The role of pre-treatment and mid-treatment 18F-FDG PET/CT imaging in evaluating prognosis of peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS)

Background It has been reported the prognostic value of MTV in predicting the disease prognosis of peripheral T-cell lymphoma (PTCL) through pre-treatment PET/CT imaging. However, these are limited data on pretreatment evaluation and prognosis assessments of peripheral T-cell lymphoma-not otherwise specified (PTCL-NOS). This study aimed to determine the prognostic values of pre-treatment and mid-treatment total metabolic tumor volume (MTV), total lesion glycolysis (TLG), and Deauville 5-Point Scale (D-5PS) in accessing the prognosis of PTCL-NOS. Methods A retrospective analysis was conducted in 31 patients with pathologically diagnosed PTCL-NOS. These patients have undergone positron emission PET/CT scanning before and during chemotherapy. Follow-ups were also done to investigate the 2-year progression-free survival (PFS) and Overall Survival (OS) of these patients. During ^18 F-fluorodeoxyglucose ( ^18 F-FDG) PET/CT scans, the MTV and TLG were recorded. Meanwhile, △ MTV and △ TLG were calculated. Furthermore, the receiver operating characteristic (ROC) curve was employed to classify and to define the threshold values. On the other hand, the mid-chemotherapy assessment and staging of these 31 patients were done by utilizing D-5PS. Subsequently, based on the D-5PS scores obtained, these patients were grouped into two categories: a group of patients with a score of <4 and another group with ≥ 4 points. For these two groups of patients, the survival analysis was done by Kaplan–Meier analysis and a multivariate COX regression model. Moreover, Pearson’s chi-square test ( χ ^2 test) and Spearman rank correlation coefficient were used to comparing the collected data, respectively. Results During the 2-year follow-up period, 15 out of the 31 patients experienced disease progression. The optimal threshold values for both baseline MTV and TLG were 158.16 cm ^3 and 677.40.Additionally, the difference in 2-year PFS between the progressive and non-progressive groups was statistically significant ( χ ^2=8.193 , P=0.004<0.05 ; χ ^2=8.872 , P=0.003<0.05 ), significant between-group difference was detected for MTV and for TLG ( χ ^2=6.494 , P=0.011<0.05 ; χ ^2=4.687 , P=0.03<0.05 ). On the other hand, when these patients were classified into two groups according to the mid-chemotherapy Deauville score of <4 and ≥ 4, the statistical difference of 2-year PFS between these two groups was significant, too ( χ ^2=14.966 , P=0.001<0.05 ),but there is no significant between-group difference in OS ( χ ^2=3.337 , P=0.068<0.05 ). COX analysis revealed that D-5PS are the independent factors influencing PFS, while MTV is the independent influencing factor of OS. Conclusion The baseline total MTV obtained by PET/CT scanning, and D-5PS are crucial prognostic factors in evaluating the prognosis of PTCL-NOS.