Analysis of Metabolic Parameters Coming from Basal and Interim PET in Hodgkin Lymphoma

Objective: Positron Emission Tomography (PET) with F-18-Fluoro-deoxy-glucose (FDG) emerged as a prognostic tool to predict treatment outcome in Hodgkin Lymphoma (HL). Moreover, a FDG-PET adapted strategy is currently assessed in clinical trial to minimize the toxic effect while maintaining the efficacy of treatment in HL. Purpose was to analyze the quantitative parameters to support the prognostic role of FDG-PET today based on the semi-quantitative Deauville 5-point Scale (D5-PS). Methods: This retrospective study included 53 patients diagnosed with advanced-stage HL between 2009 and 2014, enrolled in the PET response-adapted clinical trial HD 0607. FDG-PET was performed at baseline (PET0) and after two cycles of chemotherapy (PET2). Analysis was based on two main approaches: on the single lesion presenting the higher FDG uptake and on the five hottest lesions. Different metabolic parameters were analyzed. Patients were classified into responders and non-responders. Optimal cut-offs were derived from Receiver Operating Characteristic (ROC) curves. Results were correlated with Progression Free Survival (PFS) using Kaplan-Meier. Results: A 71% threshold in SUVmax reduction (Delta SUVmax) was found to be the best cutoff quantitative parameter able to identify responders vs. non-responders, also with a multivariate analysis, joining clinical data with SUVmax. After a mean follow-up of 34.2 months (95% CI, 26.2 to 39.1), the median PFS for non-responders was 8 months vs. not reached for responders. These results were superimposable to that obtained by an independent group of reviewers using the D5-PS. Conclusion: Semi-quantitative analysis by Delta SUVmax outperforms qualitative assessment by D5-PS in predicting treatment outcome in ABVD-treated advanced-stage HL.