Prognostic Value of Interim and Posttherapy 18F-FDG PET/CT in Patients with Mature T-Cell and Natural Killer Cell Lymphomas

The prognostic value of interim PET or PET/CT performed after 1-4 cycles of chemotherapy has been widely confirmed in Hodgkin lymphoma and diffuse large B-cell lymphoma but remains unknown in T-cell and natural killer (T/NK) cell lymphomas. Therefore, our aim was to investigate the prognostic value of interim and posttherapy PET/CT in T/NK-cell lymphomas. Methods: A retrospective analysis was conducted on data from 88 patients with newly diagnosed T/NK-cell lymphoma who underwent interim (after 1-4 cycles of chemotherapy, n = 62) or posttherapy PET/CT (after the completion of first-line therapy, n = 47). Interim and posttherapy PET/CT status (positive vs. negative) was visually interpreted according to criteria of the International Harmonization Project, and PET/CT status was assessed for its ability to predict progression-free survival (PFS) and overall survival (OS). Results: Interim PET/CT results were negative in 17 of 62 (27.4%) cases, and posttherapy PET/CT results were negative in 29 of 47 (61.7%) cases. The 2-y PFS and OS rates were 71.9% and 80.2%, respectively, in patients with negative results at interim PET/CT versus 20.5% and 46.9%, respectively, in patients with positive results (P < 0.001 and P = 0.022, respectively). The 2-y PFS and OS rates were 57.8% and 78.0%, respectively, in patients with negative results on posttherapy PET/CT versus 0% and 20.4%, respectively, in patients with positive results (P < 0.001 and P = 0.003, respectively). Bivariate analysis showed that interim PET/CT status and posttherapy PET/CT status remain independent predictors of PFS and OS after controlling for the score on the Prognostic Index for Peripheral T-Cell Lymphoma, Unspecified. Conclusion: Both interim PET/CT status and posttherapy PET/CT status are independent predictors of PFS and OS in T/NK-cell lymphomas.