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

Methods  The clinical data and imaging data of 91 patients (36 males and 55 females, median age 60 years) confirmed by histopathological examination in the First People′s Hospital of Jining from November 2019 to August 2024 were retrospectively collected, including 25 patients with sarcopenia and 66 patients without sarcopenia. 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, and sarcopenia was diagnosed with SMI<44.77 cm²/m² in males and 32.50 cm²/m² in female<s. According to the diagnosis results, the patients before treatment were divided into two groups: with and without sarcopenia. The psoas maximal standard uptake value (SUV_max) and mean CT value (CTavg) were measured at the L3 level. The gender, age, abdominal lymph node involvement and extranodal involvement, as well as the relationship between SUV_max, body mass index (BMI), muscle CTavg and sarcopenia before and after treatment were analyzed. Comparisons between groups were made using either the Mann-Whitney U test or the chi-square test. Univariate logistic regression analysis was used 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 power of this factor. The Kaplan-Meier method was used to analyze the association between sarcopenia and progression-free survival (PFS) and overall survival (OS) before and after treatment.

Results  The SUV_max of patients with sarcopenia was lower than that of non-sarcopenia patients before treatment (1.00(0.90, 1.10) vs 1.10 (1.00, 1.30), Z=−4.318, P<0.001) and after treatment (0.90(0.80, 0.93) vs 1.00(0.90, 1.20), Z=−3.197, P=0.001). Univariate Logistic regression analysis showed that muscle CTavg, SUV_max, BMI and extranodal involvement were the influencing factors for the occurrence of sarcopenia after treatment (HR=1.203, 95%CI: 1.008~1.437, P=0.041; HR=0.001, 95%CI: 0.000~0.072, P=0.002; HR=0.739, 95%CI: 0.596~0.917, P=0.006; HR=3.889, 95%CI: 1.196~12.644, P=0.024). The results of multivariate logistic regression analysis showed that SUV_max was an independent predictor 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 had a high predictive performance 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 was shorter in patients with sarcopenia before treatment than in patients without sarcopenia (P=0.028). There was no significant difference in PFS between the two groups (P=0.289). PFS was shorter in patients with sarcopenia after treatment than in patients without sarcopenia (P=0.006), while there was no significant difference in OS between the two groups (P=0.623).

Conclusion  The SUV_max of skeletal muscle at the L3 level before treatment can predict the occurrence of sarcopenia in patients with DLBCL; The presence of sarcopenia before and after treatment was an influencing factor for the poor prognosis of patients with DLBCL.