Impact of solitary pulmonary nodule size on qualitative and quantitative assessment using 18F-fluorodeoxyglucose PET/CT: the SPUTNIK trial

Abstract

Purpose To compare qualitative and semi-quantitative PET/CT criteria, and the impact of nodule size on the diagnosis of solitary pulmonary nodules in a prospective multicentre trial. Methods Patients with an SPN on CT ≥ 8 and ≤ 30 mm were recruited to the SPUTNIK trial at 16 sites accredited by the UK PET Core Lab. Qualitative assessment used a five-point ordinal PET-grade compared to the mediastinal blood pool, and a combined PET/CT grade using the CT features. Semi-quantitative measures included SUVmax of the nodule, and as an uptake ratio to the mediastinal blood pool (SURBLOOD) or liver (SURLIVER). The endpoints were diagnosis of lung cancer via biopsy/histology or completion of 2-year follow-up. Impact of nodule size was analysed by comparison between nodule size tertiles. Results Three hundred fifty-five participants completed PET/CT and 2-year follow-up, with 59% (209/355) malignant nodules. The AUCs of the three techniques were SUVmax 0.87 (95% CI 0.83;0.91); SURBLOOD 0.87 (95% CI 0.83; 0.91, p = 0.30 versus SUVmax); and SURLIVER 0.87 (95% CI 0.83; 0.91, p = 0.09 vs. SUVmax). The AUCs for all techniques remained stable across size tertiles (p > 0.1 for difference), although the optimal diagnostic threshold varied by size. For nodules < 12 mm, an SUVmax of 1.75 or visual uptake equal to the mediastinum yielded the highest accuracy. For nodules > 16 mm, an SUVmax ≥ 3.6 or visual PET uptake greater than the mediastinum was the most accurate. Conclusion In this multicentre trial, SUVmax was the most accurate technique for the diagnosis of solitary pulmonary nodules. Diagnostic thresholds should be altered according to nodule size. Trial registration ISRCTN - ISRCTN30784948. ClinicalTrials.gov - NCT02013063

Can dynamic imaging, using 18F-FDG PET/CT and CT perfusion differentiate between benign and malignant pulmonary nodules?

“…Table 2 and Figure 4A show diagnostic accuracy of conventional PET/CT derived parameters with pre-specified and derived cut-point values though ROC analysis. 36 , 37 SUR BLOOD parameter had overall highest accuracy, however, pairwise comparison of AUCs showed no significant difference (p = 0.5308 vs . SUV max ; p = 1.0000 vs .…”

“…Table 2 and Figure 4A show diagnostic accuracy of conventional PET/CT derived parameters with pre-specified and derived cut-point values though ROC analysis. 36,37 highest accuracy, however, pairwise comparison of AUCs showed no significant difference (p = 0.5308 vs. SUV max ; p = 1.0000 vs. SUR LIVER ; p = 0.1083 vs. PET grade). ROC analysis and diagnostic accuracy for the diagnosis of malignancy by dynamic 18 F-FDG PET/CT parameter K i , and perfusion CT indices BV and AF compared to SUR BLOOD are further detailed in Table 2 and Figure 4B.…”

“…This has been confirmed in a larger multicenter trial by Evangelista et al 36 Different to the SPUTNIK trial which has shown SUV max to be the most accurate and reproducible technique with a caveat of introducing additional cut-point values altered according to the nodule size, we did not see significant improvement in diagnostic accuracy when replicating the multiple cut-points in our group of nodules (see * in Table 2). 37 The accuracies of the new metabolic parameter K i and perfusion parameter BV were not signifi-cantly different to the conventional 18 F-FDG PET/ CT. The derived K i cut-point for malignancy was ≥0.01 min -1 resulting in sensitivity/specificity/accuracy of 77.8%/85.7%/81.3%, respectively.…”

“…Qualitative specified criteria for malignancy was PET grade ≥ 3. 36 , 37 VOIs were placed over the nodules, the ascending aorta at the level of the arch, and within the right lobe of the liver for determination of the SUV mean and SUV max values using OsiriX software (OsiriX, version 8.0.1 64 bit; OsiriX Imaging Software, Geneva, Switzerland).…”

“…* = adding cut-points standardized uptake value (SUV max ) ≥ 1.75 and ≥ 3.6 for nodules < 12 mm and > 16 mm, respectvely,37 resulted in sensitivity, specificity and accuracy of 72.7%, 70.0% and 71.4%, respectively; AF = Arterial flow; BV = blood volume; CI = confidence interval; K i = influx constant; SUR = SUV ratios; SUV = standardized uptake value…”