Background:Recently, there are many reports from Japan about methotrexate associated lymphoproliferative disorder (MTX-LPD). We are investigating the predictive factor of spontaneous regression (SR) in MTX-LPD. On the other hand, FDG-PET/CT is used for diagnosis of LPD including malignant lymphoma. In addition, it was reported that imaging biomarkers such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG) could predict the prognosis of malignant tumor (1, 2). However, there is no

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... report that these imaging biomarkers could predict the SR of MTX-LPD.Objectives:We investigate the usefulness of FDG-PET/CT for predictive factor of SR in MTX-LPD.Methods:We enrolled 24 RA patients who diagnosed MTX-LPD and performed FDG-PET/CT from 2005 to 2019. We divided these cases into spontaneous regression cases (SR group; 15 cases) and cases that treated with chemotherapy after MTX discontinuation (CTx group; 9 cases), and compared the difference as follow subjects between two groups; clinical data including histopathological findings, SUVmax to evaluate malignant tumor activity by FDG-PET/CT, MTV and TLG which refer to metabolically active volume of the tumor segmented FDG-PET/CT. In addition, we analyzed cut off levels, sensitivity and specificity using statistical software JMP.Results:Diffuse large B cell lymphoma (DLBCL) and Hodgkin lymphoma (HL) were 5 and 1 cases in SR group, and 1 and 5 cases in CTx group. In addition, MTV and TLG by FDG-PET/CT was significantly lower in SR group, although SUVmax is no difference between two groups (figure 1). Cut off levels of MTV and TLG were 103.12 ml (sensitivity; 88.9%, specificity; 86.7%) and 361.75 ml (sensitivity; 88.9%, specificity; 86.7%), respectively.Conclusion:We suggested that MTV and TLG were useful for predict of SR in MTX-LPD.References:[1]Chen HH, Chiu NT, Su WC. et al. Prognostic value of whole-body total lesion glycolysis at pretreatment FDG PET/CT in non-small cell lung cancer. Radiology. 2012 Aug;264(2):559-66.[2]Chu KP, Murphy JD, La TH. et al. Prognostic value of metabolic tumor volume and velocity in predicting head-and-neck cancer outcomes. Int J Radiat Oncol Biol Phys. 2012 Aug 1;83(5):1521-7.Figure 1.Comparison of the level of MTV(a) and TLG (b).Disclosure of Interests:None declared