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)
Authors: Zhang Yafei , Wang Guangfa , Zhao Xin , Hu Yongxian , Tan Su Yin Elaine , Chen Donghe , Wang Huatao , Zhao Kui 
Published: October 2021

Abstract
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 $${}^{18}$$

18

F-fluorodeoxyglucose ($${}^{18}$$

18

F-FDG) PET/CT scans, the MTV and TLG were recorded. Meanwhile, $$\bigtriangleup$$
△
MTV and $$\bigtriangleup$$
△
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 $$\ge$$
≥
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 ($$\chi ^{2}$$

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$$^{3}$$

3

and 677.40.Additionally, the difference in 2-year PFS between the progressive and non-progressive groups was statistically significant ($$\chi ^{2}=8.193$$

χ
2

=
8.193

, $$P=0.004<0.05$$

P
=
0.004
<
0.05

; $$\chi ^{2}=8.872$$

χ
2

=
8.872

, $$P=0.003<0.05$$

P
=
0.003
<
0.05

), significant between-group difference was detected for MTV and for TLG ($$\chi ^{2}=6.494$$

χ
2

=
6.494

, $$P=0.011<0.05$$

P
=
0.011
<
0.05

; $$\chi ^{2}=4.687$$

χ
2

=
4.687

, $$P=0.03<0.05$$

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 $$\ge$$
≥
4, the statistical difference of 2-year PFS between these two groups was significant, too ($$\chi ^{2}=14.966$$

χ
2

=
14.966

, $$P=0.001<0.05$$

P
=
0.001
<
0.05

),but there is no significant between-group difference in OS ($$\chi ^{2}=3.337$$

χ
2

=
3.337

, $$P=0.068<0.05$$

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.