Utility of PET-CT for Evaluation of Patients With Peripheral T-cell Lymphoma

Background: Fluorine-18 fluorodeoxyglucose (FDG) avidity varies in peripheral T-cell lymphoma (PTCL). We evaluated FDG avidity of pretreatment positron emission tomography/computed tomography (P-PET/CT), to appraise the prognostic significance of interim PET/CT (I-PET/CT) and end of treatment PET/CT (E-PET/CT) in PTCL.

Patients and methods: We performed a retrospective cohort study of patients with newly diagnosed or relapsed PTCL who had received any chemotherapy regimen from 2008 to 2015 in a tertiary center. P-PET/CT, I-PET/CT, and E-PET/CT studies were centrally reviewed. The primary outcomes were the prognostic role of I-PET/CT and E-PET/CT on progression-free survival (PFS) and overall survival (OS). The secondary outcomes were P-PET/CT avidity, the prognostic role of other baseline characteristics, and the correlation between the PET/CT and bone marrow biopsy findings.

Results: We included 40 patients in the present analysis. The median OS and PFS for the whole cohort was 39 and 16 months, respectively. Of the 40 patients, 36 had positive P-PET/CT findings. A total of 23 patients underwent I-PET/CT, with positive findings for 10. Of the 40 patients, 34 underwent E-PET/CT, 26 of which had positive findings. The sensitivity, specificity, and negative predictive value of P-PET/CT for bone marrow involvement was 40%, 83%, and 89%, respectively. The factors significantly associated with PFS and OS on univariate analysis included elevated lactate dehydrogenase, and low lymphocyte, hemoglobin, and albumin levels. On multivariate analysis, only lymphopenia remained prognostic for PFS and OS. The E-PET/CT and I-PET/CT results were not prognostic for PFS or OS.

Conclusion: Our study has shown that 90% of PTCL cases will be FDG avid. However, PET/CT was not predictive for PFS or OS at any point. The only predictive factor was the presence of lymphopenia.