Enhanced diagnostic performance of delayed/multiple time point quantitative FDG-PET/CT: A lesion-based analysis of suspected lung malignancy

Objectives Delayed/multiple time point FDG-PET/CT imaging (DTPI/MTPI) has been shown to enhance benign/malignant differentiation of lesions using SUVmax or visual scoring. The purpose of this prospective study was to assess the potential value of other quantitative FDG­-PET/CT measures including SUVmean, partial volume corrected (PVC) SUVmean, metabolic tumor volume (MTV), total lesion glycolysis (TLG=SUVmean*MTV), pvcTLG (pvcSUVmean*MTV) in differentiation of suspected lung cancer patient lesions

Methods One hundred suspected lung cancer lesions (60 benign; 40 malignant) with histopathological diagnosis were included. Patients with suspected lung malignancy underwent whole­ body FDG-PET/CT at 1st, 2nd & 3rd hours (H1, H2 & H3) after 18F-­FDG injection. SUVmax, SUVmean, pvcSUVmean, TLG, pvcTLG and SUVpeak were calculated. Retention index (RI) [(P3­-P1)/P1] was calculated. The diagnostic performance was assessed by pairwise comparison of receiver operating characteristic (ROC) curves.

Results All parameters of malignant lesions showed moderate increase from H1 to H2 & from H1 to H3. Tumor­ negative lesions showed mixed pattern of changes between early & DTPI but the average changes were less than malignant lesions for all indices with statistical significance. The AUC of ROC curves of all indices increased at H2 & H3; however, only some indices at H3 showed statistically significant improvement in comparison with H1 while AUCs were 0.91, 0.90, 0.86 for 3h SUVmean, SUVpeak, pvcTLG vs 0.85, 0.83, 0.81 for corresponding H1 indices. In subgroup analysis considering only lymph nodes, H3 pvcSUVmean &SUVmax had the highest diagnostic performance compared to other PET/CT indices but the differences were not statistically significant. RI didn’t provide any significant added value over H3

Conclusions Based on this study, DTPI slightly improved the diagnostic performance of PET/CT in differentiating suspected lung lesions while RI did not increase diagnostic accuracy