International Metabolic Prognostic Index Is Superior to Other Metabolic Tumor Volume-Based Prognostication Methods in a Real-Life Cohort of Diffuse Large B-Cell Lymphoma

Baseline metabolic tumor volume (MTV) is a promising prognostic marker in diffuse large B-cell lymphoma (DLBCL). We assessed the prognostic value of 4 novel metabolic risk scores in a real-life DLBCL cohort and compared them with the revised International Prognostic Index (IPI). Methods: We included a consecutive series of untreated DLBCL, not otherwise specified cases that were diagnosed in our hospital from 2008 to 2021 with available baseline [¹⁸F]FDG PET/CT. Clinical data were collected retrospectively, including the individual components of the revised IPI. MTV and other radiomic features, including lesion dissemination and tumor volume surface ratio, were calculated. Four novel metabolic risk scores including the international metabolic prognostic index (IMPI), the MTV/World Health Organization performance status, the MTV/standardized maximum distance, and clinical PET models were used to calculate the risk of progression using predefined cutoffs. Survival outcomes considered were 3-y progression free survival (PFS), 3-y time to progression (TTP), and 3-y overall survival (OS). The Harrell C-index was used to assess the discriminative performance of the risk scores. A multivariable model was built. Results: We included 355 DLBCL, not otherwise specified cases with a median MTV of 219 cm³ (range, 0-5,656 cm³). The IMPI had the highest C-index for 3-y PFS, 3-y TTP, and 3-y OS among the 4 metabolic risk scores (0.674, 0.696, and 0.677, respectively). For the 3-y TTP, the IMPI outperformed the strongest clinical risk score, the IPI, although the difference in the Harrell C-indices was small (0.696 vs. 0.693). Regarding the 3-y PFS and 3-y OS, the IPI has the highest C-index of all risk scores (0.696 and 0.693). The IMPI, the MTV/World Health Organization performance status, and the IPI score can recognize a poor risk group with a 3-y OS below 50% (43%, 32%, and 39%, respectively). In multivariable analysis, the IMPI remains an independent prognostic factor (P = 0.0089; hazard ratio, 1.207; 95% CI, 1.048-1.389). MTV and standardized maximum distance have the strongest prognostic values when used as a continuous variable. The tumor volume surface ratio has no significant prognostic value in our analysis. Conclusion: The IMPI has the strongest prognostic performance compared with the other 3 novel metabolic risk scores. However, in our real-world dataset, the IMPI could not replace the IPI, and further prospective trials are needed to compare their performance.