Objective To investigate the predictive value of quantitative parameters of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT in sarcopenia after treatment of diffuse large B-cell lymphoma (DLBCL) and analyze the relationship between sarcopenia and the prognosis of DLBCL.

Methods The clinical and imaging data of 91 DLBCL patients (36 males and 55 females, median age=60 years) confirmed by histopathological examination in Jining First People′s Hospital from November 2019 to August 2024 were retrospectively collected, including 25 patients with sarcopenia and 66 patients without sarcopenia before treatment. All patients underwent ¹⁸F-FDG PET/CT before and after treatment. Skeletal muscle area was measured at the level of the third lumbar vertebra (L3), and the skeletal muscle index (SMI) was calculated. Sarcopenia was diagnosed with SMI<44.77 cm²/m² in males and SMI<32.50 cm²/m² in females. The psoas maximum standardized uptake value (SUV_max) and mean CT value (CT_avg) were measured at the L3 level. The gender, age, abdominal lymph node involvement, and extranodal involvement, as well as the relationships among SUV_max, body mass index (BMI), muscle CT_avg, and sarcopenia before and after treatment, were analyzed. Comparison of measurement data between groups was made using Mann-Whitney U test. Comparison of counting data between groups was made using chi-square test. Univariate Logistic regression analysis was conducted to predict the influencing factors of sarcopenia after treatment. Multivariate Logistic regression analysis was used to screen out the independent influencing factors. The receiver operating characteristic (ROC) curve was used to evaluate the predictive efficacy of the independent influencing factors. The Kaplan-Meier method was used for survival analysis to evaluate the relationship between sarcopenia and progression-free survival (PFS) and overall survival (OS) before and after treatment, and Log-rank test was performed.

Results SUV_max (1.00(0.90, 1.10) vs. 1.10(1.00, 1.30), Z=−4.318, P<0.001) in patients with sarcopenia before treatment and SUV_max (0.90(0.80, 0.93) vs. 1.00(0.90, 1.20), Z=−3.197, P=0.001) in patients with sarcopenia after treatment were lower than those in patients without sarcopenia. Univariate Logistic regression analysis showed that muscle CT_avg (HR=1.203, 95%CI: 1.008–1.437, P=0.041), SUV_max (HR=0.001, 95%CI: 0.000–0.072, P=0.002), BMI (HR=0.739, 95%CI: 0.596–0.917, P=0.006), and extranodal involvement (HR=3.889, 95%CI: 1.196–12.644, P=0.024) before treatment were the influencing factors for the occurrence of sarcopenia after treatment. The results of multivariate Logistic regression analysis showed that SUV_max before treatment was an independent influencing factor for the occurrence of sarcopenia after treatment (HR=0.001, 95%CI: 0.000–0.200, P=0.011). The results of ROC curve analysis showed that SUV_max before treatment had a high predictive efficacy for the occurrence of sarcopenia after treatment, with an area under the curve of 0.796 (95%CI: 0.685–0.906) and an optimal cut-off value of 1.150. The results of Kaplan-Meier survival analysis showed that the OS of patients with sarcopenia before treatment was shorter than that of patients without sarcopenia (χ²=4.829, P=0.028), whereas no significant difference in PFS was observed between the two groups (χ²=1.122, P=0.289). The PFS of patients with sarcopenia after treatment was shorter than that of patients without sarcopenia (χ²=7.590, P=0.006), whereas no significant difference in OS was found between the two groups (χ²=0.242, P=0.623).

Conclusions SUV_max of psoas at the L3 level before treatment can predict the occurrence of sarcopenia in patients with DLBCL after treatment. Sarcopenia before and after treatment is an influencing factor for the poor prognosis of patients with DLBCL.