Prognostic Significance of Pretreatment <sup>18</sup>F-FDG PET/CT in Patients with Relapsed/Refractory B-Cell Non-Hodgkin's Lymphoma Treated by Radioimmunotherapy Using <sup>131</sup>I-Rituximab

Abstract

<b><i>Aims:</i></b> It was the aim of this paper to identify prognostic factors in patients with relapsed or refractory B-cell non-Hodgkin's lymphomas, treated by radioimmunotherapy (RIT) with radioiodinated human/murine chimeric anti-CD20 monoclonal antibody rituximab (<sup>131</sup>I-rituximab). <b><i>Methods:</i></b> Twenty-four patients were enrolled prospectively and were treated with unlabeled rituximab 70 mg and a therapeutic activity (median 7.3 GBq) of <sup>131</sup>I-rituximab. Contrast-enhanced <sup>18</sup>F-FDG PET/CT scans were performed before and after 1 month of RIT. Tumor sizes and maximum standardized uptake values (SUV<sub>max</sub>) of scans were measured. <b><i>Results:</i></b> Four of the 24 patients survived. High SUV<sub>max</sub> in a pretreatment scan was found to be related to poorer overall survival (OS) and progression-free survival (p = 0.04 and 0.02, respectively). Furthermore, a large tumor size in a pretreatment scan was associated with poorer OS but not with progression-free survival (p < 0.01 and p = 0.07, respectively). By multivariate analyses, a high SUV<sub>max</sub>, a large tumor size in a pretreatment scan and diffuse large B-cell lymphoma histology were significantly associated with poorer OS [p = 0.04/hazard ratio (HR) = 3.54, p < 0.01/HR = 5.52, and p = 0.02/HR = 3.38, respectively). <b><i>Conclusion: </i></b>SUV<sub>max</sub> and tumor size determined by a pretreatment <sup>18</sup>F-FDG PET/CT result as significant predictors of OS in patients with relapsed or refractory B-cell non-Hodgkin's lymphoma treated by RIT.