Prognostic value of quantitative parameters based on pretreatment positron emission tomography/computed tomography (PET/CT) in patients with newly diagnosed T cell lymphoma

Purpose: Compared with B-cell lymphomas, T cell lymphomas are associated with a more aggressive clinical behavior and worse prognosis. The identification of prognostic factors at diagnosis is needed. This study is designed to explore the potential prognostic value of baseline FDG-PET-derived quantitative metrics in T cell lymphomas in a retrospective single-center study.

Methods: Among sixty four patients with newly diagnosed T and NK cell lymphomas from July 2010 to December 2017 in Peking University First Hospital underwent positron emission tomography/computed tomography (PET/CT) scans, 47 cases who were followed up with complete clinical materials were retrospectively reviewed and analyzed. Patient's clinical characteristics included Ann Arbor stage, clinical symptoms, lactate dehydrogenase (LDH) levels, international prognostic index (IPI), the prognosis index for peripheral T-cell lymphoma-unspecified (PIT), etc. Overall survival (OS) and progression-free survival (PFS) were recorded. The maximum standardized uptake value (SUVmax) in 47 cases, mean SUV (SUVmean), peak SUV (SUVpeak), whole-body metabolic tumor volume (WBMTV₄₁) and whole-body total lesion glycolysis(WBTLG₄₁) in 27 cases were measured from the PET/CT scan. MTV was computed with the 41% SUVmax threshold method. The study population was dichotomized at their medians into high and low groups. Kaplan-Meier log-rank tests were then used to compare high with low PET/CT parameter groups, and multivariate Cox proportional hazards regression analysis was carried out to identify predictors of OS and PFS. P<0.05 was considered statistically significant.

Results: With a median follow-up of 19.0 (0.7~83.8) months, 3-year PFS rate was 32.9% and 3-year OS was 54.7% in 47 patients. Among them, 28 cases had disease progress, 21 cases died. Univariate analysis revealed that SUVmax, LDH level, IPI and PIT were the significant predictive factors of OS, while presence of B symptom, SUV max, LDH level and IPI were predictive in PFS (P<0.05). In multivariate analysis, LDH was the only significantly independent parameter for both PFS and OS. And, in the 27 patients, Kaplan-Meier analysis with log-rank tests found SUVmean, SUVpeak, WBMTV₄₁ and WBTLG₄₁ were not associated with the prognosis.

Conclusions: Standard PET/CT quantitative parameters, such as SUVmax, as well as newer measures of metabolic tumor burden, WBMTV₄₁ and WBTLG₄₁, were not correlated with outcome in our study population of newly diagnosed T and NK cell lymphomas. Larger studies with longer follow-up periods are needed to confirm these results. Keywords T cell lymphomas, PET/CT, Maximum standardized uptake value, Metabolic tumor burden, Prognosis