Comparison between LUGANO, EORTC, PERCIST and IHP criteria at interim PET in patients with Follicular B-cell Non-Hodgkin’s Lymphoma

650 Objectives FDG PET/CT has become a standard clinical tool for response assessment in aggressive lymphoma. However the best interpretation criteria are still under exploration. The aim of this preliminary study is to compare different PET interpretation criteria at interim therapy (i-PET) to find out which criteria would be the best predictor of clinical response. Methods This study is part of an Eastern Cooperative Oncology Group (ECOG) randomized phase II multicenter trial, comparing bendamustine hydrochloride and rituximab together with or without bortezomib followed by rituximab with or without lenalidomide to see how well they work in treating patients with high-risk stage II, stage III, or stage IV follicular lymphoma (ECOG protocol E2408). The trial enrolled 250 patients with a histologically confirmed diagnosis of follicular non-Hodgkin lymphoma. Among these 250, 90 patients were included in our preliminary analysis. All patients performed at least two 18F-FDG PET/CT scans: at diagnosis (baseline PET) and after 3 cycles of chemotherapy (i-PET). Response evaluation at i-PET was retrospectively performed according to LUGANO criteria, EORTC (European Organization for Research and Treatment of Cancer), PERCIST (PET Response Criteria in Solid Tumors) and IHP (International Harmonization Project), classifying the patients into 4 categories: complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease (PMD). All criteria were correlated to the best-observed response after 6 cycles of chemotherapy (referred to as “step 1” or end of initial round of treatment). Results LUGANO, EORTC and IHP criteria were registered in 90 patients while PERCIST criteria was recorded in 81 patients. For the first group of 90 patients, the best observed response was CMR for 67/90 patients (74.5%), PMR for 19/90 (21.1%), SMD for 2/90 (2.2%) and PMD for 2/90 (2.2%). For the second group of 81 patients, the best observed response was CMR for 62/81 (76.5%), PMR for 17/81 (21%), SMD for 0% and PMD for 2/81 (2.5%). According to the LUGANO criteria, the rate of CMR at i-PET was 92,5% (62/67), for EORTC and IHP was 89.5 (60/67). For all these three criteria the rate of PMR was 21% (4/19), the rate of SMD and PMD was 50% (1/2). For PERCIST criteria CMR rate at i-PET was 90.3% (56/62), PMR 17.7% (3/17), SMD 0% and PMD 50% (1/2). The overall response rate (defined by i-PET indicating at least stable disease or better) for LUGANO and IHP was 96.5%, for EORTC was 95.3% and for PERCIST was 93.7%; all criteria gave the same percentage of subjects with progressive disease. The rate of SMD was higher with LUGANO, EORTC and IHP criteria; however, the difference between them and PERCIST criteria was not significant. The strongest correlation (~ 90% or higher) for all criteria was found between CMR and the best-observed response at step 1. Conclusions Our preliminary study demonstrated a strong correlation between interim-PET CMR assessed with all the criteria and treatment response after 6 cycles of chemotherapy. All criteria correlate similarly to the observed response. We are still collecting data and the enrollment of the other ECOG patients will be used to confirm these data. Another future research direction of our study is to correlate the tumor metabolic burden with outcome, to potentially make lymphoma staging and prognostication more accurate and quantitative, with the goal of optimizing and personalize treatment choices.