Quantitative Assessment of Interim PET/CT Could Have More Prognostic Relevance than Visual Assessment for Predicting Clinical Outcome of Extranodal Diffuse Large B Cell Lymphoma

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

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.

Clinical Outcomes in Patients With DLBCL Treated With R-CHOP According to Radiotherapy and Interim PET Response

Background/Aim

Interim positron emission tomography/computed tomography (PET/CT) scan is a valuable tool for assessing the early metabolic response to chemotherapy in diffuse large B-cell lymphoma (DLBCL). Although radiotherapy is an effective treatment for lymphoma, especially for local tumor control, the role of consolidative radiotherapy in diffuse large B-cell lymphoma (DLBCL) remains controversial. This study analyzed the clinical outcomes of patients with DLBCL treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), stratified by interim PET response and the administration of radiotherapy.

Patients and Methods

We conducted a retrospective review of 107 patients with DLBCL treated with R-CHOP chemotherapy between January 2012 and December 2016. Overall survival (OS), recurrence-free survival (RFS), and freedom from disease progression (FFDP) were calculated using the Kaplan-Meier method and compared using the log-rank test.

Results

Forty-six patients were included in this analysis, with a median follow-up time of 65.9 months (range=4.7-125.3 months). The metabolic CR (mCR) group exhibited superior OS, RFS, and FFDP compared with the metabolic PR (mPR) group (p=0.003, p=0.001, and p=0.008, respectively). The 1-, 2-, and 5-year FFDP were 92.97%, 89.3%, and 85.6%, respectively, in the mCR group and 78.6%, 61.9%, and 44.2%, respectively, in the mPR group. In subgroup analysis, the FFDP of the mPR group without radiotherapy was significantly lower than that of the other groups (mCR with/without radiotherapy and mPR with radiotherapy, p=0.001).

Conclusion

Consolidative radiation therapy using interim PET can benefit patients who do not achieve mCR. Further well-controlled prospective randomized trials are required.

Diagnostic Accuracy and Prognostic Relevance of Immunoglobulin Heavy Chain Rearrangement and 18F-FDG-PET/CT Compared With Unilateral Bone Marrow Trephination for Detecting Bone Marrow Involvement in Patients With Diffuse Large B-Cell Lymphoma

BACKGROUND

In diffuse large B-cell lymphoma (DLBCL), bone marrow involvement (BMI) has an important clinical implication as a component of staging and International Prognostic Index. This study aimed to determine whether molecular analysis of immunoglobulin heavy chain (IgH) genes and positron emission tomography-computed tomography (PET/CT) could overcome the limitation of defining morphologic BMI by trephination biopsy and could increase the diagnostic accuracy or prognostic prediction.

METHODS

A total of 94 de novo patients with DLBCL underwent PET/CT, polymerase chain reaction (PCR) test for detection of IgH gene rearrangement, and unilateral bone marrow (BM) trephination at diagnosis.

RESULTS

A total of 9 patients (9.6%) were confirmed to present morphologic BMI (mBMI) based on trephination biopsy. On the other hand, 21 patients (22.3%) were confirmed to have IgH clonality (IgH BMI), while 16 (17.0%) were classified with BMI based on the assessment of PET/CT (PET BMI). Each IgH rearrangement PCR and PET/CT showed the high negative predictive value of detecting the BMI. However, the combined assessment of IgH rearrangement and PET/CT could increase the diagnostic accuracy and specificity with 87.2% and 97.0%, respectively. The survival outcome of patients with double positive PET BMI and IgH BMI was significantly worse than that with either single positive PET BMI or IgH BMI, and even less than patients with neither PET BMI nor IgH BMI (3-year PFS: 50.0% vs. 75.4% vs. 97.9%, P = 0.007, 3-year OS: 50.0% vs. 75.6% vs. 80.1%, P = 0.035, respectively).

CONCLUSION

This study suggests that the combined evaluation of PET/CT and IgH rearrangement could give additional information for predicting therapeutic outcomes in patients with negative morphologic BMI as an important part of the prognosis.