Senjo H, et al. - In 64 patients with diffuse large B-cell lymphoma (DLBCL), the correlation between the serum levels of soluble interleukin-2 receptor (sIL-2R) and total metabolic tumor volume (TMTV) was assessed, with a goal to explore a surrogate marker for TMTV. For verification, an independent cohort of 86 patients was used. Findings revealed a significant correlation between serum levels of sIL-2R and TMTV. In receiver operating curve (ROC) analysis, failure to achieve 2-year event-free survival (EFS) [EFS24] could be predicted by TMTV ≥150 cm³ or sIL-2R ≥ 1300 U/mL with areas under the curve (AUC) 0.706 and 0.758, respectively. Worse 5-year overall survival and event-free survival were reported in significant relation to each of TMTV ≥150 cm³ and sIL-2R ≥1300 U/mL. Among NCCN-IPI (National Comprehensive Cancer Network-International Prognostic Index) high-intermediate and high-risk group, those with favorable prognosis could be detected by each of sIL-2R <1300 U/mL or TMTV <150 cm³. Overall, metabolic tumor burden measured by ¹⁸F-FDG PET/CT can be conveniently assessed by a surrogate marker, serum level of sIL-2R, that can predict treatment outcomes of patients with DLBCL.