Objective：The aim of this study was to investigate the prognostic role of baseline metabolic parameters of 18F-fluorodeoxyglucose positron emission tomography/computed tomography(18F-FDG PET/ CT)imaging in patients with extranodal natural killer/T-cell lymphoma(ENKTL). Methods：Eighty-three patients newly diagnosed with ENKTL who underwent pretreatment 18F-FDG PET/CT scans were enrolled in this study. The baseline maximum standardized uptake value(SUVmax)，total metabolic tumor volume (TMTV)，total lesion glycolysis(TLG)，and clinical characteristics were collected for the retrospective analysis. TMTV was defined using the 41% SUVmax threshold. Kaplan-Meier curve(Log-rank test)was used for survival analysis. The statistically significant factors in the univariate analysis were incorporated into the Cox proportional hazards model for multivariate survival analysis. Results： Thirty-seven(44.6%)patients progressed and 32(38.6%)patients died within a median follow-up time of 21.6(8.9，38.3)months. The receiver operating curve(ROC)analysis indicated that the optimal cut-off values of SUVmax，TMTV and TLG were 16.7，64.9 cm3 and 490.4，respectively.Patients with higher SUVmax，TMTV and TLG had worse prognosis. In multivariate analysis，TMTV，TLG and prognostic index of natural killer lymphoma(PINK)were independent prognostic factors of both PFS(HR 5.411，P=0.001；HR 7.905， P ＜ 0.001；HR 2.858，P=0.011)and OS(HR 6.137，P=0.002；HR 8.014，P ＜ 0.001；HR 2.666，P=0.023)，treatment mode and β2- microglobulin(β2-MG)were independent prognostic predictors of PFS and OS，respectively(HR 2.323，P=0.021；HR 2.627，P=0.021）. TMTV，together with PINK，may have better risk stratification performance in ENKTL patients. Conclusion：Baseline high SUVmax，TMTV and TLG can predict a relatively poor prognosis in patients with ENKTL，TMTV，TLG and PINK are independent predictors for survival outcomes. Moreover，the combination of TMTV and PINK may provide better risk substratification in PFS and OS.
