FDG-Positron Emission Tomography in T-Cell Lymphoma

Few data are available on the role of fluoro-deoxy-glucose positron emission tomography (FDG-PET) in T-cell non Hodgkin Lymphoma (NHL). We compared standard contrast-enhanced computerized tomography (CECT) and FDG-PET for initial staging and restaging after treatment in T-cell NHL.

We reviewed 58 FDG-PET scans performed in 29 patients (pts) affected by T-cell NHL and we focused on the 42 cases for which a simultaneous standard CECT was available for comparison. The specific T-cell histology was Peripheral T-Cell Lymphoma Not Otherwise Specified in 12 pts, Angioimmunoblastic T-Cell Lymphoma in 4 pts, Anaplastic Large Cell Lymphoma in 10 pts, other T-NHL hystologies in 3 pts. Twelve pts were males and median age at diagnosis was 57 years (range: 25–77). Baseline FDG-PET scans were 20, while FDG-PET performed for disease reassessment were 22.

FDG-PET performed at baseline was positive in all cases. In 6 cases (30%) FDG-PET identified fewer disease sites than CECT, while in 14 cases (70%) FDG-PET identified additional disease sites. New sites identified by FDG-PET were: other nodal sites (11 pts), spleen (2 pts), nasopharynx (1 pt) and testicles (1 pt). Different disease extent evaluation according to FDG-PET modified clinical stage in 10 pts (50%): one pt was downstaged and 9 pts were upstaged. FDG-PET-based stage was not considered for therapeutic decision. FDG-PET scans performed at restaging were negative in 16 cases (72%) and positive in the remaining 6 cases (28%). In 13/16 (81%) negative cases CECT was concordant and showed a complete remission, while in the remaining 3 cases CECT showed a residual nodal disease. In the 6 FDG-PET positive cases, CECT was as follows: abnormal in the same site of FDG-PET in 1 case, abnormal in fewer sites than FDG-PET in 3 cases and abnormal in more sites than FDG-PET in 2 cases. With a median follow-up of 32 months, the median overall survival (OS) of the 6 positive FDG-PET cases at restaging was 26 months. With a median follow-up of 23 months, the median OS of the 16 negative FDG-PET cases at restaging was not reached.

FDG-PET can be useful in the initial staging of T-cell NHL, since it can allow a more accurate disease extension evaluation: in our experience it could identify additional sites, both nodal and extra-nodal, in 70% of pts. A change in clinical stage according to FDG-PET was observed in 50% of cases, with an upstaging in the majority of pts. We could confirm the high sensitivity of baseline FDG-PET in T-cell NHL. A high level of concordance was observed between PET and CECT at restaging. However, independently on CECT result, the worse OS of FDG-PET positive cases confirms the role of FDG-PET as prognostic factor for survival. Larger prospective trials are needed to confirm the utility of FDG-PET in baseline staging, reassessment after chemotherapy and treatment planning.

No relevant conflicts of interest to declare.