Prognostic value of pretherapy metabolic tumor volume (MTV) and total lesion glycolysis (TLG) in patients with diffuse large B-cell lymphoma (DLBCL)

Objectives To investigate whether MTV and TLG, as measures of metabolic tumor burden, may have a prognostic value in patients with DLBCL.

Methods MTV and TLG were measured in 120 patients with newly-diagnosed DLBCL, who underwent FDG PET/CT at baseline and after 2 cycles of a rituximab-containing regimen, with no therapy change based on the latter. For each scan, MTV was computed by summing the volumes of all lymphoma lesions after thresholding at 41% of the SUVmax using a semi-automatic software. TLG was computed by summing the volume×SUVmean products. Prognostic value of interim FDG PET/CT was assessed by Kaplan-Meier estimates of event-free survival (EFS) and overall survival (OS).

Results Median follow-up was 39.8 months. Pretherapy MTV and TLG averaged 499±570 mL and 4160±4382 mL, respectively. Interestingly, 2-y EFS was significantly higher in pts with MTV<550mL than in pts with MTV>550 mL (79% vs. 53%, P=0.009), and prediction of 2-y OS was even better (93% vs. 64%, P<0.0001), while TLG was not predictive of outcome. Cox proportional-hazard regressions showed independency of MTV and ΔSUVmax (cutoff 66%), P=0.01 and P=0.0002 for EFS prediction, respectively, and P=0.0001 for each variable for OS prediction. Combination of MTV and ΔSUVmax allowed identification of 3 outcome profiles: 2-y OS was 96% in pts with both MTV<550mL and ΔSUVmax>66% (n=68), 83% in pts with discordant MTV and ΔSUVmax (n=42), and 15% in pts with both MTV>550 mL and ΔSUVmax<66% (n=10, P<0.0001).

Conclusions MTV is highly predictive of OS before initiation of therapy and, combined with interim FDG PET/CT response, allows identification of very good and very poor prognosis patients in 2/3 of cases