FDG PET/CT As a Diagnostic and Prognostic Tool for the Evaluation of Patients with Peripheral T-Cell Lymphoma

Abstract

Background and aims: Positron emission tomography (PET) using 18F fluorodeoxyglucose (FDG) with computed tomography (CT) is increasingly used for staging and treatment evaluation of lymphomas, especially in known avid-FDG lymphomas as diffuse large B cell lymphoma and Hodgkin lymphoma. In peripheral T cell lymphoma (PTCL), FDG avidity is variable. The purpose of this study is to evaluate FDG-avidity in PTCL and to appraise the prognostic significance of baseline and interim PET/CT in this sub-group of lymphomas. Methods: A retrospective cohort study of patients with newly diagnosed or relapsed PTCL, treated with any chemotherapy regimen between 2008 and 2015 in a single tertiary center. Patients who did not have pre-treatment PET/CT (P-PET/CT) were excluded. Patients were identified through the computerized system. Demographic, clinical and laboratory data were collected from patients' files until the latest follow-up available and for at least 6 months after completion of chemotherapy administeration. P-PET/CT, interim (I-PET/CT) and end-of-treatment (E-PET/CT) studies were centrally reviewed and reported using 3 methods of evaluation: visual assessment, maximal SUV reported and Deauville 5-point score (DS) evaluation. DS of 3 and above was considered positive. PET/CT was interpreted as positive if any of the three evaluation methods was positive. The primary outcome was the avidity of P-PET/CT in PTCL. Secondary outcomes included the prognostic role of P-PET/CT, I-PET/CT and E-PET/CT on progression free survival (PFS). Survival curves were calculated by SPSS software and Kaplan-Meier plot. Baseline characteristics were analyzed in a cox regression model: including data regarding P-PET/CT, I-PET/CT and E- PET/CT. Results: Data of 60 patients with PTCL was collected. 20 patients were excluded due to absence of P-PET/CT. Thus, 40 patients (38 with newly diagnosed disease) were included in this analysis. The most frequent histological diagnoses were PTCL-N0S and anaplastic large cell lymphoma-ALK negative (ALCL-ALK negative). Median age was 54 years. 17/40 (42.5%) patients did not have co-morbidities, 9/40 (22.5%) had another malignancy. The rest of the patients had other co-morbidities including diabetes mellitus, congestive heart failure and other cardiovascular risk factors. Patient characteristics are detailed in table 1. The median follow-up was 31 months (23-40). The median overall survival and the PFS for the whole cohort were 39 months (27-51) and 16 months (7-24), respectively. 36/40 (90%) patients had positive P-PET/CT. 23 patients had I-PET/CT, all of them with newly diagnosed disease: 10 studies were positive and 13- negative. 34/40 patients had E-PET/CT, 26 studies of them were positive and 8 - negative. Factors significantly associated with PFS on univariate analysis were: elevated lactate dehydrogenase (LDH), lymphopenia, low hemoglobin and albumin levels. In multivariate analysis, the only factor that remained prognostic for PFS was lymphopenia. P-PET/CT and I-PET/CT were not prognostic with respect to PFS. Conclusions: Our study shows that 90% of PTCL are FDG avid, as one would expect with aggressive lymphoma. Yet, neither PET was not predictive for PFS at any time point. The only predictive factor was lymphopenia. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.