Prognostic significance of volumetric parameters of FDG PET/CT in patients with malignant lymphoma.

Objectives To investigate the feasibility of measuring metabolic tumor burden using FDG-PET/CT in patients with relapsed or refractory malignant lymphoma treated with bendamustine-rituximab.

Methods Fifty-five patients with relapsed or refractory malignant lymphoma were enrolled. FDG PET/CT was acquired before treatment, after 2 cycles, and after the last treatment cycle. Maximum standardized uptake value (SUVmax), SUV corrected for lean body mass (SUL), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were measured for the lesion with the greatest amount of FDG uptake. The sums of MTV (ΣMTV) and TLG (ΣTLG) for a maximum of 6 target lesions per patient were also calculated. Evaluation of the metabolic response was accomplished by comparing the changes from baseline in △SUV, △SUL, △MTV, △ΣMTV, △TLG, and △ΣTLG. Treatment response was assessed using the Lugano classification.

Results The mean PET/CT parameters after 2 cycles of treatment were significantly lower in CR patients than in non-CR patients (p<0.01). The percent change in all PET/CT parameters was significantly greater in complete response (CR) patients than in non-CR patients after 2 cycles and the last cycle. The percent change of △ΣTLG after the last cycle was independent predictor of progression-free survival (relative risk, 5.24; p=0.003).

Conclusions ΔΣTLG calculated from FDG-PET/CT can be used to quantify the response to treatment and can predict progression-free survival after the last treatment cycle in patients with relapsed or refractory malignant lymphoma treated with bendamustine-rituximab.