Mid-Treatment 18-FDG-Positron Emission Tomography/Computed Tomography (PET) Does Not Impact the Outcome in Patients with Aggressive Non Hodgkin Lymphoma (NHL)

Introduction and aim of the study. PET is used in staging and restaging of aggressive NHL patients at diagnosis and at the end of treatment. Early evaluation of PET after few courses of chemotherapy was reported to predict final response, progression-free survival (PFS) and overall survival (OS) in Hodgkin’s lymphoma patients, whereas contradictory data were shown in aggressive lymphomas. The aim of our study was to evaluate mid-treatment PET (PET-2) results in aggressive NHL.

Patients and methods. From April 2004 to December 2007, 42 consecutive aggressive NHL patients were referred to our Hematology Department and enrolled into the study. Clinical characteristics were as follows: 29 males and 13 females; median age of 53 years (25–73); 34 diffuse large B cell, 5 mantle cell, 2 anaplastic and 1 follicular grade III NHL; 37 stage III–IV; according to International Prognostic Index (IPI) 1 patient was at low-intermediate risk, 21 at intermediate-high and 20 at high risk. Treatment plans were: Rituximab-CHOP-like chemotherapy (R-CHOP) for 6–8 courses in 18 patients and R-CHOP for 4 courses followed by high-dose chemotherapy with autologous stem cell transplantation (HDC+ASCT) in 24 patients respectively. All pts were evaluated according to standard imaging procedures completed by PET at diagnosis and at the end of the treatment. During treatment, PET-2 scan was performed after 2 or 4 courses of R-CHOP in 24 and 18 patients respectively.

Results. Complete response at the end of treatment was achieved in 33 patients and partial remission in 1; in 8 patients progression disease was detected. With a median follow-up of 22 months, 2-yr PFS and 2-yr OS rates were: 72% and 80% respectively. PET-2 was negative in 30 patients and positive in 12. Two-year PFS and 2-yr OS rates were not different between PET-2 negative and PET-2 positive patients: 71% vs 75% (p=.98) and 82% vs 74% (p=.29) respectively. Final PET scan was negative in 33 patients and positive in 9. The final PET assessment was highly predictive for 2-yr PFS: PET negative 86% vs PET positive 22% (p=.000). Also the 2-yr OS was influenced by final PET: 96% vs 26% in PET negative and PET positive patients respectively (p=.000). In univariate analysis the only parameter that influenced the outcome was the final PET; conversely, IPI, sex, histology, time of PET-2 evaluation, plan of therapy had not a statistically significative impact.

Conclusions. The PET is an important imagine technique for staging and end-treatment evaluation in lymphoma disease, because it can better define CR patients. In contrast to Hodgkin disease, our data suggest that the on-course evaluation of response by PET has not predictive value of response assessment: patients, even if positive at PET-2 analysis, can achieve a continuous CR at the end of therapy. More large studies are need to determine the real impact of on-course PET as response assessment in aggressive NHL patients.