Abstract
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Objectives: Non-Hodgkin Lymphoma (NHL) accounts for about 70% of malignant lymphoma. Follicular Lymphoma (FL) is the second most frequent form of NHLs and FL is frequently refractory or relapses after a temporary response to the treatment. Targeted radioimmunotherapy (RIT) is approved for adults with relapsed/refractory FL. The aim of this study was global assessment of disease activity in lymphoma patients by using 18F-FDG-PET/CT scan before and after RIT.
Methods: We retrospectively studied seventeen patients (8 females and 9 males, aged 43-75) with relapsed/refractory lymphoma who were treated with targeted-RIT (I-131 Tositumomab or Y-90 Zevalin) after chemotherapy/radiotherapy. FDG-PET scans were performed 3 months before and 6 months after RIT approximately. The regions of interest (ROIs) were placed manually on all focal malignant lesions by sphere mask of ROVER software (ABX GmbH, Radeberg, Germany). Segmentation was applied using automatic/standard method (threshold 40% of SUVmax) for the quantitative analysis in pre and post RIT scans. Measurements of Total Lesional Glycolysis (TLG) and partial volume effect corrected TLG (pvcTLG) were done for global assessment of disease burden.
Results: In all patients, pre-treatment to post-treatment changes in pvcTLG was more than that of TLG (P-value <0.001). The average decrease in pvcTLG in patients with at least 3-year survival was 123.9g, while in deceased patients the pvcTLG increased 55.6g in post-RIT scans (P=0.049). The TLG changes in patients with at least 3year survival versus the deceased were a decline of 107.0g and 34.7g respectively in post treatment scans (P=0.056).
Conclusion: The results of this study indicate that TLG and pvcTLG may be useful measurements for global assessment of lymphoma burden, Additionally the changes in pvcTLG is a more evident compared to TLG. We suggest a larger study to evaluate the correlation of pvcTLG with disease burden, response to treatment, progression free survival and overall survival.