A Comparative Evaluation of Mediastinal Nodal SUVmax and Derived Ratios from (18)F-FDG PET/CT Imaging to Predict Nodal Metastases in Non-Small Cell Lung Cancer

SIMPLE SUMMARY: Lung cancer is a major cause of premature death worldwide. The majority of lung cancers are considered non-small cell lung cancer (NSCLC). Positron emission tomography with computed tomography (PET/CT) is part of routine clinical staging, but inadequate accuracy in detecting cancer invasion in nearby lymph nodes prevents optimal surgical treatment. To improve the objectivity of PET/CT reporting, we analysed objectively obtained measurements of signals from suspicious lymph nodes inside the chest. We further obtained derived (corrected) values based on the respective measured signals of the lung tumour and blood within the core tissues in the chest and liver as well as the size of the lymph nodes. We found that the use of objectively measured signals improves the accuracy of cancer detection in the lymph nodes with potential improvement observed when using derived values (ratios). Future research may test the value of our findings in routine clinical practice. ABSTRACT: (18)F-FDG positron emission tomography with computed tomography (PET/CT) is a standard imaging modality for the nodal staging of non-small cell lung cancer (NSCLC). To improve the accuracy of pre-operative staging, we compare the staging accuracy of mediastinal lymph node (LN) standard uptake values (SUV) with four derived SUV ratios based on the SUV values of primary tumours (TR), the mediastinal blood pool (MR), liver (LR), and nodal size (SR). In 2015–2017, 53 patients (29 women and 24 men, mean age 67.4 years, range 53–87) receiving surgical resection have pre-operative evidence of mediastinal nodal involvement (cN2). Among these, 114 mediastinal nodes are resected and available for correlative PET/CT analysis. cN2 status accuracy is low, with only 32.5% of the cN2 cases confirmed pathologically. Using receiver operating characteristic (ROC) curve analyses, a SUVmax of N2 LN performs well in predicting the presence of N2 disease (AUC, 0.822). Based on the respective selected thresholds for each ROC curve, normalisation of LN SUVmax to that for mediastinum, liver and tumour improved sensitivities of LN SUVmax from 68% to 81.1–89.2% while maintaining acceptable specificity (68–70.1%). In conclusion, normalised SUV ratios (particularly LR) improve current pre-operative staging performance in detecting mediastinal nodal involvement.