P1.03-080 The SUVmax Ratio of Two Tumors on PET/CT May Differentiate Separate Primary Lung Cancers and Intrapulmonary Metastases

Abstract

Differentiation between separate primary lung cancers and intrapulmonary metastases (IM) has significant therapeutic and prognostic implications in lung cancer patients with multiple pulmonary nodules. In this retrospective study, we investigated the diagnostic ability of ratio (MSR) and differences (MSD) of maximum standardized uptake values (SUVmax) between two tumors in discriminating separate primary lung cancers from metastases. We evaluated 5641 lung cancer patients between March 2009 and March 2016 at the Chinese People’s Liberation Army General Hospital. Patients underwent PET/CT and pathology confirmed as multiple lung cancers were included. Patients with ground glass opacity lung cancers or underwent preoperative radiotherapy or chemotherapy were excluded. All lung cancers tissues were reassessed and discriminated from separate primary lung cancer to metastases by two pathologists independently according to comprehensive histological assessment criteria, which was proposed by IASLC lung cancer staging project as pathologic definition to distinguish multiple primary lung cancers from metastatic in the forthcoming eighth edition TNM classification of lung cancer. The MSR and MSD were determined and compared in diagnosing separate primary lung cancers. Receiver-operating characteristic (ROC) curve analysis was performed to determine the area under the curve (AUC), sensitivity and specificity with an optimal cut-off value. Example of MSR and MSD deduction was given in Figure. 1. Totally 24 patients with 24 pairs-tumor (18 primary, 6 metastases) were included. The area under the curve of MSR (AUC, 0.843; 95% CI, 0.637-0.958; p=0.001) was significantly higher than MSD (AUC, 0.685; 95% CI, 0.465–0.857; p=0.240) with p value 0.022. The optimal cut-off value for MSR and MSD was 1.61 (83.33% sensitivity, 83.33% specificity) and 1.94 (83.33% sensitivity, 66.67% specificity). The MSR from PET/CT may helpful in differentiating separate primary lung cancers from intrapulmonary metastases and larger studies were needed to confirm this result.