18F-FDG PET for Mediastinal Staging of Lung Cancer: Which SUV Threshold Makes Sense?

Abstract

18 F-FDG PET is the most accurate noninvasive modality for staging mediastinal lymph nodes in lung cancer. Besides using visual image interpretation, some institutions use standardized uptake value (SUV) measurements in lymph nodes. Mostly, an SUV of 2.5 is used as the cutoff, but this choice was never deduced from respective studies. Receiver operating characteristic (ROC) analyses demonstrated that SUV thresholds of more than 4 resulted in the highest accuracy. But these high cutoffs imply high false-negative rates (FNRs). The aim of our evaluation was to determine an optimal SUV threshold and to compare its diagnostic performance with the results of visual interpretation. Methods: This retrospective study included 95 patients with suspected lung cancer who underwent mediastinoscopy/mediastinal lymphadenectomy after 18 F-FDG PET (90-150 min after 250 MBq of 18 F-FDG). Maximum SUV was measured in 371 lymph node regions biopsied afterward and visually interpreted using a 6-level score (2 2 2 through 1 1 1). Diagnostic performance was assessed by ROC analysis. FNR and false-positive rate (FPR), the sum of both error rates (FNR 1 FPR), and diagnostic accuracy were plotted against a hypothetical SUV threshold to determine the optimum SUV threshold. Results: SUVs in metastatic lymph nodes were higher (mean 6 SD, 7.1 6 4.5; range, 1.4-26.9; n 5 70) than in tumor-free lymph node stations (2.4 6 1.7; range, 0.6-14.9; n 5 301; P , 0.01). Inflammatory lymph nodes exhibited slightly increased SUVs (2.7 6 2.0; range, 0.8-14.9; n 5 146). The plot of error rates featured a minimum of the sum FNR 1 FPR for an SUV of 2.5. With increasing SUV threshold, the FPR decreased most prominently up to that value whereas a continuous rise of FNR was noticed. Highest diagnostic accuracy was achieved with an SUV of 4.5. The areas under the ROC curves demonstrated that visual interpretation tends to be more accurate than SUV quantification (visual, 0.930 6 0.022; SUV, 0.899 6 0.025; P 5 0.241). Using an SUV of 2.5 as the threshold, the resulting sensitivity, specificity, and negative predictive value were 89%, 84%, and 96%, respectively. Conclusion: For mediastinal staging, the choice of an SUV of 2.5 as the threshold is justified because FNR 1 FPR is minimized. The resulting high negative predictive value of 96% allows the omission of mediastinoscopy in patients with negative mediastinal findings on 18 F-FDG PET images. For the experienced observer, visual analysis should be relied on primarily, with calculation of the SUV used, at most, as a secondary aid. For the less experienced observer, the SUV may be of greater value.

Diagnostic Performance of 18F-FDG PET/CT for Lymph Node Staging in Patients with Operable Non-small-cell Lung Cancer and Inflammatory Lung Disease

“…Furthermore, maximum SUV was as accurate as mean SUV in lymph node staging of lung cancer [25]. Optimal cutoff values of maximum SUV for lymph node metastasis in the present study were 4.4 for N1-N3 and 4.8 for N1-N2 lymph nodes, values that are similar to those of recently published results (SUVmax = 4.4-4.5) [26,27]. These values were not significantly changed in the ILD 1-3 and ILD 1-2 groups , and their sensitivity and specificity were moderate (sensitivity = 68.8%, specificity = 74.6-75.8%).…”

“…It is quite possible that patients with inflammatory lung disease had more false-positive lymph nodes with low to intermediate 18 F-FDG uptake and, thus, a higher-than-usual SUV was obtained for the highest accuracy. A visual interpretation is widely used for clinical PET interpretation of lymph node involvement [25][26][27][28][29][30][31]. Most of the previous comparative studies demonstrated that visual analysis of PET is superior or comparable to the semiquantitative method except for N3 lymph nodes [25][26][27][28][29].…”

“…A visual interpretation is widely used for clinical PET interpretation of lymph node involvement [25][26][27][28][29][30][31]. Most of the previous comparative studies demonstrated that visual analysis of PET is superior or comparable to the semiquantitative method except for N3 lymph nodes [25][26][27][28][29]. On the other hand, according to our results, the diagnostic performance of the visual criterion ''localized FDG uptake'' was inferior to a semiquantitative criterion, SUVmax (p = 0.002 for N1-N3 and 0.001 for N1-N2).…”

Heterogeneity Analysis of 18F-FDG Uptake in Differentiating Between Metastatic and Inflammatory Lymph Nodes in Adenocarcinoma of the Lung: Comparison with Other Parameters and its Application in a Clinical Setting

“…Uptake of the 18 F-FDG-avid LNs was also visually scored using three grades of intensity of mediastinal blood pool (0=similar with mediastinal blood pool, 1=faintly positive, 2=definitely positive). SUV threshold of 2.5 was used for differentiating between metastatic and benign LNs in lung cancer [13][14][15]. Highly attenuated nodes were defined as those that had HU max >120 [16] as one of the diagnostic criteria in determining benign LN in patients with non-smallcell lung cancer.…”

Automated High Uptake Regions Recognition and Lymphoma Detection Based on Fully Convolutional Networks on Chest and Abdomen PET Image

“…The standardized uptake value (SUV) is a semi-quantitative analysis method for measuring FDG uptake and further evaluating the conditions of disease [3]. In general, both the tumor regions and the sFEPU regions have a higher SUV value (SUV≥2.5 [5]), and highlights in PET image. Therefore, in order to accurately detect the lymphoma, it's necessary to precisely distinguish them.…”