Intra-patient Variability of FDG Standardized Uptake Values in Mediastinal Blood Pool, Liver, and Myocardium during R-CHOP Chemotherapy in Patients with Diffuse Large B-cell Lymphoma.

Purpose: ¹⁸ F-fluorodeoxyglucose (FDG) PET/CT is useful for staging and evaluating treatment response in patients with diffuse large B-cell lymphoma (DLBCL). A five-point scale model using the mediastinal blood pool (MBP) and liver as references is a recommended method for interpreting treatment response. We evaluated the variability in standardized uptake values (SUVs) of the MBP, liver, and myocardium during chemotherapy in patients with DLBCL.
Methods: We analyzed 60 patients with DLBCL who received rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) treatment and underwent baseline, interim, and final FDG PET/CT scans. The FDG uptakes of lymphoma lesions, MBP, liver, and myocardium were assessed, and changes in the MBP and liver SUV and possible associated factors were evaluated.
Results: The SUV of the liver did not change significantly during the chemotherapy. However, the SUV _mean of MBP showed a significant change though the difference was small (p = 0.019). SUV _mean of MBP and liver at baseline and interim scans was significantly lower in patients with advanced Ann Arbor stage on diagnosis. The SUV _mean of the MBP and liver was negatively correlated with the volumetric index of lymphoma lesions in baseline scans (r = -0.547, p < 0.001; r = -0.502, p < 0.001). Positive myocardial FDG uptake was more frequently observed in interim and final scans than in the baseline scan, but there was no significant association between the MBP and liver uptake and myocardial uptake.
Conclusions: The SUV of the liver was not significantly changed during R-CHOP chemotherapy in patients with DLBCL, whereas the MBP SUV of the interim scan decreased slightly. However, the SUV of the reference organs may be affected by tumor burden, and this should be considered when assessing follow-up scans. Although myocardial FDG uptake was more frequently observed after R-CHOP chemotherapy, it did not affect the SUV of the MBP and liver.
Competing Interests: Soo Jeong Kim, Hyun Kyung Yi, Chae Hong Lim, Young Seok Cho, Joon Young Choi, Yearn Seong Choe, Kyung-Han Lee, Byung-Tae Kim, and Seung-Hwan Moon declare that they have no conflicts of interest. Ethical Statement Our study was performed in compliance with the regulations of our institution and generally accepted guidelines governing such work. Each author participated sufficiently in the work to take responsibility for the content. We confirm that this manuscript is original, is not under simultaneous consideration by another journal, and has not been previously published. There are no financial associations that might cause a conflict of interest.