Achievement of FDG-PET Negativity Does Not Predict Durable Responses in T-Cell Lymphoma.

Background: T-cell non-Hodgkin’s lymphomas represent approximately 12% of all lymphomas and in general are associated with a worse prognosis compared to their B-cell counterparts. In patients with Hodgkin’s disease and aggressive B-cell lymphoma (¹⁸F)fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) represents an important early prognostic tool for predicting outcome. Very little information is available regarding the role of FDG-PET in T-cell lymphoma.

Patients and Methods: A total of 20 patients with newly diagnosed and histologically proven T/NK cell lymphomas where staged with both conventional methods and whole-body PET scanning. Patients underwent FDG-PET, concurrently with CT of neck, chest, abdomen, and pelvis within 3 weeks prior to induction treatment, after 2–4 cycles, and after the end of induction. All patients but three received HCVIDDoxil, using pegylated liposomal doxorubicin as a substitute for doxorubicin in the HyerCVAD regimen, alternating with methotrexate and cytarabine. Three patients received the standard CHOP (cyclophosphamide,hydroxydaunomycin, vincristine, prednisone) regimen. According to the International Prognostic Index (IPI), 35% of patients were stratified as low risk, 25% as low/intermediate, 35% as high/intermediate, and 5% as high risk. Baseline scans were strongly positive in all patients.

Results: During induction therapy (at 2–4 cycles) FDG-PET became negative in 16 (80%) patients and remained positive in 4 (20%) patients. Twelve out of 16 (75%) patients who were PET negative during induction therapy relapsed, and four out of four (100%) in the PET positive group. Two of the “ early” PET negative patients became positive after 4 cycles. Median progression-free survival was 240 days in the PET negative group and 85 days in the PET positive group (Log-rank p=0.07).

Conclusions: In this limited number of patients homogeneously treated with newly diagnosed T cell lymphomas the assessment of metabolic activity by FDG-PET during induction therapy did not predict long-term prognosis.