Prognostic Value of Interim PET/CT in Patients with Poor Risk Diffuse Large B-Cell Lymphoma (DLBCL). Experience of the Spanish Geltamo Group

Interim FDG-PET appears to be useful to guide risk stratification of patients with DLBCL, but remains controversial because the absence of consensus criteria for assessment. The reduction of maximum Standardized Uptake Value (SUVmax) between baseline and interim PET improves the accuracy and reproductibility of this method (Casasnovas, Blood 2011).

A prospective non randomized phase II trial (EudraCT:2006-005254-68) was undertaken in young patients (pts) newly diagnosed of poor risk DLBCL. Therapy was changed after 3 cycles of R- MegaCHOP based on PET (using local assesment and visual scale); pts with positive PET received early salvage therapy. Primary end points were Progression free survival (PFS) and Overalll survival (OS). Retrospectively, central review was done by three experts using visual assessment (Deauville criteria) and semiquantitative asessment. Baseline and interim SUVmax, and ΔSUVmax were evaluated (cutt off ΔSUVmax: 66%). Significance of PET parameters in OS was analyzed.

71 pts were enrolled and central review was possible in 50 pts, from which 80% have complete follow up (mean 37, 6 months, 3. 4–56. 4). OS was significantly influenced by interim PET result, using visual (p=0. 046) but mainly by semiquantitative analysis (p=0. 0008). ΔSUVmax had impact on the overall survival (p=0. 007) whereas basal SUVmax did not.

Our preliminary results show that outcome of DLBCL pts with a positive interim PET is worse despite change of therapy. Semiquantitative PET evaluation seems to be necessary, being ΔSUVmax a good prognostic parameter.

No relevant conflicts of interest to declare.