Pre-treatment partial-volume-corrected TLG is the best predictor of overall survival in patients with relapsing/refractory non-hodgkin lymphoma following radioimmunotherapy

The role of fluorodeoxyglucose-positron emission tomography (FDG-PET) has been well established in assessment of lymphoma, including non-Hodgkin lymphoma (NHL). The aim of this study was to compare changes and survival predictive values of various quantification parameters of FDG-PET/CT in patients with relapsing/refractory lymphoma before and after radioimmunotherapy (RIT). Data from 17 patients with relapsing/refractory NHL, treated with targeted RIT after chemotherapy/radiotherapy, were retrospectively collected. FDG-PET/CT scans were performed approximately three months before and six months after RIT. An adaptive contrast-oriented thresholding algorithm was used to segment lesions on the FDG-PET images. Wilcoxon signed-rank tests were used to assess changes in SUVmax, SUVmean, partial volume-corrected SUVmean (pvcSUVmean), total lesion glycolysis (TLG), and pvcTLG before and after treatment. The patients were followed up after completing RIT for up to 10 years. Kaplan-Meier and Cox regression analyses evaluated the association between the quantification parameters and survival data. In the survived group, the decrease in mean percentage of change for TLG and pvcTLG was greater than SUVmax, SUVmean and pvcSUVmean [TLG: 253.9 to 106.9, -81.4%; P = 0.052 and pvcTLG: 368.9 to 153.3, -58.4%; P = 0.04]. In addition, overall survival (OS) was shorter in patients with pre-RIT pvcTLG more than 644 compared to those below this value (log-rank P < 0.01). In univariate Cox regression for OS, a higher baseline pvcTLG was a significant prognostic factor (HR: 6.8, P = 0.02). Our results showed that pre-treatment pvcTLG was the best predictor of OS in patients with relapsing/refractory NHL following RIT.