Optimal index for detecting splenic involvement on 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging in diffuse large B-cell lymphoma

Abstract

Accurate clinical staging is important in diffuse large B-cell lymphoma (DLBCL) to adapt to optimal therapy. Splenic involvement of DLBCL has been recently more detectable with the advancement of a diagnostic scan by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT). Our clinical question is whether splenic involvement was adequately diagnosed by FDG-PET/CT imaging. This retrospective study aimed to determine the optimal index for evaluating splenic involvement in patients with DLBCL. Patients with newly diagnosed DLBCL who were examined with FDG-PET/CT at diagnosis and the end of induction chemotherapy (EOI) was enrolled. The splenic involvement with the splenic FDG uptake value higher than that of the liver at diagnosis or with the decrease of splenic uptake at EOI by visual evaluation was evaluated as positive. The calculative evaluation of splenic involvement, based on the data of standardized uptake value (SUV) of the spleen, used maximum SUV (SUVmax), mean SUV (SUVmean), spleen total lesion glycolysis (spleen TLG), and spleen length. A change in each index following induction chemotherapy was expressed as an index. Receiver operating characteristic analysis was used to set the cutoff value for each index. This study included 52 patients. Spleen TLG (0.904) showed the best accuracy, followed by SUVmax (0.885) and SUVmean (0.885), among the 5 indexes for splenic involvement at diagnosis. Splenic involvement was predicted with a higher accuracy level (0.923) when selecting the cases with values higher than the cutoff level on both spleen TLG and SUVmax. The decision at EOI was more suitable by selecting both positive cases of ∆ TLG and ∆ SUVmax. Obtaining both the positive spleen TLG and SUVmax is recommended at diagnosis to predict splenic involvement. The assessment by ∆ spleen TLG and ∆ SUVmax seems to be optimal.

Figure 1.

FDG-PET/CT imaging of splenic involvement in 5 patients with no obvious positivity at diagnosis. FDG-PET/CT imaging of the 5 patients who were fixed as positive with the comparison of both the FDG-PET/CT result performed at diagnosis and EOI. FDG-PET/CT accumulation in the spleen was decreased following induction chemotherapy. About 3 patients (cases A, B, and C) had unconfirmed splenic involvement at diagnosis. Splenic involvement was not suspected with Deauville 5-point scale criteria at diagnosis in the remaining 2 patients (cases D and E). While decreasing the accumulation of splenic signal was shown at EOI, the interpretation of positive splenic involvement at diagnosis was confirmed. Dx = diagnosis, EOI = end of induction chemotherapy.

Figure 2.

The index in FDG-PET/CT imaging at diagnosis. The index of spleen TLG, SUVmax, SUVmean, and spleen length were shown with the division of 2 groups by the presence or absence of splenic involvement. The radiographic interpretation at diagnosis and the additional interpretation at EOI are used as the basic data for determining splenic involvement. TLG = total legion glycolysis, SUV = standardized uptake value, Pos = positive for splenic involvement, Neg = negative for splenic involvement.

Figure 3.

The index alteration between diagnosis and end of induction chemotherapy in FDG-PET/CT imaging. The quantitative level of index alteration was expressed as ∆ index. Each ∆ index was calculated with (the value at EOI minus the value at diagnosis). TLG = total legion glycolysis, SUV = standardized uptake value, Pos = positive for splenic involvement, Neg = negative for splenic involvement.