Correlation of ¹⁸F-FDG PET/CT metabolic parameters with clinical staging and pathological classification in thymic lymphoma

  Background   ¹⁸F-FDG PET/CT can display abnormal functional metabolism and structural changes by using image fusion technology, but there are still relatively few studies on differential diagnosis, staging and classification of thymic lymphoma.

  Objective   To investigate the relationship between ¹⁸F-FDG PET/CT metabolic parameters of thymic lymphoma and its pathological staging and typing.

  Methods   Patients who underwent PET/CT at the Department of Nuclear Medicine, Chinese PLA General Hospital from January 2015 to May 2022 and were diagnosed with thymic lymphoma on pathology were selected for the study. The maximum standard uptake values (SUVmax), mean standard uptake values (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG) and tumor-to-normal liver standard uptake value ratio (SUVR) were recorded. Ann Arbor staging was performed based on state of lymph nodes and extra lymph nodes, and the main pathological types were classified. Spearman correlation analysis was made between metabolic parameters of ¹⁸F-FDG PET/CT and Ann Arbor stage.

  Results   A total of 85 patients (46 males and 39 females, aged 30.34-14.48 years) were enrolled in the study, including 35 cases of primary mediastinal large B-cell lymphoma (PMBcl), 29 cases of nodular sclerosis Hodgkin lymphoma (NSHL) and 19 cases of T-lymphoblastic lymphoma. There were 2, 29, 10 and 44 patients in Ann Arbor stages Ⅰ, Ⅱ, Ⅲ and Ⅳ, respectively. The differences of metabolic parameters between PMBCL, NSHL and T-LBL were statistically significant (P<0.05). The differences of metabolic parameters in different Ann Arbor periods were also statistically significant (P<0.05). Ann Arbor stage was positively correlated with various metabolic parameters, including TLG (r_s=0.494, P<0.01), MTV (r_s=0.469, P<0.01), SUVR (r_s=0.378, P<0.01), SUVmax (r_s=0.296, P=0.006), and SUVmean (r_s=0.273, P=0.012).

  Conclusion   There are certain differences in ¹⁸F-FDG PET/CT metabolic parameters among different pathologic types of thymic lymphomas. The metabolic parameters TLG, MTV, and SUVR are moderately correlated with the Ann Arbor stage of thymic lymphoma, which can provide evidence for clinical treatment planning.