Assessment of FDG-PET Imaging in T-Cell and NK-Cell Lymphomas

Abstract

BACKGROUND: Malignant T-cell lymphomas are a heterogeneous group of disorders that frequently involve extranodal regions. Treatment and prognosis depend on accurate staging and histological evaluation. PET is widely used in staging and response evaluation of B-cell lymphomas, however, the use of FDG-PET have not been well studied for T-cell and natural killer cell lymphomas, and there is controversy if PET can detect accurately extranodal tumor activity.PATIENTS AND METHODS: We retrospectively evaluated FDG-PET in 38 patients with active T-cells, and T/NK-cells lymphoma diagnosed according to the World Health Organization (WHO) classification, from May 2007 to May 2008. We also evaluated the Standard Uptake values (SUV) according the different subtypes and the accuracy of PET in detecting tumor activity in the skin and nasal region.RESULTS: Histological subtypes included were extranodal NK/T-cell lymphoma nasal type (ENKL, n=12); Anaplastic T-cell lymphoma (ATCL, n=11); peripheral T-cell lymphoma (PTL, n=7); mycosis fungoides and Sezary syndrome (MF/SS, n=5), angioimmunoblastic (An=3). FDG-PET detected a lymphoma lesion in at least one site in 35 out of 38 patients (91%). The positivity rate was high in all histological subtypes ENKL 92%, ATCL 100%, PTL 86%, MF/SS 80%, A 100%. Among 13 patients who had cutaneous lesions only 7 had FDG-avid skin lesions (sensitivity =53.8% and specificity=100%) and among 11 patients with nasal region lesions, 91% had FDG-avid cutaneous lesions (sensibility = 91%, specificity=100%). The SUV Value in the different subtypes is shown in the table and there was not statistical differences between the groups (p= 0.067)LymphomaNMeanSD(+/−)RangeAn34.11.72.7–6MF/SS54.23.01.9–8.6ATCL118.35.31.6–20.8PTL73.51.62.2–6.0ENKL127.24.12.2–13.8Total386.354.31.6–20.8CONCLUSIONS: Most of the T and T/NK cell lymphomas were detected by FDGPET. All cases, except one, of ENKL nasal type were FDG-avid, but only half of cutaneous lesions were detected by PET. In the whole T-Cell lymphomas group the mean SUV was 6.35, ATCL had the highest SUV, and we did not find any statistically differences between the groups. We conclude that PET has a high sensitivity for detection of active ENNK nasal type lymphomas and this information should be the basis for designing further studies to assess its value in staging, tumor response and as a prognostic factor.