Comparative Diagnostic Performance of Digital Versus Analog PET/CT for Lymph Node Metastases and Glut-1 Correlation in Resected Non-Small Cell Lung Cancer

Katsuhiko Shimizu,1 Yoshihiko Fukukura,2 Shinsuke Saisho,1 Yuji Nojima,1 Shogo Takeuchi,2 Takashi Matsutani,1 Hiroki Sugiyama,1 Masao Nakata1 1Department of General Thoracic Surgery, Kawasaki Medical School, Kurashiki, Okayama, Japan; 2Department of Radiology, Division of Functional and Metabolic Imaging, Kawasaki Medical School, Kurashiki, Okayama, JapanCorrespondence: Katsuhiko Shimizu, Department of General Thoracic Surgery, Kawasaki Medical School, Matsushima 577, Kurashiki, Okayama, 701-0192, Japan, Tel/Fax +81-86-464-1124, Email [email protected]: Recent innovations in technology have significantly advanced the imaging capabilities of positron emission tomography/computed tomography (PET/CT). Digital PET/CT provides sensitive and high-resolution imaging and can improve the detection of small lesions as compared to conventional (analog) PET/CT. This study aimed to compare the diagnostic performance of digital versus analog PET/CT for detecting lymph node metastases and to assess the maximum standardized uptake (SUVmax) values in patients with resected non-small cell lung cancer (NSCLC).Methods: We enrolled a total of 103 patients with lung adenocarcinoma or squamous cell carcinoma who had undergone preoperative PET/CT in either analog or digital scanners. The primary endpoint was comparison of the diagnostic performance of the two modalities for lymph node metastasis, and the secondary endpoints were comparison of the SUVmax values and correlation of the SUVmax values with the Glut-1 (glucose transporter type 1) expression.Results: Of the 103 patients enrolled in the study, 61 had undergone analog PET/CT, and 42 had undergone digital PET/CT. Significantly higher SUVmax values on digital as compare with analog PET/CT were obtained for cT1b tumors (D/A ratio = 3.42, p = 0.002) as well as cT1c tumors (D/A ratio = 2.10, p < 0.001). However, no significant difference in SUVmax values between the two types of PET/CT was obtained for tumors exceeding 3.0 cm in diameter. A stronger correlation was found between tumor Glut-1 expression and the SUVmax values obtained digital PET/CT as compared with the values obtained with analog PET/CT. Digital PET/CT also showed a higher sensitivity (71.4% vs 37.5%) for detecting lymph node metastases, although the specificity was slightly lower (88.6% vs 96.2%), and the overall accuracy was comparable (85.7% vs 88.5%) between the two types of scanners. False-positive lymph nodes on digital PET/CT were obtained in conditions such as pneumoconiosis and anthracosis, while false-negatives results were obtained in conditions such as micrometastases and/or low lymph node Glut-1 expression.Conclusion: These results suggest that digital PET/CT shows improved diagnostic sensitivity and that the results of digital PET/CT are better correlated with tumor metabolic activity, which results in improved detection of lymph node metastases. These results support the clinical usefulness of digital PET/CT for optimizing perioperative strategies and increasing diagnostic confidence in the management of NSCLC. Future multicenter prospective studies and a standardized redefinition of SUVmax are urgently needed to validate our findings and to establish more reliable clinical application of digital PET/CT in patients with lung cancer.Keywords: digital PET/CT, SUVmax, lymph node metastases, Glut-1