maximal standardized uptake value (SUVmax cut-off value of 3.0). Results: Sixty-seven patients (41.6%) presented in advanced stage disease and 27 (16.8%) had bulky lesions. At diagnosis, 53 patients (32.9%) were classified as high/high-intermediate risk by the IPI and two patients could not check the interim response due to treatment-related mortality (TRM). Forty-three patients (26.7%) continued to have positive metabolic uptakes with a significantly high relapse rate (62.8%) compared to the patients with a negative interim PET/CT (12.1%) (P<0.01). After a median follow-up of 30.8 months, the positivity of interim PET/CT was found to be a prognostic factor for both OS and PFS, with a hazard ratio of 4.07 (2.62 – 6.32) and 5.46 (3.49 – 8.52), respectively. In the low-risk IPI group, the 3-year OS and PFS rate was significantly different in the patients with positive (53.3 and 52.5%) and negative (93.8 and 88.3%) interim PET/CT, respectively (P<0.01). These significant prognostic differences of interim PET/CT responses were consistent with the results of the patients with high-risk IPI group (P< 0.01). Conclusions: Interim PET/CT scanning had a significant predictive value for disease progression and survival of DLBCL in post-rituximab treatment; it might be the single most important determinant of clinical outcome in patients with the same IPI risk. Disclosures: No relevant conflicts of interest to declare.