Prognosis estimation under the light of metabolic tumor parameters on initial FDG-PET/CT in patients with primary extranodal lymphoma

Abstract

Background: Non-Hodgkin's lymphomas arising from the tissues other than primary lymphatic organs are named primary extranodal lymphoma. Most of the studies evaluated metabolic tumor parameters in different organs and histopathologic variants of this disease generally for treatment response. We aimed to evaluate the prognostic value of metabolic tumor parameters derived from initial FDG-PET/CT in patients with a medley of primary extranodal lymphoma in this study.

Patients and methods: There were 67 patients with primary extranodal lymphoma for whom FDG-PET/CT was requested for primary staging. Quantitative PET/CT parameters: maximum standardized uptake value (SUVmax), average standardized uptake value (SUVmean), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were used to estimate disease-free survival and overall survival.

Results: SUVmean, MTV and TLG were found statistically significant after multivariate analysis. SUVmean remained significant after ROC curve analysis. Sensitivity and specificity were calculated as 88% and 64%, respectively, when the cut-off value of SUVmean was chosen as 5.15. After the investigation of primary presentation sites and histo-pathological variants according to recurrence, there is no difference amongst the variants. Primary site of extranodal lymphomas however, is statistically important (p = 0.014). Testis and central nervous system lymphomas have higher recurrence rate (62.5%, 73%, respectively).

Conclusions: High SUVmean, MTV and TLG values obtained from primary staging FDG-PET/CT are potential risk factors for both disease-free survival and overall survival in primary extranodal lymphoma. SUVmean is the most significant one amongst them for estimating recurrence/metastasis.

Keywords: 18-fluorodeoxyglucose positron emission tomography/computed tomography; metabolic tumor parameters; primary extranodal lymphoma.

Figure 1

ROC curve for SUVmean, MTV and TLG.

Figure 2

Kaplan-Meier curve of SUVmean with a cut-off value of 5.15.

Figure 3

There was a mass in antrum of stomach on transaxial CT (A), PET (B), fusion (C) and MIP images (D) (arrows) of a 60-year old female patient with primary gastric lymphoma of DLBC type. She had metabolic tumor parameters of SUVmax: 11, SUVmean: 5, MTV:34 cm³, TLG:150. Her outcome was excellent with a DFS and OS of 111 months.

Figure 4

61-year old female patient was diagnosed with primary CNS lymphoma of DLBC type. There was a mass in right periventricular region adjacent to right thalamus on transaxial PET (A), CT (B) and fusion (C) images (arrows). She was in serious risk because of her high metabolic tumor parameters (SUVmax: 35, SUVmean: 25, MTV: 425 cm³, TLG: 2543) and died of the disease 11 months after the diagnosis.