Metabolic tumor volume and total lesion glycolysis for predicting prognosis in diffuse large B-cell lymphoma: a retrospective PET/CT study.

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is characterized by marked clinical heterogeneity, and conventional prognostic indices provide limited individualized risk prediction. We investigated the prognostic value of baseline 18F-FDG PET/CT-derived volumetric metabolic parameters in newly diagnosed DLBCL.

METHODS

This retrospective study included 176 consecutive patients with histologically confirmed DLBCL who underwent baseline 18F-FDG PET/CT before first-line R-CHOP or R-CHOP-like immunochemotherapy between January 2022 and December 2024. Metabolic tumor volume (MTV) was measured using a 41% SUVmax threshold, and total lesion glycolysis (TLG) was calculated as MTV × SUVmean. Optimal cutoff values were determined by ROC analysis. Survival outcomes were evaluated using Kaplan-Meier analysis and Cox proportional hazards models. Predictive performance was assessed by Harrell's C-index.

RESULTS

The median age was 58 years, and 54.5% of patients were male. After a median follow-up of 26.4 months, 48 patients experienced progression; including 5 deaths without documented progression, the composite progression-free survival (PFS) endpoint comprised 53 events, and 30 patients died. The optimal cutoffs were 274.8 cm³ for MTV and 1,886.3 g for TLG. High MTV was associated with significantly inferior 2-year PFS (50.7% vs 79.9%; P<0.001) and OS (71.3% vs 92.8%; P<0.001). In multivariable analysis, high MTV remained the only significant independent predictor of PFS (HR 3.16, 95% CI 1.82-5.50; P<0.001). Incorporating MTV into the IPI improved discrimination compared with IPI alone (C-index 0.697 vs 0.567).

CONCLUSIONS

In this single-center cohort, baseline MTV was a robust independent prognostic biomarker for PFS that substantially enhanced risk stratification beyond the IPI; its association with OS was exploratory given the limited number of events. Integration of volumetric PET/CT metrics into prognostic models may facilitate more individualized therapeutic decision-making. The optimism-prone, internally derived cutoff requires external validation; prospective, multicenter validation with standardized measurement protocols is warranted.